baron95

(sorry - the text of this post got erased - I retyped best I could)

I got to drive my Z51 coupe on two track events, with OEM PSS tires, OEM brake pads, OEM brake fluid and cooling rings installed for a baseline first impression.

A cumulative 95 min of track time (over six and a half sessions) were run at speed, before overheating and oil venting issues intervened in each session (I'll post about that on another thread). Sessions were run in the instructor group (track 1) and advanced group (track 2), and I'm reporting only the at speed time, not warm up, cool down, or overheating diagnosis time.

Car was run with early upshifting and reduced downshifting, due to being too new.

I'm an HPDE instructor and occasional racer. Braking used style used was normal track style (firm for max deceleration to light and trail as needed), but short of the ABS which I avoid to preserve tires.

Pads were properly bed-in prior to the track events (BTW, not using GM's ridiculously prolonged, lawyery procedure). They were pushed to near total fade, smoked a ton, smelled like they should, during the bed-in, and were excellent after it.

Track 1 was a high speed track with 2 strong brake zones (140->70 and 125->60), and little braking elsewhere. Temperatures were 60 early to 75 late with partly sunny skies.

Track 2 was a mickey-mouse oval/road course combo, with just one strong brake zone (135->45), but many other brake application zones. Temperatures around 50F partly cloudy.

Results/Impressions

Brakes performed as I expected - that is, well. Pedal feel was a bit mushy and imprecise (from the get go, even before the track) likely due to caliber flex (no center bridge or screw on these) and one expansion. Light-moderate fade set in after about 5 min in each session, but was totally predictable, easy to manage, and and only got slightly worse with more laps. Brakes remain effective, with only minor adjustments to braking points. Fade was 100% from pads overtiming, *not* fluid.

The stock brakes, under the very typical conditions above, would serve any beginner to intermediate driver that does only occasional track days very well. I feel the benefits of staying totally stock (warranty, dealer service, hassle-free) outweigh any benefit gained by starting to replace brake components for those drivers. Advanced drivers would probably dislike the mushy pedal feel and early fade, but again, the car is totally drivable/enjoyable by all as a street car for an occasional track day as is.

After about 60 min of cumulative at-speed track time, the pads started to leave irregular (streaking) deposits on the rotors, and flake. After 95 min of at-speed track time, the pads were worn to 50% of original thickness on the back and a bit more worn on the front. I'd feel comfortable driving one more session for a cumulative 120 min of at-speed track time on them.

Next Steps:
I have now installed Carbotech XP10 (front) and XP-8 (back) pre-bed pads.

The Carbotech pads don't have the OEM pad weights or wear resonators. The front pads are the same I used on my 2012 Mustang GT with Brembo pack, wince the Z51 uses the same front calipers as the Boss 302, 2012-2014 Mustang GT with Brembo/Track pack. I think those weights are anti-squeal aids.

I bled the brakes refilling with ATE200 fluid at home since I had everything off - I probably didn't get all of the GM fluid out, but will rebleed on-track as needed.

I'll be driving with just the change of pads and the new fluid mix at Watkins Glen next Monday/Tuesday, and will report back on the improvements if any. It will be my first time ever at the Glenn (and instructing at that )

I had a short test drive with the Carbotechs - they squealed a bit, but still need to scrub the rest of the OEM material deposited on the rotors (that didn't come off via brake cleaner/brushing), then do an abbreviated material laying. I'll report on the squealing after I drive some more.

Here are the pictures of the front pads as I removed them today, I didn't take pictures of the rear ones, but they looked about the same.

baron95

Done editing - that was painful. Hope it is useful info for those trying to evaluate if they will run stock pads/fluid or change prior to first track session.

Magister Ludi

Thank you. Very helpful. I appreciate your taking the time. Looking forward to your results at the Glen.

descartesfool

I wore out my OEM rear pads on my M7 Z51 in one day on track (6 x 30 minute sessions). Front were Hawk DTC-60's and those pads held up well. But leaving those front pads on the front on the street caused severe wear of the OEM front rotors within 1000 miles, plus a ton of rusty rotor dust that got stuck on inside of wheels. OEM rotors are very soft compared to a PFC or AP Racing rotor, and OEM pads are not up to any kind of serious track work.

baron95

That is 180 minutes of track time on the OEM pads.

