Tire pressure for 235/40/18

[black g50]

Should I go with factory door sticker,or up it a lill?

[goody90q45]

NICO lore says go with 80% of the max pressure stated on the tire sidewall and see where that puts you compared to the door sticker.

[black g50]

40 it is once again thanks........

[maxnix]

What's the load rating? Seems way to skinny. 255/40 18 is the correct size on a 9" wide wheel. 245/45-18 is taller but will work quite well.

[szh]

Should I go with factory door sticker,or up it a lill?

I tend to start at 36 psi (properly cold measurement ... in garage in the morning before sun hits the tire) and then adjust up (never exceeding 40 psi) or down (never going below mftr setting - which is 34 psi as I seem to recall) just 1 psi at a time, till I get reasonably even tread wear across the width using a tread depth tool. Takes a few weeks to get it right, then I stick with that value ... checking every other week to replenish the air as it leaks (this is normal).

On my old Q45's, I typically ended up at 36 psi on almost all the brands of tires I tried, and on my current M45, I tend to run at 35 psi on my current Continental ExtremeContact DWS tires (using a 245/45-18 size).

By the way, I think "up a little" from the mftr recommendation is safer also, since between bi-weekly checks, the pressure can drop a psi or two over time and given weather changes.

As maxnix also asked: what is the load index of the tire you are using? If it isn't at least 95 (and never below 93 for the Q!), I would keep the pressure at least 36 psi or higher to get higher load capacity. If below 94, I would replace them with a 95 or higher load index brand/model, tire with a speed rating of H (preferably higher).

Z

[black g50]

95xl...Rim is 8inches wide.Rims were on 225/40/18,thought that was too narrow so went wider.Wanted 245/45/18 but tire rubbed in front.

[maxnix]

Wrong offset then.

[szh]

Wrong offset then.

Depends on whether he meant the rubbing occurred when the steering wheel was straight.

If yes, then the offset is most likely wrong, as you mentioned.

If the rubbing occurs only when turning, then it is also possible that he has lowered springs (and/or wrong offsets too!) ... too far perhaps ...

Z

[black g50]

Wouldn't have rubbed when straight,only lock to lock ,but boy did I like the look better.Off in 30's cant remember,would've need spacers in front and longer studs.Car is at factory height no mods.