So I'm going to an autocross event. I was thinking of pumping my tires (19" oem) from the recommended 35 to 40-45 on the morning before I head to the event so I won't have to do it when I'm there. Any harm in this? The drive is about an hour away.

Only down side to having that much tire pressure, they might explode. I've attended several autocross events/mountain road runs with SLICK, never raised the tire pressure because I wanted my Michelin's to grip....Gary

Tires usually have a max psi rating on the sidewall, you'll be fine as long as you don't exceed that. I always over-inflate my tires when taking a trip, it lowers rolling resistance and increased mpg's.

Doesn't the tire pressure go up a little on its own when you drive for a while? I wouldn't over inflate them too much, 40psi you should be ok with though.

As you drive the air in the tire heat up, so as you drive they do inflate a bit more. I have my front low-profiles at 37, and my rears at 40, and I drove 2 hours to LA with them, everything was fine.

Before I track my car I deflate the tire some. They can get pretty hot, normally I use the OEM's recommended 35psi cold F&R for around town, but lower it to about 30F 28R before I get on track.

i hear in autocrossing, you dont really heat up the inside of the tire because of the low speeds and short times. i dont think you need to worry too much about the tire pressure changing in autocross. you can bring a gauge and check after every run to be sure.

45 sounds kind of high though. you should go look around and see what people recommend for your tire and weight.

As long as you don't exceed the max psi listed on the sidewall, or take them lower than Infiniti recommends, you'll be fine. No harm in presetting them the night before. Inflate them cold btw.

So I did 45 front and 38 rear, which felt better than last time where I did 40 all around.

By the way, the vredesteins ultracs are kinda crappy for autocrossing. I think they belong solely on the street.

agree on the sessantas comment, great tire for street, not so much for the autocross. As far as the inflation, if you inflate with nitrogen, the pressure stays constant compared to oxygen. oxygen once it heats up, does expand like most gases. like neal said, on oxygen, try to inflate when cold.