Sounds very consistent with my experience, since I wore them to 45%-50% of total thickness (down to about 1/3-1/4 of usable material life left) in 95 minutes of at-speed track time.

We already knew that they are not dedicated track pads, and therefore can't perform as such.

Question is, did they prevent you from enjoying the car during those six sessions?

I still think they are totally fine for a beginner-intermediate driver who just wants to experience track driving with their C7-Z51. After they drive it 100-150 min at speed on track, you can determine if/what they need to change.

I'll see how my OEM rotors do with Carbotechs. I find them (up to XP12) to be very rotor friendly, as in your routor will have surface cracks all over before it gets worn off material wise. With Carbotechs I ended up replacing rotors based on precaution not wear (even though I know surface cracks are "normal").

descartesfool

Well the rear pads wearing out on my Z51 in one day added $150 to my track day cost plus having to wait for new pads, so that is annoying. I was running with Hawk DTC-60 pads in front and they lasted fine but the same compound rear pads were not available so I ran the OEM ones. Then I left the DTC-60's in the front and they chewed the OEM front rotors within 1000 miles on the street because they are such a soft metal rotor. Definitely not track ready for my use. Needs racing rotors like AP or PFC and track pads. Car is fast, has lots of power and need more serious brake hardware.


For the occasional lapper, probably fine. Just not for me.

baron95

Did you replace the rotors? What did you go with?

The only ones that keep popping up on my searches are expensive ($1,800 for a set of 4) and have an 8-week lead time. (and incredibly, they charge more for the rear ones)

http://www.corvetteguys.com/c7-corve...front-z51.html

Adam@Amp'dAutosport.com

Your pads are pre bed go 1 lap easy 2 laps pick it up 3rd lap hammer down you should be good.

MrGTC

Excellent review. I think this is the only thread I've seen where the driver acknowledges that OEM pads and lines are fine for track use. I took my Z51 on the track a month ago and had a great time. I ran 4 20-min sessions with no heating or brake issues. Good info for those out there who think spending hundreds of dollars on aftermarket parts is a necessity to have fun on the track.

baron95

Thanks Adam - I do all my pad conditioning before heading to the track.

I installed the XP10 (F) and XP8 (R) did a nice rotor re-coating and headed to Watkins Glen. My first time ever at the Glen.

Pads worked out fine, but I've worn the XP10s by about 45% in 6 15 min hard run sessions, and a couple of shorter/baby sessions. I was expecting more durability from them. The XP8s in the rear held up much better showing around 30% wear.

Now, my problem is that they squeal like crazy - ear piercing - both before and after track use. I wanted to leave them in the car in between track days (like I used to in my Mustang GT), but I don't think I'll be able to. The squeal is deafening. I have tried cleaning/washing multiple times but not stopping the squeal. I'm going to try to put some brake lube on some parts (though I always avoid those), and see if it helps.

I think I need to switch to a Bobcat or factory pads in between events - did I mention I hate to change pads without a lift

Any way the XP10/XP8 provided a much improved bite/pedal feel, and had only tiny hints of fade.

So if the OEM pads were a 6, these are like an 8 (on a 1-10 scale). Would be a 9 if it were not for the higher than expected wear in the front.

Air temps on track were very cold, by the way. 39F and drizzle much of first day. 40F to 50F and partly cloudy for second day.

Now, if I only could solve my transmission overheating problems, I could give a report on running 20-25 min hard sessions.

P.S. I should mention that the OEM pads were much harder on the rotors (grooviing, etc) than the Carbotechs. The Carbotechs are simply slightly resurfacing my rotors to smoother look, removing some of the OEM pad grooving.

I have now decided that I will not make any rotor changes on the Z51. The factory rotors are quite good with Carbotech pads. They are much lighter than the solid DBAs and only slightly (2.5 lbs) heavier than the available 2-piece rotors of the same size.

Rob Willis

The squeal won't go away, just the nature of the beast.

Adam@Amp'dAutosport.com

I understand the noise issue, I can not help that under track temps they are fine but on the street you will not see those temps. Yes, you can go to 1521 for the street and have no noise issue. Also, that car is heavy and the cooling is not great. I could put you on XP12 but it all depends on driver and their braking. Feel free to call me at 216-780-8825 to discuss.

Adam@Amp'dAutosport.com

So if the OEM pads were a 6, these are like an 8 (on a 1-10 scale). Would be a 9 if it were not for the higher than expected wear in the front.

