Clutch Spline Failure Analysis

[vwdoctor]

For bikes in the 2 wheel BMW price range, NONE of them have this kind of failure!! Not even 1 percent!!

I agree completely!!!

This whole subject has attained mythical proportions!!

I understood CycleRob's statement to say: "There should not be a failure of this type on a machine of this caliber period, regardless of percentages." But, I could be wrong.

[kirby]

For bikes in the 2 wheel BMW price range, NONE of them have this kind of failure!! Not even 1 percent!!

I agree completely!!!

This whole subject has attained mythical proportions!!

I understood CycleRob's statement to say: "There should not be a failure of this type on a machine of this caliber period, regardless of percentages. But, I could be wrong.

I stand by what I said, the key word is "should", thank you for adding that, also "not even 1%", is definitive.

It is courious that BMW can get away with a "10% failure rate", of such a critical componet, don't ya think?

[DKSTRWER]

BMW Service - R1100RT Transmission & Clutch Replacement


https://www.youtube.com/watch?v=6gzR4WHD-94

[DKSTRWER]

Video section showing short cut to spline lube or clutch replacement:

https://www.youtube.com/watch?v=-PdVvxMwz_A

[sykospain]

Ironic isn't it that despite never acknowledging for a moment the undeniable proof of the existence of a serious design flaw in the hydraulic clutch actuation mechanism on a 6-speed R- or K- bike with a dry clutch, BMW has quietly revised the entire design of the Boxer engine for the new range of bikes, to incorporate a WET clutch as in Jap bikes, and with an actuator of a much more robust design.
Bloody typical....

[vwdoctor]

Here is my opinion on the whole BMW spline thing. If there are those that know more feel free to chime in.
The original BMW spline issue is not the clutch spline but the final drive spline.
Due to the design, there is a connection between final drive and drive shaft that not only has to transfer torque but also has to accommodate changing geometry of the suspension. In another words, it has to get longer and shorter. This is the case on early K bike, probably early R bikes (but I don't know intimately). While there is a torque transfer between drive shaft and final drive, you have rubbing between these two parts due to the mentioned suspension geometry changes, as they slide in and out of each other (I know). There is a lot of friction here and lubrication is absolutely necessary (I know). Additionally, there is also limited length of engagement which makes things worse. This joint has been failing for a long time and became a known issue "spline wear". This issue has been addressed with the paralever and addition of second U joint. Now there are two shafts that slide in and out of each other with much longer engagement length. There is no more final drive spline failures regardless of lubrication. Clutch splines do not need lubrication, since there is no rubbing motion between the parts while under torque. Lubrication is OK but only to allow smoother disengagement and engagement of the clutch, input shaft should not care. When first spline failures started happening on the input shaft the "spline failure" got merged with the final drive spline failures. Same logic was applied, and the reason was "lack of lubrication". To make things more confusing, there was apparently and number of misaligned cases on some early R bikes a long time ago and this got added to the mix. But, the basic fact is this:

Other than BMW Oilhead 6 Speed transmissions, there is no instance in the design world (or real one) where clutch hub does not fully engage the input shaft period.

And these are the bikes that suffer from input shaft failures the most.
Now, you can either put 2 and 2 together, or you can go with the dy/dx(ln(exp^-1 (sqrt(e^2.73)/pi*76) and come up with your own explanations.

[P_Jensen]

The other factor that is not mentioned is the gear ratios of the 6 speed, with the R1150 bikes (except the GS Adventure/RTP) requiring a lot of "Clutch Slipping" to pull away from stops especially when 2 up or loaded. The engagement, disengagement, and re-engagement of the clutch puts a lot of stress on the input shaft and clutch plate interface. All of the R1150R transmissions had the same 1-5 gear ratios with the touring transmissions having a .73 6th gear and sport transmissions having a .83 6th gear. After having ridden a 04 R1150R for 36,000 miles and now riding the R1200R, I can say there is a big difference in what it takes to ride off from a stop, with a lot less effort required on the R1200R.

