I have a 2014 Z51 with 20K miles. I have DBA4000 rotors with Carbotech XP12/10 pads. Everything else on the car is OEM/stock. The only exception is the torque tube which I had to replace last year. I also had to replace the front right caliber with an OEM stock caliper because it was sticking.

The last two track events (Eagles Canyon Ranch) I’ve been getting really spongy break pedal about halfway of the 20 minute session. I was running Motul 600 and thought it was the fluid. I switched to SRF this past weekend. I still starting got soft pedal but it was at 15 minute mark as opposed to the 10 minute mark.

This was on brand new fluid each time with plenty of brake pad surface (not thin pads). The breaks got so hot this weekend that it discolored my calipers (see the pics). The performance shop tech at the track said there’s no way i should be boiling SRF as a weekend warrior, especially in the Blue group! I do threshold brake some but not the a lot. I have an automatic so I’m not riding the break around the track. It only happens after I’ve been on the track for a while. At the beginning of the session the bite and the pedal is great. If I pump the pedal, the bite is still great at the end of the session. As you can see from the pics, the OEM cooling ducts appear to be in place. (The tech thought that might be the problem).

I’m vexed. Could it be the new DBA rotors vs the OEM rotors? I’ve run XP12 for a few years without problem but could it be an issue with the new rotor combo? how can i tell if it’s a bad master cylinder? I’d like to have some sense of the problem BEFORE I take it to the shop and they tell me I need to replace my entire brake system!?

 

From what you described and the color of those front calipers, you need more cooling. The bumper to fender ducting isn't enough. You could try Z06 ducts or go fully ducted to the spindle.
https://www.lgmotorsports.com/lg-c7-...oling-kit.html

 

Besides needing more cooling, it looks like you're fading the pads based on the pad smear on the rotors. When this happens with new folks, it tends to be related to braking technique.

If you're at ECR, I'm local to you. I tend to run MSR-Cresson (in fact I'll be there this weekend teaching for BMW).

Shoot me an IM and we can talk more trouble-shooting.

On track, I drive the below....

 

You need to do a J56 brake upgrade which is pretty common. Essentially that's installing the Grand Sport brakes on the front which have a much larger thermal load.

 

Did this about a month ago along with Torque brake fluid and braided lines. Massive difference.

 

Same experience. Just FYI: The big oem brake cooling package doesnt help much.

 

That's a good call out. The stock stingray brembos are identical in size to my old STi. I ran the same XP12/10 combo as @Sugast in that car. It was 250lbs lighter and had 150 less whp, but still required fully ducted cooling to the spindle to play nice.

 

I was running carbotechs on my c7 grandsport w SRF fluid and found the brakes would over heat pretty frequently, I wasnt boiling the fluid but it felt like the pads were glazing over. I picked up an AP brake kit for the fronts and havent had any issues, using hawk pads this year, much more reliable and consistent reaction all weekend long

 

Are you getting into the ABS? Also, what drive mode are you running? If it's anything less than Sport 2 the stability control might be getting into the brakes without you knowing. I've been tracking my Z51 for a few years now and have never had brake fade / overheating issues. Use Carbotech XP20/12 and ATE type 200 fluid.

 

I’m not flushing the ABS. I have and I use Track mode. You’re probably right about trannies using the breaks. I’m running XP10s next weekend to see if it makes any difference. Thx

 

There's so little fluid in the ABS system that it doesn't matter if it's flushed. The only time someone needs to worry about that is when there's air in the system from replacing the module.

Do you have PTM modes on your 2014? If yes, then you need to be in Sport 2. Plain "Track" is as intrusive as hell.

If you smeared the pads using XP12s, the XP10s will be worse.

Running Streets? I used to enjoy that track





The below is with XP20 pads. Longitudinal is braking and acceleration. With those pads with J56 brakes I'm at -1.32 Gs. I've seen as high as -1.42. BS'ing with the GSpeed guys the other day, -1.5 G hits the limit on the C7 braking. The point of all this is that you need to get the right pads and the right amount of cooling. There's a myriad of ways to go about that, including an aftermarket BBK. As for the "why"....it may be happening now because you're faster than you were 2 years ago

 

The z51 brakes are not good enough. Ecr is very hard on brakes. You need to just bite the bullet and upgrade fronts to z06/gs brakes.

 

I'm curious what tires he is running. 300, 200, 100 treadwear? Pirelli scrubs? usually makes a huge difference also. Not saying the brakes he has are phenomenal, but stiction plays a huge part.

By the way. The Grand Sport 6Piston Calipers are around $400 ea (Black) on Parts Giant. Rotors are actually more expensive at 500-600 ea. (includes Aluminum Hats) - I might do it, but haven't really researched the AP option yet as mentioned above and many others on here swear by them.

Here's a 6 piston AP kit for the C7. Not sure if this is the one everyone is happy with. $3100 isn't all that bad including rotors (front only) Click here for AP Brake kit

 

With stocking power, the oem gs/z06 brakes are plenty