drewz06

So in preparation for my first HPDE event @ pbir this past weekend I had purchased LG brake upgrade (ss lines, motul 600, stoptech track pads).

I also picked up some new slotted stoptech rotors "SPORT SLOTTED CRYO-TREATED ROTOR" to go with the pads... I had read that the OE drilled are prone to cracking under track events.

I purchased the z with 52k on the clock and figured the rotors probably could use the change.

I changed the whole set (fluid,lines,pads,rotors) and went through the break-in/burnishing process. I drove on the street with the new equipment for about a month to ensure everything was functioning properly.

Since this was the first time (i assume) that motul was run through the lines, i bled off some more from each caliper the day before the hpde.

My first session around i felt no indication of vibration braking before the corners and was ready for session #2 so i could try braking later before the corner.

About my 3rd lap in, i was running harder than any previous lap (harder being subjective). I felt a little shuddering as i was coming into a corner so I backed off some. I ran down the back straight and as i was braking it was happening more.

I came off the track and idled (no e-brake) checking all 4 tires/wheels/calipers/rotors for any indication of trouble, and seeing none, went back on the track.

The 3rd or 4th corner I came into, i experienced the shuddering again. I left the track and checked again then noticed some interesting "spots" on the front passenger rotor.

I had to drive home, so i let everything cool for a few minutes and proceeded to drive 30 minutes home. No shuddering or indication slowing for lights/etc.

Not sure if there is something up with the rotor, or maybe I didn't break-in properly?

Are the pads not matched properly with the rotor to cause this?

It's my DD so i will be pulling the stoptech's tonight and replacing with a new set of OE so I can see whats up with the fronts if anything.

I don't think this is pad deposit because the discoloration of the rotor material looks similar to annealed metal (i think thats what its called).

Here's a rough picture, i will post more tonight once i get the OE's on.

Thanks in advance!

Also, my best time around was a 1:41... not too bad for my first time on a track in a car

Dano523

Which pads, since it looks like you were getting them beyond their intended heat range, and starting to burn them up instead.

Also, on the heat being generated, single piece rotors are not the way to go as well.

Hence your slowest corner at PBIR is about 60mph in any kind of race prep'd vet, and you should be hard scrubbing down from about 175 into the right hand corner at the end of the straight; with the heat to the pads and rotors being full race High speed race temps after your first warn up lap, and not any type of pad you would want to run on the street since they would never get up to temp on the streets to even give you 50% of their braking force still below their optima working temps (Read stock Z51 HD pads would be on fire about lap 5, since they are only rated to slightly above street use for autocross temps instead).

drewz06

thanks! yeah that sounds about right...

i'm not sure what the pads exact make/model are, but it looks like they over heated the rotors...

here are a few new pictures, the "dots" match up with the vanes inside the rotor.

so i suppose after i get the 2 piece rotors, i should stick with "performance street" for daily and swap the pads for track days...

is there any difference between ap racing and brembo since its' the parent company?

-drew

Adam@Amp'dAutosport.com

You don't need a 2pc rotor for begging track days what you do need is a track pad that can handle the heat especially a beginner they tend to over brake.. The pads you used definitely where over there temp limit. I would suggest going with a Carbotech XP12 or XP10 front and XP10 or XP8 rear you can about them here http://ctbrakes.com/brake-compounds2.asp. I would need to know what tires you are using to determine pad compound.

The great thing about Carbotech pads is all their compounds are compatible with each other so, you would use there street pad the 1521 for street and switch to XP series for track there is no re-bedding no cleaning of the rotors just swap pads and go this eliminate the need for 2 sets of rotors.

Let me know what tires you are using.

jaredtxrx

If you got the Stage 1 LG brake upgrade kit you probably got a set of street performance pads and you fried the heck out of them. Honestly the rotors you have should have performed just fine depending on the tire. Which prompts the question; What kind of tires are you on? Did you use the e-brake when you parked the car?

drewz06

Correct, the c6 z06 lg brake upgrade kit with the pads/lines/fluid...

To the best of my knowledge, the entire vehicle is stock...

Stock wheels with MPSS non ZP 2k miles of street usage.... I was able to run the track for the entire first event (20ish minutes), but i don't have any metrics like speed/etc... I was trying to learn the track and how my car would handle off-street. I didn't push it hard, i let off the gas well before the brake zone and gradually applied the brakes before i started to corner, no jabbing at the pedal.

When i came off track, i parked in the flat, no brakes engaged... shut off the engine and put it in 2nd or something instead of pulling the e-brake because i had read this over and over again.

I even rolled the car back a touch to change where the pads/rotors were lined up after i stopped.

It wasn't until the second session when i started to push the car farther into the braking zone that i experienced the "warped rotor feeling" but as i said, when i was driving home, i did not feel any vibrations when coming to a stop at the lights.

