Too Tall Z06

Does anybody know if you can adjust brake bias? I have come back from the track a few times and had a considerable amount more brake dust on the back than the fronts. And a few times when my ABS went inoperative, I locked the back wheels pretty easily.

Any advice would be helpful.

Thank you.

leaftye

Only the early C5's could have it adjusted manually. The new system is constantly adjusting the brake bias. I'm pretty sure all Z's have the new system.

Bill Curlee

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XPC5R

A brake bias valve can be spliced into the front circuit BEFORE it enter the ABS control valve. This way the ABS operates normally, but cannot generate any more pressure than you feed it on the input side.

I bought a new front line (about $35 from fichtner) and cut and flared a section just below the master cylinder and plumbed in a Wilwood screw-type proportional valve.

This will reduce the onset of front abs, and help the car turn in better under heavy braking. The brake dust disparity is more of a pad compound issue.

Too Tall Z06

BP - thank you for the informational response. I don't know if I want to get into it that deep for a daily driver that I track once a month.

As far as brake dust, I am running the same compound front and rear. Could it be possible that the system needs to be bled and if so can it be done manually or is there a special machine for bleeding ABS?

Ls1Rat

what about the DRM spring ?

66ImpalaLT1

Run a different pad compound on the back than the front.

dmtnt

Only works on '01's or earlier.

Richin Chicago

Couple of things.
All 01 and later cars have electronic bias so there is no manual adjustment such as DRM available.

I would guess you are getting a lot of rear dust because you are overdriving and the competiton mode in active handling is kicking in quite a bit?

What were the indications that the ABS went inoperative? That should produce a trouble code.

Lancer033

to my knowledge, that's the only way to use the rear brakes more than the front brakes.

Option 2 would be to use a different pad compound on the back. Something like carbotech XP9 on the front and XP8 on the rear.

Too Tall Z06

My ABS, Active Handling and Traction Control go inoperative all at once and it lets me know by way of the DIC. I happens quite a bit especially when I'm in dry climates. I have stainless steel lines and the only constant is dry weather. Driving conditions have nothing to do with it. It happened about 15 times last week on my way to and at the Las Vegas track event.

As far as brake dust, I get more on the rear just driving around town nonaggressively. Besides, I usually take the Active Handling off at the track unless it's raining. I usually don't put it in competition mode.

Another possibility - is it possible that there is an air bubble in the ABS? I have changed my brake fluid 3 or 4 times and the first time I might have let the master cylinder bowl go dry. If that's the case, could that reduce braking power to the fronts? And, can I bleed that myself with a vacuum pump or does that need to be professionally done?

Richin Chicago

I think a bunch of things are going on here. First you didn't mention whose stainless steel lines you are using but my guess is one of the ends (or more) is not properly installed (for electrical grounding) and you are building static charges that causes trouble codes. This happens most often in dry wether where the staic charge does do not bleed off as they will with wetter air on damp days. Usually a dirty, reused, or improperly torqued crushed washer will cause this. Also it has been my experience that the Russell lines are more prone to this than the Goodridege.

As to an air bubble, unless the pedal is really feeling soft I doubt you have a problem. Any dealer can purge the ABS with a Tech II if you are not sure.

Finally it is not the usual pattern for A C5 to have more dust on the back brakes than the front. I would check to see if these pads are dragging. If the slide pins have not been properly greased they may not be releasing fully.

Too Tall Z06

Thanks for the info Chicago. I'm not sure the brand of lines that I am using. I got them from Porterfield brakes in Costa Mesa CA. He custom built them so they didn't come in a box with a name. Will changing the washers and torquing correctly be a solution? Do you know what the torque specs are for the brake lines?

As for the brake dust problem - I did happen to notice that the pads in the rear on one side (don't remember which one) one pad was thicker than the other. I will pull the slide pins and regrease and see if that fixes my problem. I hope that's it.

Richin Chicago

I would start with all new crush washers and make sure everything is very clean. The banjo bolt requires 30 ft. lbs, but I don't know what the other end is as it requires an open end wrench and I just tightened to feel.

Before you start see what trouble codes show up next time you see the ABS warning. It may isolate it to a particular wheel.
http://www.stengel.net/diccodes.htm

On the rear wheels also make sure you are getting good movement on the caliper pistons and the boots are not torn. It takes very little contamination to hang a piston.

Too Tall Z06

Thanks a lot for your help Bichus. I'll give it a shot and see what happens.