KCblues

I will be a 54 year old novice at Autocross this year in A Stock.

My car is a very low mileage, 2004 Z06 that is fully stock except for air filter, brake pads, fluids and tires. It’s in amazing condition, 5,800 miles and feels like a time capsule.

I plan to drive the car to local and regional events within about 4 hours of Kansas City. It’s also going to be a fair-weather daily driver. With those considerations I plan to leave the alignment at the stock settings this season.

The first local event is April 13, then I’m doing a 3-day EVO course in Salina April 17-18-19, nearby events in Topeka on April 25-26, and a Starting Line school in Lincoln May 2-3. Will be a busy month!

The car has Continental Extreme Contact DW tires with about 3,500 miles on them. I have been researching tires a lot and have about decided on a set Hankooks for this summer, but the rears won’t be available to ship until the end of April and by then I’ll have a lot of runs on the existing tires. Have a couple newb tire questions I haven't found the answers to yet:

1. Where should I start with tire pressures on the Continentals? I know the conventional guidance is 5 psi over nominal but suspect there is better advice for the C5 Z06 on these tires.

2. The 3-day course in Salina has a total of 72 runs. How much of my tires should I expect that to use up?

Thanks!

froggy47

Not sure on pressure for street tires, I use a6/a7, someone will respond.

I would go a little more than bone stock alignment, but that's your call.

72 runs is over a season's wear and I don't know the surface you will be on, or the Conti tires, but I would not expect much left of the tires.


2 cents

CONE RACER

The Conti is a relatively square edged profile, which means it will wear the outside edge very fast if you run it underinflated. This will be compounded when running "stock" alignment settings (due to little negative camber).

5 psi over is probably a reasonable starting point. The Conti's are marked on the sidewall with a series of circles called TPI's (Tuned Performance Indicators). Check the scrubbing on the tread pattern after your first run to make sure you aren't rolling the sidewall past the TPI mark. Don't confuse the other series of circles with the TPI markers - they are clearly marked TPI. If you do scrub past the marker, add a little pressure to keep the sidewall a little stiffer. Lower the pressure if you didn't reach the TPI. Don't forget to check your pressure after each of the first few runs and account for any pressure increase due to heating. A piece of sidewalk chalk to mark the sidewall can be helpful if you have gone past the TPI mark and are having a hard time distinguishing scuff marks from runs 2+.

Fronts will wear faster than rears, especially the edges. You may end up running an extra psi or two in the front. If that throws the balance of the car off (too much push), you can add a bit of pressure to the rear to loosen it up, but you'll have a bit less overall grip.

If you can keep the outside edges on the tires, 72 runs will use a lot of the tire.

AX is a ton of fun. Enjoy the challenges. The best adjustment you can make is to constantly work on " tightening up the loose nut behind the wheel"!

froggy47

I should clarify, those may be 72 "short" runs depending on how the course is set. So maybe you won't wipe out the tires in 72, still it's a lot.

KCblues

Thanks Froggy & Cone Racer,

I've been giving this a lot of thought because I need to complete the 3-day EVO, get home, and then on to next events.

A friend is willing to give me a set of standard C5 wheels for free that were on his 99 FRC. And there is a set of SSR Competition lightweight wheels in the stock Z06 widths for $800.

What tires would you guys recommend for a 1st year novice to learn on that would be likely to get me through, lets say 80 runs?

LateBreak

Hi KC, I run Dunlop Direzza's on my C5 for endurance racing. 255/40-17's will fit your front wheels and 275/35-18's will fit the rears. I get about 16 hours from a set of tires on my car, so I would bet that they'll last 80 runs for you depending on how much you're spinning them on the auto-x course. They're grippy tires but very forgiving and easy to drive at their limit.

froggy47

I am a big advocate of having 2 (or more) sets of rims, one for your high(er) mileage (harder) street tires and one for your more sticky autox/track ones.

Lot's of debate on the current 200tw autox tires. I don't use them so will hold my opinion.

For streets, I say spend less money on them as you just cruise around / commute on them.

2 cents

Sox-Fan

I did the two day evo school not very long ago. single driver on day one, two drivers for day two. The course they set out for us was short, 23 to 26 seconds per run. 24 and 26 runs per driver per day. FWIW, upfront I'll say that it was very cold. It started in the 40's and never made it over 53 or 54 degrees.

