Automotive Smog Check Tips
Tire Tread Wear
Tread Wear - Tread wear grade is a comparison rating based on the wear rate
of a standardized tire, tested under carefully controlled cinditions , which is
assigned a value of 100. A tire rated 200 should have a useful life twice as long
as the standard tires.
Note : The standard tire has a rating for tread wear of 100. This vehicle has
generally been accepted to mean a useful life of 20,000 miles of Normal driving.
Therefore, a tire rated at 200 could be expected to last 40,000 miles.
Tread Wear Rating Number Approximate Number of Miles
100 20,000 miles
150 30,000 miles
200 40,000 miles
250 50,000 miles
300 60,000 miles
400 80,000 miles
500 100,000 miles
The tread wear life of any tire is affected by driving habits ( fast stops, fast cornering
can decrease tread life ), Tire Rotation or lack of Tire Rotations, under inflated, wheel
alignment, road surfaces and climate conditions will play a role in your Tires life.
Traction - Traction performance is rated by the letters AA , A , B and C.
AA is the best.
Note : The traction rating is for Wet Braking distances only ! It does not include
cornering traction or Dry Braking performance. The traction rating is only one of
many factors that affect wet braking traction, including air inflation, tread depth,
vehicle speed and brake performances.
Temperatur Resistance - Temperature resistance is rated by the letters A, B and C ;
with A being the best rating. Tires generate heat while rotating and flexing during
normal driving conditions. A certain amount of heat buildup is desirable normal
drivung conditions. A certain amount of heat buildup is desirable because tires
produce their highest coefficient of traction at normal operating temperatures.
Forexample, rare car drivers frequently swerve their cars left and right during
pace laps, causing increased friction between the tire and the road surfaces,
which warms their tires to operating temperature. However ; if temperatures
rise too much, a tire can start to come apart -the oils and rubber in the tire
starts to become a liquid !
Automotive Principles Technology - James D. Halderman