More general airhead questions: Paralever vs. Monolever

[ultracyclist]

They both do the same thing.
What are the trade-offs for each?
The Para is more modern, but is the Mono easier to maintain?

You will earn bonus points for participation if you post a close up pic of your Mono or your Para!

[mneblett]

They both do the same thing.
What are the trade-offs for each?
The Para is more modern, but is the Mono easier to maintain?

You will earn bonus points for participation if you post a close up pic of your Mono or your Para!

The paralever eliminates the jacking of the rear end of a shaft-drive motorcycle up with acceleration, down with deceleration.

One way to think of this is that as torque is applied (throttle opened), the pinion gear at the end of the drive shaft tries to "climb" up the teeth of the crown gear in the final drive. As a result, you feel the rear end of the bike rise under you as you accelerate. More significantly, if you suddenly chop the throttle in the middle of a way-leaned-over turn, the chassis drops, which can result in hard parts of the bike touching ground -- a real laundry moment for the inexperienced. If you are aware of the jacking effect, this isn't an issue (i.e., you know not to chop the throttle in mid-turn!).

The paralever eliminates this issue by articulating the final drive housing on pivots at the end of the swingarm and by careful location of a "torque arm" roughly parallel to the swingarm to effectively eliminate the torque reaction.

Here's the most recent version of the paralever (newer K1200) -- different side of the bike than an airhead, but otherwise the same principles:


This is a monolever -- note the fixed mounting of the final drive on the end of the swingarm:


This is a crappy pic of an airhead paralever -- note the torque arm under the swingarm (where it was always located until the wedge K12's came along), and the pivot pins connecting the final drive to the swingarm at the side of the rear end of the swingarm (the rod above the swingarm is the lower end of the shock absorber, which is generally oriented in the same place as on the monolever):


As far as other advantages/disadvantages, two universal joints in the paralever vs. only one in the monolever. The paralever GS universals have a poor reputation for longevity, apparently due to the more extreme angles the swingarm moves through than the other paralever bikes. I'm sure others will pipe in with more thoughts from there.

HTH,
Mark Neblett
Fairfax, VA

[ultracyclist]

Now I understand!
So simple, yet so elegant...
You must be a teacher in the real world.
Is that an R80/7 on the lift?
H

[mneblett]

You must be a teacher in the real world.

Worse -- a former engineer, now an attorney

Is that an R80/7 on the lift?

Nope (the monolever is a clue it's later than the /7's; also, the black valve covers are a clue it's not an R80/7 -- the R80/7's had the same shape valve covers, but were not painted black).

It's my new-to-me 1988 R100RT in the process of being stripped down for a going-through to sort out a number of issues and to prep for dual plugging. Engine is out; forks & steering head have come out for head bearing replacement and have already been reinstalled.

[carockwell]

The jacking effect of the shaft drive bikes 800cc and under isn't that much. You really have to be 95% of the way to the outer limits before it starts to slow you down. With the 1000cc bikes it can be an issue at "only"80%. What the jacking effect does is make the bike drop if you get off the throttle while leaned over in a turn. As you may know, you aren't supposed to get off the throttle while leaned over in a turn...

[AntonLargiader]

Once you're used to a suspension that doesn't have this quirk, you notice it on 750/800cc pretty easily.

Some more info: http://www.largiader.com/paralever/

Monolever is generally more rubust, but so is a hardtail.

[fracture]

I remember feeling much more shaft effect on the old two sided swingarm bikes versus the monolever. I have not ridden one of the two sided bikes for quite some time now so I have to rely on a somewhat faulty memory. The monolever swingarm, at least for me, does not exhibit as much shaft effect. Anyone else notice this?

There is something else I have been wondering about---final drive failures appear to have increased with the introduction of the paralever. I have not heard much regarding final drive failures on older (monolever or two sided swingarm) bikes.

[20774]

I must have a numb butt...I don't notice the shaft effect at all on my bike(s). It must be A) I've not ridden any of the later version of Airheads and B) I don't ride to anywhere near the 80% level suggested in a previous post.

There's probably another reason but my CRS is kicking in at this point...

[VANZEN]

Shaft-effect will be pretty obvious on any pre-Para BMW
if you have the regular occasion to ride chain drive bikes or Paralever BMWs.

The "motorcycle press" whined and complained about it for years !
IMO, not that this necessarily makes shaft-effect a "bad" thing –
but it certainly would be "very different" for those magazine test riders used to chain-drive motorcycles.
Shaft-effect can also be used to the rider's advantage ...

I would venture to say that many riders of older BMWs are simply "accustomed"
to this behavior and do not take notice.
The compensations in riding style become automatic.

[Manfred]

I moved to shaft driven bikes in 1985 (Yamaha) and heard and read all about the drive shaft bounce. Never noticed it on any bikes (until I let off the gas really quick in a turn on my airhead) - but I did notice it in a big way on a Pontiac rental car made in Korea in the early '90s.

[lkchris]

I must have a numb butt...I don't notice the shaft effect at all on my bike(s).

You can notice it in your garage.

Apply front brake.

Put in 1st gear

Slowly let out clutch.

Rear end will rise.

[20774]

You can notice it in your garage.

That might be true, but I was saying I don't notice it when I ride the bike...I'm not sensitive to it and there's too much else going on.

[ohiorider]

Back several years ago, I was riding my first Beemer, a 1985 K100RS. I'd just finished reading a few books on road riding, and thought I knew all there was to know. As I headed toward a very sharp curve to the right, I dropped the K bike from 4 to 2nd gear, revved her a bit to coordinate wheel and rpm ( I thought). As I went into the turn, the rear of the bike went into a violent hop, hop, hop. It was as though the engine braking was causing the rear suspension to compress to the point where the shock spring would rebound, then it would do it again. I finally had enough sense to pull in the clutch, though in retrospect I probably should have given the bike some throttle. I would attribute the hopping to my basic ineptness, along with the shaft drive characteristics + light flywheel + high compression of the K bike. My dealer at the time called it the "K bike hop'. Not sure if he was humoring me, or stating what was a known problem with these early K bikes. However, under the same circumstances, I don't believe this would have happened on either a chain drive or Paralever suspension-equipped bike.

Bob

[ultracyclist]

Not to hijack my own thread, but have the other shaft driven bike manufacturers gone through this same evolution or did they do something better on earlier bikes?

[mneblett]

Not to hijack my own thread, but have the other shaft driven bike manufacturers gone through this same evolution or did they do something better on earlier bikes?

Basically, they had the same jacking issues. On some bikes, (like the early GoldWings) the swingarm was so long and the bike so heavy, the jacking effect was hardly notable. Others, like the MotoGuzzi, were much like BMWs in their response.

The Guzzis also share the trait of leaning a bit to the right whenever the throttle is blipped (torque reaction to the accelerating crankshaft/flywheel.