Didn't see as much wear in the tires as I planned. First off, we were not running 10/10ths for a lot of the day. We were learning how to drive, not winning trophies, and pushing as though every run counted. I'd guess that wear was a lot less than it could have been because of that. Secondly, as we got more and more familiar with the courses and got better as drivers the stress on the car became less and less. Much less sliding, much less tires abuse.

I came into it with a set of tires that had 4 autocrosses on them and expecting to need tires when I left. I left there having only added maybe the equivalent of 2 full autocrosses on them.

Evo school isn't about pushing the car hard. I never even had to bleed down my tires on either day.

That was my experience anyway.

jking32

Hi KCblues,

Looks like we will be running together, as I am in the Kansas City Region and will be there. I am also running the Hankooks RS-3 V2's on my 04 Z06, I had them mounted yesterday. I ordered the front tires from Tire Rack, but as you said, they show out of stock until after our first 3 events. I went to one of this sites supporting vendors at speedfreaksusa. Matt has 285/30/18's in stock or he did when he sold me a set a couple of weeks ago.

https://www.corvetteforum.com/forums...estions-7.html

Look about half way down the page for his post. They are actually cheaper than Tire Rack as he ships for free.

KCblues

Thanks much to everyone for your very helpful comments and advice.

I will look into the Dunlop Direzza's and sent a message to Matt to see if they still have the tires I was looking for.

I'm gonna go look at a local set of SSR Competition forged aluminum wheels tomorrow morning. Makes sense to have an extra set of rims.

Understanding more about the EVO school really helps my planning. I was worried about possibly getting stranded in Salina with cords showing.

jking32, thanks for the tip on sourcing the Hankooks amd look forward to running with you this year. I didn't get registered for the test and tune before all the slots filled up but will see you on the 12th.

jking32

I hope you find the tires you want. Good luck and we'll see you on the 12th.

Xian

Piggybacking onto this; I'm running the Z2 Star Spec in this size on my AS C5Z. Currently at 40 full runs, ~26 test course runs, and maybe 700 street miles. I've used roughly 2/32nds on the rears and 1/32nd on the fronts.

I haven't run the DW's but I've got to think you'll be just fine from a wear standpoint unless you manage to chunk a treadblock or something equally odd/unlikely.

Christian

Solofast

You really should get an alignment that is a bit more aggressive than the stock settings.

The reason is that you'll eat your tires on the outside edges and they will end up corded and you won't be able to use them on the street.

I would go to a local alignment shop and put in at least -1.5 degrees in the front and about a half a degree less in the back and then you won't destroy the tires. You'll learn more and enjoy the event more if you aren't worried about tires.

Don't worry about street tread wear. Toe out is what eats tires, camber not so much. I would suggest about 1/8 of an inch of total toe in all around and that will be fine for what you are doing.

Lastly, mark the alignment eccentrics with a stripe of nail polish so that if they slip you can reset them back to where they were and you won't have to go back to the alignment shop and get it fixed WHEN they slip.

KCblues

Thanks for the advice Solofast!

Just to confirm, you suggest a little toe IN both front and rear? Asking because from what I've been reading most suggest a little to no toe Out at the front, and a little to no toe In at the rear.

Solofast

For track and autocross duty you want some toe out, but for a beginner it really doesn't matter that much. The only difference is that the car turns in a bit better.

Toe out on the street when coupled with negative camber can eat front tires. If you are so inclined, mark the front tire rods with a similar stripe of nail polish or paint and have the alignment shop set the front toe to 1/8 of an inch of toe in.

When you get to where you are running the car, or even the night before, jack up the car and turn the tie rods one full turn towards toe out for your autocross day. When you get done (either at the track or when you get home), loosen up the tie rods and turn them back one turn till the stripe on the tie rod end lines up with the one on the rod.

It only takes about 5 minutes to do each side (or less if you are changing tires) and that will give you a more aggressive turn in and you won't eat your tires in short order.

That's the way to have it both ways, decent tire life and good turn in at the track or autocross course. If you aren't willing to do that, then you'll give up a bit of turn in, but you won't destroy your tires in 7,000 miles, or you'll eat tires and tramline over ruts with the toe out on the street.. Pick your poison.

KCblues

Thank you kindly for the generous and detailed advice !

63Corvette

I recommend NT-05s if you are on a budget, and Michelin PSS if you are not. For alignment specs, be advised that TOE is probably the most important setting for tire wear. You can be pretty aggressive with your camber and caster settings as long as you keep your front toe at ZERO "0".
Since you drive very few miles per year, your tires will last a long time.