> If you replace "in pairs" you run the risk of unbalancing the car's
> handling.
ah, you see, this only applies to cars that HAVE this "Handling" feature.
it explains why i never understood tire rotation. other than that, you make
some excellent points!
i can report that bald kumhos dont work at GGF no matter where they are!
-james c
----- Original Message -----
From: "Donald R McKenna" <donbarbmckenna@earthlink.net>
To: "james creasy" <james@thevenom.net>; "Matthew Rehrer"
<mrehrer@rehrer.com>; "Bay_Area_Autocross_List" <ba-autox@autox.team.net>
Sent: Monday, August 12, 2002 12:22 AM
Subject: Tire rotation, was: Re: Unsolicited Newbie Commentary and Questions
> James writes:
>
> >i never understood the rotating tires business...
>
> Here's some general observations from what I've experienced over the
years:
>
> When you start out with a new "set" (same brand/spec, even if different
size
> F/R) of "R" tires, all corners of the car can have the same (potential
for)
> traction. If the car has acceptably balanced handling, once the new tires
> are adequately scrubbed-in and heat-cycled, the car may be at its best, or
> close to its best, performance level. If the tires either wear at a
greater
> rate and/or see greater heat on either end of the car, then the end of the
> car "working" the hardest will loose traction quicker than the other end.
> Therefore, rotating tires front-to-rear (when all are same wheel/tire
size)
> and, if necessary, side-to-side to equalize wear and heat exposure, will
> tend to keep the handling balanced for a longer span of the total tire
life.
> The total grip will, eventually, be reduced as the tread rubber gets both
> harder and thinner but, as the tires wear, the changes in handling balance
> will not be as pronounced as they would be without rotation. However, at
the
> end of tire life as overall traction falls off, that once "balanced
> handling" car will understeer going into turns and oversteer comming out
of
> turns.
>
> >you replace in pairs anyway right?
>
> If you replace "in pairs" you run the risk of unbalancing the car's
> handling. Again, after the new pair is "adequately scrubbed-in and
> heat-cycled", the end of the car with the new tires will, most often, have
> better traction than the end with the older tires. New tires on the front,
> car loose; new tires on the rear, car pushes. Now, if the car has adequate
> and easilly accomplished bar/shock/toe adjustment ranges, along with
> possible tire pressure changes, the handling changes can be "chased"
through
> the un-even wear rate/life of the tires to maintain handling balance.
Trust
> me here, this "game" requires a real art (and some luck) in order to be
able
> to, regularly, pull-off this feat.
>
> When the car has different tire/wheel sizes/offsets on each end AND wears
> and/or heat-cycles one end quicker than the other end then, obviously, the
> rotation "fix" won't work. In that case, as with my current AS '96 GS, new
> tires, most effectively, get introduced either as full sets in advance of
> "important" events or get introduced as new or fresher pairs to the
> higher-usage front end of the car before the traction imbalance is
> excessive. Additional wheels are necessary to be able to maintain this
kind
> of traction balance through "platooning" pairs of fronts.
>
> >the one thing that can be helpful on stock suspensions with
> >inadequate camber or roll control is to swap them so the "fresh" edge
that
> >was to the inside of the wheel is now on the outside
>
> Not just stock suspensions, but on any car where the optimum, or best
> possible, set-up wears either the inside or outside edges at a greater
rate.
> BTW, this only works if the tire's casing (not tread pattern) has a
> symetrical design. For example, the BFG R-1 226s and 230s (predesessors to
> the G Force) could not be "flipped" as their casing was asymetrical. When
I
> was running bias-ply Hoosier "Autocrossers" on my '85 SS Vette, I not only
> followed the front-to-rear rotation discipline but by making regular tread
> wear measurements would pick a point about half way through the tires'
life
> to flip the tires inside-out on the rims. I determined that the additional
> cost of the re-mounting was significantly less than the value of the
> additional extended "life" (total run time) of a set of tires. However,
> after "flipping", it took a few runs to re-scrub the tires before getting
> back to some decent traction.
>
> Don
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