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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Wheels and Tires Forum Sponsored by The Tire Rack > Tired of 18's, want to downgrade to 17



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Wheel offset calculator courtesy of BimmerPost.com. You may use this calculator to calculate what tire sizes you might need if you upgrade your tires, or what wheel sizes/offsets are compatible with your car.
    Current Wheel Width  inches             Current Wheel Offset  mm.
         New Wheel Width  inches                  New Wheel Offset  mm.
 
TIRE WIDTH
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ORIGINAL TIRES
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NEW TIRES
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Based on your stock wheel setup, your new wheel will have:
Original Tires Diameter (in.)
      New Tires Diameter (in.)
  Difference in diameter (in.)
           Percent Difference %
                     
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      12-11-2013, 05:07 PM   #1
Bbox
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Tired of 18's, want to downgrade to 17

Right now I have a 2006 330 with the Style 162 staggered 18" rims. But at least 2 or 3 of them are bent. So I want to downgrade to 17" rims, specifically the Style 286 from a newer E90.

Old --------------------> New
Front 225/40-18 -----> 225/45-17
Rears 255/35-18 -----> 255/40-17

The rears would have the same rolling diameter, but the fronts would be a tenth of an inch smaller in diameter. Would this screw up the FTM tire monitors? (I have FTM, not TPMS).

Also, the rims are the same width (8/8.5 staggered), but the new ones have different offset (34/39 instead of 34/37). This means the rears would be pushed in by 2mm. Would I even notice this?

Last edited by Bbox; 12-11-2013 at 05:22 PM.
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      12-11-2013, 05:27 PM   #2
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Quote:
Originally Posted by Bbox View Post
Right now I have a 2006 330 with the Style 162 staggered 18" rims. But at least 2 or 3 of them are bent. I want to downgrade to 17" rims, specifically the Style 286 which are staggered like mine.

Old --------------------- New
Front 225/40-18 -----> 225/45-17
Rears 255/35-18 -----> 255/40-17

The rears would have the same rolling diameter, but the fronts would be a tenth of an inch smaller in diameter. Would this screw up the FTM tire monitors? (I have FTM, not TPMS).

The rims are the same width (8/8.5 staggered), but the new ones have different offset (34/39 instead of 34/37). This means the rears would be pushed in by 2mm. Would I notice this?
FTM, TPMS, aren't they the same? I don't think '06's have a low tire pressure indicator anyway. Either way, it shouldn't effect FTM.

I was fine with +38 rear offset, shouldn't be noticeable.
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      12-11-2013, 05:41 PM   #3
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The FTM system on the 2006 measures the rolling diameter to detect whether there's been a pressure loss.
It doesn't actually measure the tire pressure, like the TPMS system does.
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      12-12-2013, 03:20 PM   #4
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The tire sizing you have selected looks fine, so you shouldn't have any issues.
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      12-13-2013, 10:33 AM   #5
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I agree with the above two posts.
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