Tyre Pressure

[thaj0ka]

Hi Peeps,

I dont have an M3, but do have M alloys and so am posting this Q here.....

Does anybody know what the correct tyre pressure is for this alloy?

sizes are:
front : 225/45 ZR17 91W
rear : 235/40 ZR17 90W

Thanks for any help / advice given.

A

[BadGTho]

Hi///

those back tires are pretty slight for that wheel... they must be fairly pulled.

that being said, most run in the 35-40 PSI range. i have experimented all the way up to 45 PSI and have come to think that at 38 PSI the car feels the best.

[thaj0ka]

Originally Posted by BadGTho

Hi///

those back tires are pretty slight for that wheel... they must be fairly pulled.

without meaning to look or sound completely stupid, what do you mean by this?

Also even with the front being a dif size would you say it is ok to have the same pressure?

[BaNzAi RaCeR-91]

Originally Posted by thaj0ka

without meaning to look or sound completely stupid, what do you mean by this?

Also even with the front being a dif size would you say it is ok to have the same pressure?

Your tire size on the back should be 245/40/17. You have 235's on. I could be mistaken but I believe those OEM wheels came 17 x 8.5 in the back. Hence the side wall on your tires look pulled in. Also, tire pressue should be located on the tire it's self.

[BadGTho]

pulled means that the tire you are running is narrower than the wheel, so the sidewalls are "pulled out"

the size of the tire in terms of a few mm in width will not greatly effect the pressure one should run.

door placards should be reviewed in terms of tire pressure, but since your car came with smaller wheels, they mean little.

the tire placard will state the acceptable pressure range, but this means little as one could run those tires on a car that weighs much more or less.

[RacerJames666]

staggered pressures front and rear so the owners manual said....but it may be cause of the staggered wheel size too...i like 36 ish psi...but its all on drivers individual tastes...I wonder what would compel a person to put a 235 in place of 245...

[BadGTho]

Originally Posted by RacerJames666

.I wonder what would compel a person to put a 235 in place of 245...

money. i ran 235s in the back briefly.. they were cheap.

but BMW actually has done this. in 1995 the LTW came with staggered wheels, but 235/40s all around.

[RacerJames666]

thats a trip! Why for I wonder...keep sidewall flex down perhaps

[BadGTho]

Originally Posted by RacerJames666

thats a trip! Why for I wonder...keep sidewall flex down perhaps

i mean in handling terms.. a pulled tire has ZERO sidewall flex.. and i am not sure if that was the reason behind the decision by BMW.. but running 235s f/r certainly aids in downplaying the oversteer that many complain of.. that was probably it.

[iraj38]

35 psi=perfect