Low brake pedal

[eyeroc87]

Most problems I’ve read about is low pedal, squishy also, but low pedal mostly. I’ve done Nbs master, rebuilt calipers, drilled and slotted rotors, rears as far as possible. All 3 stainless brake lines, rear whl only abs deleted and removed. Ok I’m a retired ASE certified brake tech. Still have low pedal, once they grab, hold that beer.! Here’s my hypothesis. Just for S&Gs. What woul happen if I got a spare brake rod from pedal to power booster, an welded 1/2 on to it.?

 

[RichLo]

On a project Drag car I've cut the clutch pedal rod in half and welded in a turnbuckle to fine-tune the pedal length that I needed.

 

[Oldblue98]

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Most problems I’ve read about is low pedal, squishy also, but low pedal mostly. I’ve done Nbs master, rebuilt calipers, drilled and slotted rotors, rears as far as possible. All 3 stainless brake lines, rear whl only abs deleted and removed. Ok I’m a retired ASE certified brake tech. Still have low pedal, once they grab, hold that beer.! Here’s my hypothesis. Just for S&Gs. What woul happen if I got a spare brake rod from pedal to power booster, an welded 1/2 on to it.?

I have read that adding Residual Pressure Valves solve the problem... I ordered and have Wilwood valves for mine but have not gotten around to installing yet ! I got the 10 psi for rear and ordered the 2 psi for the front while I was at it. I have done everything from stem to stern on my brakes, nothing left undone ! New calipers,new drums etc etc adjustment on rear per spec. And I bled abs as well. If you google residual valve on GMC truck there is a lot on it. I just cant say for a fact it works because I have not gotten to it yet !

 

[eyeroc87]

On a project Drag car I've cut the clutch pedal rod in half and welded in a turnbuckle to fine-tune the pedal length that I needed.

Yes, good thinking, better than building one static.

 

[Schurkey]

WHAT VEHICLE???

There are two main reasons for low pedal:

1. Air in the system. Makes for low-and-squishy pedal. If it's bad enough, the brakes just plain don't work.

2. Brakes not adjusted properly. Makes for low-and-firm pedal. Has to be REALLY bad to affect stopping power.

For fukk sakes, don't start welding until you're ABSOLUTELY sure there's no air and the brakes are properly adjusted. Front disc brakes shouldn't be a problem for adjustment, but rear drums can be, as can rear discs depending on the design.





IF (big IF) this is a 1500 with the ******, hateful Leading/Trailing Shoe rear brakes, you can about count on the shoes NOT being adjusted properly, because almost no one uses the park brake any more--and the park brake is required for the rear brakes to adjust. This is the style of rear drum with the adjuster ABOVE the axle shaft.

Using the park brake lifts the adjuster mechanism--then applying the service brake "triggers" the adjuster. So you have to kick the park brake, release it, then kick the service brake pedal. Then repeat about a dozen times. Be prepared to do it another dozen times--or pull the drums and adjust 'em by hand.

AND, any time the park brake is adjusted too tight, the service brake adjustment won't work properly. Always adjust the service brakes FIRST, and you will probably never need to adjust the park brake mechanism.

 

[eyeroc87]

These no air, pressure bled, rears adjusted to slight drag, never heard of twin leading shoe rear brakes, don’t know what that is.

 

[hatzie]

These no air, pressure bled, rears adjusted to slight drag, never heard of twin leading shoe rear brakes, don’t know what that is.

Mis-adjusted drum brakes will cause a low hard pedal.

If you have a 1500 GMT400 or a 2500, 3500 etc you have drum brakes in the back.
Even the "normal" drum brake adjusters on the GMT400 chassis trucks will not auto adjust without using the parking brake... OFTEN.

I'll say it again. GMT400 drum brakes, and drum brakes in general, will not auto adjust without using the parking brake.

You can micky mouse them with residual pressure valves and longer pushrods but those bodges will screw up the brakes.

Adjust them and then use the parking/service brake every time you park the truck. Just pretend you have a manual transmission. The additional benefits of using the parking brake for its' intended purpose is the cables won't seize up and the truck won't roll and bounce against the parking sprag in the transmission when you let off on the hydraulic brake pedal.

 

[eyeroc87]

I have a brake mic. Shoes are hitting drum, there’s no air in system. Everything is better than brand new, stops on a dime near perfect brakes....but,,it’s got a low, very solid, but low pedal.

 

[hatzie]

I have a brake mic. Shoes are hitting drum, there’s no air in system. Everything is better than brand new, stops on a dime near perfect brakes....but,,it’s got a low, very solid, but low pedal.

Then it's working properly.
Light truck drum brake shoes are not cut to mate with the drums like heavy trucks and transit coaches so there will be some or sometimes even substantial change in adjustment in the first 100 miles from the linings "bedding in" (wearing to the inner profile of the drums).
Setting and releasing the parking brake will take up any slack from bedding in the linings. Set-and-release five times and drive a bit then do it again. I usually do this five days in a row when I get to work and when I get home. I do this around 100 miles after I replace a set of brake shoes. You'll be surprised at what ten sets of five set-and-release sessions with miles between will do to the pedal feel after the first 100 miles driven.

 

[eyeroc87]

Thank you, I’m going to do just that. Never heard that but sure gona give a shot.