First auto-x next sat. Tire pressure questions

[2002maniac]

Where should I start off with tire pressures? suspension is stock (not for long) with a m3 rear swaybar. Thanks!

[Mystikal]

Whatever you are used to on the street, as in what your reflexes are accustomed to. Then change as you see fit.

[KenC]

make sure it's not too high or you're going to understeer hardcore

[Schniddy]

you live on antarctica :?:

[cgregory]

Actually, in auto-x you want high tire pressures to keep the sidewalls from rolling. I usually start off with 40f/40r cold. After the first heat I check again and adjust them.

Bring some shoe polish and use that to check how far your tires are rolling. If they roll too much, add pressure.

Also, if you understeer, increase front tire pressure or lower rear tire pressure. If you oversteer, increase rear tire pressure or decrease front. This seems completely opposite to what you would think, but it works.

[tommyboy]

^winner
I use 38f/38r

[2002maniac]

Awesome, thanks for the help!!

you live on antarctica :?:

Yeah dude, we are in summer right now though...

[Mystikal]

I wholeheartedly disagree with the 40psi statement. If you are new to the entire sport and all you're trying to do is not get lost or otherwise draw attention to yourself, make the car as familiar as you can and learn the lines first. You shouldn't be pushing hard enough to exceed sidewall strength at your first event.

[Charlie]

Is it me, or did he leave out what sort of car and what sort of tires he was running?

I mean, those are the two most relavant points right there.

Whatever you run on the street plus a few PSI to prevent rollover.

-Charlie

[tommyboy]

I wholeheartedly disagree with the 40psi statement. If you are new to the entire sport and all you're trying to do is not get lost or otherwise draw attention to yourself, make the car as familiar as you can and learn the lines first. You shouldn't be pushing hard enough to exceed sidewall strength at your first event.

You disagree with what, the fact that he uses 40psi? He didn't necessarily recommend it, just stating what he uses.

[Mystikal]

I wholeheartedly disagree with the 40psi statement. If you are new to the entire sport and all you're trying to do is not get lost or otherwise draw attention to yourself, make the car as familiar as you can and learn the lines first. You shouldn't be pushing hard enough to exceed sidewall strength at your first event.

You disagree with what, the fact that he uses 40psi? He didn't necessarily recommend it, just stating what he uses.

Fair enough, but you know the guy was planning to run that from his response, or at least a very strong chance. If he drives around all day at the BMW-spec 29/32, that could be a shocking transition.

[nando]

yeah, but trying to drive fast with low tire pressures can also destroy his tires, chunking off the sidewalls etc. plus you can always go lower..

[cgregory]

yeah, but trying to drive fast with low tire pressures can also destroy his tires, chunking off the sidewalls etc. plus you can always go lower..

yeah..I usually start at 40psi and then lower the pressure to compensate for the tires heating up. I start with 40 so I don't have to lug a compressor along.

Usually, when I get back home afterwards they are at 37F 38R cold before I lower them back down to normal.

[mgold]

yeah, but trying to drive fast with low tire pressures can also destroy his tires, chunking off the sidewalls etc. plus you can always go lower..

yeah..I usually start at 40psi and then lower the pressure to compensate for the tires heating up. I start with 40 so I don't have to lug a compressor along.

Usually, when I get back home afterwards they are at 37F 38R cold before I lower them back down to normal.

Same here.

[oh2fly]

I will try to explain the shoe polish trick a little bit. Use white in a squeeze bottle. You only need a little bit in 3 or 4 spots on each tire. The idea is to place a half dollar size spot that is on the sidewall but also extends a little on to the tread. Look closely at the sidewalls where the tire contact patch stops contacting the sidewall. Ideally you want the sidewall to stay covered with the polish and all of the tread to be wiped clean by the asphalt. Too far down the sidewall, add more air. Not using all the tread area, lower the pressure. I suggest only making 2 psi changes whatever you are doing and look again after adding a new spot of polish and making the next run. Above all, have fun!