Q. I remember
years ago when we had a flat tire, we were told we had to purchase
three new tires to match the new one or the car would be unstable.
This was a great burden to us as young marrieds, and I was always
suspicious of that advice. Iíve not heard that advice for years.
Now my granddaughter in Denver is being told the same thing. Is that
valid advice, or just the tire businesses hoping to make more money?
Thanks so much for your attention!
recommendation may be valid in some cases but not all. All-wheel
drive vehicles require all four tires to be very close in diameter
and identically inflated to avoid causing heat, stress and wear of
driveline components. Depending on the manufacturer, the maximum
tread depth deviation between tires is approximately 2/32 inch and
4/32 inch. Letís say your four tires are worn to 50 percent of
their original 13/32-inch tread depth and one becomes damaged beyond
repair. Purchasing an identical new tire is the best choice, but youíd
be out of specs on the tread-depth difference. Rather than being
hustled to renew the other three, it is possible to have the new
tire shaved to match the others (it may take some searching to
obtain this service). This hurts but is preferable to buying four
On a typical
two-wheel drive vehicle, itís best to have all four tires be the
same size, speed and load rating, tread style and compound to insure
optimum road handling. In cases where an exact match (brand and
model) canít be obtained for a single replacement tire, some will
opt for as close a copy as possible. Others will tell you to replace
in pairs, or all four. I donít believe the difference in tread
depth is an issue unless the remaining three are worn below 50
percent tread. If you replace a pair of tires, mount the new ones on
the rear. The reasoning is if driving in rain and hydroplaning
becomes an issue, itís better to have the front tires lose
traction than the rears. This seems counterintuitive, but understeer
is easier to correct for than oversteer. Releasing the throttle and
perhaps braking lightly helps restore front traction, along with
additional turning effort in order to stay on track. Should the rear
tires lose traction, the vehicle is more likely to spin, which is
difficult if not impossible to manage.
Q. My driverís
side power window has stopped going up at times. This has me worried
as I might not be able to lock my truck, which I work from. Any
ideas? Itís a 2011 GMC with 174K miles. New window motor? Switch?
A. Try this
the next time it quits: Hold the switch in the up position
continuously and slowly sweep the opened door throughout itís
range. If nothing happens, try repeatedly operating the button as
you move the door. If the window begins to function, even briefly,
itís likely one of the wires in the plastic conduit bringing wires
to the door is breaking and intermittently making connection. This
is not uncommon in vehicles that see a lot of door action,
particularly the driverís door. If the window reliably goes down,
and up is the only concern, itís not the motor. A scan tool test
would be the next step, to prove out the switch request. Also, any
other faults with other windows, mirrors or such at this same time?
This might also hint at the broken wire theory.