rear brake piston Dia.
Thread Starter
Burning Brakes
Joined: Apr 2004
Posts: 792
Likes: 1
From: Stanfield NC
rear brake piston Dia.
I am looking at upgrading the brakes on my C4, but need to know the piston diameter of the stock brake caliper piston. Service manual does not give that data. Anybody help? Thanks in advance.
Thread Starter
Burning Brakes
Joined: Apr 2004
Posts: 792
Likes: 1
From: Stanfield NC
Thanks twin 540. Appreciate the help. I AM starting at the front and I already have 13" aluminum hat rotors on the rear, but in order to calc the piston bore for the MC, and, the piston bore and quantity (4 bore vs. 6 bore) for the front replacement calipers, I need to know the total piston area for the existing ( I currently run C5 calpers on the front) setup. The goal is proper peddle preassure to achieve proper brake clamping force for maximum tire adhesion for minimum braking distance. Races are won in the braking zones, not the acceleraton zones.
Nobody on C5 tech has been able to tell me the bore of the std. front C5 caliper and if anyone has that info, I would appreciate it. I admit to being lazy and do not want to tear the front calpper apart to measure. Thanks again everybody.
Nobody on C5 tech has been able to tell me the bore of the std. front C5 caliper and if anyone has that info, I would appreciate it. I admit to being lazy and do not want to tear the front calpper apart to measure. Thanks again everybody.
Melting Slicks
Joined: Oct 2006
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From: College Station TX
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Burning Brakes
Joined: Sep 2001
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That's 14% more piston area than the both the early and late C4 calipers. That may explain why some of the people who converted to the C5 fronts seem to be reporting symptoms of not having enough master cylinder.
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
Last edited by Mr6spd; Oct 23, 2009 at 10:15 PM.
Melting Slicks
Joined: Oct 2006
Posts: 2,238
Likes: 10
From: College Station TX
That's 14% more piston area than the both the early and late C4 calipers. That may explain why some of the people who converted to the C5 fronts seem to be reporting symptoms of not having enough master cylinder.
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
Supporting Vendor
Joined: Jun 2008
Posts: 2,199
Likes: 119
From: tempe Arizona
14% is on the high side of a change....net result: longer pedal travel, less 'feel' and other issues not withstanding a 3% increase in rear bias.
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
That's 14% more piston area than the both the early and late C4 calipers. That may explain why some of the people who converted to the C5 fronts seem to be reporting symptoms of not having enough master cylinder.
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
I'm guessing that the C5 Master cylinders have a bigger bore diameter and/or longer stroke?
I've been considering the C5 front brake upgrade, but this is the main potential issue stopping me doing it. I'm sure it works for many, but it may be marginal. Is there a good aftermarket master cylinder & proportioning valve solution for this?
One thing to consider is that the later C4 calipers have dual pistons and the later M/C's may have more a larger bore/stroke than the earlier C4 M/C's to account for the dual pistons.
