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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > Wheels and Tires > 18" Winter F30 ET37
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      10-17-2013, 11:12 AM   #1
sroghen
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18" Winter F30 ET37

25/40/18 18x8.5 x120 +37 offset

Someone plz confirm whether the above is a good fitment all around for 2013 F30 320i x-drive?

Let know asap as Im about to pull the trigger

Thanks
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      10-17-2013, 12:00 PM   #2
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13mm LESS clearance on the strut side, and the outside edge of the wheel will EXTEND an extra 13mm

new wheels - 3% too small in overall diameter and speedo will be 3km/hr lower than it really is.

This I would consider to be in the border line area, namely, the lesser front strut clearance. Therefore, if you can do a test fit before buying, then it's better.
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      10-17-2013, 01:02 PM   #3
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Detailed info much appreciated.

Thanks
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      10-17-2013, 01:32 PM   #4
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Quote:
Originally Posted by sroghen View Post
25/40/18 18x8.5 x120 +37 offset
Not sure if you mean 225/40-18 or 255/40-18?

255/40-18 is OEM size for F30, 225/40-18 will be 3% short.

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13mm LESS clearance on the strut side, and the outside edge of the wheel will EXTEND an extra 13mm.
I don't agree.

8.5x18" ET37 will have 9mm less inner clearance and extend 3mm on the outside compared to OEM 8x18" ET34.

If compared with staggered 18" M Sport, the rear will looks like a 10mm spacer on M Sport 400 wheels.
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      10-17-2013, 02:15 PM   #5
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the guy has a 320xdrive. he is going +1 . it comes in 17*7.5 et37 stock.
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      10-17-2013, 02:40 PM   #6
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Sorry, my bad!

My calculations was based on OEM 18" wheels.
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      10-17-2013, 11:16 PM   #7
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sorry i meant: 225/40/18

stock on my 320xdrive car came with 225/45/18
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      10-18-2013, 12:40 AM   #8
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Then my calculations are correct after all!

I still don't think 225/40-18 is an optimal choice, they are 3% shorter than OEM and will look a bit stretched on 8.5" wide wheels.

However wider tires can give problems with front strut clearance.
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      10-18-2013, 07:20 AM   #9
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Damn, I checked with the seller the wheels are 18x8
Does it make a difference in the calculations above?

(Also, how do you guys come up with the numbers? Is there a chart out there that explains all this?)
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      10-18-2013, 07:54 AM   #10
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http://1010tires.com/Tools/Wheel-Offset-Calculator

http://1010tires.com/Tools/Tire-Size-Calculator

http://www.willtheyfit.com/
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      10-18-2013, 09:00 AM   #11
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Thanks it is very useful.

Besides the speedometer issue, it looks like it may fit fine. Am I correct?
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      10-18-2013, 10:05 AM   #12
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Correct!

The wheels will be fine since you have confirmed that they are 8x18", the only difference compared to OEM is 3mm in offset. That will be hard to notice.

225mm wide tires will fit better on 8" wheels aswell!

There will be a speedometer error and the 40% tire profile (compared to OEM 45%) will increase wheel gap slightly.
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      10-18-2013, 02:02 PM   #13
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Quote:
Originally Posted by ss0803 View Post
Correct!

The wheels will be fine since you have confirmed that they are 8x18", the only difference compared to OEM is 3mm in offset. That will be hard to notice.

225mm wide tires will fit better on 8" wheels aswell!

There will be a speedometer error and the 40% tire profile (compared to OEM 45%) will increase wheel gap slightly.
Great stuff.
For winter tires, is it anything to worry about the minus 5% tire profile in terms of stability and security. I dont want to compromise security because of child in the car.

Thanks
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      10-18-2013, 03:41 PM   #14
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Generally I would say that higher sidewall is better for a winter tire!

But the difference isn't that large:
225/40-18, sidewall hight 90mm
225/45-18, sidewall hight 101mm

You find some good infomation about winter tires here: tirerack.com
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