Manual Brake System Trouble Shooting: Expected Line Pressure?

[BANKO]

Hey guys, I converted from a power booster w/ front disk and rear drum to manual brakes running Z06 6-piston fronts and still have the rear drums (for now).

Under panic braking I can't lock up the fronts and I feel a little scared at how much pedal input is required to slow down. Not sure if I have air in my MCs or if my proportioning valve is reducing the pressure.

Here is the setup I have:

Wilwood 6.25:1 pedals (http://www.wilwood.com/Pedals/PedalProd.aspx?itemno=340-11295)
Wilwood High Volume 3/4" bore (front) (http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-6764)
Wilwood High Volume 7/8" bore (rear) (http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-6765)
Wilwood adjustable proportioning valve (http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-11179)

My balance bar is set equal front to rear and the proportioning valve is full open, with 57% reduction to the incoming line pressure. I think the pedal is too hard for being a 3/4" bore and have had others drivers give me the same feedback. Next action I'm going to take is to check the line pressure at the front calipers, does anyone know how much pressure is expected?

[Matt@BOS]

I can't tell you exactly what line pressure is expected, and don't want to throw out a number that is wrong, but I might be able to help with the pedal setup.

I'm running dual master cylinders for the brakes, and I have Wilwood W6/W4 calipers. The W6s, (if I recall correctly) have a similar piston bore volume to the C6 Z06 calipers, but I don't know the rear Wilwood calipers would compare to the drum brakes.

I am using 3/4" front and 7/8" rear master cylinders and I have the balance bar set significantly towards the front brakes, and no proportioning valve. From my experience the 7/8" seems to move enough volume in relation to pedal travel that you need to make sure the pedal is pushing a lot more towards the 3/4" master cylinder. At the last RTTC I had the bar centered, or maybe even towards the rear after some tinkering the previous week, and I could not get the car to slow down at all!

As for the pedal feel. The pedal in my car is pretty firm. It isn't what I'd call rock hard, but it doesn't feel anything like manual brakes with a single tandem more master cylinder. There isn't a ton of pedal travel, and the pedal isn't what I would describe as "springy" like something you'd find in a new car.

If you have any other questions, or a better or more specific description I would be happy to try and help further.

[transam]

Wllwoods site has some great tech advice for this topic as well. I have manual brakes with a willwood master and i had horrible pedal feel, u needed both feet to stop the car and i couldnt lock the wheels, i looked on wilwoods site and i was reading on the ratio you need for your brake pedal ,mine was way off,i redrilled and relocated the push rod and i got a really good pedal feel and stopping power. worth looking into.

[Payton King]

correctly size the masters to the calipers. May be hard in your case with drum rear brakes. Personally I would not run the proportioning valve.

Most calipers do not want more than 1200 psi. You can get some caliper pressure gauges from Longacre for about $100 for 2 gauges and a cool metal case. For C5 sized brakes front and rear I was getting 1100 psi front and 850-900 rear with about 100 lbs leg pressure. I ended up with a 3/4 front and 3/4 rear on mine, but the rear sizing was due to 335/19 tire that was 27 inches tall. It could take more rear brake and still be ballanced.

I am going to guess that your problem lies in what brake pad you have up front. If you are running a street pad, I would change to something more agressive. I tried the Wilwood BP10's and could not get my car to stop no matter what I tried. Went to a Carbotech Ax6 (autocross pad with good cold bite) and it was a night and day difference. They will be dusty and will make some noise. Mine never made any noise, but I have heard other people say they do.

I have not tried but heard good things about the Hawk HP+ as well.

[Blake Foster]

correctly size the masters to the calipers. May be hard in your case with drum rear brakes. Personally I would not run the proportioning valve.

Most calipers do not want more than 1200 psi. You can get some caliper pressure gauges from Longacre for about $100 for 2 gauges and a cool metal case. For C5 sized brakes front and rear I was getting 1100 psi front and 850-900 rear with about 100 lbs leg pressure. I ended up with a 3/4 front and 3/4 rear on mine, but the rear sizing was due to 335/19 tire that was 27 inches tall. It could take more rear brake and still be ballanced.

I am going to guess that your problem lies in what brake pad you have up front. If you are running a street pad, I would change to something more agressive. I tried the Wilwood BP10's and could not get my car to stop no matter what I tried. Went to a Carbotech Ax6 (autocross pad with good cold bite) and it was a night and day difference. They will be dusty and will make some noise. Mine never made any noise, but I have heard other people say they do.

I have not tried but heard good things about the Hawk HP+ as well.

I was also going to say pads, but our red 69 has 14" proplus front and rear with a 1" wildwood master and it is awesome with the pads supplied by Baer. my nova has 3/4 f and 7/8 rear with 14" proplus and it to is good but I do run a wildwood auto x pad

[Matt@BOS]

I should also mention I've run BP20 (street) E (autocross, okay cold. needs a tiny bit of heat to work best), and B pads (road course, terrible cold) and could lock all of them up during a panic stop. The B pads took a ton of effort though.

It doesn't take much to dial out too much front brake on the balance bar. With rear drums I bet it would be down right scary trying to stop if out of adjustment.

[IMPALA MAN]

I would check with the caliper manufacturer, however 3/4 bore master seems small for the two front calipers. I typically recommend 3/4 bores for clutch only. Looking at the last few posts on clutch issues, it's beginning to look like 3/4 is too small for some of them also.
Simply put, if the master cylinder does not have enough volume,(more than the volume of both of the calipers) it will not fully engage the calipers.
This is the second post today I have replied to with this suspected "volume" problem. Best of luck and hope this helps. Check the link below, same issue, just with a clutch master cylinder.

http://www.lateral-g.net/forums/showthread.php4?t=40386

[Apogee]

Josh, are you still running the HPS 1-piece pads you purchased with your kit? I know you were going back and forth between those and the HP+, but didn't want the increased dust/noise/wear associated with the more aggressive pads. You basically have three ways to reduce pedal effort, increase the pedal ratio, decrease the MC bore size and/or increase the pad CoF. The pedal ratio on your Wilwood pedals is fixed at 6.25:1 and I don't know whether a 5/8" bore MC will have the necessary volume to supply the front calipers without excessive pedal travel, leaving the pads as your best option IMO.

What bore size wheel cylinders are you running? If I'm not mistaken, there are some larger bore wheel cylinders that are a direct swap which might help get your balance beam adjustment a little more centered.

Tobin
KORE3

[BANKO]

For C5 sized brakes front and rear I was getting 1100 psi front and 850-900 rear with about 100 lbs leg pressure.


Payton, how do you estimate 100 lbs of leg pressure? I've read that one can exert up to 300 lbs in panic situations, but is there a way to truly know how much pedal input one is exerting?

@Tobin

Yes, I'm running the HPS pads, should have gone with the HP+ pads. Forget the noise and dust, I want higher CoF!

I'll be updating my brakes in the coming weeks to Wilwood W6A in the front and moving my Z06 PBRs to the rear. Trying to decide if I buy 4 sets of line pressure gauges or use a clamping force pressure tester. Has anyone used this tool (http://www.genesisparts.com/index.cfm?tpc=Genesis-Dual-Brake-Pressure-Tester&form_prod_id=4&action=product)?

[Apogee]

...Yes, I'm running the HPS pads, should have gone with the HP+ pads. Forget the noise and dust, I want higher CoF!

