Bill B 1

I have an 02 Z06 that I am setting up as my dedicated autocross car in SSP with Hoosier A7's. I ran my stock 2014 Z51 last season in the SS class on 200 TW Hankooks but am new to Hoosier tires and am wondering what PSI is a good starting point. Running a 315 30 18 square setup with -3 deg camber front with 1/32 toe out per side and -1.75 rear 1/8 per side toe in. T1 front spring and Strano hollow sway bars front and rear & Yellow Konies.

maniac719

I run my 2004 Z06 on Hoosiers, last season it was R7s, this year its A7s and its all roadcourse work. My alignment is -3.5* of camber up front and -1.75 out back. It works really well, its my understanding that these tires REALLY need a lot of camber.

Good luck.

Bill B 1

Thanks man, but my question was about air pressure for autocross. I know you a road race guy but what starting pressures do you run?

maniac719

On the road course I run 22-24PSI cold. Shooting for 32PSI hot. Any more than that and the tire starts to slide around a lot more than I'd like.

UrbanKnight

For Autox- I shoot for 36 hot on A7's with a 3300# C6, Usually means I start at 28-29#'s cold on hot days, and 30-32 cold on warm days and adjust pressure after 1st and second runs

CHJ In Virginia

Check the Hoosier website for suggested pressures.

EdsC6Z06

I run R7's on road course and Hoosier rep advised a starting pressure of 30-32psi.

strano@stranoparts.com

Or, we can make it easy... 32 front 28 rear. Start there cold, set back after every run. Tire gauges vary a little so keep that in mind. And that's the pressure setup I use on my car as a baseline. Often end up 30 front 28 rear. However you have bigger front wheels and such so it's very possible you end up a little lower.

Here's the trick. Watch tire wear. Run them as low as you can until you start to see a little step or groove form on the shoulder. If you get that, it is too low on pressure. I cannot run my A7 less than 28 rear or I get it, but A6's I could run to 25. Front though I can run A7's down to 30 and be ok, A6's couldn't go under 28.

SouthernSon

R7's start at 30/30 and adjust down to the same after a good run. I usually see them warm up to about 37 or 38 right after the run. At that pressure they slide a lot. Let air back out to 30/30. I don't adjust anymore for the rest of the day. Sometimes, not even the next day. Works for me.

Racingswh

Starting pressure at 22 psi is too low and quite honestly you are risking a failure.

Call Hoosier and ask them if they agree.

GSpeed

We shoot for 29-31 hot, no more, on the road course. we see the same grip in time trials with one lap wonders, so I would say that sam is spot on with hot pressures.

Hot pressure dictates starting pressure.

We see 18/19 psi cold, with nitrogen in the winter time. At the end of the out lap, the tires have grown 2-3 psi, and everything is fine. Remember, youll end up at your hot pressure of 30 in the end.


As for asking what the hoosier rep says to run, go ahead and do that. And then lower the pressure down from their recommendation and watch the laptimes fall.

Racingswh

18-19 lbs cold? I believe you may be putting drivers and others on track with them at risk in the quest for lower lap times.

After doing some research I see who you are and I am surprised you would give this advice. Based on my own experiences and what I have seen with my own eyes I have to respectfully disagree.

This was thought to be caused by cold under-inflation. Fortunately the result was not catastrophic. Others have not been so fortunate. Friends have fallen victim to failures that have caused them to crash. The common denominator has been cold under-inflation and going quickly almost right away.

Possibly a better way is start at higher cold pressures for a couple laps, pit in and air down to what is deemed an appropriate pressure and go back out.

Lastly if a driver can't put down quick times in a car that's moving around a good bit and instead needs to feel like it's on rails it's the driver that needs the work not the setup. We don't have to look any further than Andrew Aquilante to prove this. He regularly puts down quick times and fastest race laps with the car moving all over. Most often times to put down faster lap times drivers simply need to drive faster regardless of car setup or what their tire pressures are.




