KNOW YOUR R… SLIP­PER CLUT TCHES

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 a at, we had a chin­wag with Sigma slip

Fast Bikes - - TECH TALK -

How good will a nor­mal clutch hold up on track?

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…

How will a slip­per clutch ben­e­fit a bike?

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 brak­ing – it’s not! As you brak ke hard into a cor­ner all the weig ght is on the front, but with the throt­tle closed the chain geom me­try will want to pull the rear whe el off the ground; the slip­per clut tch helps keep the rear wheel on t the ground and so keeps the back k wheel be­hind the front.

How does it work?

Each clutch has a se­ries s of ramps, typ­i­cally one be­twe een each spring. When the engine e turns the wheel, the clutch op­er­ates nor­mally, but when it’s the other way round (so slow wing down), the cen­tre rises and pokes the pres­sure plate off th he clutch pack and lets the clutch h slip a lit­tle. All in all, this mea ans that the rear wheel won’t try to over­come the engine brak­ing and will help to com­bat the b back wheel hop­ping on cor­ner entr ry!

Would it help on the road?

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...

How should you main­tain one?

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 hap­pen­spp youy have a big gp prob­lem. At the first sign of the clutch slip­ping, you should check the plates for wear and re­place them if needed.

What dif­fer­ence does ad­just­ing the clutch slip give?

Essen­tially, the clutch needs to be held to­gether hard enough not to slip go­ing for­wards, and once that’s okay you can have more spring for more engine brak­ing and ad­just it to the rider’s pref­er­ence. You need it to hold to­gether enough to ac­tu­ally work, so we set the max­i­mum ramp angle (how much it slips) and rec­om­mend a spring to work with it, but the end user can ad­just it to suit their pref­er­ences from there on. It’s a very per­sonal item that can be tuned specif­i­cally, like an in­stru­ment.

What’s the best way of us­ing one?

At the end of the day, a slip­per clutch is essen­tially there to as­sist you, which means it isn’t an au­to­matic sys­tem. It will work with­out us­ing the lever to shift down the ’box, but we don’t rec­om­mend that. Not us­ing the lever will de­stroy the clutch plates a lot quicker so be aware of that. When you first start us­ing one as well it will prob­a­bly feel slightly alien; this is be­cause it will feel like the clutch lever is click­ing in your hand where the clutch is ac­tu­ally op­er­at­ing on the other end of the wire. It will all be­come nat­u­ral with time, so don’t over­think it.

Do they work with mod­ern bikes and auto-blip­pers etc?

Auto-blip­pers are in­cred­i­bly help­ful and are a welcome ad­di­tion to per­for­mance ma­chines, and will work ex­tremely well along­side a slip­per clutch unit if they are de­signed to work to­gether. The per­fect ma­chines are more like your pre-elec­tronic Su­per­sport, Su­per­stock and Su­per­bike ma­chines, as you re­ally need to have ei­ther so­phis­ti­cated elec­tron­ics or a so­phis­ti­cated slip­per clutch to work at their op­ti­mum level – put them both to­gether and they al­most ar­gue about who’s in charge.

So high per­for­mance ma­chines won’t be run­ning them?

Even Mo­toGP bikes, with all of their elec­tronic wizardry, still run a slip­per clutch. This is the best ex­am­ple of show­ing just how much of a per­fect fall-back they are, as it makes life easy if you ac­ci­den­tally go down a gear ex­tra or have an is­sue. It all de­pends on the elec­tron­ics. If you have per­fect cor­ner spe­cific cor­ner en­try elec­tron­ics then you can have sim­ple slip­per clutch set­tings. Those with less so­phis­ti­cated elec­tron­ics, for ex­am­ple Bri­tish Su­per­sport, still get a lot more out of a bet­ter race slip­per clutch. Over the last few years Kyle Ryde, Bradley Ray and the Gear­link Kawasaki team have done a lot of win­ning on them, along­side tak­ing three cham­pi­onships in the Du­cati Tri-Op­tions Cup. If you’ve never rid­den a bike with one, I’d en­cour­age you to try one be­cause it will make a mas­sive dif­fer­ence to your rid­ing.

A thing of beauty...

Sim­ples! Even su­per­stars like Fa­gan use slip­per clutches.

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