Can you explain paralever/telelever?

Discussion in 'GS Boxers' started by gweaver, Mar 26, 2007.

  1. gweaver

    gweaver NorCal is Best Cal!

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    Mornin' all. I watched the BMW marketing DVD over the weekend, and it was pretty informative. Motivating too. The GS is on my Next Bike short list.
    Anyway, they did a decent job explaining engine architecture, but they completely glossed over the telelever/paralever technology. I found a couple of websites, but they didn't explain it well either.
    So- for the record- How do paralever/telelever work, and what are the advantages over conventional designs?
    If I understand correctly, paralever is a result of chosing shaft drive? Does chain drive eliminate the torque flex inherent in shaft drive?

    I don't know if I'm asking the right questions; I'm just trying to understand why BMW uses tele/para designs while almost all other manufacturers use a more traditional fork/swing arm layout.

    One of the things that got me thinking is that I remember reading a thread where someone (motozilla? gaspipe?) removed the telelever and replaced it with a conventional fork.

    Thanks,
    Greg
    #1
  2. JimVonBaden

    JimVonBaden "Cool" Aid!

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    I'll let Poolside or Ricardo explain the physics of them, but I can tell you the result.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    <o:p></o:p>
    The telelever applies opposing forces and allows the front to take on a lot of weight during braking and hard cornering without traditional fork dive. This means we can handle much rougher roads and brake harder without upsetting the chassis like conventional forks.<o:p></o:p>
    <o:p></o:p>
    The paralever is not a product of the shaft drive, but an innovation to it that keeps the rear from jacking up under acceleration like a standard shaft drive does. Many other companies use a variation of the paralever rear on their shaft drive bikes.<o:p></o:p>
    <o:p></o:p>
    The result of the pairing of the Telelever and Paralever is that Nate Kern can take a bike that is heavier, has less horsepower, and is wider, and still kick ass on the track. You and I will find that it is a very forgiving platform that allows us to do stupid stuff like braking and shifting in corners, and hitting bumps in corners with less chance of an unintentional dismount!<o:p></o:p>
    <o:p></o:p>
    Jim :brow<o:p></o:p>
    <o:p></o:p>
    PS Now Poolside and Ricardo, and a few others, will tear up what I just wrote!<?xml:namespace prefix = v ns = "urn:schemas-microsoft-com:vml" /><v:shapetype id=_x0000_t75 stroked="f" filled="f" path="m@4@5l@4@11@9@11@9@5xe" o:preferrelative="t" o:spt="75" coordsize="21600,21600"> <v:stroke joinstyle="miter"></v:stroke><v:formulas><v:f eqn="if lineDrawn pixelLineWidth 0"></v:f><v:f eqn="sum @0 1 0"></v:f><v:f eqn="sum 0 0 @1"></v:f><v:f eqn="prod @2 1 2"></v:f><v:f eqn="prod @3 21600 pixelWidth"></v:f><v:f eqn="prod @3 21600 pixelHeight"></v:f><v:f eqn="sum @0 0 1"></v:f><v:f eqn="prod @6 1 2"></v:f><v:f eqn="prod @7 21600 pixelWidth"></v:f><v:f eqn="sum @8 21600 0"></v:f><v:f eqn="prod @7 21600 pixelHeight"></v:f><v:f eqn="sum @10 21600 0"></v:f></v:formulas><v:path o:connecttype="rect" gradientshapeok="t" o:extrusionok="f"></v:path><o:lock aspectratio="t" v:ext="edit"></o:lock></v:shapetype><v:shape id=_x0000_i1025 style="WIDTH: 11.25pt; HEIGHT: 11.25pt" alt="0" type="#_x0000_t75"><v:imagedata o:href="http://s3.amazonaws.com/advrider/icon10.gif" src="file:///C:/DOCUME~1/ebg9qaf/LOCALS~1/Temp/msoclip1/01/clip_image001.gif"></v:imagedata></v:shape>:D
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  3. PaleHearse

    PaleHearse Road Ranger

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    Let's start with the back. Yes, your correct, chain drive will eliminate what's known as "shaft climb" as the forces applied to the rear wheel are ALL in line with the direction of the wheels travel. At issue is that you then have a chain driving your bike. The reason for BMW going with the shaft on their long distance bikes is that you don't have to screw with it as much. At issue is that it's a heavier piece of engineering though.

