Hi guys:

I own a Corvette C7 Z51 and have done around five track days with it. Recently, no matter how often I bleed the brake fluid, it turns extremely dirty after just one session. I suspected a leak, but after a thorough inspection, my mechanic friend found none.

The main issue is that my brake pedal gets soft very quickly—within about two laps. For the first 60% of pedal travel, the car barely slows down, and I have to push it to the floor to get any real braking force, which feels inconsistent and nonlinear. I’m considering rebuilding the calipers to address this.

My current setup:

• Pads: Carbotech XP12 (Front), XP10 (Rear)
• Rotors: DBA 4000

Additionally, I recently installed a set of APEX wheels with wider tires. However, I’ve noticed that even in Track Mode Sport 1, the traction control is overly intrusive. Would it be better to turn off traction control while keeping stability control on?

Any suggestions would be greatly appreciated!

 

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Don't know about the brake fluid or pedal but the traction system will intervene if the outside diameter of the tires you have on the new wheels are out of spec.

 

I might get flamed for this but I think the stock Z51 brake system just isn't cut out for track days. In spirited street driving they are great but really push the car and they just don't inspire confidence.

 

when you say bleed how much fluid are you getting out?
Like fully bleeding the whole system which would take a minimum of 2 quarts if not 3?

or you just bleed a little out of each caliper, top off and call it done?

 

You already have Traction control turned off.

In Sport 1, Stability Control, Throttle Dampening and PTM are active but TC is off. In Sport 2 Throttle Dampening and PTM are active while Stability Control and TC are off. In Race Mode, PTM is active while Stability Control, Throttle Dampening and TC are off. Throttle Dampening doesn't limit max throttle it limits how quickly the throttle opens and closes.

Why do you think TC is active? PTM may be active when powering off a corner. You can tell when it is active as the exhaust will change to a blatty sound somewhat similar to a truck using its diesel engine as a jake brake. Track bystanders sometimes think the engine is misfiring. From the 2014 OM here is a description of PTM and how the driver can use it:


Be careful following this advice as I have found my Z06 can overpower the system on some turns where going full throttle can cause the rear of the car to break loose.

The brake fluid in the caliper will get dark after it gets hot. That doesn't necessarily mean the fluid is dirty.

It sounds like you are describing a long pedal Vs a soft pedal. A long pedal means you have increased pedal travel before the brakes engage while a soft pedal means the pedal feels squishy but the brakes are engaging just not as hard. A long pedal can be caused by caliper piston knockback which can be caused by wheel bearings that are loose or with too much lateral run out.

A soft pedal could indicate air in the ABS module or if you are boiling the brake fluid you are generating air bubbles in the calipers. Boiling the brake fluid would cause the fluid to get dark.

The 2014s came with a so-called two-piece rotor that was really a single rotor having spoke like attachment of the outer ring to the hub portion. When using that rotor for track events the owner had to safety wire rotor cooling plates onto the front rotors to stop air flow from passing through the spokes. The plates enhanced rotor cooling while on track. If you are using the original OEM rotors without the rotor cooling plates you may be overheating the brake fluid. See page 9-7 in your 2014 OM.

Later on, these rotors were replaced by a better solid rotor that didn't have the spokes.

Bill

 

What kind of brake fluid are you using?

 

Try a full flush running new Castrol SRF fluid, sounds like you may be boiling your fluid if this happens after running on the track a bit and doing some hard braking.

Also I do find Sport 01 intrusive, and this can also heat up your brakes a bit too I found. Go for Sport 2, and/or Race if you feel it slowing you down too much.

Hope this helps you get more confident braking and better times out there!