Question:When I buy replacement tires for my vehicle,
do they all have to be the same size?
Answer:Yes and no. If you want to rotate the tires on
your vehicle to maximize tread life, then all the tires have to
be the same size. Rotating the tires every 5,000 to 7,500 miles
is a good idea, especially on front-wheel drive cars and minivans
where the front tires tend to wear out long before the ones on
the back. Wide, low profile tires also tend to develop unusual
wear patterns if left in the same wheel position for their entire
life.
If you don't plan to rotate your tires, however, then the
front fires can be a different size than the ones on the back.
But the tires on both front or both rear wheels must be the same
size for proper handling and braking. Mismatched tires side-to-side
can cause a vehicle to lead to one side and/or to pull when braking.
CAUTION: Never mismatch types of tires either on the front
or rear wheels. A bias ply tire should never be paired with a
radial tire, and vice versa. Likewise, tread design, belt type
and overall tread wear should be the same (or similar) side-to-side
for proper handling, steering and braking. Intermixing different
brands and styles of tires may cause similar problems in some
instances.
As for the size of replacement tires, some people will try
to use anything that fits. This may not be a good idea because
a vehicle's handling, steering and braking characteristics can
all be adversely affected by using tires that are too large or
too small for the application.
Some people may want oversized tires on their rear drive wheels
to improve fuel economy. Switching to a larger diameter tire
reduces the number of revolutions per mile. But it also affects
the accuracy of your speedometer and odometer readings. Others
may want wider or larger tires on the rear drive wheels to improve
traction or to achieve a special kind of "look." Wide
tires, however, typically provide reduced traction on wet roads.
Clearance problems can arise, too, if the tires are too wide
or too large. They may rub against the body when turning or when
the vehicle hits a bump. This can not only damage the vehicle
but also the tires, possibly causing a blowout.
On cars and trucks that have antilock brakes (ABS) equipped
cars and trucks, most vehicle manufacturers say replacement tires
should be the same size as the originals. This is necessary because
the diameter of the tire affects how the wheel speed sensors read,
which in turn affect the operation of the ABS (and traction control)
system. Changing to a larger or smaller diameter tire, or installing
different sized tires front and rear can upset the operation of
the ABS system. This may create braking problems and/or cause
the ABS warning light to come on (which means the system is deactivated).
Vehicles with all-wheel drive or full-time four-wheel drive
must also run the same sized tires front and rear to maintain
the proper drive relationship between axles. If one set of tires
is larger or smaller than the others, it will create slippage
between the front and rear axles that will accelerate tire wear
and adversely affect handling.
