Last month I put four 15" wheels from a 300SDL onto my 1981 300SD. The size of those wheels was 7x15 with a 25mm offset. I'd like to put a 15" spare in the trunk and have found a 15" wheel that is 6 1/2 x 15 with a 21mm offset. Will the narrower rim make a big difference in the car's ability to track straight? I doubt that I would drive for more than a week on a spare tire. Thanks

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'81 300SD

It would drive fine I doubt you would notice any difference. The tread would have more crown due to a narrower wheel. Tire edges will wear slightly more compared to the wider wheel but, you would have to run the tire long term for that to happen.