Buick 1993 Skylark Owner's Manual page 246

The tire has a puncture, cut, or other damage that
can't be repaired well because of the size or location
of the damage.
Buying New Tires
To find out what kind and size of tires you need, look at
the Tire-Loading Information label.
The tires installed on your vehicle when it was new had
a Tire Performance Criteria Specification (TPC Spec)
number on each tire's sidewall. When you get new tires,
get ones with that same TPC Spec number. That way,
your vehicle will continue to have tires that are designed
to give proper endurance, handling, speed rating,
traction, ride and other things during normal service on
your vehicle. If your tires have an all-season tread
design, the TPC number will be followed
by a "MS"
(for mud and snow).
If you ever replace your tires with those not having a
TPC Spec number, make sure they are the same size,
load range, speed rating and construction type (bias,
bias-belted or radial) as your original tires.
A
CAUTION:
Mixing tires could cause you to lose control
while driving. If you mix tires of different sizes or
types (radial and bias-belted tires), the vehicle
may not handle properly, and you could have a
crash. Be sure to use the same size and type
tires on all wheels.
It's all right to drive with your compact spare,
though. It was developed for limited use on your
vehicle.
I
Uniform Tire Quality Grading
The following information relates to the system
developed by the United States National Highway
Traffic Safety Administration which grades tires by
treadwear, traction and temperature performance.
(This applies only to vehicles sold in the United States.)
Treadwear
The treadwear grade is a comparative rating based on
the wear rate of the tire when tested under controlled
conditions on a specified government test course. For
example, a tire graded 150 would wear one and a half
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