I'm just not sure if its the pads or rotors... My train of thought was just to put up for a complete brembo gt kit (rotors, calipers, pads) or one of the nice touring AP front kits....

Is it possible that something is causing the brake pads to drag on the rotors somehow? Does the stock caliper have a spring in the piston that pushes it out? I definitely don't leave either of my feet on the brake pedal...

I suppose one question is would the rotors still be okay? I would assume that the color change as significant as it is that I probably shouldn't trust them... a failure @ 130 would be catastrophic to say the least....

Thanks for everyone's input again, i do appreciate the advice!

-drew

jaredtxrx

If you got the Hawk HPS pads and tried to track them for any length of time my guess is you cooked 'em and they couldn't handle it. Correct answer on the e-brake
The HPS are fine on the street but I wouldn't put them on track for long. You should head down the forum a little further until you hit the roadrace/autocross section. There are tons of threads on brakes in there. The Corvette is too fast and "heavy" for a dual purpose pad like a Miata can pull off. You will need a street pad and a track pad and for every forum member you'll get a different answer on what's best.

Adam@Amp'dAutosport.com

With that tire I would start with the 10 & 8 combo for pads and move up from there as you get faster.



Carbotech™ XP10™

When Carbotech™ unleashed the XP10™ to the general public it immediately gathered multiple regional, divisional, and national championships. The XP10™ has a very strong initial bite with a coefficient of friction and rotor friendliness unmatched in the industry. Fade resistance is in excess of 1475°F (801°C). XP10™ still maintains the highly praised release, excellent modulation and rotor friendliness that have made all Carbotech™ compounds so successful. Carbotech™ XP10™ is not recommended as a daily-driven street pad due to possible elevated levels of dust and noise.


Carbotech™ XP8™

A high torque brake compound with a wide operating temperature range of 200°F-1250°F+ (93°C to 676°C+). Carbotech™ XP8™ is the first of our racing compounds. Good initial bite at race temperatures, high coefficient of friction, excellent modulation and release characteristics. Extremely high fade resistance and very rotor friendly. Perfect for track day use with any tire and can still be driven safely to and from the track. Carbotech™ does NOT recommended XP8™ as a daily driven street pad due to elevated levels of dust and noise. Carbotech™ XP8™ is a great compound on the front & rear of most open wheel and sports racers.

As far as rotors you can clean them up and keep as spears I would start with a fresh set of plane face rotors.

You did mention about going to a Aftemarket caliper not a bad idea on this car but you need think are going to do end ugh days to justify the cost.

drewz06

Thanks for the info!

I took some 160 grit sand paper and hand sanded the rotors.... looks like the "dark spots" were able to be "coaxed" off...

I am going to try mounting them with some XP12's and seeing if that helps.

I'd really like to hit the track hard this time around and don't want to be concerned with the pads overheating.

Are the XP12's up to a whole day of HPDE? 5 sessions of 25 minutes?

I attached a pic of the "bad rotor" which is the one that was cleaned up in the pics....

I made sure to sand from the center out, not AROUND the rotor in a circle. (perpendicular not parallel)

Adam@Amp'dAutosport.com

There should be no issues with the XP12. They more abrasive than the pads you used previously so, they should clean the rotors up as you use them. Give me a call to order or order online use promo code z28. Use XP10 for rear.

Carbotech™ XP12™

Another highly successful XP™ series compound with an excellent initial bite, torque and fade resistance over and above the XP10™ compound. XP12™ has temperature range of 250°F to 1850°F+ (121°C to 1010°C+). The XP12™ has that excellent Carbotech™ release and modulation that has made all other Carbotech™ compounds so successful. The XP12™ is more rotor aggressive than XP10™, but compared to the competition the XP12™ is still very rotor friendly. XP12™ is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise.

fisher auto

Got to get to another one of these and get some real seat time, awesome man! Driving it hard like this is what there for...

AIR_RAM

Is it possible you where feeling the annoying effects of the traction control system?

I know when I hit the track for the first time I left the traction control on and it was the most annoying feeling to have the front tires start dodging around when scrubbing speed then heading into a corner. I had to turn that **** off.. after turning traction control off my problem went away.

Keep us posted.

SPEED SAFE, NICK

AORoads

^That's a possibility, too, or at least a contributing factor. I was also wondering: did you clean the rotors and pads thoroughly before burnishing? My thinking is residue left of something on the rotor but seems unlikely; just asking the question.

Dano523

Could have been a little of ABS ( the quick pedal pulse when it kicks in), and maybe even a little AH if he was running with it on, but looking at the disc patterns and material on the discs, more of such started by burning the pads up since they where not rated for the temps that they where achieving.