I'll be updating my brakes in the coming weeks to Wilwood W6A in the front and moving my Z06 PBRs to the rear. Trying to decide if I buy 4 sets of line pressure gauges or use a clamping force pressure tester. Has anyone used this tool (http://www.genesisparts.com/index.cfm?tpc=Genesis-Dual-Brake-Pressure-Tester&form_prod_id=4&action=product)?

That's a cute tool, but I don't know anyone who has one or who has even used one, so I can't comment on its worth in a toolbox for troubleshooting. It kinda reminds me of a valve spring tester to be honest. As for caliper pressure gauges, you should only need two since you only have two brake circuits, front and rear, and they should provide the same pressure to both calipers on the same circuit per conventional hydraulic principles. Alternatively, they make the brake pressure gauges intended to be mounted in the dash to provide feedback to the driver when adjusting in-cab detent proportioning valves and/or balance beam position with the remote adjusters.

As for pads, any "GG" friction rated pad is going to be a step in the right direction given a manual track application, so Hawk HP+, EBC Yellowstuff, Carbotech AX6, or something similar should provide significantly higher brake torques with less pedal efforts.

Tobin
KORE3

[Vegas69]

I found the HP Plus to be the best all around pad for a pro-touring car and manual brakes. All out road course performance would be their weakness.

[Ron Sutton]

I find the challenge is ... when someone goes to one of the aftermarket 6-piston caliper brake set-ups looking for bad ass brakes ... they are occasionally disappointed with the braking result ... because the pistons are so small, the total piston "area" is insufficient ... and they didn't account for that in the total system

Most car guys don't know the piston area formulas ... so when you glance at the piston sizes written on paper ... and there are 6 of them ... it seems they should add up to more brake caliper clamping force ... but often they do not.

The problem is compounded if we make any one (or more) of these changes:
A. Utilize brake calipers designed to have a strong power booster ... now running without one.

B. Utilize brake calipers designed to run .50 to .65 CoF racing brake pads ... and now have street pads in the .35-.42 CoF Range.

C. Utilize brake calipers designed around systems typically with a 6-1 or higher pedal ... but some factory pedals have less.

D. Utilize brake calipers designed for a 2700# car ... now on a 3500# car.

The charts below, use the standard brake formulas all brake engineers use for manual brake systems. It accounts for every aspect of braking except the tire. This graph shows several front brake calipers ... ALL using the same pedal ratio, same brake pads & same master cylinder size.
*The pedal ratio, brake pads & master cylinder size do not represent what comes from the factory. I made these 3 items a constant only for comparison.

The rotor sizes are different ... to better represent how they're being sold & used. Regardless ... look at the braking force numbers at the bottom. The 3 common GM factory brake calipers are for Gen 2 F-body, G-Body & Impalas are highlighted with blue columns.

Go down to the 2nd line from the bottom ... marked "Brake Torque" ... and compare the factory numbers with aftermarket options. When you wonder why some don't stop stronger ... simply go to the line marked "Caliper Piston Area x2" ... and you'll see important differences.

There is nothing wrong with any of these brake calipers. But if we are building a better brake system for our PT cars ... we need to better understand the total picture. We can't put a caliper on our cars with significantly less piston area ... without running the proper:
1. Pedal ratio
2. Master cylinder size
3. Brake pad CoF
4. Rotor Size
Even then ... we still can't run too small of piston area for our weight of car & expect it to work well.

The numbers can be kind of confusing. All most of us want to know is how much do I need?
In my experience, for 3500# cars, here's a GUIDELINE that is based on total braking force including the front & rear brake systems.

GUIDELINE:
2500# = Average passenger car
3000# = Performance production car
3500# = Good street & track braking system
4000# = Track braking system with good tires
4500-5500# = Full race brake systems

The very bottom line of the chart shows total braking force with that combination if you were looking for 70% front braking, as I often do in race cars.

If anyone is putting together a system & has questions on one part or another, I'll be happy to calculate things and/or advise you. I have spread sheets to work out front & rear systems & compare options. I can also change inputs in this chart to show you how they all look with a different brake pad, pedal ratio, master cylinder, etc.

[FETorino]

In my experience, for 3500# cars, here's a GUIDELINE that is based on total braking force including the front & rear brake systems.

GUIDELINE:
2500# = Average passenger car
3000# = Performance production car
3500# = Good street & track braking system
4000# = Track braking system with good tires
4500-5500# = Full race brake systems

The very bottom line of the chart shows total braking force with that combination if you were looking for 70% front braking, as I often do in race cars.

If anyone is putting together a system & has questions on one part or another, I'll be happy to calculate things and/or advise you. I have spread sheets to work out front & rear systems & compare options. I can also change inputs in this chart to show you how they all look with a different brake pad, pedal ratio, master cylinder, etc.




Ron

I have a dumb question.

The figure at the bottom is total braking force of the front brakes when they are doing 70% of the work or is it an estimation of the total including the 30% contributed from the rear brakes? :headscratch:

I have W6A front calipers with a 7/8" master cylinder and I have a 6 to 1 pedal ratio. So I read 3141 lbs of force with this set up. Is that 3141 for the front and 4487 total or 3141 total?

[carbuff]

Rob,

Looking at the math, I think the answer is that the Brake Torque line represents the amount of work that the front brakes on an application would be doing while the Total Braking Torque if 70% line means that if 70% of your total car braking is done in the front, and 30% in the back, then you have a combined braking torque equal to that last line. Thus, if you multiply the value in the bottom line by 70%, you get the number in the Brake Torque line (at least for your W6A caliper):

3141 * 0.7 = 2198.7 (2199 rounded)

Now, exactly what the Total Braking Torque number actually means, I'm not sure. I think it refers back to Ron's Guideline, meaning that the 3141 total would fall between the 3000# (Performance Production Car) and the 3500# (Good street & track braking system) areas. Ron, could you please confirm that I'm understanding what that row of the table is referring to?

(I've said it before, and I'm saying it again... I love all this tech you are providing!!! THANX! )

[Ron Sutton]

Ron

I have a dumb question.

The figure at the bottom is total braking force of the front brakes when they are doing 70% of the work or is it an estimation of the total including the 30% contributed from the rear brakes? :headscratch:

I have W6A front calipers with a 7/8" master cylinder and I have a 6 to 1 pedal ratio. So I read 3141 lbs of force with this set up. Is that 3141 for the front and 4487 total or 3141 total?

Hey Rob,

A quick brake bias primer ...
For track performance ... "high travel/low roll suspensions" need a brake system with approximately 70% front braking & 30% rear. Conventional "low travel/high roll suspensions work better around 65/35.

The W6A front calipers you have with a 7/8" master cylinder, 6-1 pedal ratio, 14" rotors & Hawk HP Plus brake pads would make 2199# of braking force from the front brakes.

Since you will be running a high travel/low roll suspension, if you decide to target a 70/30 brake bias, you would be shooting for 3141# of total braking force. Meaning you would want your rear system to produce 942# of braking force to go along with your fronts making 2199#.

If you'll let me know what your rear brake specs are, I can calculate what they are & you can evaluate it as a system.

Frankly, knowing what you're looking to do with your Torino, I do not feel 3141# is enough total braking force for your goals. I suspect you would be happiest with 3500-4000# for track days on slicks. That will require a higher CoF pad.

