tire rotation on AWD

[BOB HOLLOWAY [ UK].]

I know the recomended rotation period is 6500 miles, but under heavy driving
conditions what would be the maximum difference in tread depth before
rotation is deemed nessesary, and should the wheels be re-balanced??

 

[Edward Hayes]

On a 215/60/16 tire on my Forester the maximum difference in
circumference should be 1/4 inch or 0.250. A 215/60/16 tire has a
listed diameter of 26.0 inches. If you put a decrease of 0.250 inches
into the equation then the maximum difference in tread depth is 0.040
inch which is close to 1/32 or 0.03125 inch. I rotate when my front to
rear tread depth difference is ~ 1/32 inch. Sometimes that occurs at
4,000 miles and sometime at 9,000 miles. Ed Hayes

 

[Greg]

You also need to take into account tread wear difference at sides and center
of tread, it's not all about keeping the same diameter on all 4 wheels it's
also equal wear across the tread. Balance should not be "necessary" every
rotation, perhaps checking it every other rotation depending on the driving
conditions of course.

 

[Gilles Gour]

You also need to take into account tread wear difference at sides and center
of tread, it's not all about keeping the same diameter on all 4 wheels it's
also equal wear across the tread. Balance should not be "necessary" every
rotation, perhaps checking it every other rotation depending on the driving
conditions of course.

If you care for a more accurate way of checking tire diameter, here's
what I did. Put a chalk mark on each tire's side in the center of the
contact patch with the ground. Roll forward in a straight line (parking
lot on sunday or small residential street) for 40 revolutions of the
tires. I measured the approx diameter of the tire X 40 and put a mark on
the ground. You could also have a helper counting the revs.
If the circumference diff front to back is 1/4 inch or more, you would
find that your front and back marks are 10 inches or more apart (radial
measurement. What I like about this method is that it takes into account
all variables : center and side tread depht and air pressure in the tire
(have your tires at normal pressure).