Sometimes it's just the tread that's directional, in which case it's not
that big a deal to run them "backwards" while there's tread on them, and
once that's gone, it's not a problem at all. I think most of the tires
we're running nowadays are built this way.
Back some years ago, Yokohama built the A008R, which was assymetrical and
directional. That meant they made "A" and "B" types, with directional
arrows on the sidewalls and the familiar very-assymetrical tread pattern.
Talking to the Yoko people, it turned out that the arrow was really
intended to indicate the direction each tire carcass would be stressed,
rather than rotated. The factory documentation backed this up. For a RWD
car, this is pretty straightforward since the front tires only do braking,
and the rear tires mostly do accelerating. FWD is trickier since the
fronts do both. AWD wasn't even considered. Ultimately, they said that it
really didn't matter, even for road racing but especially for autocrossing.
I was privy to some of the conversations with their contract drivers, many
of whom received 3 of one type and one of the other, leaving no possibility
of a "correct" arrangement. The Yoko people there convinced us all that it
was not a problem.
Now none of this has anything to do with a tire tread being directional in
its construction (as opposed to its tread pattern). But as I mentioned
before, front tires on a FWD would be SOL in this case....
Paul and Meredith Brown
MR2: "Not the easiest car in the world to work on"
|