Regular Maintenance, Pre- and Post-trip Inspections Protect Wheel Ends

An driver does an wheel-end inspection

Inspectors often focus on wheel ends, which include the wheels, rims, hubs and tires on a commercial motor vehicle. Wheel-end components support the heavy loads carried by commercial motor vehicles (CMVs), maintain stability and control, and are critical for braking.

Violations involving wheel-end components historically account for about one quarter of the vehicle out-of-service violations discovered during inspection blitzes, such as the Commercial Vehicle Safety Alliance’s International Roadcheck.

“Wheel ends contain numerous moving parts, whether it is the brake system, the bearings or the hubs, that can leak, wear or seize due to lack of preventive maintenance. Wheel end systems require routine daily pre- and post-trip inspections, and a sound maintenance program is key to reducing breakdowns,” said Chris Hough, vice president of maintenance design and engineering for Penske Truck Leasing.

Wheel-end failures may lead to a catastrophic crash. “When a wheel end component fails and you have a wheel run-off situation, major damage could result,” Hough said, adding that wheel-end fires often result from brake system air leaks that prevent the brakes from completely releasing.

Completing pre- and post-trip inspections is one of the best things drivers can do to help prevent issues. “Check the wheel-end brake system for air leaks, lubricant leaks, proper adjustment, etc., and when defects are discovered, write them up and have them addressed by a qualified technician before you dispatch the unit,” Hough said.

Wheel seals, lube levels, lug nuts and brake components are among items that should be inspected daily, Hough said. Drivers’ observations during the inspection are the first step in detecting a wheel-end problem.

CVSA has said that drivers may also find abnormal or uneven tire wear, see or smell smoking or extremely hot hubcaps (too hot to touch), notice smoke from a wheel end, or feel wheel vibration, wobble or noise. Increased stopping distance or decreased braking power, abnormal side pull when braking, wheel lock-up and skidding are all signs that wheel ends may need maintenance or replacement.

During the inspection of wheel ends on a commercial motor vehicle, inspectors will:

  • Check for cracks or unseated locking rings, studs or clamps
  • Check for bent, cracked or broken rims on the inside and outside wheel rims
  • Check for loose, broken, missing or damaged wheel fasteners and elongated stud holes
  • Check spoke wheels for cracks across spokes and in the web area or slippage in the clamp areas
  • Check the hub for lubricant leaks, missing caps or plugs
  • Check the inner wheel seal for leaks
  • Check the tire and valve stem for leaks
  • Check for improper inflation, cuts and bulges on all tires, including the inside tire on a dual set
  • Check for regrooved tires on steering axle
  • Check tread wear and measure major tread groove depth
  • Inspect the sidewall for improper repairs, such as tire plugs
  • Check for exposed fabric or cord
  • Check for tire contact with any part of the vehicle or another tire
  • Check for markings on the tire that would exclude its use on a steering axle
  • Check for debris between the tires
  • Check for tires touching one another or any part

Hough added that drivers and technicians also need to be careful not to over-torque lug nuts; over-torquing will stretch the studs. “Once a wheel stud is stretched, the stud will never maintain the correct torque,” he said.

The residual damage from over-torquing a lug nut could take months to develop, but eventually will cause problems. “A bolt/stud acts as a tension/clamping device when torqued properly. If over-torqued, it loses the ability to maintain the correct clamping force,” Hough said.