Frame, Suspension, and Steering
Domain focus
This domain covers frame condition, steering head bearings, forks, shocks, linkage, swingarm, and wheel alignment. The exam tests how spring preload, sag, damping, and bearing preload affect stability and tire contact.
Core rules
- Check frame and mounting points for cracks, bends, and loose fasteners after a drop or collision. Do not straighten a compromised structural frame without the manufacturer's procedure.
- Steering head bearings need correct preload: too loose causes shake and wander; too tight causes notchy steering and weave.
- Fork oil level, viscosity, spring rate, and damping affect ride height and control. Bleed cartridge forks and measure oil level with the fork vertical and fully compressed, as specified.
- Rear suspension uses spring preload, compression damping, and rebound damping. Linkage and swingarm bearings must be free of play and properly greased.
- Set rider sag with the rider aboard and in riding gear. If the target sag cannot be reached within the preload range, the spring rate is wrong.
- Wheel alignment and tire condition affect handling. Check steering bearings, swingarm bearings, and tire pressure before adjusting suspension.
Worked example
A rider complains of handlebar shake when decelerating. The technician checks tire pressure and wear, wheel balance, steering head bearing preload, and fork oil level. The steering head bearings are slightly loose, so the front end moves under load. The technician supports the frame, loosens the triple clamps in the specified order, sets bearing preload with the specified torque-and-rotate procedure, and retorques the clamps. A road test confirms the shake is gone. If it remained, the next checks would be fork alignment, wheel runout, and tire cupping.
Traps
Over-tightening steering head bearings to remove play; jacking the bike under the engine or plastic bodywork; mixing fork oil viscosities; measuring fork oil without bleeding the cartridge; adjusting compression when the fault is rebound; ignoring swingarm or linkage bearing play; and diagnosing suspension before checking tire pressure and wear.