Wheels, Rims, Tires, and Hubs
This domain tests wheel mounting systems, torque practice, multi-piece rim safety, tire wear analysis, and wheel-end bearing service. Questions often compare hub-piloted and stud-piloted systems and ask you to interpret wear patterns.
Wheel systems
Hub-piloted wheels center on the hub and use two-piece flange nuts on ten studs, typically torqued in the 450-500 ft-lb range with oiled threads, re-checked after the first road miles. Stud-piloted wheels center on the studs with ball-seat inner and outer nuts; left-side studs may be left-hand thread. Never mix nut types or omit inner nuts on a stud-piloted dual.
Rims
Multi-piece rims store enormous energy. Deflate before disassembly, use a tire cage, never pry a lock ring, and never weld or heat a rim. Inspect for cracks, severe rust, elongated stud holes, and damaged flanges.
Tires
Size markings give section width, aspect ratio, construction, and rim diameter - for example, 295/75R22.5. Load range and maximum pressure at maximum load are on the sidewall, along with the DOT date code (week and year). Duals must be matched in diameter within the OEM limit to prevent scrub and differential wind-up.
- Center wear: overinflation. Both shoulders: underinflation.
- One-side wear: camber or axle alignment. Cupping: balance, shock, or runout.
- Diagonal wear: misalignment or brake drag.
Hubs and bearings
Oil versus grease lubrication, seal condition, and bearing end play set by the spindle nut method the OEM specifies; excessive end play damages seals and causes runout. ABS tone rings mount on the hub.
Worked example
The inner dual of a pair wears on its outboard shoulder while the outer looks normal. Reasoning: check the inner tire's pressure first, then measure both tire diameters - a mismatched pair scrubs the smaller tire - and finally check axle and hub condition. Correcting pressure or replacing the mismatched tire fixes the cause.
Traps that cost marks
Mixing radial and bias tires on an axle, mismatched dual diameters, over-torquing with an impact, reusing a cracked rim, and assuming a wear pattern means inflation when alignment is the cause.