Dry vs Wet Clutch

[beemergirl]

I just picked up a used '09 RT and I read through a lot of old posts on wet vs dry clutches. I've been riding wet clutched bikes for a few years.

Practically speaking, do you need to treat the dry clutch differently when riding as opposed to a wet clutch. I understand the dry clutch gets hot in traffic....but is there something you're supposed to do to prevent that?

 

[Motorwerk]

Congrats on the new bike! You're going to enjoy it!

A dry-clutch is less forgiving in regards to slipping and wear. Also, because it's not bathed in oil it can feel a bit rough compared to a wet-clutch. You may notice an odor similar to brakes being agressively applied if it's been in the friction zone longer than desired.

For longevity you'll want to be expediant with changing gears, only to keep it in of the friction zone for as short a time as possible, especially starting from a stop. Early on, if you have not already experienced this, the engine may stall if not given enough RPM's when starting out. As the engine wears it will gain power at lower RPM's and this is no longer an issue. Generally, just try get started as quickly as possible while using as low an RPM without stalling. With practice you can usually get the clutch fully engaged within a single tire rotation.

A dry clutch can have a very long life if treated appropriately.

Good luck with the new ride!

 

[PGlaves]

If you go to 15 or 20 rallies a year and always enter the field events then wear on the dry clutch will be significant. Probably wear it out in 50,000 miles. If you normally commute and/or tour expect 100,000 to 200,000.

They do not like to be slipped - and can get hot when you do it. So use it like the dry clutch in your car and expect long life and good service.

 

[peterb]

Clutch

I would never argue with Paul G [I'm afraid of his wife! <g>] but, I believe you will have good life from your clutch if you remember to put the bike in neutral as you roll to a stop. It is easier to put in neutral while still moving than it is to try to find neutral while stopped - which of course is heating up the clutch.

I can't be doing much wrong as I have never replaced a clutch in any vehicle, 2 or 4 wheels in my 50+ yrs of driving/riding.

Its pretty intersting to see bikes stopped at lights and the rider is holding in the clutch, gunning the engine, letting the clutch out a bit, then gunning some more. That will surely get you the smells, the heat, the worn clutch quickly.

Have good and safe rides.

 

[beemergirl]

Thanks for the replies. In MSF class they tell you to stay in first at stop lights....so that you can prevent getting rear ended. So I've always been one to hold the clutch in and stay in first while everyone else is handsfree. Guess it's time to join them and be handsfree.

Of course when I drive a manual transmission, I'm the one sitting there gunning the engine waiting for the light to turn too.....I guess I have some habits to unlearn.

So far I'm just trying to feel comfy on this huge thing. Only stalled once today. Trying to figure out what all the things on the computer are and I'm going to have to reset the clock as we silly Americans have to change the time twice a year.

 

[PGlaves]

If properly adjusted - and if pulled all the way in - the dry clutch will be fully released and not get hot or wear at those stop lights. BUT - as long as it is pulled in there will be pressure on the throwout bearing which will then encounter accelerated wear.

I understand the MSF position about being poised to accelerate to escape a rear-ender. It has merit. At the risk to the long run health of the throwout bearing. For very short stops I keep the clutch in. At long red lights at traffic signals I feel fairly safe going into neutral as soon as one or two cars have stopped behind me.

I am paranoid however in those construction zones where a person with a hand held stop sign has me at a dead stop, exposed to the rear, in a 55 or 60 or 65 mph speed zone. Once a semi has stopped behind me I'm less paranoid. Or 5 or 6 cars.

 

[F1Turbo]

I'll always err on the side of safety versus possible earlier wear and maintenance, especially as drivers seem to grow less attentive (cell phones, texting, dvd watching...) every week.

 

[Polarbear]

Good points;

Watching mirrors as you stop and use neutral often, when stopped are both good advice, imo...I use neutral most always, BUT never take my eye off whats approaching my six, either. I can find first gear, very "rapidly" if needed and if you're watching, you'll know when! CHP(Ca.M/C Cops) are getting, I think an avg. 60000 on clutches(avg.) and they are HARD use RT Bikes...This is what I heard at a BMW shop, servicing CHP RT's...They are known for rapid accel starts as they chase down speeders. A few other clutch TIPS, I find useful. Once under way, very "little" clutch lever is needed to shift gears and you'll find the "sweet spot" for shifting with practice. Less lever travel, equals less wear....Higher gears, 4th to 5th shifting is soooooo very easy without a clutch AT ALL. The ratio is so close in these gears, that a shift without the clutch is elementary. Roll the throttle off and shift up. I do not downshift mine this way, as I find it a different proceedure entirely and not as smooth for me. I think you'll find many road racer types use much less clutch and mostly none! Randy

 

[blongb]

So why doesn't our R1200RTs have a wet clutch? Other than it probably is more expensive (like I didn't pay enough for it), why in the world didn't they put a wet one in? Seems like the wet clutch is the perfect arrangement for a "made to be abused" motorcycle.

 

[darrylri]

A wet clutch means having the transmission share oil with the engine. This means that the oil and especially the additives package that gives it multi weight viscosity, get chewed up by the gears. It also limits to a certain extent which oils you can use so that the clutch works properly. The byproducts of combustion which form an acidic brew will then be circulating in your transmission as well as in your engine, and the clutch wear ends up circulating in both your transmission and your engine.

