Thread: Low Pedal

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I cant seem to get very much of a brake pedal on my Buick. The system is a generic under the floor power brake pedal kit with a corvette master cylinder and a 7" power brake booster. The rear is stock 2000 blazer disk brakes. The front are camero calipers. I have Wildwood 2 PSI check valves on both lines. the linkage from the pedal to the booster is adjusted to give as much stroke as possible. The rod between the booster and the master cylinder seems to be the correct length. I have bled and bled. I have brakes but only at the bottom of the stroke and not enough stopping power. Any suggestions????

Assuming you have a dual-reservoir master cylinder block off the front or back brakes and try to adjust the system if the pedal returns you may have a defective or blocked port in your master cylinder.

Also you can reduce a spongy pedal by removing the check value from the master when using disk brakes and in-line residual check values.

Brake Trouble Shooting Guide

Deep pedal

· Air trapped in fluid
· master cylinder too small
· incorrect pedal ratio (too high)
· Rotors warped
· Calipers not mounted square\
· check value out of adjustment or blocked

Pedal to floor

· Air trapped in fluid
· old or contaminated fluid
· master cylinder failure
· caliper or line leaks
· linkage failure


Good luck...

29, What does "incorrect pedal ratio (too high)" mean?

Incorrect pedal ratio means the pushrod attach point on the pedal is the wrong distance from the pedal pivot point, in your case it would be too close, reducing the amount of stroke at the cylinder. If that can't be changed, you might try a bigger bore master cylinder.

how much preload pressure do you have at the calipers .. do they still have a bit of drag on disc brakes like they used to .. some old time racers used to swap back to drum brakes to gain a few zillionths of a second in quarter times due to less brake drag ..

Pedal ratio is a design point based on the ratio of leverage your brake pedal applies to the master cylinder.

check out the following link.

http://www.hotrodheaven.com/tech/brakes/brakes6.htm

It's possible you still have air in the system. If those are GM "Metric" calipers the bleed screw isn't located at the top as it should be. I found on my truck I had to remove the caliper to get it into the right position to remove all the air from it. It was a pain in the butt.