Checking PSI and Reading
The tire and rim assembly is an air chamber,
which supports the weight of the vehicle.
- air pressure supports 95% of the
- the tire just 5%
- inflation is critical part of the tires
ability to perform.
Underinflation is the #1 enemy
- causes tire stress
- irregular wear
- loss of control
- a tire looses up to 1 psi per month
- can loose half of its pressure and not
- psi is specified by vehicle manufacturer and is
shown on the door edge, door post, glove box door
or fuel door and in the owners manual.
- check air pressure when tires are cool not hot.
PSI rises 1-2 lbs for every 10 degrees of temerature.
- visually inspect tires for objects embedded in the
tread leading to air leaks, also check sidewalls for
gouges, cuts, bulges or other irregularities.
Misalignment of wheels in the front or rear can cause
uneven and rapid treadwear.
An indication of trouble is “pulling” or vibration.
Front wheel drive and IRS, require alignment of all four
Tire dealers should check caster, camber, toe-in and
-Promotes uniform tire wear.
-Each tire supports a different amount of weight, this
unusual weight causes tire to wear at different rates.
-sometimes front and rear tires use different pressures,
-Tire Pressure Monitoring System (TPMS) warns drivers
when tires are 25% underinflated
When tread is worn down to 2/32nds of an inch
the tire must be replaced.
Some tires have “wear bars” (small raised bars of
rubber in the groove) If tread is even with “wear bars”
it’s time for a new tire.
If a tread depth guage is no available a penny is a
reliable way to check tire tread, place the penny in the
tread groove upside down, if you can see all of Lincoln’s
head replace the tire.
Reading Tire Wear:
The way your tires wear is a good
indicator of other parts of the
suspension. Abnormal wear patterns
are often caused by lack of tire
maintenance, or front end alignment.
If your tires are overinflated by 6 psi, they could be
damaged more easily when running over potholes or
debris in the road. They will ride harsher but
responsiveness will improve to a point.
Tire pressure must be checked with a quality air gauge,
it cannot be estimated through a visual check.
Over-Inflation: Excessive wear at the
center of the tread indicates that the
air pressure in the tire is consistently
too high. The tire is riding on the
center of the tread and wearing it
Under-Inflation: This type of wear
usually results from consistent
under-inflation. When a tire is
under-inflated, there is too much
contact with the road by the outer
treads, which wear prematurely. If
the psi is correct, a bent or worn
steering component or the need
for wheel alignment could be
One-Sided Wear: When an inner or
outer rib wears faster than the rest
of the tire, the need for wheel
alignment is indicated. There is
excessive camber in the front
suspension, causing the wheel to
lean too much putting excessive
load on one side of the tire.
Misalignment could also be due to
sagging springs, worn ball joints,
or worn control arm bushings.
Second-Rib Wear: This is usually
found only in radial tires, and
appears where the steel belts end
in relation to the tread. It can be
kept to a minimum by paying
careful attention to tire pressure
and frequently rotating the tires.
Check for understanding:
1. What are three causes of uneven
2. What supports the weight of your
3. Why is tire pressure checked
4. How is tire pressure checked?
5. What are some of the capabilities
considered when selecting tires?
6. What is the effect of low tire