When drag racing my 240SX, what tire pressure should I use? 25?

What about when autocrossing? 40?

Tire size is 205/60r15, Michelin MXV4 Energy

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-When you are dragging on street tires, you should run enough tire presure to keep the tire from shifting on the rim. There is no magic number here, as the different tires and rims will yield different results. But, to help figure what psi you should be running, mark a vertical line on your tire and rim with white shoe polish. Deflate your tire until the side wall *starts* buldging at the bottom. Now, you have to do a few hard launches and see if the tire shifted on the rim. If it did, add more pressure. If it didn't, you can lower the pressure a little more. Although, on a street tire, I wouldn't go lower 20psi. Simply because the tire was not design for dragging.

-For slicks, you can pretty much use the same testing procedure, but you can generally go much lower in psi. I use MT ET 22x8" slicks on my car, and depending on what the temp is, I usually run between 15-19psi. Slicks are design to stay put on your rim, so you can play with the pressure more and increase your contact patch.

What tire pressure should I use when Autocrossing?

-When autocrossing, you are trying to keep sidewall flex to a min. So the testing procedure for this is: mark the very outer edges of your tires with white shoe polish. In flate your tires to about 36-40psi, depending on what tires you are running. Make sure the side looks "flat", then take it around the course! When you come back from your run, check your markings to see if they rubbed off. If your markings are gone halfway down the sidewall, you know you have too little pressure. If your markings are still there and not affected, you can decrease your pressure until it starts to rub a little polish off the edges. Then your set!

Mike Yuan

What tire pressure should I run?

See this site to calculate the best tire pressure for your car based on weight distribution and tire size:

Based on their recommended pressures, I'm running 42 front and 37 rear on 205/60R15's on my 1991 hatchback.

David Huguet
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