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Brake Question

bosssho

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bosssho Enthusiast

bosssho

Posted
Posted

As most everyone knows...GM did something to the brakes when they switched to the 4 wheel disc brake set up in 99...and the rumor I hear is that they biased the brakes towards the rear a lot more knowing the discs were there now vs. the drums, but b/c the rear discs are smaller, the brake pedal still feels awfully mushy vs. nice and solid.

 

What is the cure for this? IE, what are you guys/girls doing so that when you depress the brake pedal it doesn't feel like you just stepped in Dog Sh*t.

 

Thanks again for any help! :flag:

GMCSierra04 Enthusiast

GMCSierra04

Posted
Posted

YA, the brake pedal feel on my 2004 Sierra feels like a**.

 

The entire braking system was re-worked when they switched from disc/drum to disc/disc. The master cylinder for the 4 wheel disc is different because with a disc/drum set-up, you need a residual check valve to keep a small amout of pressure on the cups of the wheel cylinders to prevent any air from entering the system, usually 5-10psi I believe. I'm sure GM uses low drag calipers to help out with gas mileage and that requires a step bore type master cylinder. The step bore is a large bore that provides initial high volume/low pressure to move the pads up to the rotors, after this is achieved a by-pass valve opens and regular brake pressure resumes. This happens so quick but maybe thats what causes the spongy pedal feel. The trucks also use EBD which depending how much weight is in the back of the vehicle, that will deturmine how much hydrolic brake pressure will be applied to the rear brakes. This prevents lock-up but also giving you the extra braking in the rear when you need it.

 

A cure, I'm not sure about that. I wounder if replacing the soft lines with stainless braided lines would help with any of the spongy feel but god, it always feels like there is air in the brake system. I hope GM find out what the problem is, maybe they will come up with some sort of re-pair. It would be nice, seems like all the other truck manufacturers have it right...

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