Shorter Paralever Arm

[Boxerpunk]

That Van Harten paralever looks cool. Wonder if its available in the US.

Actually Van Harten doesn't make them, just sells them.
It's produced by the famous (well, at least in Holland it is) framebuilder Nico Bakker
You can always contact them......

[sweatmark]

Hey - Thanks for the tip on that Nico Bakker piece... he has a special place in BMW customizing history, and using one of his parts would have significance.

Anybody price the R1150GS OE piece for comparison?

[boxermania]

The diference in length between the R1150R and the GS arm is about 20 mm, the R at 386 mm center to center and the GS at 366 mm. That is if my recollection doesn't fail me.

The adjustable arms are typically limited to a 15 mm adjustment. The two halves of the arms and the bushing is the only thing that has to be obtained from BMW for the conversion and I belive it comes to less than $60.

It does raise the back about 1/2 ", shifting soem weight to the front and helping with the turn in of the bike. Ergo, making the steering crisper.....it does enhance the handling of the bike........

[bebecar]

This looks like a very interesting modification!

I don't even have Rockster (yet) but it is really interesting to see that the performance can be enhanced in this way without sacrificing anything serious.

[Rog(UK) - Yorkshire Dales]

The big problem with this modification - and I am surprised that nobody has mentioned it - is that if the back end is jacked up, the BMW badges on the oil-coolers will no longer be level. In addition, the headlights will require readjusting.

Is it all worth it.......?

Rog

[boxermania]

Rog (UK)

Look two posts up from yours, yes it has been mentioned that it will raise the back end.

Yes, you are correct on all the other comments.

Is it worth it?....well, the Boxer is not a crotch rocket, but it does have a lot of grunt down low and will embarrass faster bikes in the twisties. That simple mod will make the bike handle better....for ~ $60 US.

[Rog(UK) - Yorkshire Dales]

Sorry guys. That was just my sense of humour. Just ignore me; most people do Shortening the paralever arm sounds like a good mod.

Ride safely,

Rog

[reidmct]

Sorry guys. That was just my sense of humour. Just ignore me; most people do Shortening the paralever arm sounds like a good mod.

Ride safely,

Rog

I'm working on a mod that will fix the emblem-level problem. I expect to be able to price the mod at less than $999.95, so place your pre-orders now!

I'm also working on a more expensive (exclusive) version that will spin the "propeller" in proportion to the bike's speed. Pricing could be as low as $2K if enough suckers... er, discriminating pilots, place pre-orders.

[boxermania]

reidmct

2K !!!! it's doable....sign me on for one........however, it better belch big fire when the throttle is closed.....like the racing Porsche Turbos......

[OU812]

Sorry guys. That was just my sense of humour. Just ignore me; most people do Shortening the paralever arm sounds like a good mod.

Ride safely,

Rog

I'm working on a mod that will fix the emblem-level problem. I expect to be able to price the mod at less than $999.95, so place your pre-orders now!

I'm also working on a more expensive (exclusive) version that will spin the "propeller" in proportion to the bike's speed. Pricing could be as low as $2K if enough suckers... er, discriminating pilots, place pre-orders.

Well, how Is the emblem?

[reidmct]

Thinking seriously about this mod: Is it possible that the paralever drive would not work right if the bar length is changed?

I ask this as someone who only recently bought his first BMW, though I have a lot of experience with other makes.

BMW calls its rear end a Paralever. I take that to mean something about parallelism. As I look at the drive system, it appears that the rod's job is to keep the final drive parallel to the primary drive. In driveshaft systems that have two conventional u-joints, maintaining such a parallel relationship between the ends of the system is what keeps the final drive speed constant throughout its rotation. Changing the rod length would change the angular relationship of the input and output shafts.

So, what say you guys? Am I worried about nothing? Can you explain why BMW uses this link bar instead of something less dynamic like a non-pivoting final drive? Is there something in the design of the driveshaft linkages that makes parallelism unimportant, such as CV joints? Why do they call it a paralever?

[riceburner]

Thinking seriously about this mod: Is it possible that the paralever drive would not work right if the bar length is changed?

I ask this as someone who only recently bought his first BMW, though I have a lot of experience with other makes.

BMW calls its rear end a Paralever. I take that to mean something about parallelism. As I look at the drive system, it appears that the rod's job is to keep the final drive parallel to the primary drive. In driveshaft systems that have two conventional u-joints, maintaining such a parallel relationship between the ends of the system is what keeps the final drive speed constant throughout its rotation. Changing the rod length would change the angular relationship of the input and output shafts.

So, what say you guys? Am I worried about nothing? Can you explain why BMW uses this link bar instead of something less dynamic like a non-pivoting final drive? Is there something in the design of the driveshaft linkages that makes parallelism unimportant, such as CV joints? Why do they call it a paralever?