But mostly, it's because of tradition. The boxers have always had a dry clutch, from 1923 to now, and it, along with the boxer configuration and the shaft drive, form a signature for this line of BMW motorcycles.

There's nothing really wrong with a dry clutch, you just have to treat it a bit differently. I've never, in over half a milliion miles on primarily 5 bikes, even gotten half way through a clutch. They are rugged and long lived, but at the expense of a somewhat more abrupt engagement. This hasn't kept Ducati and Moto Guzzi from using it, either.

 

[blongb]

Excellent reply, thanks much!!! I support tradition!!!

Regards,
Bill

2008 R1200RT Sand Beige
2006 Kawasaki Z750S Black
1985 Mooney 201

 

[ragtoplvr]

It actually would be possible, to seal the area of the clutch, use a wet clutch starter, and have a single or multidisk wet clutch. Of course we would have lots of threads about leaks. It would weigh more, and we would have to put up with more best brand and viscosity of oil threads.

I think I am preferring dry.

Also remember, a wet clutch is not indestructible.

An alternate transmission arrangement, where the current compensator shaft extends to the end of the transmission, and a wet clutch located there, could be changed without dropping the trans, but it would be longer and weigh more.

One of the reasons we love our beemers is the light weight for the size. Given the engine arrangement the dry clutch is simple and light, but a PIA to change.

If only BMW would extend the spline thru the friction disk, and machine the housings correctly (German machinists used to be famous) it would be quite suitable.

Rod

 

[blongb]

Doesn't the multi-disk feature of the wet clutch make it much much more reliable?

 

[darrylri]

Doesn't the multi-disk feature of the wet clutch make it much much more reliable?

That's not clear to me. Each of the friction disks and the pressure disks represents a potential failure point. What a wet clutch does is fit into a smaller diameter area, because the friction material is stacked up rather than being spread out over a larger single disk, as our BMW boxer clutches are.

You do get a softer engagement because, as you release the clutch, you can control it as each individual disk becomes locked to its pressure plate. In a dry clutch, you only get the space as the single clutch plate becomes locked to the pressure plate for feel.

In the late 1920s and early 1930s, BMW did try to add more feel to their clutch operation by including two dry clutch plates with a separating pressure plate between them. When I get my R12 on the road, which has this arrangement, I'll let you know how well it works.

 

[osbornk]

The difference between a dry clutch and a wet chutch is simple (for the mechanically inclined) if you compare it to a car. A dry clutch is just like the clutch you find in a standard transmission car. A wet clutch is just like a clutches you will find in an automatic transmission (multiplate with friction plates sandwiched between each clutch plate).

You treat a dry clutch on a motorcycle exactly like you treat the clutch on a standard transmission car.

 

[FredRydr]

In the late 1920s and early 1930s, BMW did try to add more feel to their clutch operation by including two dry clutch plates with a separating pressure plate between them. When I get my R12 on the road, which has this arrangement, I'll let you know how well it works.

I take it you've done some interesting customizing. Are you going to write an article? Did you make the parts, or adapt them from another vehicle?

Fred

 

[darrylri]

I take it you've done some interesting customizing. Are you going to write an article? Did you make the parts, or adapt them from another vehicle?

Fred

Not customizing at all, just putting it back to stock. The R12/R17, the preceding R11/R16 and some late R52/R57/R62/R63 models all had two clutch plates and a separating pressure ring all sandwiched inside the flywheel. Parts, while not cheap, are available. If you look carefully at this photo, you can just see the two individual plates' splined teeth:

 

[texanrt]

Various clutch images

Here's a page with some exploded views of various clutches. http://www.dansmc.com/clutchexploded.htm

The clutch on my HD sits on the transmission's input shaft tied to the engine by way of the primary chain. It's lubricated independent from the engine, so clutch oil isn't affected by combustion as far as I know. The problem with this configuration is that it's big, bulky, and heavy -- but that's part of being a Harley.

It took me some practice to get acclimated to the dry BMW clutch -- I stalled it a few times until I got used to how quickly it engages compared to the HD. I smelled that dry plate smell a couple times, but as Paul mentioned, the more miles I've got, the freer the engine revs and there's ample power to motor away from a stop even two-up.

 

[PGlaves]

I've owned lots of cars in the past 50 years. Most of them "stick shifts" with a manual transmission and a dry clutch. To my knowledge I've never seen a car with a multi-plate wet clutch. So since BMW uses this system on some of their motorcycles - the ones with longitudinal crankshafts and drive shafts for which they make sense - that is somehow inferior to the Asians???

There is virtually no downside to a dry clutch in typical motorcycle commuting or touring. Slipping it for lots of very slow speed maneuvers during field events or law enforcement operations is of course the exception.

 

[Motorradfahrer]

Ceramic Clutch plates

Lousy clutcher?..wanna long life clutch that lasts the life of the bike...No smell...No overheating...can clutch the be-Jesus out of it....? Get a $$$$$ Ceraminc clutch disc plate. Clutch won't wear out but pressure plate might.

http://www.toursforafrica.co.za/old/accessories/General Access/A-Ceramic Clutch Plate.htm