After a crash the obvious damage (a broken lever, scraped panel) is easy to see. The dangerous damage often is not: a twisted fork, a bent frame or a hairline crack at a weld can make the bike pull, weave or break later. This page is a careful home assessment followed by a workshop hand-off for measuring and repair.
Safety
- Check yourself and any passenger first. A rider with a head knock should not ride.
- Turn the engine off. Lift the bike with help, bending your knees. Look for fuel, oil, brake fluid and battery acid leaks.
- Electric bike: if the battery pack is dented, swollen, wet inside, hot or smells, keep away from it and follow Handle a damaged battery pack.
- Never weld on a frame with the fuel tank fitted or near the battery. Frame welding and straightening are specialist jobs.
Home assessment (bike stationary)
- Look at the frame closely with a torch: steering head, engine mount brackets, swingarm pivot, footpeg and stand brackets, rear sub-frame, every weld. Cracked or wrinkled paint at a joint can hide a crack.
- Stand in front and look down: is the handlebar square to the wheel? See Handlebar is not straight when the wheel is straight.
- Look at the forks from the front: legs parallel, mudguard centred. See Fork legs are twisted or uneven and Align the front wheel, forks and handlebar.
- Turn the bars lock to lock. Smooth, and the same angle each side. Unequal lock suggests a bent stem or damaged stops. Check steering head bearings.
- Wheel alignment: run a string line or two straight edges along both tyres at axle height. Both tyres should touch the line the same way on each side. A difference means bent parts or wrong chain adjuster settings.
- Spin both wheels: check runout (Check a wheel for runout) and brake discs.
- Controls: levers, pedals, footpegs, gear lever, throttle snap-back, cables not pinched, switches and lights working.
- Engine cases: cracks, oil leaks. Exhaust mounts. Swingarm straight.
What the workshop should do
- Measure frame alignment on a jig or with laser tools: steering head, swingarm pivot and engine mounts.
- Measure axle bend (K-Light 125 limit: 0.2 mm) and rim runout (K-Light 125 limit: 2.0 mm).
- Crack-test suspect welds with dye penetrant.
- Replace bent fork tubes, triple clamps, handlebar, levers and pedals rather than straighten them.
- Decide whether the frame can be straightened by a frame specialist or must be replaced. Aluminium frames are usually replaced.
What to ask for
- A written list of damage and measured values, for insurance and for you.
- A test ride report after repair: the bike must run straight hands-light at low speed and stop straight.
Do not attempt at home
- Heating or hammering a frame, fork or wheel straight.
- Riding a bike that pulls to one side, has unequal steering lock or a cracked frame.