Wheels and Tires Diagnosis and Repair
Transit bus tire and wheel work centers on load capacity, inflation, wear patterns, and wheel integrity. Candidates must understand tire size and load rating, dual tire matching (diameter within the manufacturer's limit), and the importance of valve stem and extension condition on duals. Know the wear patterns: center wear from overinflation, edge wear from underinflation, cupping from shocks or balance, diagonal wear from misalignment or worn suspension, and flat spotting from lockup or sitting.
Wheel integrity matters on heavy buses: inspect for cracks, corrosion, loose or missing lug nuts, and proper torque. Disc wheels and demountable rims require correct torque sequences and re-torque after the specified interval. Never mix radial and bias tires on the same axle, and match duals by diameter and construction.
Traps
- Diagnosing a vibration as balance when it is actually a bent wheel, worn bearing, or irregular wear.
- Ignoring dual tire matching, which causes overload and rapid wear on the larger tire.
- Assuming low pressure is a leak when it is a faulty gauge or valve extension.
Worked example
A drive tire shows diagonal wear across the tread. Diagonal wear usually indicates misalignment or a worn suspension component rather than inflation. Check alignment and suspension play before replacing the tire, or the new tire will wear the same way.