Master Cyl Size???

[Leadfoot1]

I have my new C6 brakes in their boxes awaiting their turn to be installed on the car. Meanwhile, i'm cleaning stuff and finishing the tubs etc.

I'm looking at some master cylinders to replace my old and rusty original unit but am now puzzled as to what i should run...I'm thinking a 7/8" but would like opinions. I REALLY like Wilwoods aluminum (polished) unit but for now all i like about it is its looks.

I searched in the forums and could not come up with the info i need. I want to do the right move.

Hydroboost is also in my mind. I've checked a few systems at abspowerbrake.com and hydratech. Just not sure on which master to use and everybody is closed for the holidays!!!

Help!

Lead.

[Leadfoot1]

Nevermind....

http://www.stoptech.com/tech_info/Pe...ster-Guide.pdf


Lead.

[ZZ3ElCamino]

All those formulas should get you in the ball park. Actually right on the money! Good find Lead!

[Leadfoot1]

Yeah....But what a pita!

If someone has an idea still. Be my guest!

I've sent a few e-mails around and will see what the manufacturers reccommend. I love ABS's black chrome unit (Hydroboost) but still need to find out what i need to make this work. My car isn't ps equipped either so i need a ps pump and bracketry too. I want to run an electric w/pump and a low mount alt.

Just a few details i'm taking care of.

Lead.

[Serpa69]

I'm running a 1.12 in Wilwood master (part# 260-8556) with a Hydroboost.
6 piston and 4 piston Wilwoods. This is per Paul at Hydratech. I would think that would work for you if you run the hydro.

[Marcus SC&C]

Those 6 piston Z06 calipers have an awful lot of piston sweep area to move with stock manual brakes. You may have to use a 7/8" or 15/16" master cyl. in order to be able to lock them up but your pedal travel is going to be excessive. I think you`re on the right track with the hydraboost. You`ll get better performance without having to get that "Legs Of Steel" excercise video. Mark SC&C

[Leadfoot1]

Hey Mark,

Nice to see you chippin' in!

I sent a few questions to Tyler this morning as i'm getting ready to buy their tall spindle with one of your A-Arms kit.

The wilwood Aluminum/tandem master i'm looking at is available in either 1.00 or 1.12" bore size. I don't really know how to calculate the aditionnal pressure that a "given" hydroboost unit would provide.

I read different statements regarding piston size (some say the bigger pistons will put out less pressure/ so smaller dia. = more pressure...and others say the contrary) I suppose line size plays a role too, no?

So, from what i understand your saying, bigger bore would brakes more? And having the choice between 1 and 1.12 then, should i go 1.12?

Is there such a thing as too much pressure? I.e w/hydroboost and 1.12 for an example? Or should i try 1.12 w/ 7-8-9" reg. booster?

Would manual still work? (info only) my wife will drive this thing.

I'm all puzzled up.

All in all i'm looking to get good (make that great!) performance and a good looking system (in that order) at a reasonnable cost. I just don't wanna end up in a phone pole with the kids you know....

Thanks for any help,

Lead.

[Marcus SC&C]

The part many people miss in their brake calculations is the one part of the system that`s not bolted to the car...your leg! Yes a larger dia. piston has more sweep area can make more pressure with the same travel all else being EQUAL. But it also displaces more fluid than a smaller piston and achieves the same amount of clamping force at the caliper with less travel. Less travel+more volume per increment of travel equals higher effort required to push the piston that distance. Think of it as hydraulic leverage. In other words a larger piston trades pedal effort for shorter travel. End result if you go too large is that while the master cyl. is capable of higher pressure your leg is incapable of pushing it hard enough to achieve it. So you may have a rock hard pedal but won`t even be able to lock the wheels up. The ideal dia. master may provide less peak pressure and you`ll have longer pedal travel but you`ll be able to make full use of it and the car will actually stop much better.
Now with a vacume booster you can run a larger dia. master without the liability of a super heavy pedal. A good hydraboost goes even further. Think of it as a bionic leg. Now you can run a much larger dia. master ,get even higher pressure/clamping force at the calipers and still have very reasonable (even pleasant) pedal effort.
Example we`re just finishing up a `61 2dr. Suburban ProTouring project "Project ProTow". This thing is HUGE and heavy. We put big Baer brakes all around and Hydratech hydraboost to stop this monster. It`s amazing,it stops like a sports car. Nicely modulated pedal feel,light effort and panic stops make you dizzy (literally!). It`s damn hard to get all 3 with manual brakes in something that BIG. Mark SC&C

[Musclerodz]

you can go too large and although you will have good stopping power, travel will be excessive. you can also go to small and restrict too much fluid which pedal travel will be very little and require iron man legs. I would start with a stock size master cylinder and then work from there if you have power brakes.

Mike

[Leadfoot1]

Thanks Guy's,

I do have a booster (9") that was the original unit (63 000 miles car) for the drums...

What about the stock C6Z master cyl and booster unit? Never heard anyone using it and tought there must be a reason...But its made to operate those baby correctly no?

Mike, what about line size, stock too to begin with?

Marcus, did the guy's at Hydratech set you up or if you called the shots on the 'Sub? Lets see pics of that monster!

Lead.