QUIKAG

I track a '10 ZR1 and the past few events, the pedal has been pretty mushy in heavy braking zones, so much so, I need to double pump the pedal. At the second pump, the brake pedal feel is rock solid. The car has SRF fluid that was flushed properly.

It almost feels like pad kickback or something? Is that possible on the Brembo CC rotors? The rotors and pads are pretty worn down too. Is it possible with some new rotors and pads, the pedal feel will return with no problem or there is another problem I should check as well?

Any help diagnosing this issue would be appreciated.

vette6aut0x

[QUOTE=QUIKAG;1586284250]I track a '10 ZR1 and the past few events, the pedal has been pretty mushy in heavy braking zones, so much so, I need to double pump the pedal. At the second pump, the brake pedal feel is rock solid. The car has SRF fluid that was flushed properly.

It almost feels like pad kickback or something? Is that possible on the Brembo CC rotors? The rotors and pads are pretty worn down too. Is it possible with some new rotors and pads, the pedal feel will return with no problem or there is another problem I should check as well?

Any help diagnosing this issue would be appreciated.[/QUO

Sounds like pad kickback and worn pads.

0Bobby @ LG Motorsports

Check piston seals, improper bleed or hubs.

Screamin Z

Its knockback.. Tap the brakes on the straights.

The further the piston is extended the more likely for knockback.. and like bobby said.. any deflection from the hubs wearing out will only complicate it even more.

Racingswh

Preferably with your left foot!!

Replace the HUBS as well as the pads and rotors. More than likely the feel will be back to what you were used to.

0Anthony @ LGMotorsports

I might also add it could be thin pads, that can cause a spongy pedal.

That is assuming you are still running the same pads/rotor combo as before correct?

You know how much track time you have on the hubs? Even though the ZR1's use the SKF's they will still wear down a bit.

varkwso

use left foot tap before brake zone...

Hi Volts Z06

Last season I went on for the first event on brand new SKF hubs, brand new pads front and back on my 6/4 piston Stoptech's and had not only just bled the brakes but replaced the ABS controller. Unless you have knockback springs installed on your calipers you are going to feel it to some greater or lesser degree but even more so with pads that are nearing the end of their useful life. I have heard of some people using an old backing plate as a shim to help compensate but haven't tried this myself because it's not that troubling. If you want that firm pedal after a long straight... Tap them up!

skxf430

Anthony,

How long should our hubs last? And, how often should they be replaced?

Also, can someone explain pad knockback? Sorry, for the total noob question.

Hi Volts Z06

Pad knockback occurs when you get a tiny amount of play in the hubs due to the tremendous force that cornering puts on them. In turn your brake pads push the pistons back slightly in the bores. When hubs are worn the play is excessive making the condition worse. When pads are worn- they have further to travel back into the bores making it that much more worse. This is known as "knockback". When you have a caliper with knockback springs- they act to keep the pads seated against the rotors when this happens thus maintain a firm pedal without the need to "tap up".

Lawdogg

If there is no play in the hubs (wheel bearings) when you check it by twisting on an unloaded tire and no cracks in the hub, can the hubs still need replacing?

dvandentop

could it be spread front calipers as well causing issue?

naschmitz

Knockback or pad taper.

varkwso

pad taper is more common then bad bearings

QUIKAG

Thanks, guys. I think my CC rotors are about done as I've gone through about 5 sets of pads and other Brembo CC owners have replaced them around this time. I need to weigh the rotors to know for sure. Also, my pads are wearing out faster and faster. When I last replaced the pads, the pedal feel was noticeably better, so pad knock back seems the likely culprit. Wish they had springs in this package to keep the pad/piston against the rotor.

So, sadly, I guess it's time for $$$$ rotor and pad replacement and hopefully that fixes the issue. One of the reasons I track this car is for the awesome brakes so it's a little annoying not being able to trust the feel 100% when I hit the brakes especially on a time trial lap. That said, I've gotten 3 years and probably 30-35 hard track days out of these rotors.

Thanks again all for comments!

kmagvette

Be sure you note all those suggestions to tap the pedal going down the straight. Even with fresh SKF's, at least on my car, it needs a tap for a high pedal.

Aside from pushing the pads back out, the tap lets you know the brakes are still there. Once your left foot learns that is is good for more than just operating the clutch, it will probably want to start pitching in by braking into turns not requiring a downshift.

waddisme

Mine turned out to be a bearing gone bad.