DannyBoyC6

Hi All,
I have an '07 Z51 (drilled rotors) C6 with Hawk HPS pads (not HP Plus) and ATE Super Blue RBF.

During my most recent roadracing experience, I had trouble getting my brakes to bite hard enough to cause the ABS to kick in. I was trying to really nail the brakes at appropriate times, but I couldn't get the car to bite down the way I wanted. The pedal wasn't "soft", but it just wasn't yanking me out of my seat the way I wanted -- and the ABS barely kicked in with the pedal hammered.

I don't think the fluid was overheated as I just flushed (though without a Tech-2 tool to open the ABS), and the HPS pads are a few months old. I broke the pads in as is instructed by most. The rotors have some grooves that I can feel (about 25k miles on them).

Any thoughts on what happened? I'm a relative noob to road racing, so I don't have a lot of experience troubleshooting these problems.

Thanks in advance!
Dan

Zip Corvettes

You are using the wrong pads. The HPS is a performance street pad, not a road race pad. Eventhough you may not be actually road racing, the class them like this for ease of understanding the different compounds, but the compounds are based off of heat ranges and your pads are past there operating temp, that is why you are not feeling them bite. Depending on what track and your speeds and tires selection you may need to go well past the HP Plus also. You have to be careful about brake pads and you need to have the correct ones in the car for what you are doing, there is no such thing as a street pad that does well and a race pad that does well that are the same pad, it is one or the other.

sothpaw2

HPS pads suck. Get something much better and switch before the event. Wilwood H, Carbo XP12/10.

AU N EGL

HPS and HP+ only last about one day on a track event.

Plus when was the last time you changed the brake fluid?

Brake fluid needs to be changed before EACH event AND the calipers bleed for the second day of the event

DannyBoyC6

Brake fluid was replaced the day before the event.

I checked the pad depth and there was over 50% left. It was the 2nd track event with the pads, but was about a month apart with minimal street driving between (and both events were a single day each).

I was trying to "get by" with pads that I can live with on the street (no squealing and good cold bite) that would perform OK on the track, but that just doesn't seem doable.

First event was a very tight track with max speeds around 75mph and known as especially tough on brakes. I boiled the cheap fluid that day. Swapped with ATE Super Blue for this event (max speeds around 100mph in a couple of sections), and now it's the lame pads that got me!

DannyBoyC6

So when the pads are over max temp, the ABS won't be kicking in because the wheel isn't locking up as the pads aren't able to grip the rotor to stop rotation?

Adam@Amp'dAutosport.com

Please look at the XP10 front and XP8 Rear for your needs. We use this combo all day long for our vette customers. Please contact me at 216-780-8825 to talk shop!

AU N EGL

Yes You getting to the point where you need a better pad


I toss my pads out at 50% thickness.

ScaryFast

Yes. The pad compound can not handle the heat generated from repeated stopping, and therefore the friction between pad and rotor is significantly reduced; it's as if you actually melted the friction material. This is brake fade. A spongy pedal usually means boiled fluid, a soft pedal (but consistant) usually means you've exceeded your pad's temp range.


As you have less pad material, you also have less pad to dissipate the heat. That's why most ditch track / race pads below 50%. Even though there is visibly plenty of material left, you will heat it up much faster than a newer pad. Think about how long it takes to boil a pint of water vs a gallon...

A street pad is usually fine until it's much thinner, street stopping usually has adequate time between brake application to completely cool the pads and rotors.

Zip Corvettes

There is an old saying with racing. "Do you know how to end up with a small fortune racing, start with a large one."

It can get pretty expensive quick, the better the pad, the more expensive and they live less. You have to have the right compound, once that is up to par you will find the next problem.

DRUGschnorr

I have been happy w/ PFS 01's on my 08.

only takes 15 minutes to change pads if someone is watching....

buy a track pad and save those others for the street.

CDN_Wolf_eh

You may want to look into a set of SS brake lines.

Gering

Good info, thanks.

spdislife

Been using this combo and it works well for me. Also use an eight inch SS shim between the caliper and pads, front only, once they get down to around 60%....reduces the heat transfer to the caliper and keeps the piston boots from tuning to ashes.

DannyBoyC6

Thanks for the info, guys! Research for next spring has begun.

Glad to know "what happened" out there over the weekend.

Dan

DannyBoyC6

One more question on my braking post: do all of the guys regularly tracking their cars flush the ABS when swapping the brake fluid? I don't have a Tech-II tool but don't want to leave residual, old RBF in the lines if possible. Flushing, driving around to set off the ABS, then doing the flush all over again, sounds like a complete beating. I don't have a lift in my garage and don't have days to dedicate to brake fluid.

Zip Corvettes

You will be fine, just bleed the brakes, you do not need a Tech2 unless you get air into the ABS module. The fluid is still going through the module when you bleed the brakes, just keep bleeding until you see the new fluid come out of the caliper.

DannyBoyC6

longdaddy

when you inspect the pads, don't look at just the thickness. pull them out and look at the surface. shiny surface - they glazed and will not work well until the surface cools down and gets scrubbed. cracks all the way through the surface - material is failing.

I have ran xp12 and xp16 (as well as many pads from other companies well known here) and ended up going with carbotech endurance compound for my last year with C5 corvette as a track car. it was the only pad out of about half a dozen I tried that would not have material deteriorate rapidly once it has been used past 50% or so, and the only pad I could run almost all the way to the backing plate safely (with shims behind it, of course, to block heat transfer to pistons)

if you want to be precise about it, get some temp paint and put it on the edge of your rotor and the side of your pad. you will likely find temps well in excess of 1000 degrees.

it is better to have squealing brakes on the way home with a real track pad, then to overheat a street pad 300 degrees past its rated max temp.

DannyBoyC6

Great info -- thanks very much!