I drive my totally stock Grand Sport mostly on road courses and have a few questions.
I wear out the outside of the stock super sport ZP front tires. Would changing to the Chevy recommended track alignment provide more even tire wear? I assume it would give a little better cornering.
I switched brake pads to Hawk HPS 5.0. How thin can they get without destroying my front rotors (again)? These new front rotors and pads have 7 track hours on them. Pads are now 4mm thick and rotors have small grooves while the original rear rotors are still smooth. Is there a better pad for this mix of track, street and rotor preservation? Thanks for sharing your experience!

 

Yes align the car, pay attention to toe and rear caster. Also use a 200TW track tire instead of those street tires.

Run a track pad instead of a street pad. Also consider adding the z06 cooling ducts to your control arms.
https://www.knsbrakes.com/products/c...ace+Brake+Pads

 

CPB - Thanks for the reply! Next level detail. Which 200 TW DOT tire works best for you? Needs to fit the stock rims. I don't plan to change wheels, only one cracked rim (so far) in 14 track days

I drive the GS an hour to Sonoma and two to get to Laguna Seca. The KNS site showed race pads. Which one do you use? Will they stop me when cool? I can accept noise and dust but want to preserve the rotors.

What wickerbill do you use? Have you tried/compared the benefit of stage 1,2 or 3?

 

It's not really a "best", but I run the ExtremeContact Force due to the street behavior and long life. There are faster 200TW tires available, but they also experience more wear.
Here are some common tire choices for each wheel size: https://apexwheels.com/fitment-guide...ment-guide#oem

Yes, they will still stop when cold. Just will have varying degrees of noise and dust. For many it's intolerable freight train noise. Right now I run the SR21/SR11, but dislike the lack of modulation. I'll likely try the Ferodo next. On my previous track car the Carbotech XP12/XP10 combination was great, but I haven't tried it on the GS.

Pad choice is really about preference and heat range. You can read some feedback on various pads on this forum and you'll find the same pad is loved or hated depending on the driver's tastes.

I'm on a stage 2 splitter and stage 2 winglets. I have heard anecdotally the GS isn't high enough HP to merit the drag added by stage 3, but I have not tried any aero changes. Not saying it isn't worthwhile, just not something I have bothered with.

 

Tire Rack shows the extreme contact force isn't available in GS stock wheel size but the extreme contact sport is available. I've talked to some folks at the track using a couple different 200TW type tires. I know some were on smaller wheels. Rather than just replacing the fronts, maybe I'll go new on all four. Maybe sport cup 2.

The drag of stage 3, or even stage 2 was a concern. The GS doesn't have the most HP in my intermediate to open HPDE sessions, but it sure is a sweet car to drive. Thanks again, time to go shopping.

 

You might have to go wider or more narrow by a few mm. It shouldn't be detrimental. I'm 295F and 325R for the ECF.

 

I have used Extreme Contact Sport tires on my GS on track and they work fine. What's really nice is they don't squeal much, unlike some other street tires. They also don't wear much. I only did 4 days on them but wear was almost un-noticeable. Clearly there are faster tires available but keep in mind - the higher the grip, the faster they will wear out. If you are not trying to set PBs they are a good tire for HPDE use.

For pad selection - best talk with someone like Ken at KNSbrakes.com. Small business, expert advice, talk directly with the owner, good prices...highly recommend. You can describe the car, tires, track vs street mix etc and he will be able to give you the best pads for your needs.

I have GS Z07 - so full stage 3. Not sure where this idea that the car isn't powerful enough came from, first I've heard of it. I've had no concerns, the package has worked very well. Even on street in 7th I have plenty of torque.

For alignment - do not take your car to any old tire store. The combination of A-arms front and rear and transverse springs is completely alien to most alignment techs who only work on strut type suspensions. You need to go to a corvette expert shop. And be prepared to pay $, it takes a lot of time to set up a vette alignment properly (assuming your go with the full camber, caster, toe, ride height and possibly corner weight (requires adj end links))

One final thing - this forum has an excellent section for advice on tracking corvettes. Go to Forums > General Corvette Topics > Autocrossing & Roadracing. Pose the same question there and you will likely get a lot more responses.