    The paralever (BMW's marketing buzz term for a lever that runs parallel to the shaft or swingarm) acts on the shaft to keep it from traveling downwards in the direction of force. If you look at the single sided swingarm of the BMW, you will see the standard pivot at the swing arm, but more importantly, you will see a second pivot where the final drive meets the main casting for the swing arm. That's the important bit.

    Here's where a diagram could come in handy... but since I don't have one showing the workings, Ill try and paint the picture. Imagine the bike, your looking at the right side of the bike so the front wheel is to your right, the back wheel to your left. The natural rotation of the rear wheel under force is clockwise. To acheive this, the splins that engage the gear in the final drive to turn the wheel are traveling appropriate for that motion, that is to say they are applying force to the final gear in a downward motion.

    If this motion goes unchecked, the result is that it attempts to drive the entire swingarm downward under the load resulting in what's called "shaft climb". To help counter this, the paralever system was developed to translate some of that force in a way that forces motion to take place at the very end of the swingarm.
    Lost you yet?
    I'm not going to go into any greater detail but suffice to say, the forces are still there, but it's effect is diminished. Basically, with the paralever there, it simulates the shaft climb trying to take place against a swingarm 6ft or more long once the forces are calculated.

    Unfortunately, this also makes the shaft a little more complex then on shaft driven road bikes. The 1200C, for example, has no paralever due to the fact that it simply doesn't see the kind of performance use the other models do.. and certainlynot the same kinds of forces on say the GS/A or HP2.

    Up front, we have something even cooler. The Telelever succeeded in doing what Bimota had been trying to do for years... make a front end that had a neutral or near neutral center of force under braking. Bimota's answer was to introduce dual swing arm bikes in an attempt to do this.. Yamaha had a production version of this in it's ST model as I recall. At issue though was that these systems had quite a few small parts that would certainly not hold up to any off road use.

    BMW's solution (as you saw in that video I'm sure) involves simply removing the fork springs and allowing the supported A arm to hold the weight. This sets up a larger width in the mount to hold the forces.. kind of like having a tripple tree that's 2 feet long. The lower pivot point attached to what I can only describe as the "mother of all fork braces".

    Again, picturing our bike... front wheel to the right, under braking, you have force applied to the contact patch trying to stop the motorcycle. The force applied to this patch is in a rearward direction. This rearward movment bends the forks backward on a standard front end. Under extreem braking or on an uneven surface, this contact patch can brake loose and chatter the front. Because there isn't much distance from the botom of the pivot point (top of the a-arm) and the contact patch, with the telelever suspension, the fork flex is minimal even with an extreemly loaded bike on uneven terrain.

    Fork dive has similar cause and the amount of dive is dictated by the rake of the fork and made worse by the weight of the bike. Again, I'm not going to go into extensive detail, suffice to say that the fork dive was actually engineered into the telelever front end. This front end can be made to have no dive at all.. but this aparently didn't go over too well with the track testers when the system was being developed. Because of this, a slight fork dive was engineered into it of about an inch or so. Test ride the bike.. roll at about 20-30 mph and apply the front brake hard... you'll notice about an inch and a half of dive. Now repeat this at 70-80 mph... it will take about an hour to wipe the grin off your face.

    Cool thing is that the response of that front end is much the same even if the bike is loaded to the gills. If you want to see how much urine your shorts can absorb, try that little trick on a goldwing for comparison.