I tend to agree with Todd that the HP Plus makes a good street brake pad, if you have enough clamping force & you do. I think the HP Plus pads ... making 3141# total braking force in your system ... would be good for the street on street tires.

But when you're running track days on Hoosier R6's, you would need to swap in a more aggressive pad, in the .50 to .55 CoF range. Each pad compound has their own unique "personality" ... so there is more to it than just a "number". I would need to discuss pads with you some to help you narrow it down to 2-4 compounds that "sound right" ... then you need to test them on the track & see what you like in the "feel".

Once you have a pad you really like, that can be your "track pad." A lot of guys have track pads & street pads, and just swap them as part of their routine.

For conversation sake, let's use the Wilwood BP-20 pad & say you're working it in the 700 degree range on track on the front brakes. That puts that pad at .50 CoF.
* If you ran the same pad in the rear, it will operate at 150-200 degrees less temp in the rear & have a lower effective CoF number for the rear.

I attached the Wilwood brake pad compound graph for your review & a new chart showing all the brake calipers using a brake pad compound with a .50 CoF.

With the BP-20 pads, you'll notice your front brake caliper, using the same M/C, pedal & rotor would make 2556# of front braking torque. Assuming that is 70% of your braking, the total system would make 3652# of braking torque.

I'd like to see it closer to 4000# for your track days with slicks, but we'll need to find a pad with a relatively predictable torque curve in the .52-.55 range to achieve that. Once I know your rear system, I'll reach out to my guy at PFC.

[Ron Sutton]

Rob,

Looking at the math, I think the answer is that the Brake Torque line represents the amount of work that the front brakes on an application would be doing while the Total Braking Torque if 70% line means that if 70% of your total car braking is done in the front, and 30% in the back, then you have a combined braking torque equal to that last line. Thus, if you multiply the value in the bottom line by 70%, you get the number in the Brake Torque line (at least for your W6A caliper):

3141 * 0.7 = 2198.7 (2199 rounded)

Now, exactly what the Total Braking Torque number actually means, I'm not sure. I think it refers back to Ron's Guideline, meaning that the 3141 total would fall between the 3000# (Performance Production Car) and the 3500# (Good street & track braking system) areas. Ron, could you please confirm that I'm understanding what that row of the table is referring to?

(I've said it before, and I'm saying it again... I love all this tech you are providing!!! THANX! )

Bryan,

You have it correct. You can look at my post answering Rob for more detail.

.

[FETorino]

Ron

As always thanks for the detailed explanation. Looking at Brian's math I see it is obvious.

Brian you obviously have a better skill set with calculations than as a food critic. :action-smiley-027:

On my set up in the rear I have a 14" rotor and a Wilwood FNSL 4 piston caliper 120-11782-BK.

:cheers:

[Ron Sutton]

Ron

As always thanks for the detailed explanation. Looking at Brian's math I see it is obvious.

Brian you obviously have a better skill set with calculations than as a food critic. :action-smiley-027:

On my set up in the rear I have a 14" rotor and a Wilwood FNSL 4 piston caliper 120-11782-BK.

:cheers:

Hey Rob ! What are we both doing up so late ?!?!

Here are the calcs for your brake system with Wilwood BP-20 brake pads & two different M/C sizes for the rear. The BP-20's CoF curve climbs pretty rapidly, hence the difference in CoF numbers for front & rear.

I'm going to suggest we find brake pads that have a flatter CoF curve but in the .50-.55 range. Once we land on brake pads, then I'll recalculate this so we can see which rear M/C is best.

[FETorino]

Hey Rob ! What are we both doing up so late ?!?!




Checking brake specs after a night out with friends.:happy23: What else?:popcorn2:

:cheers:

[Ron Sutton]

Checking brake specs after a night out with friends.:happy23: What else?:popcorn2:

:cheers:

Me too ... sorta. We were at a family get together for a birthday party. I couldn't resist checking stuff on here when I got home.

Did the brake calcs make sense with your system?

[carbuff]

Brian you obviously have a better skill set with calculations than as a food critic. :action-smiley-027:

Hmm, 25 years as an engineer vs. 45 years of eating, what's wrong with this picture? :catfight:

[carbuff]

Ron,

Do you happen to have the piston size numbers for the Baer 6P caliper? My guess is that it's very similar to or the same as the 6S. I'm running the 6P front and rear on my car with 14" rotors.

Given your definitions, I would consider my setup to be more conventional, not a high-travel setup. So I would be leaning towards the 65/35 setup. I'm using the DSE booster and master cylinder, which is obviously a power brake setup instead of a manual setup...

[BANKO]

Ron, thanks for the charts! I've been studying and pondering many questions. It is great to see a line up of all the calipers. Interesting that the GM single piston on and 11.88" rotors have almost as much clamping force as the Wilwood massive TC6R. Can this TC6R caliper be used on a 13" rotor, the smallest size rotor i saw offered is 16", reading the caliper drawing shows it may accomodate a 14" rotor. With a 16" shouldn't this lead to a dramatic brake torque increase? This got me thinking it might be an alternative to the W6A (5.4) on a 14" rotor since it provides 6.9 piston area!!! Key downside is the availability for more tack oriented pads, looks like the highest CoF is .40, comparable to the HP+ pads.

I was also thinking of the benefits of adapting the GM single piston caliper to a larger rotor. Not very sexy, but effective. Quite disappointing to see the Z06 6 pistons have such low clamping force.

[Flash68]

Another thread made even better by our main man Mr. Sutton. :thumbsup:

Ron, do you happen to have a chart for the AP6000 fronts and AP6050 rears?

:cheers:

[Ron Sutton]

Oops! I had the Baer caliper model listed as 6S ... but those specs are for the 6P ... as Ron in SoCal's post reminded me. I have updated the two charts to properly reflect the caliper model. No details change.

Ron,

Do you happen to have the piston size numbers for the Baer 6P caliper? My guess is that it's very similar to or the same as the 6S. I'm running the 6P front and rear on my car with 14" rotors.

Given your definitions, I would consider my setup to be more conventional, not a high-travel setup. So I would be leaning towards the 65/35 setup. I'm using the DSE booster and master cylinder, which is obviously a power brake setup instead of a manual setup...


So the specs in the charts ARE of your 6P. But I need the rest of your system specs to calculate braking force & bias.

If you will provide me with front & rear:
Brake piston sizes (all)
Rotor diameters
pedal ratio
Master cylinder bores
Brake pad brand & compound name

I'd be happy to calculate your braking system bias & total braking force.

BUT ... I do not have experience factoring in the hydraulic booster. So the bias will be accurate, but the total braking force will be lower than you actually have, as long as you have booster assist.

Maybe Baer or Tobin can provide us with a correction factor based on the amount of assist from your specific booster ... or at a minimum, a guideline.

[Ron in SoCal]

Ron,

Do you happen to have the piston size numbers for the Baer 6P caliper? My guess is that it's very similar to or the same as the 6S. I'm running the 6P front and rear on my car with 14" rotors.

Given your definitions, I would consider my setup to be more conventional, not a high-travel setup. So I would be leaning towards the 65/35 setup. I'm using the DSE booster and master cylinder, which is obviously a power brake setup instead of a manual setup...

