Equipment Inspections - Tires

     Tires are one of a trucking companies largest expenditures, next to fuel and employment costs. In an effort to help minimize the number of on-road failures and MTO/DOT infraction we receive, I’ve put together a small sample of some of the things you should be looking for when doing your tire checks.

When checking tires during a roadside inspection, the DOT or MTO will typically pay attention to two things:
  • Is the tire flat, blown out, or have an audible air leak
  • Does the tread of the tire meet the minimum requirements

A - Blowouts and Flats

Tire Pressure Chart
Tractor Steers
95 psi
Tractor Drives (duals)
90 psi
Tractor Drives (super singles)
95 psi
Trailer Tires
90 psi

  The root cause of tire failure is under-inflation, but this is not the only reason that tires fail. Shown below are some examples of tires showing imminent failure. It is easier, and much more cost effective to replace a tire like this in the yard, rather than taking the chance that it will last the duration of your trip.

Side-Wall Failure
In this example the tire was still holding air, but it certainly wouldn’t have lasted the duration of its next trip. Side wall damage could include cuts caused from curb rash, or in this case, dry rot simply due to the age of the tire.

side wall failure

Broken Cord
- In the example below, the tire had a broken cord, which would lead to premature tire failure. Broken cords can be spotted by the raised vertical edge along the distance of the sidewall. This can be caused by a few things, however with this tire it looks like the cut shown let salt and water into the steel belts causing them to rust and eventually break.

broken cord side    broken cord front

B - Tire Tread

Minimum Tread Requirments

Steer Tires
Minimum 4/32"
Drive and Trailer Tires
Minimum 2/32"

Tire manufacturers are required by law to place
“wear bars” into the tread of the tire. If the height of the wear bars is equal to the tread on the tire, then the tire must be replaced. Shown below is a tire that is due for replacement, as indicated by the wear bar.
Tire Wear Bar

     In many cases tires don’t wear evenly, they get lumpy, or wear heavily on one side more than the other. Uneven wear is much more prominent when looking at trailer tires, than say a drive or a steer position. This could be caused by a re-treaded tire being out of alignment, or poor alignment of the axles on the trailer for example. When you spot a tire that is wearing unevenly during your inspections, take the time to look it over and make sure that there are no spots on the tire where the tread is less than 2/32” across two tread grooves. An easy way to measure 2/32” is to take a US penny and place it upside down in the tire tread, if you see all of Lincoln’s head then the tire needs to be replaced. In some cases, the tire may have full tread at one point in its circumference and be bald on the opposite side. In either case, the tire should no longer be in service and must be replaced.

One Sided Wear
- Bare tread on the inside of this tire all the way around.
onesided wear

Lumpy/Uneven Wear
- Both examples show uneven wear with points in the tire that are either bald or less than 2/32” tread.

lumpywear1 lumpy wear 2

Straight up worn out
- Quite frequently tires do work until the end of their useful life, as in the example you see below.
worn out

Disclaimer: K.A.M. makes no guarantees regarding the accuracy of this information. It is intended for educational and assistance purposes, for the drivers of K.A.M. Trucking Inc.