I'm prepping my car for an event and i just realized that my tires on the passenger side (front & rear) are newer having been replaced because of a pothole.. Passenger side @ 9/32 vs. Driver side @ 6/32. Anyone see any issues keeping it this way, or should I swap the Driver side too?

Tires are P4S and track is Laguna Seca with alot of lefts. Turn#9 after the corkscrew is a pretty fast left hand turn with a slope, and probably the one that's getting me worried about the tire difference.

 

Are you racing or HPDE? For an HPDE it won't matter at all.

 

Hpde. Should I at least try dropping the tire pressure on the newer set?

 

Also, my main concern wasn't laptimes or anything like that. It was just more about safety (dry or wet).

 

No. Waste of time and effort, just set them all the same.

Only a very experienced track driver will feel the difference in those tires and only at full tilt. If this is something you do occasionally, the most important thing is to not be stupid. Drive within your limits. The car will more than likely be far more capable than you are, and even if you've got some experience, you're going to spend the first couple of sessions just figuring out what the car likes and doesn't like. The tire difference won't amount to anything you'll notice because your senses will be overloaded anyway. If it were a race or if you had considerable track experience, I'd still say you can get away with it, but you won't be pulling the last few percent out of the car with a tiny bit of stagger you'll have.

If anything, having the passenger side wheels slightly larger will help the car turn left. In dirt track racing, we put some pretty considerable stagger left/right to help the car drift and turn left. Those cars are actually pretty difficult to drive straight. Lots of tire scrub fighting the driver down the straights.

 

Quick math...9/32 - 6/32 is 3/32" difference. If you're running stock size tires, they're ~26.1in diameter, so 3/32 * 2 (because diameter) is a 0.7% difference. Yea, you and your car are going to be hard pressed to know the difference. If you're super bored, at 120mph, your tire is rotating at ~1546rpm, and the difference would be ~11rpm between the two.

It's less concern regard size difference than heat cycles the tire has seen. Which that varies based on usage and the particular make of tire. So I cannot definitively provide an answer from behind a keyboard, but I highly doubt they're cycled out at the tread level. It's more of a discussion point as you get to doing this more frequently and go through more tires.

With that said, I would have the tires in the orientation you describe as you will wear the passenger side more at Laguna. So you can finish the day with even'ish wear. Go out there and have fun. Keep an eye on tire pressures. I'd probably shoot for 34~36psi with those tires when hot coming off the track. I'd start them at 27'ish for your first session of the day and check them after every session (which you'll need to bring them down) to that target area. At the end of the day, you'll need to add air back in. If you're driving it home, and you've found by your afternoon sessions that you let out about another ~4psi per corner (beyond the initial setting of 27 cold), jack up to 40'ish before heading out. You'll find they will dip back down to ~35 by the time you get home.