Random question from mechanical ignoramus

What are the advantages and disadvantages of dry clutches vs. wet clutches
for bikes? I've just noticed that my RT has a dry clutch, but the K1300GT
has a wet clutch.

I'd hazard a guess that a wet clutch is more resistant to heat damage from
slipping, and a dry clutch allows longer service intervals because of
reduced oil contamination, but why would a manufacturer use different ones
on bikes with approximately the same purpose?

 

Wet clutches are compact and can be made to handle quite reasonable
amounts of power for their size - it's all about the frictional area and
clamping force that dictates the slipping point. The cooling of the oil
helps considerably and when the clutch is fully engaged the oil no
longer functions as a lube.
Single-plate dry clutches are ok up to a certain point but to handle
serious amounts of power they have to get bigger and unwieldy or use an
intolerable amount of spring pressure - through a bar lever. Multi-plate
dry clutches tend to rattle like buggery and don't have any cooling -
worse, they get too hot internally.

 

Makes me wonder why cars don't have wet clutches. Even high performance
cars have dry clutches? Anybody know if any cars past or present have
experimented?

 

They've got a large bellhousing. Practically, the Beemer bike clutch is
as big as you could go on a bike. Car clutches can have really heavy
springs on them, which is mitigated by the pedal leverage and in extreme
cases, a hydraulic servo.

 

So why would you ever use a dry clutch?

 

Cheap and simple to make, can handle large amounts of torque, suitably
designed. Of all the advantages, none holds more sway for the makers
than the 'cheap' bit.

 

One of the reasons I got rid of my RS was the dry clutch. Ok it wasn't
slipping and had done 50k miles but I was doing a lot more stop/start
commuting and by what I'd read those clutches don't take kindly to a lot of
that. The BMW clutch is a real task to change, apparently (according to the
people in the BMW forum I used to frequent) BMW would charge something in
the order of £700 + to change it and an independant would be at least £500.

--
Malc

Rusted and ropy.
Dog-eared old copy.
Vintage and classic,
or just plain Jurassic:
all words to describe me.

 

Dry clutches sound great when they're rattling like a bag of spanners.

 

I've seen a Ferrari F1 engine dismantled. It had a multi place dry clutch
with carbon fible plates.

 

Clutch failure on boxer twins is not a big issue, for R-GS owners at least.
Not even amongst the mad sods who go off roading and will give their
clutches a harder time than road riders.

 

Do you have a cleft keyboard?

 

Not surprising.

 

BMW have always built their bikes around the clutches (and the
batteries). Fortunately, they do seem long-lived.

 

Kiran's 1098 does have certain "je ne sais quois" about it, yes.

 

Mine rattled a bit too. The garage told me it was ok so I never
worried about it. It didn't get much worse over the time I owned it.

 

<waves>