Frame & swingarm

How it works

The frame is the structure that ties everything together: it carries the engine, the steering head at the front and the swingarm at the rear. Depending on the bike, it is steel (tubular or backbone), aluminium (perimeter) or uses the engine as a stressed member. The swingarm, pivoting on the frame, holds the rear wheel and passes its movement to the shock. A frame hardly wears, but it can be bent or cracked after a crash or impact, which upsets the geometry: the bike pulls to one side, won't hold a line or the wheels are no longer aligned. The swingarm pivot runs on bearings or bushes, which do wear and develop play. Mounting points (engine, footpegs, exhaust hangers) must stay tight to avoid vibration and cracks. Checking a frame after an accident (jig, measurements) is done by a specialist.

Maintenance tips

• ✓After a fall, visually check the frame, brackets and swingarm: any crack, crazed paint or bent part should be checked.
• ✓Test swingarm play: rear wheel lifted, push it sideways; you should feel no play at the pivot.
• ✓Regularly check engine and bracket bolts are torqued to the manual's values.
• ✓If the bike pulls to one side in a straight line, first check wheel alignment and tyre pressures.
• ✓A bent frame is checked on a jig by a specialist; never straighten it yourself.