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Thread: Brake conversion concerns
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08-03-2022 #1Registered User
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- Aug 2022
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Brake conversion concerns
I'm not sure if I'm posting in the right forum or not. I have an 85 El Camino that just came back from a local rod shop. They installed a Quick Performance 9" rear with their disc brake upgrade and S10 front spindles w/ 2 piston calipers along with UMI's Power Tour suspension kit. They also installed a Wilwood master cylinder (7/8" bore) and a 4 wheel disc brake proportioning valve. The problem is brake pedal travel. It's 2-3", almost to the floor. It's way more than the original set-up, which was disc/drum. The shop said they had a hard time with the brakes. They said that QP's brackets did not mount the caliper with the bleeder screw at the top. They claimed to have removed the caliper from the bracket, bled it and remounted the caliper. I was told they spoke with a tech at Wilwood who recommended a drop from the 1 1/8" bore MC to 7/8". Less volume=longer stroke but higher pressure. I was told mine is 1200psi. I've read systems need 600-1000 psi to operate properly. Although I think what I've read concerns manual brake systems because they talk about pedal pressure, pedal ratio and bore size equaling system pressure. Mine is vacuum assisted and I'm not sure how much that plays into the equation. Engine has 12" vacuum. The brakes work fine although I have not done any panic stops. I just don't like that much travel! Adding disc brakes to the system that requires more fluid volume and then decreasing MC bore size, just seems opposite of logic! Am I missing something? Is my logic flawed? This project has been off the road for 7 years for various reasons and, now that it's driveable, I want to get out and enjoy it. I just don't feel comfortable. So, I'm hoping to find someone to help me. Do I have a wrong size MC? Is the system OK and I just need to get used to it? Thank you for any assistance.