Bryan - I've given RS the 6P piston bores w 14" rotors so I'm sure he'll post as soon as he wakes up :D. Post up your MC size? IMHO I also think you could achieve a high travel set up with the proper springs/sway bars.

[BANKO]

Another thing I noticed on your charts is an assumed static line pressure of 499psi for 7/8" MC and 679psi for 3/4" MC, can you speak to the what is an expected maximum line pressure in a manual setup. Some guys have mentioned measuring pressures of 800-1000psi. I assume this is primarily achieved by a greater input to the pedal rather than reducing MC size. Do you have numbers for the following driving styles: normal (non fatiguing pedal input), semi-aggressive pedal input (spirited driving / auto cross), aggressive pedal input (high speed track braking and panic stop situations).

As always thanks for your wealth of knowledge and willingness to educate us!

[Ron Sutton]

Bryan - I've given RS the 6P piston bores w 14" rotors so I'm sure he'll post as soon as he wakes up :D. Post up your MC size? IMHO I also think you could achieve a high travel set up with the proper springs/sway bars.

Thanks for catching that Ron. I mistakenly put the caliper as a 6S in my charts.

I have corrected the charts in this thread to read "6P" ... and corrected my comments in my post to Bryan.

[FETorino]

Me too ... sorta. We were at a family get together for a birthday party. I couldn't resist checking stuff on here when I got home.

Did the brake calcs make sense with your system?



Yes very clear this am.:thumbsup: Something was making them a little fuzzier to review last night:happy23: Not certain what that was:headscratch:

Hmm, 25 years as an engineer vs. 45 years of eating, what's wrong with this picture? :catfight:

Formal education has helped you on the engineering front. Your eating habits are Feral. :stirthepot:

:cheers:


Another thing I noticed on your charts is an assumed static line pressure of 499psi for 7/8" MC and 679psi for 3/4" MC, can you speak to the what is an expected maximum line pressure in a manual setup. Some guys have mentioned measuring pressures of 800-1000psi. I assume this is primarily achieved by a greater input to the pedal rather than reducing MC size. Do you have numbers for the following driving styles: normal (non fatiguing pedal input), semi-aggressive pedal input (spirited driving / auto cross), aggressive pedal input (high speed track braking and panic stop situations).

As always thanks for your wealth of knowledge and willingness to educate us!


The chart assumes a 100lbs of driver force on the pedal resulting in a 300lb force on the master.

So I guess the question boils down to why the 100 lb number is used and how do we relate the figure to an amount of pedal pressure that is familiar?

[Ron Sutton]

Hi Josh,

Another thing I noticed on your charts is an assumed static line pressure of 499psi for 7/8" MC and 679psi for 3/4" MC, can you speak to the what is an expected maximum line pressure in a manual setup.
Just to be clear ... I did not input that line pressure. That is an actual calculation of the line pressure with 100# of force from the driver's braking foot ... into a 6-1 pedal ... with those specific master cylinders.

I don't ever manually input line pressures into my calcs. I always calculate them. I use 100# of force from the driver's braking foot "most of the time" ... because for most adult males I have found that number to be representative of the driver pressing hard ... without tiring his leg out over the course of a race.

I have not performed calc's with "panic stop" level of pressures. But I know it can easily be double & more, because I see it when we're testing pressure at the calipers.

Using 100# is a good baseline starting point, but in the real world of racing, if I'm working with a driver long term, we're tailoring the brake system to him or her.

I've had 12 year old phenoms that weigh 74# body weight, so I had to "up" the brake system for them with more pedal ratio, smaller master cylinders and/or more aggressive brake pads.

Same with some bad ass female drivers I've had. Jessica Clark won two USAC Midget Championships & a NASCAR Modified race with us. She weighed 115 pounds. You don't want the driver to have to overexert themselves to achieve optimum braking force. Tiring them out over a race doesn't make sense.

On the other hand, you you don't want it too sensitive for them either. I had this crazy strong driver that could ... and did ... dead lift the front of a Midget (over 400#). We had to reduce the braking force for him, by switching to larger M/C's.

Make sense?


Some guys have mentioned measuring pressures of 800-1000psi. I assume this is primarily achieved by a greater input to the pedal rather than reducing MC size.
Yes.

Do you have numbers for the following driving styles: normal (non fatiguing pedal input), semi-aggressive pedal input (spirited driving / auto cross), aggressive pedal input (high speed track braking and panic stop situations).
Refer to my comments above.

As always thanks for your wealth of knowledge and willingness to educate us!

No worries.

[Ron Sutton]

Good morning Rob,

Yes very clear this am.:thumbsup: Something was making them a little fuzzier to review last night:happy23: Not certain what that was:headscratch:
I have a pretty good idea "why".



The chart assumes a 100lbs of driver force on the pedal resulting in a 300lb force on the master.

So I guess the question boils down to why the 100 lb number is used and how do we relate the figure to an amount of pedal pressure that is familiar?

Read my post to Josh & that should provide clarity.

[Ron Sutton]

Hey Josh,

Ron, thanks for the charts! I've been studying and pondering many questions. It is great to see a line up of all the calipers. Interesting that the GM single piston on and 11.88" rotors have almost as much clamping force as the Wilwood massive TC6R.
That's what fools a lot of car guys. You see all those pistons & think the math adds up but it often does not. The formula for piston area (or area of any circle) is Radius x Radius x Pi. Remember radius is half of diameter.

So a stock GM Camaro, Impala or C10 pick up caliper from the 70's has a piston size is 2.9375. Divide by 2 for radius = 1.46875.

1.46875 x 1.46875 x 3.1416 = 6.777 inches of piston area. Times 2 calipers on the front = 13.55 total piston area for the front.

The PBR/Z06 Caliper has 6 pistons, but you only account for one side, so 3 all the same size at 1.30". When you run the braking formula, you end up with 7.964 total piston area for the front.

There isn't anything wrong with these PBR/Z06 calipers. The Z06 system was designed with larger rotors, higher CoF brake pads & more pedal ratio than the Camaro, Impala or C10 pick up. I'm not sure if the M/C size if different. But when you're swapping a brake system into a car, you need to account for these details in the total system.

Important Note: I'm not sure if I read this correctly or incorrectly ... but if you have the proportioning valve all the way "out" ... that should reduce the rear brake force by 57% ... and is reducing your total braking force.

If that is correct ... you need to start by opening it up to restore rear braking force ... and then go test your brakes in a safe place & see how it does. If you get it where it's locking the rear brakes up ... reduce the rear braking force just to the point it doesn't lock up the rears ... and let's see if that's better.


Can this TC6R caliper be used on a 13" rotor, the smallest size rotor i saw offered is 16", reading the caliper drawing shows it may accomodate a 14" rotor.
I do not know, as I have not worked with this caliper. It was designed by Wilwood to be a street caliper for pickups & SUVs. That's outside my wheelhouse.

With a 16" shouldn't this lead to a dramatic brake torque increase?
You don't need 16" rotors. I have designed brake systems with 5500# total braking torque utilizing 11-3/4" rotors front & rear. The main reason to increase rotor size is to increase the thermal capacity of the rotors to survive long races.

I never run a rotor larger than needed, because the rotational weight KILLS performance. It adds to unsprung weight ... making the suspensions job of controlling that wheel harder. And it adds to the rotating weight. Not only is the rotor heavier ... but you're moving it out on a bigger radius.