Cheers and have fun out there! B

 

I agree fast tires wear out faster, but something like the ExtremeContact Sport will also overheat and chunk if pushed hard. They aren't happy on hot and dry tracks. They do dominate on a wet HPDE though. I've killed a few being too lazy to swap them out during an event that dried out mid-day.

You can go too far in either direction of durability and speed, then lower tire life.

 

Well you must push pretty darn hard then - I've been doing DE's for years and years and never had a tire 'chunk'.

 

A squealing tire is a happy tire!

 

As I recall it was Tadge that stated it when asked. Regardless, it came from GM. You'll never notice it on the street other than a ding to the mpg from the added drag.

On the 2018/2019 cars you can look at the ride height data if you have the PDR. If you compare data from the same track with/without different aero bits installed, you can see the ride height difference due to down-force (or sometimes just the reduction in lift). The bridge on a stock GS has very little benefit. When I was in SoCal running Auto Club Speedway (RIP), changes in ride height were basically nothing until speeds were well in excess of 130mph. The trade for the minor benefit I saw was an average reduction in top speed of 2mph entering T1 but a little more speed through T1/T2 (NASCAR banking) along with a very minor reduction in speed elsewhere on track when above ~80mph. "Net/Net" with the bridge, lap times were about the same to a couple tenths slower....ie within the noise. On slower/tighter tracks I saw no difference.

For the OP regarding brakes, I tried all manner of pads and when the car was stock, I settled on Carbotech XP12/XP10 (Front/Rear). Absolutely can't stand the SR21/SR11s for the same reasons CPB mentioned. Beyond the specs, braking style also is a factor. These days, I'm just out having fun so I'm a 7/10ths driver and my braking is less aggressive. In the past.....Get to the last marker, count to 3, brake when you see God.

Alignment is critical. You can get away with a lot of camber on the street and not mess up the tires. The Chevy specs are pretty tame. You could easily run -2.3* up front and -1.6* in the rear. 0 toe in the front. Slight toe-in for the rear. 0* ****Rear**** caster. Many shops are not aware the C7 has adjustable rear caster and not all have the tool to set it. Whacked caster really makes the car drive like ****. The backend does not like to play nice, especially under heavy braking.

 

On my GS, I ran the stock MPSS tires which had good grip, but was replacing fronts after 3-5 track days (Intermediate run group). I started with stock alignment (1.5*? camber), but as you pointed out, the outsides wore quickly. Had Corvette alignment specialist set front camber at 2.5*, but inside tread wore quickly. Finally went to dealer and had them adjust fronts to 2.0* and that was my sweet spot.

For pads, I run the Carbotech XP8/XP10 on the track and 1521s on street. The track pads have great stopping power at 135 mph and I never had any fading issues - ever. Also pad life was great and they are easier on rotors. Really happy with pad choice. I changed brake fluid to Motul RBF 600.

Regarding aero, I run either stage 2 or 3. It does shave off 2-3 mph at top speed, but car feels much more planted on high speed sweepers.

I wouldn't worry about the rotor thickness too much. They are more likely to crack first. If you are hard braking on the track, they will form small cracks. That's okay until the cracks go to the edge. I ran 6-10 track days a year and replaced every year or two.

 

JIm - Thanks for the good ideas. Regards wicker bill. I started the not powerful enough stuff just based on my stock '18 GS M7 not catching GT3RS or GT4's on long straights on Laguna Seca or Sonoma with stage 1. I assume more drag = less speed. More driver skill would of course solve all problems. Your conclusion wasn't clear to me on use of stage 1,2 or 3. My top speed on these tracks is 110 (for about 2 seconds). I like the idea of more down force on initial braking at that speed.

I will get the GM tack alignment Monday at the best regarded Chevy dealer in Northern Cal. They will replace the 6 year old stock brake fluid with SRF.

