Comprehensive wheel fitting chart and guide for Mercedes. Information on tyre and wheel sizes, offsets and PCDs. Find out which wheels will fit your vehicle
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I went the other way on my R129 SL500 (from 17x8.25 front & back to staggered 18x8.5 / 18x10) and both drove fine. TBH a change of tyre brand/model is probably more likely to be noticeable in normal road driving.