[sykospain]

P Jenson and Esmir are both correct - their arguments about sliding movement of components and standing start take-off requirements, all point clearly to the fact that Berlin has finally acknowledged the inadequacy of the entire dry-clutch concept on a high-powered high-geared bike by silently changing the design of its new models to wet clutches. But hasn't told us existing owners of dry-clutch models in a bulletin or offered any factory upgrades - modified friction plate, or whatever. Very depressing.

[peels]

But, the basic fact is this:

Other than BMW Oilhead 6 Speed transmissions, there is no instance in the design world (or real one) where clutch hub does not fully engage the input shaft period.

And these are the bikes that suffer from input shaft failures the most.
Now, you can either put 2 and 2 together, or you can go with the dy/dx(ln(exp^-1 (sqrt(e^2.73)/pi*76) and come up with your own explanations.

answer: potato.

pickin up what you're layin down....I got confused as well a few times when first researching. final drive...input shaft...which is it? LOL you gotta look close, but the info is all out there on the webz.

[wncbmw]

Since this old thread has been revived, I will only add this. Whatever the failure rate, it is apparently above normal for BMW if not the industry. I care not one bit what the technical issue is. I have no desire to disassemble my transmission periodically to check it out and never had to do that in any of my previous 4 BMWs.

In fact, with about 200,000 miles on the brand, I have only had 3 transmission issues ever on BMWs - all three with my current R1150R. 2 final drive bearings and an clutch spine failure headed off by having my non-dealer (i.e. trusted) mechanic check it out.

Bottom line, I love my bike and with nearly 80K on it, I intend to take it to 100,000. But my next bike is more than likely Japanese.

[rocky2ie]

Can't help but stick my nose in here, having recently done the clutch spacer mod I think I can give my views.
At 17500 miles there were early signs of spline wear, thankfully minimal. My word of advice to anyone with a 6 speed 1150 is to do the spacer mod. It will add years to the life of your splines, doesn't rattle on tickover, smoother gear changes, it's a no brainer when you get in and see how much of the splines are unused. I think the reason some bikes manage to do bigger mileages before failure is more to do with riding styles and type of journeys (ie. stop/start as opposed to long fast rides). I'm not buying japanese , I'm riding my rockster until I can't hold it up anymore.
Cheers.

[peels]

Since this old thread has been revived, I will only add this. Whatever the failure rate, it is apparently above normal for BMW if not the industry. I care not one bit what the technical issue is. I have no desire to disassemble my transmission periodically to check it out and never had to do that in any of my previous 4 BMWs.

In fact, with about 200,000 miles on the brand, I have only had 3 transmission issues ever on BMWs - all three with my current R1150R. 2 final drive bearings and an clutch spine failure headed off by having my non-dealer (i.e. trusted) mechanic check it out.

Bottom line, I love my bike and with nearly 80K on it, I intend to take it to 100,000. But my next bike is more than likely Japanese.

How many miles were on yours when the spline issue presented itself? Mine has 19k on it, and im in no hurry to unload it. Id like to see at least 100 over the next 5-10yrs. For as little as I paid for it....if it does drop dead in 5 yrs, Ill probably just roll it into a grave, and not feel bad about it.

I dont think I'll "go japanese" while theyre drivetrains are arguably top dog, in reliability, and power(mostly) Most of them lack in the "i want to ride all day, everyday" dept. where the boxer shines, and does so whilst still "feeling" sporty"

Going italian is feasible to me though.

cheers.

[vwdoctor]

Can't help but stick my nose in here, having recently done the clutch spacer mod I think I can give my views.
At 17500 miles there were early signs of spline wear, thankfully minimal. My word of advice to anyone with a 6 speed 1150 is to do the spacer mod. It will add years to the life of your splines, doesn't rattle on tickover, smoother gear changes, it's a no brainer when you get in and see how much of the splines are unused. I think the reason some bikes manage to do bigger mileages before failure is more to do with riding styles and type of journeys (ie. stop/start as opposed to long fast rides). I'm not buying japanese , I'm riding my rockster until I can't hold it up anymore.
Cheers.

