rim size/tire pressure

[inkegra]

ive heard that its better to buy small rims (15s or so)and tires because theyre easier to turn but is that true?also is that the best for autocross?does it give a big enough foot print?also what about tire pressure to autocross? is it better to have low pressure to get the maximum contact patch or does taht slow you down too much?

[CSMsi311]

wheel diameter does not affect the footprint. The footprint is affected by the width of your tire (closely related to wheel width) and your tire pressure.

smaller wheels are lighter than larger wheels. therefore you save unsprung weight which is always important.

I know you can change the attitude of the car some by adjusting the front and rear tire pressures. Too low of pressure will cause the edges of the tire to be hotter than the center. Too high causes the center to be hotter. i don't know if there is any magic number, as it is affected by many other variables. Ideally you want the tire temperature to be even across the width of the tire. Therefore, you know the load is evenly distributed across the tire.

[inkegra]

so is it safe to say the smaller the tire/rim the better?

[djet820]

Rims and tires are not the same thing. Wheels/Rims are what I guess "holds" your tires. Just get wider tires is what I think he was trying to say and make sure the heat is evenly distributed across the width of the tire.

[CSMsi311]

i guess you could say there is a trade off between wheel weight and sidewall flex. In general the taller the sidewall of the tire, the more it will flex and give a "squirmy" feel.

Maybe some people with actual autocross experience will chime in.

Jason

[Weston-work]

15x6.5 is a good size for most Hondas. 15x7.0 is better, but harder to find.

As for the sidewall flex, generally the larger the rim, the less sidewall there is, therefore you have less sidewall flex. But the real solution is to just get tires that have stiff sidewalls. Decent performance tires will have this feature. The Falken Azenis are steel reinforced.

The pressure will depend on the rim, tire, car's weight, car's suspension, and driver's preference. I run my 205/50-15 Azenis at around 34 psi on my Integra and it feels really good to me, a few PSI higher and it feels really sloppy. But there are some people who run them at higher pressures with great results. Just don't run them so low that they're underinflated (that risks a blow out or them seperating from the rim), and not high enough to be close to the tire's maximum PSI. Remember that tire pressures do increase as heat increases, and even if it's cold outside, your tires will warm up when you drive on them.