Whats the optimal psi rating for 18 inch wheels 235/40/18

 

It's dependent on the tire, but typically 10lbs less than the max rating.

What exactly are you trying to achieve when you're asking for the "optimum" tire pressure?

The more air in the tire, the better the gas mileage
The less air in the tire, the more comfortable the ride quality is.

What is optimum for one person may not be optimum for someone else.

 

So I guess the recommended psi on the door means nothing really.

 

That's the recommended pressure based on the original OEM rim/tire setup. Once you start changing that then it becomes irrelevant and personal preference as Wizard stated takes precedent.

 

34si-36si I would think....look up your tire manufacture specifications!

 

Solid, the max psi on the tire is 51psi

 

what?? i have 17 inch wheels and my psi is 38 i think. i can't believe that 18's are 51 psi

 

MAX PSI is 51, he said...which means he's fill to like 41 or so.

 

i figured, tired i guess

 

The 255/40/18s on the wife's Lexus also have a 51 psi max.

I think that as you go into the lower profile tires, the psi goes up so you don't bend a rim every time you hit a pothole. You don't have much space for flexing. I hit a pothole with the car last fall and it cost $600 to replace the tire and get the rim repaired.

 

I think I'll try 38 first, I'm glad I have road hazard protection and a new wheel would only cost $125 for a remanufactured one(murano wheels)

 

I like 34 front / 36 rear on 18" rims on a gen 5

 

Silly Canadians...using PSI. That's OUR measurement! use your own Metric one, ya commie!

 

Not our fault you Americans so stubborn!

*cough cough* metric vs imperial

 

Hmmm I thought Imperial was a car that Chrysler quit making back in the 1980s.

 

 

I found that 34 to 36 front and 32 to 34 rear works well with mine.

My choice isn't necessarily based on straight math (i.e. max PSI-10) ... it's based on evenness of tire wear.

 

38 all around with nitrogen and yoko avid invigors here

 

Whats the OE tire size?
If OE is P205/65R15: OE holds 1,279 lbs at 29 PSI
If OE is P215/60R15: OE holds 1,290 lbs at 29 PSI

Therefore, if you new tire size is 235/40R18 95 Load Index, 34 PSI will carry 1,284 lbs in each tire position, therefore it is equivalent to what your OE tire was meant to carry.

Keep in mind this is cold inflation pressures, and since you have a lower profile tire, it is recommended you keep a good eye on your tire psi since they are easier to damage and lower psi's.

 

oe tire is P215/55/16