    Basically it's a great front end.. but only for the street. In a purely offroad environment, there isn't the flex, nor the suspension travel in the front that to allow for stepping over larger obsticles and it's limited travel will become rather noticable. But then, it's a tour bike.. not a dirt bike. Basically it comes down to what your doing with the machine. You can still take the GS off road, you just have to do it more slowly and pick your line more carefully. The HP2, for example, will step over obsicles much more easially... but you can't load it like you can load a GS.

    Now, the choice is yours.. hope this helped a bit.



    Looks like we were both typing at the same time.. and yes, perhaps Ricardo and others have other points to add as well.

    Yup.. a while back, I was getting ready for a "brisk" ride with some sport bike friends. They had a new guy join them... and one of the first things they told him on a trip up to Mt. Hamilton was.. "Oh, and don't try and keep up with the GS in the bumpy corners.. if you do.. your in for a nasty surprise.."
    #3
  4. JimVonBaden

    JimVonBaden "Cool" Aid!

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    I didn't mean that there were no others capable, jusy those two came off the top fo my head. Your explaination was very good, especially in laymans terms we can all understand.:thumb



    Fun isn't it!:lol3

    Jim :brow
    #4
  5. PaleHearse

    PaleHearse Road Ranger

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    Oh yeah..

    Also, one of the groups I ride with has taken to pointing out road disasters with their feet.. kind of cute and all, but when the pavement is f-ed to high heaven... it gets old... so I told them.. "Hey, if your wondering about the pavement in front of me.. just look for daylight under my ass.. if my ass is off the seat.. you had better slow down and watch your ass.."

    They have since been passing that little bit of advice along also. :evil
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  6. eric2

    eric2 ®egister this:

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    Papa and Mama Lever were always interested in riding motorcycles. One day while riding their early model airhead, Papa downshifted one gear to many as him and mama hurtled out of control into a tight hairpin, and the resulting submarining of the ring under the pinion gears pulled the ass end down resulting in major scrapeage of hard parts with extensive road rash as the result.

    How to prevent this from ever happening again? The levers got together and after some awkward positioning and trials and tribulations they had their answer:

    Para was the apple of their pivots, and the parents thought: If one is OK then the more the merrier? The next ride they took, papa grabbed a handful of front brake, and the missus, arse end high in the air from the accursed telescoping forks. So with more awkward psotioning combined with extra weight they begat a sister for Para.

    Tele was quite a woman, able to stop quickly without diving but a bit overweight for the squids, and about as feeling as cheney during an anti-war rally. So the Lever family once again got to work and begat the littlest and smallest lever, duo.

    I think the next family member will be named trya, ymmv
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  7. AntonLargiader

    AntonLargiader Long timer

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    Mine was probably one of those, but just in case it wasn't...

    http://www.largiader.com/paralever/
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  8. Poolside

    Poolside Syndicated

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    <BR>
    Did you ever bolt up traction bars to your live-axle leaf-springed 400hp american sedan? That's 'paralever'. It transfers or 'levers' weight to the rear. And on the shaft drive, that lever is working opposite to 'jacking'.

    'Telelever' creates a fulcrum (aka pivot) and lever in the front suspension, and locates that fulcrum close to the same height as the bike's center of mass. Since the fulcrum is near the same height as the center of mass, the bike does not want to rotate around it. That equals no brake dive.

    A typical front fork and steering head on a bike isn't a lever and fulcrum, it's a cantilever. The attachment point of the cantilever is well above the center of mass.

    - Jim<BR><BR>
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  9. gweaver

    gweaver NorCal is Best Cal!

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    Fantastic Explanation, PaleH! It was actually quite easy to follow, but I still have questions about it..
    To whit:
    You said, "If this motion goes unchecked, the result is that it attempts to drive the entire swingarm downward under the load resulting in what's called "shaft climb"."
    I then ask, "Wouldn't that downward motion be good? It seems like that would apply more pressure to the rear wheel, leading to more traction. Much like a ladder bar or anti-wrap bar on a car."