I cringe when I see guys spend $1200 a wheel to shave 2-4# off ... then add rotors that weigh 6-8# more.

I learned long ago, if we cool the rotor properly, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a priority.




This got me thinking it might be an alternative to the W6A (5.4) on a 14" rotor since it provides 6.9 piston area!!! Key downside is the availability for more tack oriented pads, looks like the highest CoF is .40, comparable to the HP+ pads.
The W6A is a real race caliper with a wide variety of pads available ... including race track compounds. The TC6R is a street caliper with a lot of piston area ... but a narrow selection of street pad compounds.


I was also thinking of the benefits of adapting the GM single piston caliper to a larger rotor. Not very sexy, but effective. Quite disappointing to see the Z06 6 pistons have such low clamping force.

Again, nothing wrong with the PBR/Z06 caliper. I think your application may need more aggressive pads & more rear braking force to be a good system. Also nothing wrong with upgrading it as you've mentioned doing.

Please go test the proportioning valve adjustment to confirm that is not a part of the problem.

[Ron Sutton]

Another thread made even better by our main man Mr. Sutton. :thumbsup:

Ron, do you happen to have a chart for the AP6000 fronts and AP6050 rears?

:cheers:

Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

[FETorino]

Hey Josh,



You don't need 16" rotors. I have designed brake systems with 5500# total braking torque utilizing 11-3/4" rotors front & rear. The main reason to increase rotor size is to increase the thermal capacity of the rotors to survive long races.

I never run a rotor larger than needed, because the rotational weight KILLS performance. It adds to unsprung weight ... making the suspensions job of controlling that wheel harder. And it adds to the rotating weight. Not only is the rotor heavier ... but you're moving it out on a bigger radius.

I cringe when I see guys spend $1200 a wheel to shave 2-4# off ... then add rotors that weigh 6-8# more.

I learned long ago, if we cool the rotor properly, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a priority.



[/COLOR]

Guilty as charged.:shakehead:

You see a lot of oversized rotors in the PT world because of the aesthetic value of filling the wheel. Many of us know better and still commit the crime.

I fell victim but reading this reminds me why I really wanted to run smaller rotors out back.


Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

Technical questions for Flash, this should be good.:popcorn2: :relax:

[carbuff]

I have found the solution for all of our braking concerns! And it's cheap too!!!

Brembo Red Disc Brake Caliper Covers (http://www.ebay.com/itm/New-Brembo-Red-Disc-Brake-Caliper-Covers-Front-Rear-Set-Universal-Car-Truck-3D/321145311835?_trksid=p2045573.m2102&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26 asc%3D298%26meid%3D178530443096734173%26pid%3D1000 34%26prg%3D1079%26rk%3D3%26rkt%3D8%26sd%3D11112994 8605%26)

:trophy-1302:

[Ron Sutton]

I have found the solution for all of our braking concerns! And it's cheap too!!!

Brembo Red Disc Brake Caliper Covers (http://www.ebay.com/itm/New-Brembo-Red-Disc-Brake-Caliper-Covers-Front-Rear-Set-Universal-Car-Truck-3D/321145311835?_trksid=p2045573.m2102&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26 asc%3D298%26meid%3D178530443096734173%26pid%3D1000 34%26prg%3D1079%26rk%3D3%26rkt%3D8%26sd%3D11112994 8605%26)

:trophy-1302:

That is hilarious. :rofl:

I'm sure they're licensed by Brembo ... NOT. :sarcasm_smiley:

.

[Track Junky]

This is great stuff guys. :popcorn2:

I think I'm just going to add a "Thanks Ron" to my sig. :)

[Flash68]

Hi Dave,

I have worked with AP calipers a LOT ... but I am not familiar with those part #s, other than knowing they're 6-piston calipers.

Two questions:
1. What is/was their intended design purpose?
2. Can you measure the piston sizes & we'll run some calcs?

.

I got these from James Shipka as they were used on his One Lap Camaro a couple years before he switched. Their intended purpose is dual street/track. I have the slotted-only version (not drilled). Here are the links he sent me:

http://www.brake-pros.com/product_files/AP6000S%7Ebroch.pdf
http://www.brake-pros.com/product_files/AP6050S%7Ebroch.pdf

Piston sizes (Hey Rob, look at that!) we measured to be as follows:

1.05 / 1.05 in the rear and 1.5 / 1.25 / 1.05 in the front.

They also came with some Mintex Xtreme and Raybestos pads. Not sure which we will try out first.

After some discussions with a couple people I was planning on starting with 3/4 / 3/4 MC bores.

Thanks Ron

Guilty as charged.:shakehead:

You see a lot of oversized rotors in the PT world because of the aesthetic value of filling the wheel. Many of us know better and still commit the crime.

I fell victim but reading this reminds me why I really wanted to run smaller rotors out back.






Yep. Nothing looks worse than an 11" rotor inside a 20" wheel. :bitchslap:

But then a lot of this talk is really helping to validate that form can be trumped by function and then form can actually be aesthetically appealing because of it.







Technical questions for Flash, this should be good.:popcorn2: :relax:

hey Roberto..... see this post by your new Crew Chief below. He has posted this more than once.... FYI. :poke:



6. I want people to ask questions. There are no stupid questions



:thumbsup:

[Ron Sutton]

Dave,

You didn't give me all the details to work with, so I "assumed" a 6-1 pedal ratio & worked up a chart with 13" rotors & 14" rotors. If you have different details, let me know what they are & I'll plug them into my calcs.

Also, since I don't know what pads you're going to run, I adjusted the pad CoF until I got the 14" rotor version to about 4000# braking force. That will require pads in the .52 CoF at the temperature range you'll use them at. That is the lower end of race pads. You may want less braking force on the street.

For less braking force, go to a pad with a lower CoF. For more braking force, go higher on the CoF.

[Flash68]

Thanks Ron.

Yes, 6:1 on the pedal ratio and 14" front and rear rotors.

I need to see if I can get an exact number/model # of the brake pads I got. I was also considering going with Carbotech XP-12 and/or XP-10 pads. I used them on my previous Wilwood setup (XP-10 front / XP-8 rear) and liked them.

Any experience with them?

[67goatman455]

I'm still completely baffled that the brakes on my 99' Trans Am are better than a C6 Z06. Would the braking force be atleast somewhat equal to the LS1 calipers compared to the Z06 after having the "appropriate/OE spec" master cylinder bores, boost assist, and pedal ratio etc?

[Ron Sutton]

Josh (Banko) has an award from Wilwood, so he's upgrading his brakes. Josh is the one that started this thread because his car is not braking strong enough. He PM'd me the system he's considering.

Brake piston sizes
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.75"
Rear: 0.75" or 0.875"
Brake pad brand & compound name
Front: PolyMatrix H
Rear: Hawk HPS

-------------------------------------------------------------------------------------------------------

I ran the calcs on this system ... an whoa Baby ... it swings the pendulum too far the other way. In the chart below, this is the system on the left. Look down at the total braking force #. It would have 7000# of braking force, which would simply lock the wheels up upon braking.

Now look at the chart on the right. By changing the pad compounds & the M/C sizes, we adjust the total braking force to about 4000#. That is a strong braking system.

Did you guys ever watch the Lassie TV show?
If you did, you remember the Dad always sat down with Timmy at the end of the show to explain the moral of their lesson. This was a planned in moment every show. The writers called it the "Ya know Timmy ..." part of the story.

