13" Brakes
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Originally Posted by 81 Vette
Well if money isnt an option for you guys, the best brake company in the world (arguably) MoveIt Brakes, makes a full on kit for C3s, unfortunately if you want to do front and back, it will cost you $5000 EUROS hahahaha. You will have the best brakes ever put on a C3 though... 
Only your wallet will be affected.
Race Director
Joined: Aug 2000
Posts: 10,854
Likes: 3
From: HONOLULU HAWAII
Originally Posted by Van Steel
Unless you are into some serious racing, I see no need to upgrade the brakes on these cars. Unless of course you want the WOW factor from other or you just like making your own stuff. These brakes are good enough to stop your car. You really can't beat a 4 piston caliper unless you got to 6 or 8 piston.
capeloutl001@hawaii.rr.com
Burning Brakes
Joined: Jul 2000
Posts: 963
Likes: 0
From: melbourne,Australia
I am currently just starting to install new brakes on my 74r,they are 350mm fronts,330 rears,6 piston AP calipers on the front and 4 piston AP on rear.....AP is a well known english brand mainly used in racing...i am making new hubs so that the rotors will bolt to them and will use the current mounting locations.....as previously said,i have 17" wheels.....also installing new m/cyl and adjustable proportioning valve...will let you know how it goes....john 
Race Director
Joined: Dec 1999
Posts: 16,945
Likes: 9
Clamping force in pounds is the product of line pressure (pedal ratio & mc ratio) in psi multiplied by the total piston area.
Fclamping = Pline x Apistons
for a floating caliper however it's twice the piston area:
Fclamping = Pline x 2Apistons
The tricky part here is in the floating part, the piston not only moves to the rotor but the caliper actually moves outside, this also increases piston displacement and therefore the total amount of volume displaced, it's twise that of what you'd think it would be.
For larger pistons you don't need a smaller MC, actually to make sure you have enough displacement you'd need a larger MC - this also to not get excessive line pressure - for the same line pressure, you could use a different pedal ratio also. Using a smaller ratio gives higher line pressures but the fluid displacement is much smaller so the pedal travel would be excessive with the same pedal ratio. A smaller MC will need less effort, a larger MC will need more effort. A bigger pedal ratio also means that you have to depress the pedal further for the same piston displacement
Fclamping = Pline x Apistons
for a floating caliper however it's twice the piston area:
Fclamping = Pline x 2Apistons
The tricky part here is in the floating part, the piston not only moves to the rotor but the caliper actually moves outside, this also increases piston displacement and therefore the total amount of volume displaced, it's twise that of what you'd think it would be.
For larger pistons you don't need a smaller MC, actually to make sure you have enough displacement you'd need a larger MC - this also to not get excessive line pressure - for the same line pressure, you could use a different pedal ratio also. Using a smaller ratio gives higher line pressures but the fluid displacement is much smaller so the pedal travel would be excessive with the same pedal ratio. A smaller MC will need less effort, a larger MC will need more effort. A bigger pedal ratio also means that you have to depress the pedal further for the same piston displacement
Melting Slicks
Joined: May 2001
Posts: 2,812
Likes: 4
From: Gig Harbor Wa
Originally Posted by Twin_Turbo
Clamping force in pounds is the product of line pressure (pedal ratio & mc ratio) in psi multiplied by the total piston area.
Fclamping = Pline x Apistons
for a floating caliper however it's twice the piston area:
Fclamping = Pline x 2Apistons
The tricky part here is in the floating part, the piston not only moves to the rotor but the caliper actually moves outside, this also increases piston displacement and therefore the total amount of volume displaced, it's twise that of what you'd think it would be.
For larger pistons you don't need a smaller MC, actually to make sure you have enough displacement you'd need a larger MC - this also to not get excessive line pressure - for the same line pressure, you could use a different pedal ratio also. Using a smaller ratio gives higher line pressures but the fluid displacement is much smaller so the pedal travel would be excessive with the same pedal ratio. A smaller MC will need less effort, a larger MC will need more effort. A bigger pedal ratio also means that you have to depress the pedal further for the same piston displacement
Fclamping = Pline x Apistons
for a floating caliper however it's twice the piston area:
Fclamping = Pline x 2Apistons
The tricky part here is in the floating part, the piston not only moves to the rotor but the caliper actually moves outside, this also increases piston displacement and therefore the total amount of volume displaced, it's twise that of what you'd think it would be.
For larger pistons you don't need a smaller MC, actually to make sure you have enough displacement you'd need a larger MC - this also to not get excessive line pressure - for the same line pressure, you could use a different pedal ratio also. Using a smaller ratio gives higher line pressures but the fluid displacement is much smaller so the pedal travel would be excessive with the same pedal ratio. A smaller MC will need less effort, a larger MC will need more effort. A bigger pedal ratio also means that you have to depress the pedal further for the same piston displacement
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Originally Posted by 70 LS1
Would switching to larger floating 2 piston calipers cause the line pressure to go down? Right now my pedal is harder to push then before with the 4 piston stock setup.
If your pedal is harder then the caliper piston(s) are smaller ( less surface area )
Thats a promise.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Originally Posted by 70 LS1
Would switching to larger floating 2 piston calipers cause the line pressure to go down? Right now my pedal is harder to push then before with the 4 piston stock setup.
I found manual brakes too much work to get a good stop so I went hydroboost. Now a light touch does the same thing as standing on manual brakes with two feet.
I did find getting rid of that brass block helped alot in both bleeding the brakes and stopping.
Melting Slicks
Joined: May 2001
Posts: 2,812
Likes: 4
From: Gig Harbor Wa
Thanks guys. With your help I think I finally figured this out.
The C3 pistons are 1 7/8" while the C5 pistons are 1 9/16". We have already determined that 2 piston floating and 4 piston fixed provide the same clamping force for a given piston size.
The C3 master cylinder is 1" whereas the C5 is either 3/4 or 7/8" (I am getting mixed results when I ask around).
This would mean that the C5 system runs at a nominally higher pressure. And the C3 master just can't keep up. That is why my pedal effort is so much more with the C5 calipers.
So it looks like I need to find a 3/4" master or use a C5 master.
Thanks again for your help and sorry for hijacking the thread.
The C3 pistons are 1 7/8" while the C5 pistons are 1 9/16". We have already determined that 2 piston floating and 4 piston fixed provide the same clamping force for a given piston size.
The C3 master cylinder is 1" whereas the C5 is either 3/4 or 7/8" (I am getting mixed results when I ask around).
This would mean that the C5 system runs at a nominally higher pressure. And the C3 master just can't keep up. That is why my pedal effort is so much more with the C5 calipers.
So it looks like I need to find a 3/4" master or use a C5 master.
Thanks again for your help and sorry for hijacking the thread.
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