Help with Paralever arm Issue

[RiceBurner]

Ok, I have Gromit's old GS-length Paralever arm on my Rockster (I measured it, and it's only 5mm shorter than the standard arm).

I had the same arm on my old Rockster for about 3 months with no issues.

I fitted the arm to my current Rockster when I bought it in April/May.

Since then my dealer has replaced the Final Drive seal twice, firstly at 6K miles because it was weeping slightly, and secondly at 11K (early 12K service) because it had been weeping slightly, virtually ever since the first seal swap.

While I was in France this weekend (about 500 miles after the seal was swapped) the swingarm was getting covered in oil AGAIN. Due to the heat it was getting quite bad, and actually dripping onto the wheel when parked over night. (on sidestand).

On talking to the dealer (Vines) they intimated that replacing the seal again may not be covered by warranty because of the non-standard Paralever arm.

I don't buy this argument simply because I don't believe the efficacy of the seal should be dependant on the angle of the final drive box to the swingarm (which is effectively all the Paralever arm alters). I mean, how can that be true? The angle of the FDbox to the Swingarm is constantly changing as the suspension moves up and down, doesn't it??

If the lesser angle caused by the short Paralever arm is taking the seal beyond a certain limit then I still don't buy it because then all GS's would have similar problems, wouldn't they?? I'm sure I've seen other bikes with an "at rest" angle between FDBox and SW that is identical to mine.


I intend to swap back to a standard paralever arm for a week (after cleaning the area up, including under the rubber gaiter) and see if the seal continues to piss oil. If it doesn't then i'll buy their argument, if it continues to piss oil I will be highly upset and will tell them so....

I personally reckon that the shaft is corroded ever so slightly somewhere (the bike did 1200 miles in 2 years and was highly corroded in the rear-wheel hub from lots of washing, but no riding and being parked up), and this corrosion is nicking the seal each time a new one is put in.

Anyone got any thoughts??

Does anyone here run a shorter than standard paralever arm? What distance have you done on it and have you had any FDBox seal issues??

[sandbar]

Anyone got any thoughts??

With all this you need to take into account that BMW use universal joints in their drive shafts. These are by no means constant velocity joints.

If the input and output shaft on a universal joint are not inline, then during each revolution the angular velocity of these shafts will not remain the same. If I remember rightly the difference is similar to a sine wave.

If the universal joint at the other end of a drive shaft is "in phase" with the first uj and if the output shaft of this second uj is parallel to the input shaft of the first uj then the differences in its angular velocity will cancel out the variations of the first one.

If they are not in phase or the shafts are not parallel then there will be vibration, increased tyre wear and eventually there must be an adverse effect on all the joints, bearings and seals.

The reality is that using the torque arm for anything other than keeping the output shaft from the gearbox and the input shaft to the bevel drive is going to cause harmful side effects. Lots of people ( me included!!! ) have used these arms to change the ride height at the rear, when the correct way to do this is to change the length of the shock and then, if necessary, to change the torque arm length to re-align the shafts.

Do I know what I am talking about??? - Probably Not!!!

sandbar

[Dog Tyred]

Anyone got any thoughts??

Do I know what I am talking about??? - Probably Not!!!

sandbar

Do I know what you talking about ??? - ABSOLUTELY NOT!!!

[Gromit]

Sandbar's hit the nail on the head - it does seem to tally aswell with those folk who run standard (ie std shock and std arm) set-ups and don't have any (or far less) Paralever bearing issues.

Having said that, Alan's 1150RS has had a weeping seal for ages now which his dealer have failed to fix, despite several attempts, which tends to negate Vines' comments about angle affecting seals.

As Bailey said, and I agree 100%, if you want more rear ride height this should be achieved by way of a longer shock, not a shorter para arm.

To back up Sandbar's comments take a look here...

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

If I can understand this, anyone can

[Boxadog 2000]

It doesent matter a toss what arm you have.

At the end of the day the shaft going through the seal only rotates it has no lateral movement.

The shaft as you suspect is either damaged or coroded OR undersize.

My 1100S did the same almost from day one it had a recall and a sleeve was put over the pinion shaft and a new seal fitted.

[winger]

I'll ditto Bob,i've run a Verholen ajustable for years and it's OK.

[Ade B]

Thought the SS and BCR run shorter paralever arms as standard.

One of the few things that hasn't gone wrong with mine yet is the final drive..

Thats cursed it

Ade.

[bigblackfalco]

I'll ditto Bob,i've run a Verholen ajustable for years and it's OK.

