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My 02 Z06 has a soft brake pedal. When the car was delivered the pedal was firm. After a track day it became soft. I've bled the brakes several times to no avail. I then took it to the dealer and he hooked up the Tech 2 and bled all four corners activating the ABS pump on each one. The pedal was still soft. So they replaced the ABS unit, then the master cylinder, I put some Stainless lines on just in case. The pedal is still soft. I've been to the track several times since. The brakes work fine but the pedal isn't where it should be. I'm open to any ideas at this point.

Dean
 

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Dean,

Welcome to the forum. :cool:

We have a couple of Vette Drs. here, hopefully they will check in and be able to help you. :)
 

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Dean,
I have seen this problem several times with other people's cars and personally with mine.
Most likely your front pads have tapered due to track use.
Try a known set or new set of front pads and see if that takes care of the problem.
The rotors may be warped or severely grooved but it would usually be the front ones and you would notice that shuddering when you brake if they were warped.
If there is no air in the lines and no leaks in the system then all that is left is the contact of the pads against the rotors.
My guess is the pads.
Let us know if you still have the track pads on.
Dave
 

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Dean Robinson said:
My 02 Z06 has a soft brake pedal. When the car was delivered the pedal was firm. After a track day it became soft. I've bled the brakes several times to no avail. I then took it to the dealer and he hooked up the Tech 2 and bled all four corners activating the ABS pump on each one. The pedal was still soft. So they replaced the ABS unit, then the master cylinder, I put some Stainless lines on just in case. The pedal is still soft. I've been to the track several times since. The brakes work fine but the pedal isn't where it should be. I'm open to any ideas at this point.

Dean

As stated by others already,

CALIPER FLEX

which causes your pads to wear at a taper.


Happens to me at the track too. At first I was frustrated and bled my brakes after every session, this did nothing. As you said, the brakes work fine but the pedal isn't where it should be. This is because the pads will exert the same force on the rotor and slow your car but you have to pump more fluid there to get the pad to push flat on the rotor.

Many people are confused about this and think that the stock brakes fade and are a weak part of the car necessitating a $4000 brake upgrade. Or they think that going to SS lines will solve this, it won't.

At this point, I don't know what to do to fix this. After all, the car stops fine its just the pedal that feels funny. When you get around to changing your pads, you'll see what I'm talking about. The fronts will be tapered (face of pad will not be parallel with backing plate).
 

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BrianK,

Off-subject sort of;

But I have done my share lapping and done a lot of brake development with friends who develop braking systems at the big-3
Interesting, any of these friends ex-Lockheed Fort Worth engineers?
 

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BrianK,
I agree with everything you say on your post except the last sentence. You say there will be no taper with good pads.
I do not want other members to get the wrong idea here.
I have done about 150 track events in the last 16 years and only used stock pads for the first one. I found out right away that you can get in a lot of trouble with the stock pads.
Since then I have used about every brand of pad out there; PFC, Hawk, Porterfield, Cool Carbon, etc.
I have experienced pad taper with all of them! Heat is a major problem here. Cooling ducts will probably help some but pad taper is a reality on C4's and C5's. On the C5's you can switch the front pads around and try to even out the wear.
The best stopping pads I used were the Hawk Blues, however the brake dust from them is murder to get off the wheels.
I tried Porterfield pads last year and wore out a set, front and rear, in one weekend. I mean to the backing plates. ($300)
Just my experiences. Hope it helps.
Dave
 

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I would .....

1. Change the pads to a good AutoX or Race pad in the Front, possibly Mallett's Gold, Hawk, Porterfield, Carbotech or Performance Friction, Make sure the new pads are burnished in correctly.

2. I would change the fluid out for AP600, Motul 600 etc., drain. flush, refill, rebleed with the ABS included with the Tech II.

3. If there is still a spongey feel I would take all four SS lines off and recheck them to see if there is an obstruction in one of the lines. A small but partial obstruction can cause cavitation.

4. If none of the above things work I would look very closely at the rotors. If I had an doubt about warping, cracking or uneven wear I would toss them and order the GM performance (T1) rotors and have them cryo'd before putting them on. Also be very carefull that all the mounting surfaces are clean of brake dusr, rust, dirt etc etc. There is a Chevy tool used to clean this area in the service manual. You must then reset in the rotors, like burnishing in the pads.

5. Next I would look at the calipers, rebuilding them and possibly exchanging the stock aluminum ones for Doug Rippies Stainless Steel Caliper Pistons

I would also replace all of the caliper bolts while doing this

You either still have air in the system (Most likely), are getting air in the system from boil out of the fluid, have water in the fluid and system or you over cooked the stock pads/rotors at the track and something is warped and something is warped.
 

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Just a Comment

Yesterday, I installed Baer Eradispeed rotors and stainless lines. When bleeding the brakes I was aware of good pedal firmness with little depression. However, later when driving, I noticed that the pedal was spongy and went down further, although the car slowed & stopped properly. I thought maybe that I needed to rebleed the brakes.

Since then I have found the pedal to be quite firm when the engine is off but spongy and depresses further with engine running. I am assuming this is normal as they seem to work fine.
 

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It could be there is still air in the system

The air expands and more is produced when hot. The initial bleed should be done cold but subsequent bleeds should be hot. Also tap the calipers with a rubber mallet to be sure the air is out of the calipers while bleeding. A small bubble can accumulate just before the bleeder valve and hide in the caliper.

Also make sure no water is in the system. Its the season for water to accumulate due to cold temps. damp conditions. Water will transfer across the rubber hose pores into the fluid which will absorb it.

Also if you don't have speed bleeders which are a one way valve the bleeding process is a 2 person job. If you pump the brakes with the stock bleeder cracked open you will suck air back into the system. also DO NOT run the master cylinder run dry while bleeding. Fill it up after each wheel/or bleed.
 

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DJ,
Everything you say is true in theory and should be follwed.
However, I have bled brakes in the C4's and C5's I owned and never used a mallet to tap on the calipers. Good idea though if you are trying to solve a problem.
Also, I have used one way bleeders for the calipers but most of the time I bleed into a container of fluid keeping the hose immersed. Sometimes I just bleed with a long hose and dump it into a large bottle, without the hose immersed. I have not had any problems with air being sucked back in.
I have never bled the ABS system either.
I have bled brakes about 150 times on my cars (before each event) and never had a problem with air in the lines.
Now pad taper, that is another story. :)
I think some members are spending too much time worrying about rotors, brake fluid and SS lines and should spend more time and money on good pads and cooling ducts. There are a lot of good DOT 4 brake fluids out there. SS lines do little if anything to give a firmer pedal. Stock brake rotors work very well if you get cooling to them. I have never used anything except stock rotors.

I am not referring to you or anyone else on this thread, just in general. No flames intended here but maybe we can help a few people enjoy their track experience without spending the weekend working on brakes like I did when I first started.
Drive more, work less. :)
 
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