Feel really dumb for asking this but what is recommended tire pressure when you have aftermarket wheels. is it still the same as factory recommendation even though it might be a different size tires? somebody else told me to go 5 psi under tire max pressure. what's correct? any help would be greatly appreciated.

thaks in advance.

 

i have the same question.... 235/40/18's will be here tuesday and i wanted to know the recommmended tire pressure...

 

For a definitive answer check with the tire rack rep. I would start at the factory recomended inflation and experiment by dropping pressure in 2# increments to note changes. You have a window that will allow proper wear between over and under inflation, in which handling and ride quality will very.

 

it doesn't change, you use the factory specific for your load psi for tires.

However, you could adjust it in same format (3 psi less in the rear) to boast a bit more stiffness for your ride or lower the psi to get more grip.

 

I found the factory recommended pressures to make the car too unsettled. I didn't like the way the car turned in.

I run the exact same pressures on my M3 - 35psi front 34psi rear. The car feels much better.

 

Run the factory pressure. You don't change the amount of air the tire/wheel holds, it just changes shape. Instead of being a narrower taller air chamber you now have a wider shorter air chamber. You can add air for handling or ride quality, but I would use the Mitsu pressure (should be 32F 29R) as a base and move up from there per your driving style. Don't drop below the factory pressures and don't exceed the tires max psi

 

I heard bad story about people running 235/40/18 with factory pressure, and when by mistake they fall in a pothole, they damage the rims.

Anyway, so Neal you recommended 32F 29R for 235/40/18.

I'm running 38F 36R, but the ride is bumpy.

will try stock pressure.

 

What's the best tire pressure on stock advans for auto-crossing?

 

I haven't been able to experiment with tire pressures too much, but try 36psi front and 35 psi rear...

a couple ways to find that ideal pressure
- keep the pressure as low as you can such that the tires aren't rolling over
- use a pyrometer that you press into the tire, and adjust pressure and camber such that you get even heat across the width of the tire.

 

Unless I am at an autocross I run 35 all around. I used the wear on the front tire edges after several spirited session on the street to determine what to do up front. The rear tires I did the same but then added a little air up to 35psi to get the balance I wanted on the street for the A046's. With the ContiExtremeContacts, I haven't had the time to figure out the correct pressures. However, the stock pressure seemed to allow too much roll over onto the edge so I have them at 34 all around.

 

I don't autocross. but why wouldn't you run higher pressure in the rear tires to make them slide out a little more? like 30psi Front and 35psi back.

 

When I autocross the tire pressures change relative to the paved surface being run on (concrete, blacktop, or whatever) and the shape of the course. Sometimes I ran with more psi at the rear. I have an 04RS so the front diff helps to rotate the car a little better I guess from talking to the standard Evo guys out there.

I think I ran at 38 psi up front and 36 in the rear on blacktop. And for the one asphalt surface I ran 37 front and 40 rear. I don't have the built up of seat time tire pressure tweeking knowledge with the car to really say more. Plus the A046's are gone now and I don't know what to ride on after the winter.

 

It's impossible to say what the ideal pressure will be, it depends on too many factors (tire type, wheel widths, camber settings, swaybars, driving style, etc., etc.). Assuming you'll be using street tires, a good rule of thumb for autocross is to run 3-5 psi above normal/street pressures. Then you can make adjustments after your first run or two, depending on how far the tire edges are rolling under (you may see people using white shoe polish on their tires to determine how much roll they are getting).

The best way to set tire pressure is by using a pyrometer - a temperature probe that reads temps across the tread, telling you whether to increase or decrease pressures or change camber for ideal/consistent temp profile. The key to using a pyrometer is to have someone waiting/ready to take temps as soon as you cross the finish line and get to a safe place to stop. The longer you wait after a run, the more the temps equalize, the less meaningful the data.

Hope this helps...

 

oh.. This is why I don't autocross. I would have no clue what I was doing. Sounds good though.

 

I run 35 psi all around on stock wheels and tires.