Brake Pressure Regulator in Vintage Race Car |
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Brake Pressure Regulator in Vintage Race Car |
jhynesrockmtn |
Jan 22 2020, 09:17 AM
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#1
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Member Group: Members Posts: 420 Joined: 13-June 16 From: spokane wa Member No.: 20,100 Region Association: Pacific Northwest |
Hi, I am in the process of refreshing a 914-6 GT tribute car that was built for PCA solo events in CA and has been mostly in storage for several years. The engine is a 2.4 that was built by GD racing in San Bruno. The suspension and brakes are 3.2 Carerra. I pulled the calipers and they are at PMB. New soft lines are going in. I was somewhat surprised to find the stock 914 brake pressure regulator still in place. There is no after market proportioning valve.
The car will be used a few times a year for vintage wheel to wheel and then some PCA DE events. I have several years of experience racing vintage FV. As I got older and saw several buddies get involved in some nasty open wheel tire to tire incidents I decided I wanted fenders and more metal around me. I am not the most aggressive driver in the world and this car will remain street legal. I also want it to remain as period correct as I can get. I don't want to go down the rabbit hole of cutting a ton of metal out of the car, etc. Should I pull the regulator and put a T in and proportioning valve in the cockpit? Should I leave as is and see how it performs? If I leave it I will send to PMB to have them rebuild it. Cheers, Jerry |
yeahmag |
Jan 23 2020, 05:15 PM
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#2
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Advanced Member Group: Members Posts: 2,422 Joined: 18-April 05 From: Pasadena, CA Member No.: 3,946 Region Association: Southern California |
The pressure bias is to account for varying conditions or non-stock brake bias ratios. They do (at least the Tilton) limit pressure, not flow. If you have too much rear bias you need one and the factory limiter won't help you as your bias ratios are already wrong, not just in a panic situation.
For example, I have 911 M calipers up front and switched from 914-4 rears to 914-4 fronts on the rear as I was originally too biased towards the front (with the stock rear brakes). We had done the calculations and knew I was on the harry edge of too much rear bias, so we put in a twist style bias regulator (wish I had done a lever style). It took a few runs to dial it in, but it's perfect now. |
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