Well ... Ya know Timmy ...
The lesson here is when building your braking system working out the details is just as important as buying great parts.

[Ron Sutton]

Hi Scott,

My concern is you're coming to a conclusion about braking systems, looking only at one part of the system ... the caliper piston area. Frankly, that's why many brake & pad manufacturers don't release specs. They're concerned a little information ... without the whole picture ... can lead to bad brake choices & incorrectly operating brake systems.

I'm still completely baffled that the brakes on my 99' Trans Am are better than a C6 Z06.
That's not accurate. Just the piston size on the calipers are smaller in the C6 Z06. But the pedal ratio, rotor diameter, brake compound all make the total C6 Z06 brake package have slightly more braking force than the '99 Trans Am.

Would the braking force be at least somewhat equal to the LS1 calipers compared to the Z06 after having the "appropriate/OE spec" master cylinder bores, boost assist, and pedal ratio etc?

As covered above, the C6 Z06 Brake system has slightly more braking force than the '99 Trans Am. The GM engineers just got there another route than caliper piston area.

[67goatman455]

[COLOR="Blue"]Hi Scott,

My concern is you're coming to a conclusion about braking systems, looking only at one part of the system ... the caliper piston area.

that would be correct.

[Ron Sutton]

that would be correct.


For me personally, I prefer to build brake systems with more caliper piston area than the PBR/Z06 Calipers utilize, because I don't want to have to get so aggressive with rotor size & pad compound to get the desired braking force.

But they make it work quite well.

[Ron Sutton]

Scott asked this in a separate post & I answered it there ... but felt it should be included in this thread too.

Wondering what the advantages/disadvantages are to the different types of rotors. Plain rotors seem to be cheaper when you need to replace them and there would be a higher surface area i assume. But i can see the slotted/drilled keeping the rotors and pads cooler to help brake fade.


Hey Scott,

I'll outline my thoughts on the pros & cons of different brake rotor features & everyone can decide for themselves what makes sense for their individual needs. I think if you ask 5 different brake experts you will get 7 different opinions, so decide yourself & go with what makes sense for your goals.


Drilled: In the early years, before we knew better, many racers thought that drilling rotors made them run cooler. Wrong. Brake experts had rotors drilled to give the brake pads boundary layer of gasses a path to escape, while the edges of the holes helped clean the pads of debris somewhat.

For a rotor to deal with the heat generated, having more “mass” increases its thermal capacity. Drilling a bunch of holes in the rotor reduces the rotor’s mass & reduces the thermal capacity of the rotor. If the rotor gets overheated often & for long periods of time … the drilled holes become "stress raisers" that can lead to three problems: Elongation and/or distortion of the rotor, cracks between the holes … and breakage. Drilled rotors still have their place. I’ll explain at the end.

Slotted/Grooved: The grooves in the rotor … often called slots … help "clean" the debris from the brake pad. That’s it. It’s a good thing. The grooves/slots need to run a specific direction. See the illustration below.

J-Hooks: AP brakes offers a neat rotor a lot of road race & short track oval guys use. Instead of a straight slot grooved into the rotor, they have these “J”s machined into the rotor surface. The “J” goes all the way through the rotor, unlike grooved slots. The perform the same function as a slot and “maybe” they’re helping the boundary layer of gasses to escape. See them HERE (http://aamcompetition.com/i-5932695-ap-racing-j-hook-front-rotors-09-11-only.html).

Cooling: is not achieved with slots or drilled holes. There are three ways to cool rotors: Vanes inside the rotor, air ducting, with or without fans, to blow cooler air on the rotor, and the Ultra Cool brake fans that mount on the hub. See them HERE (http://ultracoolbrakefans.com/main/).

Important: I learned long ago, if we cool the rotor optimally, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a serious priority. I don’t want to provide the rotors “a little cooling” … I want to provide “as much cooling as practically possible” so we can run lighter rotors & reduce that rotating mass.

Vanes: Are the most important cooling feature of the rotor itself. The vanes of the rotor … spinning on the hub axis … create a vortex, sucking air into & through the rotor’s vanes … helping to cool the rotor. These are simply referred to as vaned rotors & they come in a lot of configurations. The details matter here. The air travels from inside the rotor to the outside, not the other way around as is commonly thought. So the vanes must face rearward when viewed from the outer diameter of the rotor.

Straight vanes do not work as well as curved vanes. There are made & sold as an economy product, because they can go on either side & the parts store doesn’t need to stock left & ride side rotors.

Curved vanes are the way to go. Just think of fan blade design. The vanes scoop the air from inside the rotor … suck it through the inside of the rotor … cooling both sides … and out the top.

More curved vanes provide more cooling … and add mass (weight) to increase the rotor’s thermal capacity. This is my preference instead of adding diameter. If we can get a 12” rotor with 48 vanes that weighs around 11# … that would be my preference over a 13” rotor with 32-36 vanes that also weighs around 11# … because the thermal capacity is the same, the 48 vanes cool better & the 12” rotor has the mass closer into the center, so it’s easier to accelerate & decelerate it.

The only advantage the 13” rotor offered (besides cool looks inside the big wheel) is 10% more braking force. But I can get that 10% braking force four other ways (pad, pedal, piston size & M/C size) … and not have the disadvantage of that weight rotating so far out there. A .05 CoF change in brake pad compound can achieve that.

Note: The vaned rotor is shooting hot air onto the inside of the wheel surface. This is where some of the tire’s heat comes from. If the brakes are overheating, this may over heat the tires too. (Seen it MANY times). Another reason to cool the brakes better.

Rotor Width: Making a vaned rotor wider adds several things: More weight & thermal capacity … and better cooling because the vane channels are bigger, flowing more air. Typical rotor widths are .81”, 1.0” 1.1”, 1.25” & 1.38”. Of course you have to have calipers capable of working on the wider rotor. I like to use the wider option as it adds minimal flywheel effect … as compared to adding rotor diameter.

If you’re not familiar with the math …
Changing the weight of a rotating mass is a one-for-one change in “stored energy” … which I think of, and call, “the flywheel effect.” Moving the weight of a rotating mass increases the stored energy by the SQUARE of the radius change. OMG! This is because as you move weight OUT from its rotating axis, you are increasing the weight's circular velocity (speed).

On the track where speeds are up significantly higher … than everyday passenger car speeds … it really matters. The faster we spin a rotating weight, the more energy it stores (flywheel effect). If we double the RPM of a rotating weight, we multiply the stored energy four times. So at twice the speed … say going into a corner at 100 mph instead of 50 mph … everything rotating has four times the flywheel effect. This is why it’s key to have lighter tire & wheel combos & not run larger or heavier rotors than we really need. My belief is to run as large as I need for thermal capacity & no more.

Rotor Diameter: A larger rotor diameter adds several things: Increased braking force, potentially more weight & thermal capacity, increased flywheel effect of moving the weight out from the centerline ... oh, and the cool factor. :)

Let’s outline braking force gains first:
Going from 10” to 11” adds 12.5% braking force
Going from 11” to 12” adds 11.1% braking force
Going from 12” to 13” adds 10.0% braking force
Going from 13” to 14” adds 9.1% braking force

Why I said potentially increases weight & thermal capacity … is because rotor designs vary. It’s possible to have an 11# 12” rotor & an 11# 13” rotor. If that is the case, you didn’t gain mass (weight) or thermal capacity. But, you still moved the weight OUT & increased the flywheel effect. Of course it is probable that you increased the mass (weight) & thermal capacity … as most 13” rotors are heavily than the same design 12” rotor … typically in the 3-6# range. So then, not only did you move the weight OUT & increase the flywheel effect … you added weight to the flywheel effect. UGLY!

