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

Motorcycle News (UK) - - Garage - Paul Cur­ran Has com­peted in the Bri­tish Su­per­sport and Bri­tish Su­per­stock se­ries and runs PCR Per­for­mance, a Dyno­jet-ap­proved tun­ing cen­tre in Can­nock, Staffs

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.

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