Yeah, but we are talking about bikes that actually get ridden..........handbags at dawn
Bailey.

[bigblackfalco]

It doesent matter a toss what arm you have.

At the end of the day the shaft going through the seal only rotates it has no lateral movement.

The shaft as you suspect is either damaged or coroded OR undersize.

My 1100S did the same almost from day one it had a recall and a sleeve was put over the pinion shaft and a new seal fitted.

Sounds like the best and easiest fix. Ditto Bobs views here.
If it were me I'd either get it machined and sleeved or find a 'DOUBLE LIPPED' seal (oink oink) in place of the crappy BMW ones.
Bailey.

[Jason M]

It doesent matter a toss what arm you have.

At the end of the day the shaft going through the seal only rotates it has no lateral movement.

The shaft as you suspect is either damaged or coroded OR undersize.

My 1100S did the same almost from day one it had a recall and a sleeve was put over the pinion shaft and a new seal fitted.

I'll agree with Bob too - there is no lateral movement where the seal is - the seal is always at 90 degrees to the shaft it's protecting. I suspect Bob is right with the size thing myself. My mate had a GS that constantly ate crown bearings and in the end they replaced the whole unit (Jefferies I think).

BTW I've had the adjustable arm on for the last 50k or more with no adverse effects on the seals - I think one of the UJs is on the way out again but that's only what I would expect on a 139k bike. Just put the normal paralever on and take it to another dealer to fix under warranty I reckon.

Jason

[RiceBurner]

Cheers guys - as the later posts pointed out - this is a SEAL issue, if the shaft is moving about within the seal I'd suspect a bearing was well fucked. That's why I don't get this argument that changing the angle of the uj will effect the seal's seal. If the bearing is ok then the shaft will be held in place properly and the seal should work - whatever the orientation.

I doubt I can get a normal BMW warranty to work - it's over 2 years old now, I'm reliant on the Dealer Warranty.

Interesting that Alan's RS is still affected by it though.

[sandbar]

- this is a SEAL issue

Of course it is a seal issue!!!!

But WHY is it a seal issue? Why is the failure of successive seals both quicker and more severe???

If the shaft is undersize - is it getting progressively more undersize?? I don't think so!

If it is corroded then, yes, the corrosion could be getting worse.

If it is faulty, then whatever the fault is - it is getting worse.

I just suspect that something else is going on. Unless they are being replaced badly, then something is making the seal say "Sorry - this is not in my job description!!!".

sandbar

[RiceBurner]

- this is a SEAL issue

Of course it is a seal issue!!!!

But WHY is it a seal issue? Why is the failure of successive seals both quicker and more severe???

If the shaft is undersize - is it getting progressively more undersize?? I don't think so!

If it is corroded then, yes, the corrosion could be getting worse.

If it is faulty, then whatever the fault is - it is getting worse.

I just suspect that something else is going on. Unless they are being replaced badly, then something is making the seal say "Sorry - this is not in my job description!!!".

sandbar

Aye, I see where you're coming from.

(is it nice there?)

[Jason M]

- this is a SEAL issue

Of course it is a seal issue!!!!

But WHY is it a seal issue? Why is the failure of successive seals both quicker and more severe???

If the shaft is undersize - is it getting progressively more undersize?? I don't think so!

If it is corroded then, yes, the corrosion could be getting worse.

If it is faulty, then whatever the fault is - it is getting worse.

I just suspect that something else is going on. Unless they are being replaced badly, then something is making the seal say "Sorry - this is not in my job description!!!".

sandbar

Are you mad Sandbar

I may be wrong but I think that the viscosity of oil changes with temperature and as Risey said, it was extreemly hot in France and no doubt working harder/differently to the normal commute so why should it come as a suprise that the oil is coming past the seal? My bike was burning shed loads of oil in the heat of Las Vagas, but vertually none in the cold of Alaska for example. It's not getting worse unless you subject it to the same regime and its failing more often which wasn't the case here it seems. If the shaft is undersize, then of course it won't change size, and I don't think corrosion would be a factor at that age but I guess there could be a scratch on it or summit that is upsetting the seal. Undoubtably the weaping past the seal is the symptom of a different problem, and if the shaft bearing is not buggered surely that implies there isn't too much vibration coming through I'd guess something is outside tolerance somewhere

just my 2ps worth, and not an exclamation mark in sight! (whoops)

Jason

[sandbar]

Are you mad Sandbar

Completely

sandbar