moespeeds

I'm having some issues with my C5 FRC. Under very hard braking it's wild, requiring a lot of steering input and pedal modulation to keep it going straight, tending to want to veer to the left. It also seems to be eating up pads and rotors on the front left faster than on the front right. The front left caliper also changed from annodized black to a pinkish color, I'm assuming I overheated it. They are Wilwood SL6 calipers, running 13" rotors. When everything it hot, the brakes also seem to drag. This happened once before, and after a bleed they loosened up. Running Motul RBF 600 fluid, changing it out every 3rd event or if it changes color. The rears are stock and they are wearing normally. I've tried a few different types of rotors, mostly cheap stuff, centric, raybestos, and centric cryo. I'm running Wilwood Poly "H" pads, though I tried Poly "B" in the front with no change other than very quickly eating a set of new rotors. My front right brake line was leaking, so I replaced it, with no improvement. Since fixing my ABS I think I tend to mash the pedal, so I tried very progressive braking, with a little improvement, but it's still dicey. An experienced driver went for a ride with me, and noted that I am "extremely late and hard on the brakes", something that mirrored comments from a PCA instructor at Summit. I also trail brake. I guess I'm just looking for some input on what to look for. My plan this week is to bleed the brakes, and check all the lines. I'm also going to get a rebuild kit from Wilwood, as I'm unsure of the total time on these calipers. I'm also going to disable the ABS next time on track to see if it could be something in the EBCM. I'll check codes this week as well. Any thoughts?

Cobra4B

The first thing I did when I bought my used wilwoods was rebuild them so I knew what I was working with. Oddly the set I bought had the left one discolored, but the right side still black. After a year of racing on them the right side one is still black and I've had no issues with them at all. I can only assume the anodizing on the one was inferior to the other. The previous owner of them is an avid poster on here and said he had no issues with them and never overheated them.



Left


Vs.

Right

JimbeauZ06

Sounds possibly like a piston could be sticking on the left caliper. Causes heat build up on one side leading to stronger bite on that side. Check while you have them off.

moespeeds

That's exactly what mine look like. I can't remember if they came that way or not though...

Cobra4B

Rebuilding them is extremely easy and the rebuild kit is cheap.

Bill Dearborn

Both of my SL6s changed color. It sounds like you have a piston hanging up. Do you use pad spacers to keep the pistons in the caliper cylinders as the pads wear? On my SL6s I noticed the pistons would **** a little sideways if they extended out very far. Installing spacers (a bare pad backing plate) kept them in where they couldn't **** sideways.

Bill

moespeeds

Todd at TCE just sent me some pad spacers 2 weeks ago, but prior to that I was not using them. BTW, can't say enough good things about that guy, he has come through for me several times, and his prices are right on.

CHJ In Virginia

I had the same problem when the pads got 75%worn, I would get piston hangup and overheating. Now use spacers - backing plate - and I can use the pads till nearly done. My left caliper also turned a nice shade of purple after a couple of events.

moespeeds

BTW the pads on the car this weekend were brand new.

0Todd TCE

Definitely sounds like some imbalance here...

Suspension bushings and tire, and track track conditions aside: I'd look/review the following items.

1. Be certain the hoses are free of any obstruction or kinks including the adapters.
2. Running the ss heat shields be sure they are in place an not shifted interfering with the piston stroke.
3. Check that you have the same pad compound in all four locations. The back of the Polymatrix pads will say 15B-xxxx or 15H-xxxx on them denoting the compound.
4. Check as others have suggested the condition of the seals and perhaps replace them if unknown life.
5. Be sure the bleeders are up on both caliper. (I know..but it's worth mentioning)
6. If the pad wear is rapid on all four you don't generate enough heat. If only one one side I'd suspect some drag or pad tapering and binding.
7. Be certain the pads fit smoothly (more loose than tight) in the caliper and file the ends some if you feel too tight. (or remove the ss tension clips as I do)
8. Run the pad spacers as the pads wear down to counter act any piston over extension.
9. Check the pistons you have, depending upon age the old parts are stamped and prone to flex whereas the later parts are cast and much thicker. (rough inside vs smooth)

Seal kits, caps/plugs, assembly luge all are easy and inexpensive.

Thx.

CP Thunder

You mentioned 'fixing your ABS'. If any of the hardlines on the ABS module got swapped your car would do exactly what you are talking about.

I would trace those lines out if they have been off lately.........its easy to put them on wrong if you didn't label them first.

AU N EGL

check for caliper spread first. Might be time for new calipers.

moespeeds

What's caliper spread? I've never heard the term.

The lines into the EBCM are ok, I did a thorough check on all the lines when I was tracing problems with the ABS. The car was throwing a 1255 code, but the problem turned out to be the plugs on the front wheel speed sensors. Once I eliminated the plugs it was fine. This problem is fairly recent, within the last 2 events I ran, but I'm still new to DE, I just started in June so I guess it could have been an issue all along but I've gotten to the point where I'm pushing the car hard enough for this to pop up. I'll run codes tonight, I'm curious to see if I have the one that tells you the wheel speed sensors had a large differential.

This weekend I'm gonna run the car a bit without ABS on, that will tell me for certain if it's mechanical or in the EBCM. So if you're at NJMP this weekend with PCA, and you see me flying up behind you with tires smoking, get the hell outa the way!

Cobra4B

The Wilwood calipers won't spread. "Caliper spread" is where the OEM caliper body distorts over time. The pressure causes it to "fan out". Put another way imagine taking the letter U and pulling it apart into a V.

I measured my old stock calipers when I took them off for the Wilwood install and they checked out perfectly. I've never had an issue with it. However, I wasn't racing T1 back in the day when they mandated OEM calipers.

vette6aut0x

Just curious, has your car been lowered and if so has it been bump steered? Just a thought. Also be careful when deleting ABS. Rear wheel lockup will happen and the results are not good ask me how I know.

moespeeds

It has coilovers, so yeah it's low. My first 10 track events were with no ABS, I got used to it, then fixed it so I've been using it the last month or so. I'm considering running a switch inside the car to cut power to the EBCM so I can start running without it again. I liked the way the car pointed into the apex while trail braking. The downside obviously is you do some locking up, but I never had any issues flat spotting tires like so many people claim. The guy I bought the car from was not using ABS, and suggested I leave it disabled.

vette6aut0x

But has the car been bump steered? Does you car have a bump steer kit installed?

moespeeds

I don't know the answer to that. The guy I bought the car from had it setup and cornerweighted. I just pulled it out of the trailer, and the brakes are dragging for sure. I'll find out which one later tonight.

moespeeds

Front left brake was dragging. Front left tire was flat spotted right to the cords, front right was corded around the inside. I pulled the calipers and ran the pistons out just before they popped, no unusual wear or scratches, pads look fine. Cleaned them all up, lubed them and did a full bleed. Fluid coming from the front left was black, everything else was clean. I have 2.5 events on the fluid (RBF600), which looked fine in the reservoir. Brakes are no longer dragging, took the car out and ran the brakes to fade, then let everything cool off. New rotors and tires for this coming weekend, I'll see what happens. Rebuild kits are on the way from TCE Performance.

Cobra4B

Nice... wonder if the pads were too tight in the caliper body? I run Carbotechs and always have to grind on the edges to get them to fit properly. I take my grinding wheel to the track with me!