Most mechanics don't ever look at the wheels on an apparatus until they have a problem. That's too bad, because some basic wheel maintenance could help avoid those problems and potentially prevent a serious accident. Here’s a checklist you may want to add to your apparatus preventive maintenance program.

Check tire pressures before you start.
Checking tire pressures is important because it helps prolong the life of the tires and improves steering and braking. It’s also important because very high or very low tire pressures indicate dangerous conditions that require immediate action before you perform any maintenance on the wheels.

If a tire pressure is above the maximum pressure molded on the sidewall, keep your body clear of the sides of the tire and carefully bleed the air to the correct load pressure. Visually check that the tire bead is still properly seated on the rim. Use an inspection mirror to check the inner side.

If the tire pressure is less than 80% of the load pressure (roughly 20psi low), stop all work and take the apparatus out of service immediately. Once a tire has been driven even a few miles in a seriously underinflated condition, the sidewall structure can be destroyed, which turns the tire into a ticking bomb.

Do not attempt to re-inflate the tire. Carefully deflate the tire, and remove the tire and wheel assembly from the apparatus. Take the entire assembly to a professional shop for demounting, inspection and possible replacement.

Check wheels for damage.
If the tire pressures are only slightly high or low, make the required adjustments and proceed with an inspection of the wheels. If your apparatus is equipped with add-on wheel covers, you’ll need to remove them to do the inspection.

Most modern apparatus are equipped with disc wheels, which have a disc in the center welded to a single-piece rim on the outer circumference. The disc is attached to the axle hub by studs and nuts. Some apparatus may have spoke wheels with demountable rims and will require special maintenance. Older apparatus with multiple-piece rims and locking rings also require special handling and maintenance.

Some of the problems you should look for on disc wheels include out-of-round rim flanges, cracks, bolthole distortion, surface gouges and corrosion. Use an inspection mirror to check the inner portions of the wheels and between the duals.

Out-of-round or otherwise distorted rim flanges are usually caused by severe impacts. If the damage is serious, the tire may leak or come off the rim. Cracks may appear anywhere on the disc, but are most common between boltholes or between a handhole and a bolthole. They can cause the wheel to fail and come off the apparatus. Bolthole distortion can be caused by loose wheel nuts or improper nut torque. Surface gouges are caused by impacts or improperly handled tools. Corrosion is most common on steel wheels and can weaken the wheel structure or cause leaks.

Severe distortion and corrosion, as well as any cracks, are serious and should be taken to a properly equipped shop for further inspection. Do not attempt to repair cracks by welding or brazing them — that will only weaken the wheel.

Retorque wheel nuts periodically.
Wheel nut torque should be checked and retorqued according to the wheel manufacturer's guidelines, or at least annually. On new vehicles, check the torque after the first 50 to 100 miles, and then regularly thereafter. Always torque nuts in the proper sequence around the bolt circle.

Some disc wheels may be designed with stud-piloted mounting holes, also known as ball-seat mounting holes. Others may be designed with hub-piloted holes. Stud-piloted holes require wheel nuts with tapered faces; hub-piloted holes require wheel nuts with flat faces. Steel wheels require different nuts than aluminum wheels, and the nuts used on the inner wheels of duals are different than those used on the outer wheels. Always use the proper wheel nuts and contact the manufacturer if you are not sure.

Consult the manufacturer's manual.
Wheel maintenance can move from "basic" to "advanced" in a big hurry. Don't try to do more complicated work on wheels (or tires) if you don't have the proper tools, equipment and training. As a guide, always consult the manufacturer's maintenance manual before you perform any work on wheels. The manual will include step-by-step procedures, illustrations, parts identifications, safety warnings and lists of the tools and equipment required to do each job properly.

Maintenance manuals are available by mail from the manufacturer. Some manufacturers also place this information on the Internet. Accuride Wheels is an excellent Internet source with lots of good information.