dream '94 Z28

I've noticed on a couple occations during autocrossing the brake pedal on my '98 Z28 feels odd. Most of the time it has a good, solid feel, but at the last event on two occations it would only depress about 1/4 of the way for the first half second (or so) of braking then get kinda spongy. I don't remember if I let off and repressed the pedal or not. This was during manuvers where i had to bring the car down from high(er) speed.

The braking force seemed relative to the amount the pedal was depressed. Do I need to have the brakes bled (and while I'm at it the fluid changed)? I'm staying in F-stock, so big changes are ruled out. thanks.

axoid

From you description it sounds like to me that the brake fluid is getting too hot or outright boiling. I would say that the first thing to do is check the pads and rotors to make sure that they are both in good shape and that the rotors haven't gotten too thin. If the rotors are too thin they cann't store and dissipate the heat efficiently. Next flush out the old brake fluid with new. If the problem persists, try better brake pads like Hawk HPS. Monitor the tire pressures and the amount of heat coming out of the wheel wells between runs.


A month ago, my co-driver and I were autocrossing on a fast course with allot of hard braking. With 2 drivers we were turning around very quickly (less than 10 min. between each run). After the third pass on the course very hot air was pouring off the brakes and after all the runs and reruns, we made 16 passes on the course and at the end, the air coming out of the wheel wells was at least 250+ degrees. The pedal never went soft because I'm using good ATE brake fluid, but stopping distances kept increasing because I was overheating the stock style pads.

KeithO

Is it possible that your cailper is sticking? Mine are sticking on my road race car and I found that the pedal feel can seem random when this happens since they don't retract when I let off the pedal. After about 2-3 hard laps (and it gets hot in there), the calipers stop sticking...

Jabberwocky

If you dont recall when the last time you bled your brakes, then definately bleed them. You might have some air in the line. It is easy enough for a home mechanic to do it. Also check your brake lines to make sure they are in good condition.

Dave B

What are your front hubs like? If they are worn they can easily lead to the "kick back" phenomenon that pushes the pads away from the rotor meaning that you have more pedal travel before rotor pressure is even. BTW if you spend any time with your pads using bad hubs you will add to pad taper very quickly making the problem even worse. Look to see if the inner pad is thinner at the top. It may be an indicator of a loose rotor due to fried wheel hubs.

TankII

I agree with axoid and Jabberwocky. Bleed your brakes. I ran my SHO around Lime Rock late August -http://web.camaross.com/forums/showthread.php?t=296604&highlight=TankII - and had a similar senario. Mine heat soaked though, and when I bled them at the track, I had alot of air. I went home and completely flushed the fluid out, dumping it into my oil-pan bucket. After I emptied the bucket out, I saw the brake fluid was beading up on the oil! Apparently the fluid had absorbed alot of moisture over the years and it took a hard run for the water to literally boil out! Once I finished, I took the car for a spin, braking hard and getting the pads up to temperature. Now my pedal has great feel and has not given me any problems.

TankII

KeithO

I have established that my caliper is not leaking.

I have replaced the melted reservior cap seal. It was distorted and the almost new brake fluid in the reservior had a black tint to it.

I have replaced the master cylinder.

I have bled my system.

The brake feel is still goofy...

I plan on replacing the booster vacuum hose today...

TankII

KeithO, have you changed your rubber brake lines yet? You may have one that is partially collapsed. Common problem with SHO's. Most SHO guys go with the Stainless Steel braided ones to fix this problem and give a firmer brake pedal.

TankII

KeithO

All brake lines are stainless. I found a leak in the seam in the brake fluid reservior while autocrossing yesterday. I am going to replace that and re-bleed the brakes and see what happens...

TankII

Did it work?
How much did your SS flex lines run you?

TankII