Frame, Steering, Suspension, Wheels, Tyres and Wheel Alignment
What the exam tests
Frame and steering condition, suspension setup, wheel and tyre service, and the alignment checks that keep a two-wheeler stable.
Frame and steering
- Frame types: tubular diamond for commuters, underbone, scooter monocoque, trellis for sport models. A bent frame shows as uneven tyre wear, pulling to one side and unequal fork protrusion above the top yoke.
- Steering head bearings are ball or taper roller, preloaded so the assembly falls slowly to one side with no free play. Rake and trail give stability; more trail makes steering heavier.
- Telescopic forks: oil level and grade set damping. Look for seal leaks, bent stanchions and an equal air gap on both legs.
Suspension and wheels
Twin shocks or monoshock: preload for load, rebound for control; worn bushes cause wallowing. Check axial and radial runout with a dial gauge, spoke tension on wire wheels, and balance; an unbalanced wheel vibrates at a road-speed-related frequency.
Tyres and alignment
Set cold tyre pressure per the manual and load. Minimum tread depth is 1 mm, with no cuts, bulges or sidewall repairs. Rear axle marks must match on both sides; a string line from the rear tyre to the front confirms that both wheels track. Misalignment feathers the tread and makes the machine pull.
Worked example
Front wheel axial runout reads 2.4 mm with a dial gauge, against a 2.0 mm limit, and the tyre shows a scuff. Reasoning: runout beyond limit with a matching witness mark points to a bent rim or uneven spoke tension, not to balance. Re-check spoke tension; if the rim cannot be trued within limit, replace it.
Traps
Measuring runout with loose wheel bearings, mixing fork oils of different grades, setting tyre pressure when hot, and skipping steering-head free play after refitting a wheel.