Glad it worked out for you. I am assuming that the spacer install went smoothly. Esmir

[wncbmw]

My clutch splines were on the verge of failure at 50k.

[rocky2ie]

Hi, Esmir. thanks to you I took the plunge and did the spacer mod. I got my local machine shop to run me up a spacer and rivet it on to a new clutch, total cost of around 150 Euro including clutch.
My shaft wear was minimal so I'd say with the full engagment it will last for a long time. It's a pity that a clutch manufacturer doesn't supply a new clutch with the extra 6mm built in. These are really good bikes let down by a weak spot that's an easy enough fix.

[sykospain]

Here I go again....
My middle son is in charge of the maintenance of a very large fleet of BMW police patrol and covert-duty chase bikes, with a team of about a dozen tecnicos ripping these bikes apart each week. He makes two relevant points in a recent comment to me:-

1) BMW's Dry Clutch design has always been contrary to basic motorcycling lore. A dry clutch is not designed to be slipped. When learning to ride nowadays, novice bikers are taught the complicated and very tricky slow speed manoeuvres such as the 'walk-speed follow' and the even slower U-Turn. To master these riding techniques, they are told to do it all with the back brake covered to control the speed, whilst slipping the clutch. When BMW recently revised the boxer-engined bikes' design to incorporate instead a wet clutch, maybe they were in a way acknowledging the oddness of their original reason for building a Morris Mini-style back-to-front dry clutch.

2) Even the new 1200 series with the wet clutch and a myriad of China-outsourced components has spline problems in my experience here. It's mostly the U.Js on the rearmost end of the shaft that go in every case. They rust, then seize. This is due to rogue officers jet-washing the bikes, contrary to every clear warning by the manufacturer never to jet-wash a bike.
We routinely replace the shaft and both rubber boots on the swing arm. When the shaft collapses, it really goes, in a frightening rear wheel lock up, but you do get a sort of warning - an horrendous vibration prior to collapse. When removed, the front half of the shaft is still metal coloured and the rear half is rust coloured. This is because the rear U.J is lower and water collects there.
We have also had the rear diff/hub bearings seize up as well, mostly due to some people's habit of indulging in frequent vicious acceleration of a heavily-loaded Authorities version bike.
Incidentally and most annoyingly, the tube's internal-diameter in the swing arm is fractionally too small to allow the damaged drive shaft to be removed rearward, without taking the swing arm off. A midge’s dingle larger in diameter and the repair bill would be halved !

Food for thought, eh ?

AL in s.e. Spain

[sliding02]

Hi to all from Aust.
My R1150r clutch hasn't failed yet, so at 50'K (Km's) I'm ordering a new plate and plan to do the spacer mod myself.
My observation about possible reasons for spline failures is that if you consider the actual RADIAL centreline of the FLEXIBLE clutch plate; a good design would have the shaft splines protruding equally on either side of that centreline to distribute the torque evenly and therefore minimise torque flex.

Ideally the Gearbox input shaft would have been manufactured it's proper 8mm longer. but we won't dwell on why it wasn't. Facts are that we have to live with ones that are way too short. This has made the issue quite serious, because now even the tip of the shaft barely reaches the centreline of the flex plate. So, remembering that the clutch plate can flex, I believe that when we apply torque to this sad situation, the plate is likely to twist every which way as far as the minimal spline contact will allow, and could cause the unusual wear pattern as they tilt relative to their axial centreline.
As another post observed, the splines are essentially cantilevered out at the far end of a flexing base. A really bad engineering situation and could be what is causing the deep wear at the area furthest from the plate.

Put another way, if the plate is deforming, it will be putting pressure on the splines to move off their center, especially at the unsupported point furthest from the plate.

I'm confident that the spacer mod will help a lot because of the far greater centering effect and wear area. However a longer shaft would be the proper fix, because it gets closer to the clutch plate axial center line. Sadly, from what i'm hearing I won't hold my breath for a new shaft to magically appear from BMW!
Thanks to all for a great forum.