Paralever shocks

[oldenoughtoknowbetter]

The rear damper on my 1990 GS Bumblebee is leaking so I've decided to fit the Ohlins from my 1996 PD Classic and put a standard shock on the Classic to get it back to original. But on measuring the Ohlins against the leaky Bumblebee shock I find it's 15mm longer than the one I've taken off. The Ohlins measures 50cm between the centres of the mounting bushes and the one from the B'bee is 48.5cm. The Ohlins fits onto the Bumblebee ok but of course the angle of the driveshaft at the gearbox end is more acute.
The B'bee shock has only done 19,000 miles so I doubt that the spring's compressed.
My mate has two PDs both fitted with Ohlins and both measure around 50cm between the centres.
Anyway, the question is:
Is the geometary of the frame on my 1990 Bumblebee the same as my 1996 PD? It's the version which pre-dates the one fitted with the PD-style roo bars. Clymer seems to suggest that they're the same but I'm concerned that the shock absorber spec seems to be different.
Any help appreciated.
Thanks.

 

[Roger Chatterton]

Can no one help this poor old boy who is struggling with his Bumble Bee ?
Surely Proff or Rob ? Anyone ?

Having had gearbox/shaft related problems myself, I'm keen to read any replies, as accentuating the angle twixt shaft and gearbox is never a good idea on the paras , is it ?

 

[Kenny]

Nothing much to say...I believe both frames are identical and the moment a taller aftermarket shock is fitted, you risk the rath of the dreaded paralever palaver !!
I'd personally fit the Ohlins and just ride her

 

[Redboots]

If there is no binding or "notchy-ness" when you rotate the wheel, it will be OK.
You can buy shorter paralevers the have the effect of jacking the back end up to match up with longer forks. Shaft UJ's need to be good though

John

 

[Box’a’bits]

One of the Wellington people has just bought a R100GS where the Ohlins allows the shaft drive to touch the swingarm at full extention. Worth checking.

Where would one purchase the shorter paralever arm?

I would envisage that that would be something that you'd do if you had the newer rebuildable shaft, & check & relube it regularly.

Apologies for sliding off topic slightly

 

[Redboots]

Where would one purchase the shorter paralever arm?

Apologies for sliding off topic slightly

Mat Beekers at bmwboxersupplies.com gets them made. He has one that is adjustable with a turnbuckle . Once the length is found he gets it made to that length.
There is no one set length that he gets made... all different.

Cheers,
John

 

[Roger Chatterton]

Hi Redboots

I think I follow your drift on this, but are you saying that altering the length of the torsion arm ( what you call paralever !), alters the angle of the shaft at the gearbox ?
This is what , as far as I understand, causes problems to shaft wear/U/Js and gearbox.

Surely the only way to minimise problems is by shortening the suspension travel, ie by fitting shorter shock ? Doing this surely "flattens" the angle of shaft v gearbox.

I'm surprised that no one else has added to this thread, as the whole paralever set-up is the Achilles Heel of these models. For example, do the paralever 1150 RS and RT models of oilheads suffer more or less shaft/gearbox problems than their higher ride height cousins, eg GS Adventures?

I would be very interested to know how many people with "standard" BMW shocks have had these problems ( on the airheads ), as opposed to people using Ohlins shocks ? The Ohlins being apparently 15 mm longer than stansard BMW shock originally fitted.

Not wishing to take over Oldenough's post here, but I know he'll be as keen as I am to hear any replies ?

Proff's solution would be to feck off all the paralevers and ride a mono .......- he might have a point !! Never had a worry on my old mono RS.

 

[cookie]

. The Ohlins fits onto the Bumblebee ok but of course the angle of the driveshaft at the gearbox end is more acute.

only when the suspension is fully extended. i wonder how much difference that makes?

i would have thought any damage caused by the shaft's operating angle would have more to do with terrain ridden, spring rate and how fat the rider was

 

[fritz]

Just sent the Wilbers for rebuild, Ohlins next, and I have a Fournales in garage too.

I'll measure them all...then probably wish I hadn't

I'll let you know the results - take it we are meassuring the distance centre to centre of the shock 'off the bike'?

 

[Roger Chatterton]

Just sent the Wilbers for rebuild, Ohlins next, and I have a Fournales in garage too.

I'll measure them all...then probably wish I hadn't

I'll let you know the results - take it we are meassuring the distance centre to centre of the shock 'off the bike'?

Yes, centre - centre of the mounting holes on the shock. Be very interested to read what the lengths will be - I was wondering what Wilbers would be myself !

PS I'm on my second gearbox rebuild on my 100GS PD - shaft was fine in both cases, - I have an Ohlins fitted !!!

 

[thornley]

Are you measuring off the bike? What length fitted with same rider seated? Spring rates can be misleading with a shock that is not loaded. Just my twopenny worth

 

[fritz]

Yes, centre - centre of the mounting holes on the shock. Be very interested to read what the lengths will be - I was wondering what Wilbers would be myself !

