Should I hold off ?

[DOOM]

I was getting ready to order my mounting hardware from KORE3. With all this talk of ''knock back'' I was wondering if I should hold off ordering this kit. I know we have some guy's on here working on this problem.

[ProdigyCustoms]

Not sure what the question is. Are you planning to run ZO6 brakes and worried about knock back?

Let me say this first, we are putting WAY to much brake on the back of these cars. We DO NOT need 14" rear rotors with calipers bigger then a size 10 shoe. I say this because I think the major brake companies are working on a floating caliper. But I do not think any of them have anything in a big impressive looking caliper yet. Well, let's say I know they do not. We are testing a floating caliper right now but are sworn to secrecy. Since you only need 30% for the rear brakes, it is working just fine and is sufficient, it just does not look real impressive like the big ole calipers we like to see. This may be a function over form thing.

We are also looking heavily into full floaters and may be very close to something that will allow a big impressive caliper and will have zero knock back issues because of the floating design. But that is still in development and right now cost are higher then i want them to be.

So, how was that for a whole bunch of nothing!

[wiedemab]

You'll have to forgive my poor memory on the specific number - - -

I talked to Kyle Tucker at Columbus about this issue and he said that they've had some issues on the rear and that they at times go through several axle bearings until they find ones that have acceptable "end play" - not sure if that is the correct term. They press them on and check them and if they don't meet spec, they scrap them and try another one.

I want to say he said they shoot for .007" total, but that my not be correct. - -Edit - - - OK not sure on my number even more now that I read this thread on PT.

http://www.pro-touring.com/forum/showthread.php?t=60256

It looks like people were having problems with .005" end play.

[Vegas69]

Master cylinder bore size plays a HUGE factor. I'm pretty sure DSE runs power brakes and that's a huge deal. Personally, I've never felt like my car has had enough rear brake. I've got a set of more agressive pads on the shelf I need to install before my next track day. Mario, your car is not even close to needing brakes. Wait......

[DOOM]

Not sure what the question is. Are you planning to run ZO6 brakes and worried about knock back?

Let me say this first, we are putting WAY to much brake on the back of these cars. We DO NOT need 14" rear rotors with calipers bigger then a size 10 shoe. I say this because I think the major brake companies are working on a floating caliper. But I do not think any of them have anything in a big impressive looking caliper yet. Well, let's say I know they do not. We are testing a floating caliper right now but are sworn to secrecy. Since you only need 30% for the rear brakes, it is working just fine and is sufficient, it just does not look real impressive like the big ole calipers we like to see. This may be a function over form thing.

We are also looking heavily into full floaters and may be very close to something that will allow a big impressive caliper and will have zero knock back issues because of the floating design. But that is still in development and right now cost are higher then i want them to be.

So, how was that for a whole bunch of nothing!

Well Frank I'm in deep on this one I purchase a complete ZR1 setup from Mark Stielow awile back. So I think this falls into your way to much brake quote. I did'nt know if someone was coming up with something to get this setup to work better? Is this deal your working on something that will alow us to use our current calipers??

[DOOM]

Master cylinder bore size plays a HUGE factor. I'm pretty sure DSE runs power brakes and that's a huge deal. Personally, I've never felt like my car has had enough rear brake. I've got a set of more agressive pads on the shelf I need to install before my next track day. Mario, your car is not even close to needing brakes. Wait......

I hear ya Todd.This is what I was thinking. Just reading all this stuff about loosing brake pedal makes me a little nervous....

[MarkM66]

What about putting front c5/c6 caliper on the rear? They're floating and fairly large. Is the bore size to large?

http://i270.photobucket.com/albums/jj114/powertvmedia/06_Project%20Cars/Vette/IMG_1897.jpg

[ProdigyCustoms]

If anyone would be working on a floating solution for that caliper it would be Toben. I do not know if he is.

As Todd mentioned, Power brakes seems to cure a lot of it because the larger bore master moves more volume of fluid and more rapidly resets the caliper piston. Most of the trouble comes with low volume, high pressure manual set ups.

A dual master set up seems to help the problem also. So we are working on a dual master cylinder solution too. One of the parts we are developing from the Unfair Project.

If you are committed to those brakes I would call Toben.

[Matt@BOS]

Yeah, call Tobin. I think I talked with him for about 45 minutes the other day.

Basically here were the main points of what we discussed.

1. small bore master cylinders work great on cars with no knockback. a dual master setup, which I believe he said could be found on later g-bodies, would theoretically help, if you still wanted to run manual brakes.