    You said, "Because there isn't much distance from the botom of the pivot point (top of the a-arm) and the contact patch, with the telelever suspension, the fork flex is minimal even with an extreemly loaded bike on uneven terrain.
    I ask, "Having not yet test ridden a GS (too afraid of having to say "Not yet!"), is fork flex a major issue with modern bikes? I'm currently on a 2K2 ZX-9R, which seems pretty solid to me. Granted, this is only my 2nd bike (1st was an 83 Interceptor 750)."

    You said, "Basically it's a great front end.. but only for the street. You can still take the GS off road, you just have to do it more slowly and pick your line more carefully."
    I ask, "How are we defining off-road? I'm not interested in single track, but certainly jeep roads and 4x4 trails. Possible? My other bike choice would be the KTM, but it seems that the GS is more comfortable and perhaps is adapted for a broader variety of conditions? Perhaps a more 'realistic' bike?"

    Again, a brilliant explanation of BMW design. Thanks!

    G
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  10. PaleHearse

    PaleHearse Road Ranger

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    Sorry to take so long responding.. I've been on a bit of a break to handle some life issues.

    Basically as far as rear end movment goes, if it comes from terrain, fine, if it comes from throttle and is smooth, fine.. but shaft climb is neither smooth nor consistant. The type of motion tends to be jerky and is of the sort that will break traction in a corner, especially on loose terrain. Having the additional lever there to quell this motion is quite an asset.

    As to the fork flex, in a modern sport bike, it's not as big an issue as it is on a tour bike. Modern tour bikes (The yamaha ST aside) have done nothing to stabalize this issue until the telelever. Most notable with this front end is how the bike responds when loaded. If you apply emergency braking force to a gold wing or large harley.. you had better hang the f-on. And heaven forbid should you have to do this on anything but PERFECT terrain (read dry, smooth, no gravel, and straight as an arrow prefferably with a pond on one side and a hedge made of nurf on the other).

    If you apply emergency braking force to a BMW equipped with ABS and a telelever front end.. the only thing the bike does ... is stop.

    And to your last point.. yes, we are, I suppose, still talking "road" as in vehicles go down them. I'd not call this a trail bike by any stretch of the imagination... but then I'd also hesitate to call many of the things I've ridden this bike down.. "roads". (smile)
    For definition here, let's call "off road" to mean off pavement. When the surface transitions rapidly due to ruts, rocks, roots, small drop offs etc. you have to take your time and choose how your going to proceed, where a light dirtbike or something like an HP2 can just crank up some power and take it.

    What I always ask myself when I'm looking to cross something really hairy is ... could this obsticle make me walk out. These bikes take to being tipped over very well (over and over in fact.. if you doubt the durability of this bike and don't own one, watch long way round). Hell if you have spare oil they even take to being submerged reasonably well... but if you drop this sucker at dirt bike speed against a big rock.. your going to become a pedisterian... and you'll be packing your shit out of the middle of nowhere.

    Please give us a shout back after your first ride on the new suspension so we can hear your thoughts.
    #10
  11. 1200gsceej

    1200gsceej Long timer

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    THANKS! Great description and explanation. :clap
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  12. cammyontheback

    cammyontheback ADV'ers

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    Since I'm a new BMW owner, with a lust for understanding anything engineering/mechanical, this was way COOL!
    I'm learning a bunch!

    Thanks to all.
    Mark
    #12
  13. Timberwoof

    Timberwoof Long timer

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    Here's the real reason the Telelever works to prevent dive under braking.

    With a conventional fork suspension, the front wheel moves back as it moves up; the amount of backwards movement depends on the rake angle. Most of the weight of the bike is in the part behind the forks, and under braking, it wants to keep going. It can do that by compressing the front suspension: the tail end of the bike moves an inch or two father than the front wheel.

