what's the point of paralever

[Sierra1]

Blitz11 speaks of side loading and how street bikes don't have to deal with them. Make sense to me, if the GS and/or the Tenere are used in their designed manner, they will see plenty of side loading. If the single swing arm does not like that....it would explain the failures. I was always told that the paralever was to reduce shaft rise. I believed it because my RT1150P would squat under acceleration. The ST1300PA would exhibit a small amount of shaft rise occasionally. Neither bike changed the way that I drove. I did like the easier tire change. I did NOT like the shaft failures. I do not know if the single swing arm was the cause though. The Tenere does seem to be built heavier; the rear hub even has cooling fins!
::022::

 

[2daMax]

It's winter in Malaysia too?

Lot's of rain if that qualifies for winter in the tropics.

 

[dietDrThunder]

Good point. Sort of starting thinking about it, and became carried away.

I think that I addressed paralever vs. not (longer swing arm on the S-10 due to its engine architecture and location of swing arm bearings) and Snakebitten's discussion of single vs. double swing arms.

Don't apologize; your post is the only one in the thread with actual information in it.

 

[blitz11]

Thanks. Gotta' do something with 12 years of engineering education. I tend to become carried away.

I had my Super 10 apart to lube the swing arm bearings and suspension linkage the day before i saw this post, and was impressed with the Super 10 design. My daughter is taking Strength of Materials, and I was explaining swing arm design to her as an example of what she needs to take away from that class - loads, deflections, stiffness, strength. (Practical stuff they fail to teach in college.) I had been explaining side loads, stiffness, why my KTM Duke swing arm is cast the way it is, and how triangulation is the secret to stiff structures (duke frame).

The other practical side of this is manufacturing - material selection, casting porosity, surface finish, fracture toughness, surface hardness, etc. I, for one, am shocked at how light the Super 10 swing arm is. It's really a nice piece of work and i presume it's designed with fracture toughness in mind in contrast to the BMW swingarm shown above.

 

[2daMax]

Blitz. It would make it easier to understand with a Free Body Diagram. Too bad there is no emoticons on 'This thread is worthless without FBD'.

 

[hogmolly]

Wow, this thread went all sorts of ways and angles.

A paralever is BMW speak for having 2 u-joints in the rear shaft. One is at the transmission side (like a monolever) and one is at the final drive (unlike the monolever). This allows the final drive to move through it's arc (during suspension travel) and remain at the same angle relative to the ground and transmission of the bike. Why is this important? Braking or acceleration upsets the suspension less (in theory). One side benefit is your brake caliper can bolt directly to the final drive hub instead of on a separate semi-floating bracket.

The big problem with a single sided swingarm is the final drive bearings. They must support the side loads created from supporting the weight of the bike/rider. BMW uses deep grove ball bearings to do this which are the wrong bearings to use for large side loads. Deep groove ball bearings will handle some side load but what you really need are back to back tapered bearings which you can't get at the size needed. BMW at one time used a single tapered bearing opposite the deep groove ball but today uses needle bearings opposite the deep groove ball bearing. I'm sure it was a weight saving thing.

Finally, the front of a BMW is called a tele lever (lower A arm below the triple tree) for the shock mount. That helps a lot with front end dive during braking.

I have rebuilt a few final drives on BMWs and it's kind of a PITA. I prefer the drivetrain setup of the S10 because it is more robust and they (the Japanese) have been doing it this way since the 80's. BMW did it this way even earlier as well.

 

[RCinNC]

I'm not a BMW guy (other than thinking they are pretty nice looking bikes), and I've never owned one, but the topic of the final drive and the failure rate always interests me. It's probably impossible to know how many have actually failed per number of units sold, since I doubt that BMW has ever released that sort of information, but do the newer models still have the same problems as the ones from, say, 2012? For you guys that know BMWs, has the design of the final drive/single swingarm design changed in any way in the past few years that would imply BMW was aware there were design flaws, and attempted to address them?

 

[Tenerester]

Wow, this thread went all sorts of ways and angles.

A paralever is BMW speak for having 2 u-joints in the rear shaft. One is at the transmission side (like a monolever) and one is at the final drive (unlike the monolever). This allows the final drive to move through it's arc (during suspension travel) and remain at the same angle relative to the ground and transmission of the bike. Why is this important? Braking or acceleration upsets the suspension less (in theory). One side benefit is your brake caliper can bolt directly to the final drive hub instead of on a separate semi-floating bracket.