The paralever is so called because the system makes a "Parallelogram" out of the different bars and arms. Nothing to do with keeping the shafts "parallel" to each other at all.

The system was designed by Arturo Magni for Guzzi engined bikes initially, then BMW picked up on it.

If you take a look at all the different models of bike that use this system (ie ALL boxer BMWs prior to the Hexheads, ALL Flying Bricks etc) there are differences in the angle of the final drive to the shaft and again to the gearbox on several models.

The drive shaft system does use UJs but the possible differences in rotational speeds of different parts of the overall shaft due to UJ peculiarities wouldn't be an issue I wouldn't have thought. (It's been a long time since I studied UJ mechanics I have to admit!)

[Ves]

The reason for the design is to eliminate jacking and lowering of the rear end during acceleration and deceleration. Don't ask me exactly how it does that, but it does.

See illustration below. Technically, I guess you could put on a pralever bar that's too short or too long so that as the rear suspension moves through it's travel, before the suspension reaches the end of it's movement, the housings at point "a" would bind or some other mechanical limitation to movement, in that area, is reached. Practically, you're not going to find a paralever bar, whether off a different model BMW or one of the adjustable ones, that would be that long or that short as to cause you problems.

Note also that BMW does this themselves. They take the same basic engine and drive system and then put on different length paralever bars to adjust the ride height. The GS and the R1100S both used the shorter paralever bar. So, by putting one on the Rockster you're not doing anything that BMW hasn't already done.

[ronnierockster]

Have just fitted R1100s/GS arm to Rock. Steering realy good now, seems more lively. The other things the seat seems better,perhaps due to being raised a tad at the rear?? I have allways thought that the angle of the std Rock driveshaft looked a bit strange with the kink in the end,thats gone now and the drive alingnement looks much more natural ie straighter. Going for a longer ride tommorow so will see about the seat,is it in my mind!!

[boxermania]

Actually driveshaft design calls for a slight angularity, 1 to 2 deg across the UJ for proper operation, like wise there is also a maximum angle before the UJ binds.

All of the above has been taken into consideration accross the BMW models with the 20 mm diference between the arms, at least on the 4 valve models.....

[ronnierockster]

Mechanicaly, the lesser angle is kinder to the shaft. Went for that long ride to London for the riders rights demo, against road pricing for bikes.. The seat seems slightly more comfortable with the different (shorter) arm. The steering is more to my liking. Bonus all round I think..

[reidmct]

Here's an explanation of my concern. Where my knowledge is lacking is in whether BMW uses U-joints or CV joints. If the latter, then no worries. If the former, then I would think it important to maintain parallelism between the transmission output shaft and the final drive input shaft, so as to nullify the varying angular velocities.

http://www.chron.com/disp/story.mpl/hea ... 31716.html

[Ves]

Here's an explanation of my concern. Where my knowledge is lacking is in whether BMW uses U-joints or CV joints. If the latter, then no worries. If the former, then I would think it important to maintain parallelism between the transmission output shaft and the final drive input shaft, so as to nullify the varying angular velocities.

http://www.chron.com/disp/story.mpl/hea ... 31716.html

I think you gave us the wrong link.... This one points to a story on "Nuns and bikers ride for the needy"...

The angle at the rear joint changes as the suspension moves up and down anyway. Again, you're not doing anything that BMW hasn't already done on other models.

[reidmct]

Here's an explanation of my concern. Where my knowledge is lacking is in whether BMW uses U-joints or CV joints. If the latter, then no worries. If the former, then I would think it important to maintain parallelism between the transmission output shaft and the final drive input shaft, so as to nullify the varying angular velocities.

http://www.chron.com/disp/story.mpl/hea ... 31716.html

I think you gave us the wrong link.... This one points to a story on "Nuns and bikers ride for the needy"...

The angle at the rear joint changes as the suspension moves up and down anyway. Again, you're not doing anything that BMW hasn't already done on other models.

Well, color me embarassed!

Here's the link I had meant ot provide:

http://en.wikipedia.org/wiki/Universal_joint

As for the angle of the rear joint changing, that is the purpose of the linkage -- to change the angle of the final drive so that it maintains a constant relationship to the transmission output shaft as the swingarm moves through its range of motion. Or, at least that's how it appears to me.

[johnnyjs1]

Kinda new here, so please excuse my newbyism . If you shorten the arm, it raises the rear end of the bike up correct? Is anyone having the problem of sliding even more forward on the seat than usual. I dont know about you guys, but my family jewels are already almost hitting the tank. Went for a ride last night, hit a bit of a sink hole, almost lost the girlfriend off the back, and nearly got a vasectomy at the same time. Felt like someone reared back and kicked me in the nads. Had to pull into a parking lot and wait for the unmistakeable lower abdomin pain to go away (you guys know what i'm talking about ). So i guess my question is: Does the seat angle towards the front more with this mod?
Thanks,
Johnny