I exhaust every option BEFORE I go larger on diameter. I go more aggressive pad compound, wider rotor, curved vanes, more vanes, better rotor material, no drilled holes and lastly more rotor material. Then, if I still need more thermal capacity than that … think GT/Trans Am road race cars … by all means I’m going up in rotor diameter.

.

[BANKO]

Ron, thanks so much for running the numbers, I appreciate you showing me that every little detail matters in the system.



If I have a goal of running Wilwood J or H on the track and E's on the Auto-x / street can I do the following: 0.875" bore on the front, 0.875" bore on the rear dropping the line pressure via my existing proportioning valve to what a 1.0" bore would provide?

I'm running the Wilwood high volume master cylinders that run in (0.75", 0.875", and 1.0" bores, no 13/16" available). I have a duplicate set of 0.875" bore master cylinders and would like to put them to use instead of buying another new MC.

So the system would be:

Scenario 1: Street / Auto-x

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix E
Rear: Hawk HP+

Scenario 2: Track Only

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix J or H
Rear: Hawk HP+

[Ron Sutton]

Ron, thanks so much for running the numbers, I appreciate you showing me that every little detail matters in the system.



If I have a goal of running Wilwood J or H on the track and E's on the Auto-x / street can I do the following: 0.875" bore on the front, 0.875" bore on the rear dropping the line pressure via my existing proportioning valve to what a 1.0" bore would provide?

I'm running the Wilwood high volume master cylinders that run in (0.75", 0.875", and 1.0" bores, no 13/16" available). I have a duplicate set of 0.875" bore master cylinders and would like to put them to use instead of buying another new MC.

So the system would be:

Scenario 1: Street / Auto-x

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix E
Rear: Hawk HP+

Scenario 2: Track Only

Brake piston sizes (all)
Front: W6A (1.75,1.38,1.38)
Rear: C6Zo6 (1.3,1.3,1.3)

Rotor diameters
Front: 14"
Rear: 14"

pedal ratio
6.25:1

Master cylinder bores
Front: 0.875"
Rear: 1.0" (via 0.875" MC + proportioning valve)

Brake pad brand & compound name
Front: PolyMatrix J or H
Rear: Hawk HP+

Hey Josh,

The proposed packages you laid out work for the street & AutoX events ... if you put a 1" M/C on the rear. Do not run a .875 M/C on the rear even with a PV.

You end up with a LOT of braking force ... total = 3893# ... with a natural 67.4% front & 32.6% rear bias ... that can be fine tuned with the Wilwood pedal system you have.

--------------------------------------------------------------------------------------------------------

For the road course track days, the combo you proposed does not work ... but I showed it anyway ... obvious by the big red letters. :confused59:

With almost 5000# of braking force, you would just lock up the tires. The F/R bias doesn't work either.

--------------------------------------------------------------------------------------------------------

The 2nd chart shows the same street & AutoX set-up ... but shows the Track Day set-up with different brake pads.

4387# is still a lot of braking force. You will need good tires ... like Hoosier R6's or comparable ... or you'll constantly be on the edge of lock up.

This package uses:
Wilwood BP-20's in the rear which are an excellent rear pad with their steep CoF curve. For the front, either PFC's new 12 pad or Porterfields R4 pad. I know the R4 has a nice flat curve from 450 to 900 degrees, which makes for predictable braking.

I "believe" the new PFC 12 has the same CoF & flat torque curve ... and should last longer. It is an endurance pad with medium bite that was on the 2013 Daytona 24 Hour Overall Winner.

-------------------------------------------------------------------------------------------------------

Tip:

For road course racing, front brake pads ... with a flat torque curve in the operating range your running ... provides predictable, consistent stopping ... even when you're braking differently ... shorter/longer, softer/harder ... for different speed corners.

For road course racing, rear brake pads ... with a steeper climbing torque curve in the operating range your running ... provides the best overall stopping performance ... because the rear brakes don't bite so hard when you first get on the brakes ... and then brake progressively harder the longer you're on the brakes ... which the car can handle.

--------------------------------------------------------------------------------------------------------

.

[Track Junky]

Ron, I'm using a carbon kevlar brake pad with a .50 CoF. Is there any specific rotor manufacturer or type of rotor you can recommend for my application. Weight is just under 3200 lbs with me in the car......probably will lose at least 180 lbs for next season though. I will also be going to slicks next season. Should I bump the CoF up?

[Ron Sutton]

Ron, I'm using a carbon kevlar brake pad with a .50 CoF. Is there any specific rotor manufacturer or type of rotor you can recommend for my application. Weight is just under 3200 lbs with me in the car......probably will lose at least 180 lbs for next season though. I will also be going to slicks next season. Should I bump the CoF up?


I don't think the carbon kevlar brake pads rerquire any special rotor. They're usually pretty easy on the rotor unless the mixologist got happy with the metallic.

As for the CoF question ...
How are they working for your track days at Thunderhill?
Are you running full events? ... or just short runs for time?

Do you feel like you have use "all the brakes you got" ?
or, do you feel like you have to be easy on them to not over slow the corner?

Any fade problems after a lot of laps?
Can you lock them up? And of so, which end first?

[Track Junky]

Pads had a stronger initial bite when I first got them and that seems to have faded. I do like a strong initial bite and am looking for a combo that will heat up quick and be best on short runs for time trials.
I haven't ever tried to lock them up so I couldn't answer that but as I previously stated I loved the way they worked when I first put them in.
So far no fade issues.
I'm running the same brake set up that Dale has but rotors are slotted only..

[Ron Sutton]

Pads had a stronger initial bite when I first got them and that seems to have faded. I do like a strong initial bite and am looking for a combo that will heat up quick and be best on short runs for time trials.
I haven't ever tried to lock them up so I couldn't answer that but as I previously stated I loved the way they worked when I first put them in.
So far no fade issues.
I'm running the same brake set up that Dale has but rotors are slotted only..

Remind me what calipers those are.

.

[Track Junky]

PBR 2 piston C5

[Ron Sutton]

Pads had a stronger initial bite when I first got them and that seems to have faded. I do like a strong initial bite and am looking for a combo that will heat up quick and be best on short runs for time trials.
I haven't ever tried to lock them up so I couldn't answer that but as I previously stated I loved the way they worked when I first put them in.
So far no fade issues.
I'm running the same brake set up that Dale has but rotors are slotted only..


When you are on slicks ... and have the grip ... the Wilwood H pads produce "mean" braking force & right now.

The braking force would go up 22% from your .50 CoF pads. Could be worth a try. Just an FYI ... never go to the track with new pads ... or anything new ... without taking your old stuff with you ... just in case you don't like the new stuff.

[Track Junky]

Thanks Ron....I'm going to look those up. :thumbsup:

[Ron Sutton]

I forgot to discuss when, where & why drilled rotors have a place.

