Braking, suspension, steering and wheels
This domain tests stopping and handling systems. Questions cover hydraulic brake service, suspension adjustment, steering bearings, wheel balance and tyre safety.
Braking rules
- Hydraulic brake: lever pushes a master-cylinder piston, fluid pressurises the caliper, pads clamp the disc. Air is compressible, so a spongy lever means bleed the system.
- Use the specified DOT fluid; DOT 4 is common. Never mix DOT 5 silicone with DOT 4. Fluid absorbs water and should be replaced on schedule.
- Check pad thickness, disc thickness and disc runout. Clean pads and discs with brake cleaner, not oil.
- Drum brakes: check shoe lining, cam wear and return springs; adjust free play.
Suspension, steering, wheels
- Preload sets ride height; rebound and compression damping control movement. Set sag with the rider aboard.
- Fork oil level and viscosity change damping. Leaking seals show oil on the stanchion.
- Steering head bearings: too tight causes weave and notchy steering; too loose causes knocking. Adjust and check for free movement.
- Wheel balance and tyre pressure affect stability. Fit the tyre in the direction arrow; check tread depth and sidewall cracks.
- Spoke tension and rim runout are checked with a dial gauge or truing stand.
Worked example
A front brake lever feels spongy after pad replacement. The pads are correct and the disc is true. Reasoning: the hydraulic system contains air. Bleed from the caliper nipple with a clear tube into a container, keep the reservoir topped up, pump and hold the lever, open and close the nipple, and repeat until no bubbles appear.
Traps
Getting brake fluid on paint; pushing contaminated fluid back into the reservoir; over-tightening steering bearings; fitting a tyre against the arrow; ignoring a warped disc.