2. rear brake size. As others have said, we don't need huge brakes in the rear. Still, a lot of us, myself included could use more rear brake. I lock up the fronts way before it will ever be possible for me to lock up the rears, and I'm not running a proportioning valve now, which means, the major limiting factor on these systems is still the type of tire being used. That said, I don't think you'd want the base C6 floating calipers on the rear of your car because you'd have way too much brake in the back. While the C6 floating front calipers aren't physically large, their total piston size (as far as I can remember) isn't appreciable different than the 6 piston Z06 fronts.

3. axles, bearings, etc. Everyone agrees the full floater is the best solution to this problem. It may be expensive, but if I could do it all over again I'd probably just get one instead of wasting all the dollars and time I have so far. I don't know if you have a rear axle assembly sitting around already, but if you do, check it to make sure it is straight after being welded, that may make a huge difference. Also tapered bearings seem to work better than roller bearings, although Tobin seemed to think the SET20s that now ship with DSE (Moser stuff) will hold up better than the ones that shipped until late (maybe) '09.

You have some kick ass rear brakes, and I think given the right bearings, and master cylinder, you won't have to worry too much about knockback.
Matt

Matt

[Apogee]

Matt, just to clarify a few things, the terminology for the G-body master cylinder is that it is a stepped bore unit, meaning that it has a larger primary bore designed to push a lot of volume and a smaller secondary bore designed to generate higher pressures, so it essentially behaves as two master cylinders in one. These master cylinder are also sometimes referred to as quick take-up units and were used on applications in conjuction with low-drag calipers which retracted the pistons further than a conventional piston seal, essentially the same thing as knockback, just induced by the square-cut piston seal versus the rotor. There are not any aftermarket options that I know of with a stepped bore at this time, although we've been contemplating it for a while since it would give the benefits of a manual brake system but with a much higher pedal and less overall travel.

A dual master cylinder setup uses two individual master cylinders connected with a balance beam, allowing for different bores front and rear. This type of master cylinder is the only way that I know of to effectively run a mismatched caliper piston area front and rear and still get away with it, but could be a solution for running the larger C5/C6 front calipers in the rear if one was so inclined.

As for axle bearings, we've had much better luck with the SET20 tapered roller bearing setups than the RW207 ball-bearings for postively retained axle setups like the Ford 9" and other aftermarket options using those 80mm bearing options. The SET20's are preloaded through the external seal with the axle reatainers whereas there is no such axial preload with the ball-bearings, so the amount of endplay is determined by the bearing tolerances and condition which will only get looser with time.

HTH,
Tobin
KORE3

[Matt@BOS]

Tobin, thanks for clarifying what exactly a stepped bore unit was, the terminology for all of this stuff often alludes me, which makes me sound like a bit of a moron at times.

While it's a bit off topic, I figure I should ask before I forget. Is the SET20 what is shipping with Moser's axles now, and can I just press one onto the 9" setup that I've got or do I have to have the ends cut, and all of that good stuff?

Matt

[Apogee]

Tobin, thanks for clarifying what exactly a stepped bore unit was, the terminology for all of this stuff often alludes me, which makes me sound like a bit of a moron at times.

While it's a bit off topic, I figure I should ask before I forget. Is the SET20 what is shipping with Moser's axles now, and can I just press one onto the 9" setup that I've got or do I have to have the ends cut, and all of that good stuff?

Matt

I wish it were that simple...but it's not.

Working from memory here, but the ID of the SET20 (http://www.moserengineering.com/other-parts/bearings/part-9mtr-timken-tapered-roller-bearing.html) is larger at 1.5625" versus 1.5312" for the OE Ford "big-bearing" application. There are larger ID versions of the ball bearings as noted below though. Another thing to keep in mind is that the widths are different as well between the tapered roller and ball bearings, so pressumably the axles are cut differently with repect to the offset dimension. Alternately, some axle manufacturers will cut the axles for the shortest offset dimension and install spacer sleeves between the bearing and shoulder of the axle to set the offset.

Moser seems to standardize on their 80mm ball-bearing unless you specifically request the SET20's. I don't know which bearing they default to, however it seems to be the #9508T or H since most that I've come across have the o-ring in the outer race. FWIW, the three different ball bearings Moser seems to offer are their #9508M (http://www.moserengineering.com/other-parts/bearings/big-ford-and-olds-pontiac-ball-bearing-requires-inner-seal.html), #9508T (http://www.moserengineering.com/other-parts/bearings/big-ford-and-olds-pontiac-ball-bearing.html) and #9508H (http://www.moserengineering.com/other-parts/bearings/big-ford-and-olds-pontiac-ball-bearing-1-771-id.html).

Tobin
KORE3

[The WidowMaker]

what is steve doing with bad penny since i cant recall him having the issues others are? he's running a rear that was set up by currie and im pretty sure the set20 bearings that they put in mine.

todd, how was the knockback with the new tires?

and once again, tobin blows my mind with his vast knowledge. i just sit and smile when i talk to him on the phone as all of technical stuff blows over my head.