Perfect explanation! ::008:: That's exactly the logic behind the paralever system though BMW may have not perfected it. The Japanese have taken the conventional route...because its cheaper to build them and less prone to failures.

 

[magic]

I'm not a BMW guy (other than thinking they are pretty nice looking bikes), and I've never owned one, but the topic of the final drive and the failure rate always interests me. It's probably impossible to know how many have actually failed per number of units sold, since I doubt that BMW has ever released that sort of information, but do the newer models still have the same problems as the ones from, say, 2012? For you guys that know BMWs, has the design of the final drive/single swingarm design changed in any way in the past few years that would imply BMW was aware there were design flaws, and attempted to address them?

First off, Blitz11 and hogmolly have made very good engineering analysis and explanations of the BMW paralever design. I would like to pass on some info about the failure rate. Before I bought my S10, the BMW GSA was the only bike I was considering and researching. Of course I read about the final drive failures. Still interested, I made several trips to BMW dealers. When inquiring about the FD failures all 3 dealers had the same explanation. They all acknowledged the problem and attributed it to improper assembly practices. They also said the failure rate was 6-7%, and each shop sees about 1 failure per year across their entire line. Still interested, I now asked about trade in value on one or both of my Harleys. This didn't go very well and I wound up with an S10. The last 8 years that I worked was as a model maker building prototypes and test units. The prototypes and test machines were always built by the more skilled model makers. These machines almost always made it through testing in good shape. However, the problems arose with the production machines built by the assemblers on the production line. So, I can see how this could be BMW's problem. Still no excuse on an expensive machine like a GSA.

 

[Davesax36]

Interesting that a dealer was that open with service numbers with you. One guy here at BMW dulles said they haven't seen any failures, especially on the new ones. At that point, my pursuit of the more expensive (but more interesting looking IMO) bike stopped, and I went for my s10. Very happy.

I also wonder about the front fork design changes on the gs.

 

[scott123007]

I'm not a BMW guy (other than thinking they are pretty nice looking bikes), and I've never owned one, but the topic of the final drive and the failure rate always interests me. It's probably impossible to know how many have actually failed per number of units sold, since I doubt that BMW has ever released that sort of information, but do the newer models still have the same problems as the ones from, say, 2012? For you guys that know BMWs, has the design of the final drive/single swingarm design changed in any way in the past few years that would imply BMW was aware there were design flaws, and attempted to address them?

Looks like Magic only half answered your question. ;D. When BMW went to the waterboxer motor on the GS's, they redesigned their driveshaft too. It now exits the left side of the bike as opposed to the right. There may have still been a failure or two since the re-design, but nothing like the previous design.

 

[charlie.c]

wow
Some very knowledgeable people on here. I had a shaft drive suzuki 850 back in the 80's along with a Kawasaki Z100st shaft drive. Both would rise and fall at the rear when you went on and off the throttle, nothing that caused a problem it was just the way they were and you accepted it. It was interesting to see the paralever system come into use and I guessed they must have made a step forward in some way to make it worthwhile. I have a BMW K1300S which has this system and I have to say using the full extent of the power available you sure don't get any rise and fall. I got my S10 in December and so far I'm loving ridng it having done nearly 2k miles already. It was looking at the simplicity of the rear end that prompted my question. If the Yamaha can do it without all those extra linkages what's the point of the BMW system. Well thanks for the answers chaps

 

[greenwall]

wow
Some very knowledgeable people on here. I had a shaft drive suzuki 850 back in the 80's along with a Kawasaki Z100st shaft drive. Both would rise and fall at the rear when you went on and off the throttle, nothing that caused a problem it was just the way they were and you accepted it. It was interesting to see the paralever system come into use and I guessed they must have made a step forward in some way to make it worthwhile. I have a BMW K1300S which has this system and I have to say using the full extent of the power available you sure don't get any rise and fall. I got my S10 in December and so far I'm loving ridng it having done nearly 2k miles already. It was looking at the simplicity of the rear end that prompted my question. If the Yamaha can do it without all those extra linkages what's the point of the BMW system. Well thanks for the answers chaps

I think someone answered that previously. It has to do with the length of the swing arm. Since Yamaha's engine configuration allows for a longer swing arm on a given wheelbase, the extra complication wasn't needed. More detail in the previous answer.

 

[BaldKnob]

The point is to keep people employed in the making of and installation of components that are merely adequate for the purpose intended.