PS I'm on my second gearbox rebuild on my 100GS PD - shaft was fine in both cases, - I have an Ohlins fitted !!!

Standard, servieable item - had rebuilt gearboxes on all my BMs, R80/7 & GSs - if you haven't had to rebuild, you haven't done the miles...


Leave that out there as a bit of bait, catchee catchee monkey

 

[Redboots]

I think I follow your drift on this, but are you saying that altering the length of the torsion arm ( what you call paralever !), alters the angle of the shaft at the gearbox ?
This is what , as far as I understand, causes problems to shaft wear/U/Js and gearbox.

I thought that, but I believe it alters the angle of the bevel box... the shock will dictate the angle of the swing-arm... Not sure.
If you look at this:

You can see that as standard, even with an Ohlins, the drive is canted up a little. A shorter arm would bring it in line and raise the back a bit.

I think a good portion of the wear is associated with the "sealed-for-life" UJ's that are used, the effects of leaking gearbox seals and final drive seals washing the grease from the needle rollers and the cush rubber letting them run out of sync.

John

 

[fritz]

Shock Lengths

Just sent the Wilbers for rebuild, Ohlins next, and I have a Fournales in garage too.

I'll measure them all...then probably wish I hadn't

I'll let you know the results - take it we are meassuring the distance centre to centre of the shock 'off the bike'?

OK Wilbers back and Ohlins about to go off for rebuild, photo below for comparison. Both same (well, not checked to mm). Basically both just about 500mm (495?).

Will check Fournales once Ohlins back.

Revs didn't have a blue spring (had it resprung as too soft for our two-up with off road use) so it's black - far better to my eye

Ohlins going off now as it'll be the base one for the upcoming trip...though looking at the crazy prices of PD Classics maybe the bike should reside in the garage and age gracefully and increase in value...

Ah **** it, out with the grinder

 

[Roger Chatterton]

Oldenough & I have both had our GS Ohlins shortened by 15mm, down to 485 mm, which is the length of the BMW shock originally fitted.
The angle of the driveshaft/gearbox now seems less severe, and hopefully will improve shaft/gearbox life. Work was done by Ohlins specialists in Stowmarket , Suffolk.
Now the only slight problem is getting the bike onto the centre stand - do-able, but hard work !
So next job is shortening the centre stand by about 12 mm - ........has anyone had this done, or know of an alternative to shortening the stand ?

Still, well worth all the effort if it saves my having to get gearbox reconditioned again.

 

[fritz]

Oldenough & I have both had our GS Ohlins shortened by 15mm, down to 485 mm, which is the length of the BMW shock originally fitted.

Now the only slight problem is getting the bike onto the centre stand - do-able, but hard work !

Roger - that would suggest the original bike is hard to get on the centre-stand? I know my PD is a hugely heavy lump of sh*te to get on the centre stand due to the large drinks console and cosmetic cow bars stuck up front and high.

Would BM have designed it to have been even harder in the first place

 

[newbuild100]

Just my ten penneth here.

Over the past 18 months or so, ive had no end of probs with my "rear end".
During one of its noisy periods, I experimented with a few things.
one of the things i did was as follows.
With the bike on its centre stand, rear wheel in the air, bike running and in gear with a few revs on. (ie, apart from the shock being compressed, normal running)The rear was very noisy
I then took out the shocker and replaced it with a strut that was a lot shorter than the shock, and enough to send the "swing arm" parallel to the ground.The result was a super smooth, and very quiet rear. (The bike wasnt actually ridden like this)
Im not real sure what this proves apart from it seems a smoother, quieter bike is one where the swing arm is being lifted towards horizontal.

To that end, does anyone know what the O/E shock length was/should be on a 94 GS100 ???

 

[Roger Chatterton]

To that end, does anyone know what the O/E shock length was/should be on a 94 GS100 ???

Hi NewBuild,
from our measurements, using the regular BMW supplied shock, shock length centre to centre of mounting points is 485 mm; hence our decision to make the Ohlins that same length.

 

[Redboots]

Roger - that would suggest the original bike is hard to get on the centre-stand? I know my PD is a hugely heavy lump of sh*te to get on the centre stand due to the large drinks console and cosmetic cow bars stuck up front and high.

I put new pins/bolts in my centrestand... works easily enough now.

If you are shortening the centre stand 'cos the back end is lower, wont that make the front look silly without shortening that as well

I want a LONGER centre stand

John

 

[andyfrizzle]

So next job is shortening the centre stand by about 12 mm - ........has anyone had this done, or know of an alternative to shortening the stand ?

You could consider trying a centre stand from a R80R or R100R.

Do you know anyone in your area that has one of the above models who would let you try the centre stand for size?