tire PSI

[SniperC4007]

What do you all like to run with 18" wheels?

Whats best for 235/40/18 and 265/35/18? 38psi?

[ShapeShifter]

What does it say on your door jamb.

[6cylinder]

I've tried various combinations on my parallels... with 3 rounds of the same tire brand and model, this is my happy place...

I've been going with 35f/40r psi in my 245/40/18f 265/35/18r Contiprocontacts.

Good even wear. :)

I used to go with 32f/43r but was getting inner/outer tread wear on the fronts. The rears were fine. I think a good range on the rears 39 to 42.

I just dropped it on Racing Dynamics Springs so I may have to do some tweaking in the future. After 2k miles... so far so good!
(I'll be doing a long write up on the RD's soon!)



My door placard wasn't thinking about 18's when it was printed! :D

[SniperC4007]

I've tried various combinations on my parallels... with 3 rounds of the same tire brand and model, this is my happy place...

I've been going with 35f/40r psi in my 245/40/18f 265/35/18r Contiprocontacts.

Good even wear. :)

I used to go with 32f/43r but was getting inner/outer tread wear on the fronts. The rears were fine. I think a good range on the rears 39 to 42.

I just dropped it on Racing Dynamics Springs so I may have to do some tweaking in the future. After 2k miles... so far so good!
(I'll be doing a long write up on the RD's soon!)



My door placard wasn't thinking about 18's when it was printed! :D

Exactly. Thanks.

[Aradaiel]

36

[K Fox]

My door placard wasn't thinking about 18's when it was printed! :D

It doesn't matter - not one little bit. The tires size you run dictates the shape of the contact patch, but it's the air pressure that dictates the size of that patch - and since your car weighs the same amount now as it did with the other tire size, you need just as much air.

With that said, there are times/occasions that you can actually safely lower the tire pressure with wider, low profile tires (as OP was asking about). If you run 18's and find your tires wearing the center more than the outsides, you can lower the pressure. Please note - this is actually the only way you can put more rubber on the ground, contrary to what most people think. Wider =/= more rubber, lower air pressure does. Wider allows lower pressure, so it's a multi-step process.

OP - if I remember my tire pressures correctly (it's been several months since I ran my Rondell's), I believe I was running 37F and 38R, both measured hot. You're supposed to measure your tires cold optimally, but as long as you understand how they increase pressure as they heat up, you can set them hot. The equivalent pressures to what I ran measured cold is 33F and 34R. I settled on that due to wear - at those pressures the tires wore perfectly even.;)

Fox (long time tire n@zi)