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[Raine]

Hi, I'm switching my winter tires on my car tomorrow and I was wondering psi I should fill the tire pressure to?

My tires' are 215/45/17 all around. I'm mainly the only occupant in the car w/ no load in the trunk and do about 70% highway traveling.

I also heard there should be a 3 PSI difference between the front and the rear, is this true?

[Evice]

it is written on the front door latch area... read it?

[thez99]

Originally Posted by Evice

it is written on the front door latch area... read it?

Dont patronize him ffs...

Pretty sure that's the obvious.
The numbers BMW gives you are for the stock tires, which with the 135i atleast are staggered and therefore differ by bout 4 front and back.

If its a straight 17" setup you want the same psi's front and back, you give the rears more if they are larger for obvious reasons. Right now my 18's are at 36F and 39-40R. Putting my 17's on soon and theyre 215/50/17 and will be filled to probably 40 all around. Tirerack also gives great suggestions for each tire, most have a max fill of 51 psi

[Raine]

Originally Posted by thez99

Dont patronize him ffs...

Pretty sure that's the obvious.
The numbers BMW gives you are for the stock tires, which with the 135i atleast are staggered and therefore differ by bout 4 front and back.

If its a straight 17" setup you want the same psi's front and back, you give the rears more if they are larger for obvious reasons. Right now my 18's are at 36F and 39-40R. Putting my 17's on soon and theyre 215/50/17 and will be filled to probably 40 all around. Tirerack also gives great suggestions for each tire, most have a max fill of 51 psi

Ok thanks man! Yeah I was asking because I thought the BMW suggestions were for the stock staggered tires.

[Evice]

Originally Posted by thez99

If its a straight 17" setup you want the same psi's front and back

You, sir, have no idea what you are talking about.

[thez99]

Originally Posted by Evice

You, sir, have no idea what you are talking about.

You sure? Why dont you enlighten us all then

[Alow]

Originally Posted by Raine

I also heard there should be a 3 PSI difference between the front and the rear, is this true?

Remember that most manufacturers build understeer into their cars, because its friendlier/easier way to deal with it when you lose control. The tire pressures they recommend are part of that balance they are setting up (plus a different recommendation accounting for extra weight from more adults in the car and trunk items).

I'd go with the recommended pressure from BMW for front and right; unless you are specifically tuning the balance of the car for a specific reason.

Originally Posted by thez99

.....If its a straight 17" setup you want the same psi's front and back, you give the rears more if they are larger for obvious reasons.

I am not 100% sure , but this sounds bogus.. larger wheels/tires may fit more air in them, but the PSI (pressure) would be the same I'd think.

[thez99]

Originally Posted by Alow

Remember that most manufacturers build understeer into their cars, because its friendlier/easier way to deal with it when you lose control. The tire pressures they recommend are part of that balance they are setting up (plus a different recommendation accounting for extra weight from more adults in the car and trunk items).

I'd go with the recommended pressure from BMW for front and right; unless you are specifically tuning the balance of the car for a specific reason.




I am not 100% sure , but this sounds bogus.. larger wheels/tires may fit more air in them, but the PSI (pressure) would be the same I'd think.

With the stock 135i setup for instance, the rear is a wider and lower profile tire than the front, in order for the tire to perform the way it should on a slimmer tire, there needs to be more air in the tire. Yes thicker tires are "bigger" technically, but theyre also not as wide, etc. Normally the amount of air in most average tires is around the same (32-36) but when you get into more performance oriented tires that are lower profile and slimmer, the psi's usually go up just a bit but really the differences arent that crazy, perhaps just a few psi. Hence BMW's oem specs of 36F 39R I believe it is. If they have 18 x 7.5 wheels and same size tires all around, itd be 36psi front and back. Only time I would think there would be an exception would be for load bearing trucks, etc. where theres significantly more weight on the rear tires than the fronts for instance. That is all

[Dackelone]

I use 2.5 Bar (37.5 psi) all around in my 205/50HR17's winters.

[Raine]

I decided to go 38 psi all around and the wheels feel more neutral now but that's probably from going staggered to square.

[zamboni]

Running 40PSI for F&R.