But yes, I don't even run in comp mode, but hold the button down for 5 seconds to run all the nannies off to run hard instead.
Note, ABS can not be turned off, just TC and AH only.

Hence comp mode will shut down TC, and even allow you to hang the back end out a little farther, but when you pushing the car hard out of a corner, you can still get into AH even in comp mode.

As for running with everything off, lets just say that you better have some driver talent skills of skating a loose car around a track, since if you get it way out of shape with all the nannies off, nothing is going to try to save you to get the car back in shape isntead.

drewz06

I think maybe the first time i drove home from the dealer i left TC/AH on...

I was trying to merge into traffic and i guess the rear tires spun (old OEM run flats) and totally cut power on me. Last time i left TC/AH on at any time.

I never drive with TC/AH on, always both off.

I had a twin turbo (then big single) 88 fox body 5.0 that could never keep traction so i got used to the rear stepping out on me. I appreciate the feeling of losing traction and know how to react to it properly.

My Yamaha R1 and Raider don't have any sort of TC/AH so I'm used to wheel spin.

I know that "spinnin aint winnin" but I am much more comfortable driving a high powered vehicle when I know and anticipate a consistent reaction to throttle inputs.

I can appreciate the "they won't engage unless you're doing something that will send you out of control" but if i wanted a vehicle that would drive for me, i would have purchased a tesla.

It could have been the ABS unit, but I'm not looking at the dash when I'm running it hard, no time to look down.

Anyway, this wasn't a rant, just explaining my driving style.

R_W

I'm not sure if you've discovered it yet, but this sub-forum is full of useful info and people as well:
https://www.corvetteforum.com/forums...roadracing-23/

This thread would fit in perfectly there.

mikeCsix

Depending on what track you were on (and direction), typically the passenger front tire is worked hardest (mostly left hand turns) and will generate the most heat.

When you burnished the pads to the new disks after the first install, then drove the car on the street for a month, you most likely scraped off the boundary layer you generated when you did the burnishing. Did you notice any brake squeal? If not, I would wonder what pads were used, with track pads, there can be a lot of squeal when not up to temperature and for some reason, I have to work at getting even XP-10's up to temp (running in the middle of the pack in 'B' group). I guess I'm just light on my brakes.

I would look at the pads to make sure they haven't glazed over, you've addressed the hard spot issue on the rotors as best you can (it's what I would have done too, just make sure you removed all of the grit from the rotors), if the pads are glazed you might be able to save them with the same sand paper treatment. I would then go through another rebedding process (I usually get car sick doing so even on run flats, I think its the hard braking motion and the smell of burning brake pad material - yep, visible smoke inside the car). You could also do this process during the warm-up session on the track. After that you should be good to go.

The next issue though is driving the car to the track with track pads or changing pads at the track. One of the reasons I like carbotech pads is the ability to change pads without contaminating or losing the boundary layer on the rotors and having to rebed the pads. Just swap street to track pads and go, or what I do is change the pads at home and drive to the track. I may have to go through a short bedding process when I get there as the track pads will be cold and just scrape off the boundary layers on the rotor by the time I get to the track.

Following the above process though, I've not had hard spot issues on my rotors like what you are seeing.

Nick__S

OP, from the pictures of your rotors I can see what your issue is. Do you see the dark colored circles on the rotor faces? Those are brake pad deposits. This means you likely got the pads hotter than their rated operating temperature range and the pad “smeared” material onto the rotor face unevenly. So what you are feeling as “shudder” is due to varying levels of friction as you are braking. The darker circles are areas of different friction than areas that are shiny.

If you get a set of good track pads and run them on the street the pads will be very abrasive at street temperatures. This will act as a grinding stone and clean the rotor face for you. If you have the rotors turned more material than need be will be removed.

I had the same issue after running OEM ZL1 pads on my Camaro at Road America. I made the switch to Hawk DTC 70’s and ran them on the street for a couple hundred miles (city driving) and they worked great to clean the rotor faces off. I had smooth braking after that.

Here is another good article discussing brake vibrations and causes.
http://www.stoptech.com/technical-su...nd-other-myths

drewz06

Thanks all for the input!

I figured I would provide some closure to this...

I received some XP20's from Carbotech and installed them on the slotted rotors that I used previously.

I got the pads "pre-bedded" so I was able to install and go right to the track.

Braking was significantly improved and I did not have any of the issues I was experiencing previously.

I was able to shave 5 seconds off my best previous visit.

I was also able to come within .5 seconds of my best time on 3 other laps for the session I recorded.

Unfortunately my dash mount camera didnt work so well so I couldn't get any video of it..

Thanks again!

-drew

Adam@Amp'dAutosport.com

Happy it worked out.