Casters - as under your old armchair

ONLY FOR OUT-AND-OUT NERDISTS. It was like meeting someone who normally wears a uniform now dressed in mufti; or a West Riding troglodyte walking down Regent Street. The mind was forced to change gear.

World economics suggest I should stick with my present car rather than replace it. But it will shortly be three years old which means an MOT, or examination of roadworthiness. I knew the tyres needed renewing since they were original and had done a remarkable 26,000 miles. Irregular wear at the front showed the wheels were misaligned so this needed doing.

The tyre guy gave me a printout of the work, adding that caster angle was marginally out of whack. Caster angle? I knew about tracking, about toe-in and about camber angle. But caster angle seemed both alien and familiar. It took me over a minute to work it out. With cars the caster angle of the wheel is a comparatively minor matter; with bikes (powered and pedalled) it’s crucial.

This chopper has an extreme caster angle. The forks reach so far forward there’s daylight between the front wheel and the engine. It wouldn’t be pleasant to steer such a bike but it would be even worse steering a two-wheeler (especially a pedal bike) with close to zero caster angle, where the forks are almost vertical. Talk about twitchy; the bike has a mind of its own.

The moral? Car drivers can forget about caster angle. Bike riders know all about it. QED.