Steve W. Hoagland

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GSpeed

Hi Steve, Having several cars compete, and win running pressures this low in the winter time, I can say with 100% complete confidence we have never failed a tire from under inflation. we have failed pirellis on the banks of homestead, regardless of pressure.

We have broken belts on cars that were too heavy for the tire (3600lb BMW v8 with 275/35s) and had to run the largest tire we could, but no matter what happened with pressure, the belt still failed. (Hoosier)

We run TA2 cars much lower on pressure. 14-16 cold, 26-27 hot. (Hoosier slick)

The US F4 championship has a minimum pressure of 15 psi.



The biggest problem we have with low starting pressure is the tire spinning on the rim.

Here is a C7 we did some testing on a few days ago. Ambient was 85* If I let this tire cool down to 60, it would be 1.5 psi lower. If I let it cool down to 40, it would be even lower. I dont dictate the start pressure. The hot pressure does.






There is Min and Max per tire, and each column is 1 lap.

Racingswh

Good to hear you aren't having any failures.

I am just going to keep doing what I am doing. Just makes me feel safer after seeing what I have over the years.

I am not very fast and it's very possible that car preparation and tire pressures has a good bit to do with why I am slow in addition to me just being slow naturally .

Last time out my lap times in my street car were only comparable to mid-pack SCCA GT2 lap times but I think my car has a little more power. I might get more serious about car setup and going quicker when my Wife's car is finished.



I bet if I was my friend Steve Katz I would really want those lower pressures. It would make the landings softer.

Olitho

I run those pressures starting on the road course all the time... sometimes even 22 front and 20 rear on 315s and 335s.

Hoosier won't agree. But that is the pressure range most every C5/C6 racer I know runs, including the drivers at the Runoffs.

I have had this discussion with Hoosier a number of times at the Runoffs. I say those pressures might be good for a 3400+ lbs American Sedan car on 275 and limited camber, but on a 3200 lbs Corvette on 315s and 335s I am not so sure. I hate posting here on this disagreement as it sounds brazen and like an "I-know-better-than-Hoosier" but that is my experience. I usually end up around 28-29 hot on both ends, at least by the time I am able to take the temps by myself.

I look forward to some knowledgeable and information based debate on this topic.

Racingswh

I get it.

I have seen too many tire failures. I would never recommend it and would never do it.

Too much risk and for me no reward whatsoever.

Olitho

I have been doing it for more than 10 years. I have seen dozens of other Corvette racers doing it for that whole time. In fact, during the era of the A6s some went out a couple of psi lighter.

You are making your whole assessment from tires failures that are blamed on low tire pressures. Were they Hoosiers? Was there another problem with the tire? How do you know low pressure was the cause? Did they go out even lower than the pressures we are recommending?

Pardon my skepticism, but perhaps you are drawing a conclusion on inadequate understanding and evidence as I have never ever seen any problems with my car, nor have I seen it with some of the fastest, multiple national champion racers. I suggest you have a false fear reinforced by your repetition of the admonition.

Looking at that tire in the photo you posted I can draw two other possibilities based upon the visual evidence, although I will point out I am not a tire pathologist:
1. A hole like that and the damage of the wires is not one I have seen with pressures too low. Damage from low pressure tends to damage the sidewall around all 360 degrees of the tire. That looks like a puncture. In fact, something pulled the wires out, too. I doubt that is low pressure damage.
2. The scrub marks on that tire do pass quite a bit past the shoulder of the tire and that might indicate it was run too low. But I can also suggest that wear was a result of driving/slowing the car after it got the flat. At any rate, it is from being run too low, I can assure you that scrubbing wear is from far lower than 20 PSI... more like 10 PSI....

Warship2k15

Lots of good knowledge.

SouthernSon

Dare I mention the use of a good tire sealer during mounting?

Racingswh

I try to err on the side of caution and keep everyone on the track with us safe. After seeing what I have in the way of failures, doing my own research and listening to Hoosier engineers I am comfortable with my recommendations when I am asked of slightly higher starting tire pressures than what others are using.









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