As an indication of my braking, I got 10 (5 x 20 minute) track days our of my PSS front tires and after 6 days my Hawk HPS 5.0 front pads are at 4+mm. Should the pads last another track day? Little time until I'm at Sonoma to obtain and replace them. Thanks again!

 

Redman - My first front rotors were replaced due to cracking. I saw bluing as well, not sure if that is a fatal flaw also. I had taken the pads to 1 mm+/- without knowing they were near end of life. As just replied to Jim, I have 4+mm left on front pads. I don't understand pads life. A track friend said he changes pads at half thickness. Maybe heat dissipation declines as they go thru the last half of their life and they wear faster? I can't find the new pad thickness of Hawk HPS 5.0 pads, so I don't know what half is. My rear pads, same age, are still around 7mm.

I like "more planted" and I think I'll try stage 2 wicker bill. More skill + correct track set up = Porsches behind not in front Thank you!

 

On a stock GS, my opinion is that Stage 2 is sufficient. When the GS came out, there was a question about why the Z07 version didn't get the center bridge like the Z06/Z07 cars and lack of power was the answer. If you're setting class records and need that last .001 second....on the right track then maybe it makes sense. This and $2 will get you a cup of coffee

Ditto regarding brake pads and opinions as you've found. I run them to 50% plus 1 track day. That will get me.....on the tracks around here in TX.....to about 3mm. The exception is if I'm going to a high speed track like COTA, I'd want a lot of meat. I'd probably run new pads and keep the used ones for a slower track or as spares in general. I get 3 to 4 days out of front pads...usually Carbotech XP20 although I just finished a set of EBC SR21s

You're lucky regarding brake fluid that you didn't lose the brakes. Super dangerous to run something that old. Brakes work......until they don't.

Alignment....again my opinion....I think the GM settings are pretty tame. I assume you're talking to Rich at Abel Chevrolet. I'd ask for something a little more aggressive.

 

Jim - You are right, Abel is the dealer. If I ask for "a little more aggressive" I might be asked "what do you want" I see above Redman found -2* on the front was best, for him,-2.5* caused fast inside tire wear. Chevy track spec is -2.0*. What do you find best? Any other deviations for Chevy spec you recommend?

Will you stick with the SR21's? From a thread a couple years ago they sounded like the perfect pad for track/street. Later I read they are to noisy for street. Did they last much longer than the XP20's?

I should have remembered from the new Corvette owner classes at Spring Mountain that the only modification they made to stock vettes was brake fluid. Stage 2 winglets arrive next week.

 

I'm running what I consider to be a pretty a "mild" alignment, since I travel about 4-5 hours on the street one-way for an HPDE.
Camber:
-2.1F
-1.7R
Toe:
1/16" out front
1/32" in rear

I hate the EBC SR pads, except for their long life. They are extremely noisy, but that will be the case with any track appropriate pad. I just swap between street and track pads.

 

Jim - Sorry, I see you had given me the alignment spec you use already. I have good options to take to Abel on Monday. Appreciate everyone's input!

 

Going to Stage 3 with the tall end caps installed on the front splitter and a center wicker installed in the rear spoiler will create a lot of drag that can be felt on longer straights. I have a 15 Z06 and I can feel the added drag once the car hits 140 mph. A GS with Stage 2 Aero (small end caps on front splitter and no center wicker (basically street aero) can run pretty close to me.

As for alignment Jim Mero (retired GM Corvette Test Driver) says to set the rear camber more negative than the front camber and if you look at the alignment specs in the FSM that is what they show. Here is his recommended setup process:





I have been running my alignment with -2.2 front and -1.9 rear with 0 toe for several years. I am wearing out the inside of the front PSS ZPs while the rears wear evenly. However, the wear on the Pirellis slicks I use on track is different. The fronts tend to wear on the outside edge while the rears wear evenly. The Pirelli's seem to be able to last up to 45 heat cycles although the last 10 heat cycles tend to be a little greasy. I usually flip the front tires on the rim about halfway through the heat cycle range I plan on using them. If you are using nondirectional tires (run-flat excluding Michelin PSS or non-run flat) that is one way you can reduce camber wear on the fronts.

Bill