For the type of competitions you're running, if ...
a. The track is short or has tight corners
b. The difference in corner speed & top speed is significant
c. Your lap times are affected significantly by your ability to accelerate & decelerate
d. Your brake temps are well within the safe range from overheating
e. You already have small diameter rotors
f. The drilled rotor is priced modestly for your application
g. You are serious about your maintenance program
h. You are serious about competing at the top level

Drilled rotors make sense then, because:
1. You can afford to replace them at the first sign of heat stress
2. The lighter rotating weight will accelerate & decelerate quicker
3. Improving your lap times

AutoX doesn't build much brake heat at all. So I love drilled rotors for AutoX competition as long as your maintenance program is good.

Same with other short track racing. We ran them on the rear of our 2550# NASCAR Modifieds, where the temperature window was around 400° or less.


P.S. Since I wrote this before having my morning coffee, I expect I'll need to edit this later. :)

.

[Motobrewmaster]

Wow, great thread. Ron you add so much helpful info, thank you very much.

Darn now I have to make some more decisions.... :confused59:

[Motobrewmaster]

Here is a link to a good 101 on brake system design.
Brake Systems 101 SAE (http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CGkQFjAJ&url=http%3A%2F%2Fwww.sae.org%2Fstudents%2Fpresenta tions%2Fbrakes.ppt&ei=AuJ0UtOLFsbNsQT9t4DwBA&usg=AFQjCNGGFJLeW0A8_zL3buKbaQt2CObTNQ&bvm=bv.55819444,d.cWc)

[Ron Sutton]

Wow, great thread. Ron you add so much helpful info, thank you very much.

Darn now I have to make some more decisions.... :confused59:

Yeah ... that's all part of the fun though. :)

[jlwdvm]

I came upon this thread in a search for finding the appropriate sized master cylinder for my application. I am building a 69 firebird track-street car with a 570 horse Texas Speed LS3, Ridetech stage 2 front and rear, Toyo R888 275 and 315's, Wilwood FNSL 13" 6 piston front and 12" D154 2 piston rear. I was considering the DSE master cylinder-booster combo, but don't know which one to order if it is even appropriate. Thoughts?

[vstol]

I find the challenge is ... when someone goes to one of the aftermarket 6-piston caliper brake set-ups looking for bad ass brakes ... they are occasionally disappointed with the braking result ... because the pistons are so small, the total piston "area" is insufficient ... and they didn't account for that in the total system

Most car guys don't know the piston area formulas ... so when you glance at the piston sizes written on paper ... and there are 6 of them ... it seems they should add up to more brake caliper clamping force ... but often they do not.

The problem is compounded if we make any one (or more) of these changes:
A. Utilize brake calipers designed to have a strong power booster ... now running without one.

B. Utilize brake calipers designed to run .50 to .65 CoF racing brake pads ... and now have street pads in the .35-.42 CoF Range.

C. Utilize brake calipers designed around systems typically with a 6-1 or higher pedal ... but some factory pedals have less.

D. Utilize brake calipers designed for a 2700# car ... now on a 3500# car.

The charts below, use the standard brake formulas all brake engineers use for manual brake systems. It accounts for every aspect of braking except the tire. This graph shows several front brake calipers ... ALL using the same pedal ratio, same brake pads & same master cylinder size.
*The pedal ratio, brake pads & master cylinder size do not represent what comes from the factory. I made these 3 items a constant only for comparison.

The rotor sizes are different ... to better represent how they're being sold & used. Regardless ... look at the braking force numbers at the bottom. The 3 common GM factory brake calipers are for Gen 2 F-body, G-Body & Impalas are highlighted with blue columns.

Go down to the 2nd line from the bottom ... marked "Brake Torque" ... and compare the factory numbers with aftermarket options. When you wonder why some don't stop stronger ... simply go to the line marked "Caliper Piston Area x2" ... and you'll see important differences.

There is nothing wrong with any of these brake calipers. But if we are building a better brake system for our PT cars ... we need to better understand the total picture. We can't put a caliper on our cars with significantly less piston area ... without running the proper:
1. Pedal ratio
2. Master cylinder size
3. Brake pad CoF
4. Rotor Size
Even then ... we still can't run too small of piston area for our weight of car & expect it to work well.

The numbers can be kind of confusing. All most of us want to know is how much do I need?
In my experience, for 3500# cars, here's a GUIDELINE that is based on total braking force including the front & rear brake systems.

GUIDELINE:
2500# = Average passenger car
3000# = Performance production car
3500# = Good street & track braking system
4000# = Track braking system with good tires
4500-5500# = Full race brake systems

The very bottom line of the chart shows total braking force with that combination if you were looking for 70% front braking, as I often do in race cars.

If anyone is putting together a system & has questions on one part or another, I'll be happy to calculate things and/or advise you. I have spread sheets to work out front & rear systems & compare options. I can also change inputs in this chart to show you how they all look with a different brake pad, pedal ratio, master cylinder, etc.




Ron I have a C3 Corvette with a custom frame and currently C4 12 rotors and calibers and may upgrade to 13 inch with C5 calibers. The car is 3200" build is in the below site. I have not had a manual master cylinder in my car since 76 but I am leaning twds it in this build. Any help in steering me to what manual master I need would be great or if you think I should stay with vacuum assisted as well. Many thanks, oh the car will be manly on the street, some auto cross events and one road race course a year.

http://www.lateral-g.net/forums/showthread.php4?t=44704

[Ron Sutton]

Ron I have a C3 Corvette with a custom frame and currently C4 12 rotors and calibers and may upgrade to 13 inch with C5 calibers. The car is 3200" build is in the below site. I have not had a manual master cylinder in my car since 76 but I am leaning twds it in this build. Any help in steering me to what manual master I need would be great or if you think I should stay with vacuum assisted as well. Many thanks, oh the car will be manly on the street, some auto cross events and one road race course a year.

http://www.lateral-g.net/forums/showthread.php4?t=44704

I think Tobin at Kore 3 would be the better guy to ask these questions. He has WAY more experience with Corvette brakes & boosted brake systems than I do.

Send him a PM.

[Hydratech®]

My input is that the C4 brakes are not adequate - go straight into at least C5 class or better with aggressive pads (they're going to dust just by looking at them, but they will stop). C4 brakes ran a 7/8" bore MC with power assist and still left an awful lot to be desired. Running them on a manual brake scenario with a 7/8" bore MC is like yanking the vacuum hose off of a C4 Vette vacuum brake booster and hoping to stop (though you will have a slightly better mechanical brake pedal ratio with your C3 as I see it is a factory manual brake car in your build pics).

If you do everything "right" and still don't like how your brakes feel, we have an exceptionally powerful highly engineered direct fit conversion package available that provides a 100% true bolt in straight into your factory manual brake car:

http://www.hydratechbraking.com/C3Corvette.html#SGROBJ7D920161312A1BD0

We had a customer recently get back to us after installing his model 3007 system into his Vette, reporting back that it stops better than his CTS-V and his sport bike.

I say get with Tobin at Kore3 either way to get into at least C5 class items at the wheels. You could then evaluate how you like the pedal feel in manual brake mode, knowing that you could install one of our manual to power brake conversion systems in place at any point if you wanted to supercharge your brakes from there on in.

Kore3 is also a Hydratech dealer by the way.

[vstol]

Many thanks for the feedback. I have not run manual brakes in a very long time and I may not like the feel and boosted is certainly an/the option