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Old 01-03-2013, 01:37 PM
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Fudman Fudman is offline
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Location: Sudbury, MA
 
Join Date: Apr 2007
Posts: 6,157
Mein Auto: '02 530i Sport auto
The tire diameter for a tire mounted on a 17" wheel should about the same as a tire mounted on a 16" wheel, irrespective of tire width. Otherwise, the speedometer would need to be recalibrated. The difference in tire sidewall height is compensated by using a different aspect ratio when sizing the tire (235/45-17 vs. 225/55-16) to a different diameter wheel. Hence, the BMW guidance does not make sense. The tire clearance should be about the same if you are staying within the recommended tire dimensions.
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