I'm doing a DE event at Mid-Ohio next Thursday and Friday, and I'm looking for tire pressure recommendations. I'll be running with the stock F1s, so any thoughts? (And no, "Buy some other tires" doesn't count. )
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30 front and rear to start. After your first session check the little wear triangles on the tire shoulders, if the scuffing is past the tip of the triangle add a couple pounds. If the scuffing isn't touching them let out a pound. Alternatively you can use some chalk and mark the tires with a vertical line from the tread to the sidewall, if the chalk wears away where the tread meets the sidewall, add a couple pounds of air. Repeat this process for either method until you are just scuffing the tires at the tips of the wear indicators but not past them.
What he said ^, but I have started my events with 32 cold psi in my tires and tires wore right to the place they should have, just as another starting point.
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Tom,
Remember also that at Mid-Ohio the ambient temp can be 40 in the early morning and 70 in the afternoon. That temp change will add about 3 psi to the tires.
Then Friday morning you might have to readjust if you dropped some pressure on Thursday.
If you still have stock brakes (pads, calipers, and rotors) be extremely careful in the back straight. With your new found power you could see 155 mph there. Stock brakes or anything close to them will not work for very long at that speed.
Hope the weather is great and all goes well.
Dave
I did a DE event at Mid-Ohio a few weeks ago. I ran 34psi and tires were wearing right on the mark. However, this was my first DE event, so I wasn't running anywhere near as fast as you probably will. Also, the weather should be warmer for your DE event.
I wish I could make this event. Have a good time .
What he said ^, but I have started my events with 32 cold psi in my tires and tires wore right to the place they should have, just as another starting point.
That is exactly what I was running a Ponoco last weekend, worked well. The biggest problem was I had way too much fun and need to do more of these events. Going to need tires before the summer is done and will be seriously considering different rims and tires for next year.
Any suggestions as to rims that I should be keeping an eye out for?
Thanks for all the great advice guys! I have a good starting point now.
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If you still have stock brakes (pads, calipers, and rotors) be extremely careful in the back straight. With your new found power you could see 155 mph there. Stock brakes or anything close to them will not work for very long at that speed.
I was thinking the same thing Dave. I've done one other event at Mid-Ohio, so I'll take it easy back there. I hit 135 when my car was mostly stock.
Well I dunno it depends on what "cold" means. After my drive up to VIR from my parents house I put the tires all at 31. The car felt like ass the first session and was squaking all over the place. After talking to a Z06 T1 racer I put them at 36 and kept them blow 40 thruoghout the day and the car handled amazingly. He said that 38ish is the "zone" for hot temps. Anyone agree?
I'm guessing that my drive up from Gboro heated the tires above "cold" I guess if I was checking the air in the morning before I ever left maybe 32/30 would work, but 32/30 on the track sucked.
Oh yeah for auto-x I go directly to 38 psi front 36 psi rear.
My interpretation of "cold" is sitting at least 3-4 hours, preferably overnight. Anyhow, I believe the correct way to measure pressure is hot, i.e. within a few minutes of coming into the pits. Cold pressures just give you a good starting point.
Not within a few minutes, but within a few seconds. The quicker the better. Ideally it's best to use a tire pyrometer and take three measurements across the tire: on each shoulder and the tread center. The temps should all be within ten degrees of one another.
This is the best way to determine if the alignment and tire pressures are working well. For instance, if the inside shoulder temp is much higher than the other two temps then reduce negative camber. If the outside shoulder is much hotter then more negative camber is needed and/or reducing understeer, as the car is pushing. Toe-in and toe-out out can also effect these temps. If the center tread temp is high then lower the tire pressure, if low, increase it.
30 front and rear to start. After your first session check the little wear triangles on the tire shoulders, if the scuffing is past the tip of the triangle add a couple pounds. If the scuffing isn't touching them let out a pound. Alternatively you can use some chalk and mark the tires with a vertical line from the tread to the sidewall, if the chalk wears away where the tread meets the sidewall, add a couple pounds of air. Repeat this process for either method until you are just scuffing the tires at the tips of the wear indicators but not past them.
This is what I start with in the am before I drive 90 miles to the track. I usually end up dropping a lb out after each of the first few sessions. Then it comes in real nice.
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I have a good starting point now. 
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