BimmerFest BMW Forum banner
1 - 10 of 10 Posts

· Registered
Joined
·
167 Posts
Discussion Starter · #1 ·
It's come time to change tires for my e90 330i. I noticed that the front and rear tires seem to have the same width but different aspect ratio 225/40R18 front vs 225/35R18 rear. Given the same width the front tires are taller by about 10mm.

Firstly, why is it this way?

Secondly, is it possible to change the rears to a tire that is the same as the front ie both have 225/40? Would it make a huge difference to handling, speedo or dsc?

Many winter tires do not go below 225/40 so was wondering if I have the option to shop around or am I limited to a very small number of winters that come in the Original rear size?

For summer I will stick with oem recommend sizes since they all come in the right sizes.
 

· Flying monkey herder
Joined
·
8,298 Posts
double check the rears they SHOULD be 255/35/18
if not, someone put the wrong tires on.
 

· Registered
Joined
·
167 Posts
Discussion Starter · #3 ·
My mistake. Guess I can't blame previous owner for poor rotation. Can anyone tell me why they are different sizes? I wanted to put the Michelin winter pa4 tires on it this season but they don't come in 255/35/18. Any recomendations?
 

· Pedant and Curmudgeon
Joined
·
6,219 Posts
Most of us recommend a separate set of wheels and tires for winter use. This saves money re-mounting them every year at the cost of a set of wheels (usually around $125 each + tpms). It also gets you a better size for winter use - 255 width gives you a lot of float in snow/slush, essentially hydroplaning. Narrow and smaller snow tires also are much cheaper than wide/big.

I prefer tires of 205/50R17 (on 7" or 7.5" width rims) or 225/45R17 (7.5" or 8"). You can find non-performance tires for these sizes, and PA4 also. You can even go non-RFT: throw one of the fronts into the trunk for a spare. One more advantage to the narrow ones: you can actually fit chains/cables if absolutely needed (you can't on the wide ones).

The staggared sizes are for looks and performance on dry roads with summer performance tires.
 

· Registered
Joined
·
167 Posts
Discussion Starter · #5 ·
So you are suggesting that I take the 18s off and replace with 17 inch rims for the winter with narrower tires than the current 255s. Would a smaller rim not screw up the speedo or dsc. how does the tpms work and what do you have to do about when you change rims and tires?
 

· Registered
Joined
·
167 Posts
Discussion Starter · #6 ·
Would I be able to fit a 225/40/18 on a rim that currently hold 255/35/18s ? Are the stock rims the same size front and back width wise with the staggered set up or are they different.
 

· Pedant and Curmudgeon
Joined
·
6,219 Posts
So you are suggesting that I take the 18s off and replace with 17 inch rims for the winter with narrower tires than the current 255s. Would a smaller rim not screw up the speedo or dsc. how does the tpms work and what do you have to do about when you change rims and tires?
Note that your 225/40R18 front tires have almost the exact same exterior diameter as your rear 255/35R18. A 205/50R17 tire on a 17x7.5" rim have almost the exact same overall diameter. Tirerack displays the diameter (or circumference, I can't remember off-hand.)

You need another set of tpms (see tirerack for price) on each rim. If you don't, the tire pressure display and ding will be present always.
 

· Flying monkey herder
Joined
·
8,298 Posts
They are different widths, there are limits and you can't do that for those rims.
you actually can. the 18" rims are 18X8 and 18X8.5
225/40/18 fits the spec for both.
interestingly enough, 8.5 is the absolute min width for a 255/35/18
 

· Registered
Joined
·
987 Posts
slightly taller tires for same staggered fitment

Firstly, i live in south texas so no winter setup necessary. I had been researching switching over to 19" 359 wheels. Conclusion i have come to is the height of sidewall is even shorter than the same setup OP is discussing. this is even thought the 19's would have a larger diameter.

So, I'm wondering about going to slightly taller tires and keeping the 18" 193s i currently have. Yes, i know the handling will fall off a little due to sidewall flex but the pot holes around here are terrible and trying to get a better ride. OEM front is 225/40R18. considering comething like a 235/45R18. there is a really long thread over on E90 post where the guys are fitting 19's onto 335i and 328i. I'm looking at the diameters that they are ending up with but then translating to the 18" equivalent diameter.

They are running 235/35R19 front and 265/30R19 rears. I like the chunkiness of Michelin Pilot super sports (go flats,not run flats) and also Bridgestone RE-11s. I do not want to fork out the 2 grand to get those wheels though. some are able to run 275/30R19 but need a generous fender roll to do this. Others even with roll are still rubbing and pretty upset. One guy had about $3700 investment for the staggered size 359s and Michelin PS2s only to be defeated by rubbing. He ended up selling it all at a loss. the rubbing seems to be happening if your car is an LCI model.
 
1 - 10 of 10 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top