EXPERT’S GUIDE TO... SLIPPER CLUTCHES
First developed for racing and now common on sporty road bikes they take the fear out of rapid downshifts
Whenever you shut the throttle on a bike the direction of drive is reversed and the fast-spinning rear wheel will start to try and turn the engine. Bang in some downchanges as you brake hard for a corner and the engine-braking will have the rear wheel hopping around.
Slipper clutches are designed to allow you to enter corners more smoothly by limiting the amount of drive fed back to the engine. The first slipper clutch or ‘back torque limiter’ was developed by Honda for their ill-fated four-stroke NS500 GP project in 1979. From there they were developed in US Superbike racing and now many road-going sportsbikes have one.
A typical system has a series of ramps in the back of the clutch centre. It looks like a little spider with ball bearings sitting in grooves on those ramps. As the drive from the rear wheel feeds back through the clutch and tries to turn the engine over, the clutch centre is pushed up those ramps, forcing the stack of clutch plates apart.