    In a car, the front wheels move only up and down; there's no front-to-back movement. So the dive that cars do happens only because of "weight transfer".

    What the Telelever does, and I'll have to dig up an old Shockwave animation to illustrate, is make the front axle move not up and back in a straight line, but up and just a little back in a slight curve. The Telelever bikes don't change their wheelbase with front suspension travel. "Weight transfer" still happens (and anyone who says that "Telelever eliminates forward weight transfer" doesn't know what he's talking about), but the geometry doesn't act to compress the front suspension (much).

    The geometric effect of the Paralever is to restrict the rear axle to an arc with a radius much longer than the rear swingarm. BMW says that the relative positions of the virtual pivots for the front and back suspensions makes the handling very good. They're certainly onto something!
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  14. NLS

    NLS My bike needs washing...

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    yes please dig out that flash

    (and it is only a matter of time until someone posts the link to the supposed original designer of telelever - like someone posts the link about rough brake-in when someone asks about brake-in)
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  15. Schtum

    Schtum Free Genie

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    [​IMG]

    From here: http://www.dinamoto.it/DINAMOTO/on-line papers/Telelever or forks/Telelever.html
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  16. NLS

    NLS My bike needs washing...

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    thanks man
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  17. DangerMoney

    DangerMoney Loud Helmets Save Lives

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    I had an '85 Honda Nighthawk 650 which was a mono-lever shaft-drive bike. At highway speeds on smooth blacktop, quickly rolling in and out of the throttle as you would do when passing slower traffic induced big twists in the bike. The higher the speed/quicker the roll on/roll-off, the greater the magnitude of the twist. The bike would twist in one direction when rolling on and in the opposite direction when rolling off. I'm not talking about the frame twisting, I'm talking about a motion where the front wheel quickly turns slightly left or right and that motion passes thru the whole bike, front to back and coupled with a roll to the left or right.


    Violent is too strong a word but at 80-90 MPH the magnitude of the twist was such that it was something you wanted to avoid if at all possible.
    #17
  18. One Eye Mike

    One Eye Mike Been here awhile

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    I took my first off-road trip today on my newly accuired 03 GS 1150 sport.
    I crossed through Hatchers Pass, Alaska. The gravel road has alot of holes / washboards and corners. I've ridden bikes for over 30 years, this was my first ride on a BMW, and i have to tell you i am impressed! The front forks were barely moving up and down through the rough stuff , and i was going betwwen 40-60 MPH. The back end did try to come around on a few corners on the braking bumps, but a quick let off of the throttle and it straightned right out. Before reading this thread, i didn't understand how the suspension worked so well, but i LIKE IT! Looking forward to many more miles on Alaska's dirt roads! Great job on explaining the suspension.
    #18
  19. Timberwoof

    Timberwoof Long timer

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    Thanks for the post, Schtum. Actually, that particular bike rise up in front under braking: it can shorten its wheelbase by lowering the front wheel. ;)

    DangerMoney, what you describe is a torque reaction of the bike to the changing speed of the drive shaft. The Nighthawk's engine and transmission shafts are all lateral, and only the drive shaft is longitudinal. So applying a torque to that means applying the opposite torque to the whole bike. And that will goof with the steering.

    BMW tries to compensate for that effect by having the engine, clutch and first transmission shaft rotate in the opposite direction from the transmission second shaft and drive shaft. The effect can be canceled out in one specific gear, and will end up working one way in lower gears and the other in higher gears as the two shafts' relative speeds change.

    Any motorcycle with a longitudinal engine (BMW R and older K, Moto Guzzi, Honda Gold Wing, etc) can easily demonstrate the effect while standing still with the transmission in neutral: blip the throttle and the bike wants to lean to one side or the other.
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  20. One Eye Mike

    One Eye Mike Been here awhile

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    How do bikes like the motozilla handle with conventional forks up front, and a shaft in the rear?
    #20