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Gill,
Many thanks for your response.
I'm not sure I fully understood your explanation. I have a 135 coupe with M-sport pkg and OEM tires/rims. Why would you have to mount and dismount the tires? Couldn't you just move the tire&rim as one unit from the right front to the left front and then move the left front tire/rim to the right front. Then do the same for the back wheels? I gather if they are directional then this may not be kosher since you are reversing the direction of rotation, but can it be done and is it a good way to even out tread wear (the Bridgestone response below seems to suggest that)? How do you know these tires are directional, they do seem asymmetrical in that one side is marked "outside", but how do you know they are directional?
I found the info on rotation from another forum where someone with a 2006 BMW 330i wrote to Bridgestone and they recommended changing tires right to left and left to right. See the response below.
Thanks
Eric
Your email was forwarded to me for response.
From your description of the situation you are experiencing with your
BMW tires I would conclude that your tires have an irregular wear
phenomenon we call "heel-and-toe" wear. Excessive heel-and-toe wear can
lead to the noise you mentioned. Irregular wear can happen when tires
are not rotated and the direction the tires turn is not reversed
periodically. Tires that are not rotated tend to wear more rapidly on
one edge of each tire element or "button" causing a saw tooth type wear
pattern. As tires are rotated, wear evens out.
The tires on your BMW are Bridgestone Potenza RE050A RFT ultra high
performance runflat tires developed specifically for BMW. These tires
use an asymmetric tread pattern to provide the wet and dry grip required
by BMW. Asymmetric tread patterns have one side that should always be
mounted outside (identified by the 'OUTSIDE' marking on the tire
sidewall), but still allow rotation. Also, your tires are different
size front and rear, so the recommended rotation pattern is to cross the
tires on an axle (i.e. Left Front to Right Front; Right Front to Left
Front; and the same for the rear axle). This will reverse the direction
of rotation and even out the heel-and-toe (saw tooth) wear. Our
experience is that it may take a couple of thousand miles to completely
even out the irregular wear, but that you should start hearing a
difference within a couple of hundred miles.
Further, by way of prevention, I would recommend rotating any new set of
tires every 5,000 to 7,000 miles. This will catch that irregular wear
earlier in the process and eliminate it building to a noise issue.
Director, Consumer Products
Sales Engineering
Bridgestone Firestone North American Tire
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