I just ordered a set of 18" wheels and tires (225/40/18) from tirerack. I saw this warning "XL/RF tires required. Customer must maintain higher tire pressure levels of 42psi for proper load." Is everyone running that high of a PSI on there 18's bigger? I had 18's on my last car and ran them at 38/39 PSI without any problems.

 

those are the stock tires sizes so i would go with what lexus recommends. i think its 38... not sure though check in the door jam.

 

I have an IS250 AWD with stock 17's. The door jam only has PSI for 17" wheels. Who has stock 18's on there RWD drive that can tell me what the door jam says?

 

It would really depend on the load of what is being carried. Manufacturer recommendation isn't always the case.

For instance, my co-worker drives a dodge diesel truck. He does runs under the recommended pressures - the reason being is that because he uses his truck to toe a boat, therefore the extra weight would bring the tire pressures up which is why he lowers it compensate for this. Even if a service shop works on his truck and brings his tire pressures up to the recommended, he will tell them to put it back down because they do not know why it was set that way until after he tells them the reason.

 

not much of a load. its just me in the car most of the time, occasionally a friend or two. nothing in the trunk but the spare tire and some car cleaning supplies.

 

Lexus recommends 35psi front, 38psi rear for all IS250/350 models (RWD, AWD, 16's, 17's, 18's). On the IS-F (19's) they recommend 36psi front and rear.

This should be in your owners manual as well.

Jeff

 

My door panel says 35psi on front and 37psi for rear.......I got 18's

 

for 19's i run 38 and 40

 

35/37 F/R here. g-Spyder 18's with stock tire sizes.

 

Im probably going to run 38/39 PSI all around. Dont want to go to much lower then that

 

Isn't it supposed to be what the tire manufacture recommends? Not the jamb? Those numbers are for the OEM tires.

 

+1. I thought I was the only one lol.

 

Just installed my fsport 19s and the installer said he put 45 in. These are 30 series tires.

Does this sound right.

 

geez, this is an on going arguement, lol. Just came back from getting my 18's put on. (225/40/18). The tire guy told me to go with what lexus recommends on there RWD 18" wheel which is 35psi for tire size 225/40/18. But that seems kinda low to me. IDK, like I said on my last car I ran 38/39 psi with the same tire size. Guess thats what ima go with since I cant find a straight answer

 

I run 40psi in mine.