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Digital Subscriptions > Fast Bikes > Issue 333 > KNOW YOUR SLIPPER CLUTCHES

KNOW YOUR SLIPPER CLUTCHES

It’s only when you ride a bike deprived of a slipper clutch that you come to realise just how genius and essential these fancy sounding plate spinners are. To get a fuller grasp of how they work and who they’re aimed at, we had a chinwag with Sigma slipper clutches head honcho and MotoGP technical wiz, Neil Spalding.
Simples!

FB: How good will a normal clutch hold up on track?

NS: It will work as it’s designed to, but then you’ll be doing things that it wasn’t designed for: if you’re arriving at a hairpin heading down the gearbox the clutch won’t be equipped to deal with that, meaning you’ll get jerk from chain, through the clutch, and into the engine. A regular clutch is always going to be as good as the environment it’s designed for – most aren’t designed for savage track riding. Going back a few years some of our early customers on board Ducati 916s at Donington used to actually knock out their primary gears going into Melbourne loop. It’s just too brutal, unless your name is Mick Doohan and you can perfect the clutch slip with the engine yourself…

FB: Howwill a slipper clutch benefit a bike?

NS: It will make life that much easier on corner entry, meaning you can focus on yourself and lap times. It does this by slipping the clutch at any point where your behaviour is likely to make the rear wheel hop, therefore taking the stress out of the drivetrain which in turn stops the chain beating up the rear tyre. If set up correctly it will give more side grip all the way to the apex on the rear rather than the engine needing the grip to force it to turn over. You feel it as engine nto a comer all the weight is on the front, but with the throttle closed the chain geometry will want to pull the rear wheel off the ground; the slipper clutch helps keep the rear wheel on the ground and so keeps the back wheel behind the front.

FB: How does it work?

NS: Each clutch has a series of ramps, typically one between each spring. When the engine turns the wheel, the clutch operates normally, but when it’s the other way round (so slowing down), the centre rises and pokes the pressure plate off the clutch pack and lets the clutch slip a little. All in all, this means that the rear wheel won’t try to overcome the engine braking and will help to combat the back wheel hopping on comer entry!

FB: Would it help on the road?

NS: Yes and no - a slipper clutch is made for a higher level of intensity than popping down to Waitrose, so unless you fancy going road racing it probably won’t work that often. Unless of course you’re a getaway rider of some description then it might just come in handy…

FB: How should you maintain one?

NS: The same as with any clutch. As the plates wear down, the pressure plate drops down, which will mean that the clutch starts slipping. This is incredibly bad for the engine as the clutch isn’t being held together enough to handle the power – if this happens you have a big problem. At the first sign of the clutch slipping, you should check the plates for wear and replace them if needed.

A thing of beauty…

If you don’t know the difference between yokes and yokes, Dzus and Zeus, suspension and suspenders – email the experts letters@fastbikes.co.uk

Even superstars like Fagan use slipper clutches.

FAST FACTS

1.Sigma slipper clutches use airframe quality aluminium to make their clutches, as this guarantees the best compromise on weight and strength.

2.If you’re wondering whether your slipper clutch is functioning properly, you should test it in every gear in a safe environment, such as a race track. On releasing the clutch, the rear wheel should refrain from locking up and the revs should not be fluctuating excessively as the engine and wheel speeds are matched by the clutch. Also, feel for the regular pulsing on the clutch lever, as this is a positive sign that things are working as they should be.

3.MotoGP clutches will probably only last two or three races, while the actual plates and springs will need changing after every session.

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About Fast Bikes

Welcome to the November issue of Fast Bike , inside ... - Exclusive interview with Marc Marquez - Naughty by nature -Burgain Bullets from the noughties - 2000 Ducati 748 - 2001 Yamaha R1 - 2001 CBR600 - 2004 GSX-R 750 - Brake like brookes in 10 steps - Suzuki GSX-R1000 L6 VS L7 with BSB's Taylor Mackenzie - Best Helmets revealed - One (track) school for all - Know your slipper clutches - MV Agusta F4 Buyer's guide - Get Started Endurance racing
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