Advantages of a single sided swinging arm...

[MikeO]

Okay, it looks pretty good - I can still remember seeing the first G/S with one. It makes changing the rear wheel pretty easy (though not as easy as if they'd split the hub so you could leave the disc on the bike - like any car).

But I'm convinced that there wouldn't be the problems with the final drive bearing (which, let's face it, is just a wheel bearing) if the rear wheel was supported by an axle held at both sides.

If you look at most cars (certainly all the ones I've had) and were to cut a line directly through the longitudinal centre of the tyre, the line would pass directly through the wheel bearing. This is achieved by off-setting the wheel (which is why car wheels are generally dished) and mounting the wheel on a protruding hub. This way, the weight of the car is passed to the bearing without any torsion or moment.

If you look at the same 'centre' of the GS wheel, it's a long way from the bearing - which surely puts additional strain on the bearing.

Any thoughts?

Mike

 

[Schtum]

Your description of the correct way to do it is, of course, exactly what Honda have done with the VFR since that went to a single sider.

 

[cookie]

didn't honda change their WSB bikes to conventional swingers a few years back as the single sided jobbies didn't handle as well?

i'd rather have normal 2 sided swing arm, i believe you are quite right about final drive durabilty.

 

[MikeP]

Never really gave it much thought before.

The single-sided swing arm came along on BMW's when they introduced the mono-shock models. I'm guessing that because the mono-shock was on one side and not centrally mounted, having a single sided set-up reduced any torque issues under load?

Once they mounted the rear shock in a central position, there seems to be little logic for retaining the single-sided set-up or would that require two Paralevers?

Must agree about the brake disc mounting. Didn't K's (at east the older ones) have the rear disc mounted on the final drive not the wheel?

 

[Mouse]

Okay, it looks pretty good - I can still remember seeing the first G/S with one. It makes changing the rear wheel pretty easy (though not as easy as if they'd split the hub so you could leave the disc on the bike - like any car).

Well the rear wheel on the 1200 comes away by itself leaving the hub and disc on the bike. So there's progress in that department anyway

 

[littleredrooster]

A very valid observation, Watson.

Don't forget that it's also supported by the taper-roller, as well.

 

[Kropotkin]

didn't honda change their WSB bikes to conventional swingers a few years back as the single sided jobbies didn't handle as well?

That's because a double-sided swingarm is lighter than a single-sided one. The single-sided jobby has to have a lot of reinforcement in places where you don't want it (e.g. near the wheel), so you have a heavier unit, and more unsprung weight.

That said, I think the BMW swingarm is lovely. But that's an aesthetic judgement, not an engineering judgement.

 

[Timolgra]

My thoughts......

Wheel bearings do wear out on cars. (ok eventually)
GS wheel bearings easy to change
For me, benefits of convenience and aesthetics gets the thumbs up

 

[Steve Peake]

I'm still not convince by single-sided swing arms.

All three beemers I've owned have had to have work done on the rear bearings.

I've never had issues with conventional swing arms, even at stupidly high mileage.

Steve.

 

[Tarka]

...and if you look back at BMWs pre 900RR Dakar twins,they had a double sided swinging arm,even though the mono arm GS was in existance....

Pedant time....

Single sider...'swinging arm'

Double sider...'pivoting fork'

But we all call them 'swinging arms'.

 

[Steptoe]

K series has a single sided arm, very very rarely gives any problems, and the internals and bearings are the same .

It's only the GS that has the disc attached to the wheel, all the other models ( including K's) have it attached to the rear bevel, on the output flange .

Normally the weakest point on swingarms/frames, is where the swingarm attaches to the frame, so all those extra beefy braced swingarms that you could buy back in the late 70's early 80's were a complete waste of money, the frame flexed at the mounting point .

 

[Steve Chip]

It's racing innit...

Honda did the single sided for endurance racing - tyre changes take less time.

BWM did it for the Dakar - so that knackered idiot who has to do his own stuff can get more sleep.

Neither situation is limited by bearing life.
Mechanically they don't make sense in (for want of a better description) the real world.

Looks pretty though.

Steve