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      02-23-2007, 11:30 AM   #18
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Drives: M340i
Join Date: Jul 2006
Location: UK

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Quote:
Originally Posted by ZiM View Post
i was thinking about tire sizes actually... do bmw set the suspension to be 5mm lower at the back (i figure they (front and back) are both 19" and the width shouldn't figure into the equation so the car would actually be higher at the back... is this the case?
The second digit in the tyre size is the 'aspect ratio'.

Aspect ratio = height/width * 100

With 18 inch wheels you get:

225/40/18 front and 255/35/18 rear

The height of the sidewall would be 90mm front and 89.25 rear. So near as damn it the wheels are the same size.

I had 19 inch rims on my 530d which were:

245/35/19 front and 275/30/19 rear.

Front sidewall was 85.75 and rear was 82.50

These are slight differences which and this ignores the curvature of the tyres.

I dont think anything would be visible and the car would not be set up any differently just because of the mixed tyres.

The BMW oem wheels are perfectly capable of using non-runflat tyres. I'm not sure about the tyre sensor though.

I though the old system measured rotational speed, but that the new one did include sensors. I have seen posts on this forum where people have had problems with this one aftermarket wheels.

In theory though, I can't see how changing from runflat to non runflat with the same size tyres could cause a problem.

My 530d tyres were not runflats as they were not available in 19 inch format then. They worked perfectly well with my tyre monitor.

The downside is that 275/30/19's are not easy to get hold of (but then that is also the case for runflats).
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