Brake cooling is a huge issue with this car.. I think when 10 is done you should move to 12 because they take some more heat..

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™ 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.

baron95

I'm not sure if heat was the issue. As I said, I was running in 40F temps, and was not getting any meaningful pad overheating fade.

I think some of it was the fact that the OEM pads had created uneven wear on the rotors, and the fact that the OEM rotors have really, really, really, sharp slot cuts. Much sharper than what I have seen with other rotors.

I used both XP8 and XP10 in my Mustang GT at the front, that had the same calipers/pads as the Z51, and with 300 lbs heavier, they lasted a bit more. I'm only about 5MPH faster on the Z51 at the end of the brake zones.

In any event, if I can't solve the squeal, and have to go to dual pad, then I can put anything -XP12 or whatever on the front.

I'd hate to have to go that route. I'm not sure what is causing the squeal on the Z51, since the same pads were 90%+ quieter on the Mustang.

MitchAlsup

It has been my experience that intermediate drivers are harder on their brakes than either beginners or expert drivers. Exactly how to use the brakes is one of the last skills accreated.

baron95

I've heard that, but don't buy it for drivers with a good instructor, interested in learning and doing multiple track days.

Even my beginner students get taught early on (or corrected quickly) the basics of hard to soft braking, not dragging it, etc.

Conversely, my advanced students on a 400+HP car like the corvette, will be entering the braking zone up to 20MPH faster than the dedicated beginners, and will be entering corners at most 10MPH faster than the dedicated beginners - often no more than 5MPH.

So that extra energy has to go somewhere.

Now, an advanced driver may recognize sooner when the braking components are over heating and modify the driving for a lap or so to let things cool down. And intermediate driver driving alone or a novice with an inattentive instructor many not notice it and overcook the pads. That is true.

I still thing that how hard you drive the car - as in an advanced student wanting to get really good, or practicing for time trials etc, running on better tires, will still put more stress on the system, not less.

Plus, an advanced driver will get more annoyed by the spongy/fading pedal, while the novice is just having so much fun and so concentrated on the next corner that they won't even notice it.

FormulaRedline

Thanks for the detailed report. My track weekend on the stock rotors and pads, cooling rings, but DOT 4 brake fluid had about the same result. The stock setup "gets the job done," but isn't really what I want under my foot when I'm trying to put a hot lap in.

Sounds like the XP12/XP8 setup with stock rotors is the logical next step.

I also think the car could benefit from wider front tires in the braking zones, especially under trail braking, but that's another topic requiring significantly more investment (wheels, tires, maybe a sway bar to compensate for the balance)!

FormulaRedline

What driving mode were you in? This sounds like a symptom of interference from the stability system.

baron95

Interesting comment. I thought that at first as well. But then, overtime I checked my tire temps and pressures I saw that the front tires were properly dividing the task with the rears. No overtemping or excessive wear in the front.

I did some massive trail braking at the Glen into the downhill turn-1 and after I got the timing right, I changed my mind and decided that the car's tire size are probably right on. I did miss the apex 1 out of 5 times early one, but that is because the track was so wide (my first time at the Glen), and I was not turning in early enough even with the binders on.

Of course, this is a very driving style type comment. All I can say is that the Z51 and the Cayman S/GTS are now my favorite street handling cars on track. 235/265 for the Cayman and 245/285 for the Vette seem to work, though 255/285 might have worked a tad better.

baron95

I only ran in Track mode, and I don't have PTM.

First time on track I tried leaving the traction control on just to see how good it was. It was way too intrusive for me on corner-out. So I never tried it again.

Then I tried traction off, stability control in competition mode. I think this one is very good, and only if I was really pushing or in very low speed corners would bother me. I ran this more, about 2/3 of the time. You can quickly learn to stay away from its intervention. I'd recommend this mode for most drivers.

I ran at least a fun session every track day with everything off, and it is a blast. Car is still so predictable, very easy to play with and get some good slip angle. For an autocross or tight track, this is probably the only mode that would work.

The funny thing though is that when I used the PDR, almost every time in the braking zone (straight line), the video showed the squiggly traction control symbol, even though I almost always stay just shy of the ABS (to go easy on tires). I suspect that it was indicating that panic brake assist went on, but not really sure. I haven't had time to watch most of the video. Has anyone else seen the squiggly TCS symbol on the video with everything off or at least traction control off?