# Correct tire size for 18x8.5 VMR CSL reps



## jimvideopro (Feb 14, 2009)

I'm leaning toward a set of VMR reps for my 06 330Ci vert. In researching, I see some people run 225/40/18, some run 235/40/18. Which is the "most" correct size? My preference would be the 225s because they are noticeably cheaper, but I don't want the tires to look stretched in any way, I want a stock look.

Also, won't the "incorrect" tire size affect the speedometer because the tire circumference is different?

Thank you.


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## jsublime (Mar 4, 2009)

225 is going to be narrow for a 8.5 rim. I would look at 245 for a "stock" look.


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## Llarry (May 17, 2002)

jimvideopro said:


> Also, won't the "incorrect" tire size affect the speedometer because the tire circumference is different?


Yes. BUT -- since BMW speedometers are calibrated to read slightly high with OE tires, bumping the size up one notch can actually improve speedometer accuracy a bit, or at least not make it any worse. So you might end up with a speedo that reads 1% low instead of 2% high, for example.

The actual difference will depend on which tire, since tires that are nominally the same size can vary slightly. Tire Rack's web site has manufacturer specs that can help you calculate the difference -- the key spec here is revs per mile.

I think I would personally be inclined to go with 235/40 in your situation...

But let me add that the "most correct" size is 225/40R-18 since that is what BMW fits in an 18-inch tire. You have not specified what width of VMR wheels you are considering. If jsublime is correct that they are 8.5 inches, I would go 235s. jsublime's recommended 245 is two sizes larger; might fit but I'd be more conservative than that...


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