Airhead Drive Shaft - inspection
 

I keep reading about drive shafts for the airheads being fragile. I am pretty sure that mine has never been changed but it has had an easy life to date having covered around 43,000 km so far.

Is there any way to undertake a condition inspection of the shaft or should I be looking at changing it out for one that is easier to maintain? If the inspection includes non-destructive testing then that should not be a problem as I have access to magnetic particle, dye penetrant and eddy currect equipment.

Thanks

I don’t think that there are any issues with the shaft per se, but like any other drive shaft the universal joint can wear, but I think they have a very long life unless abused.

Back in 1978 Bmw introduced a sprung dampener in the drive shaft, occasionally the spring will break but it’s not very often.


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Drive shafts - G/S and GS pre-1996 models
 

This question is like "Are deer whistles any good."


You did not say what year or model? The below applies to Pre-1996 GS and G/S models:



On my 1981 R80G/S, resting in Bob's BMW Museum, the original monoshock drive shaft has 240,000 miles, never changed or a problem.


One my 1989 R100GS, at unknown miles, but in excess of 50,000 miles, the U joint was going, so replaced it. My pal, with 30,000 miles on his paralever 1995 R100GS Classic (end of airhead GS production), had his U joints starting to go, so we replaced it.



Airhead "Rule of Thumb" for GS paralever GS models: After 20,000 miles you are on "borrowed time," change it or carry a spare :-(


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The shafts on Paralever GS (88 to 95) can wear quite quickly, I have heard of them failing with as little as 30,000km and rarely lasting 100,000km. About the only way to test them on the bike is to put it in first gear, rotate the rear wheel to take up the backlash in the gearbox then try to rotate it further using quite a lot of effort, do this in both directions and any movement requires further investigation.
You can also slide back the rubber gaiter and inspect the front bearing which is the most common one to fail, although the rear bearing occasionally fails first, apart from that you need to remove the shaft to inspect it.
The R100R which is basically the same bike but with a shorter rear shock and forks suffers much less from the problem, I have run my GS with a shock from this bike for the last 20 years and 200,000km and had 160,000km from a shaft, I did the same to a friend's bike with similar results.
If you do need to replace the shaft there are some rebuildable ones available now which seem to have a good reputation.

A very fair point. It is a plain Jane R80 from 1986.

In my experience of inspecting or replacing broken shafts, they seem to go notchy in their universal joints when they wear. All movement in the joint should be smooth and offer a little resistance.

If it's notchy or 'floppy' then it's a sign of wear but that does not necessarily mean immediate failure. But monitor it !!

At BMW we use Castrol Optimol grey Paste TA on the splines. It disperses heat and acts as a lubricant.

The angle of the shaft is a massive contributor of wear. Shaft failure is fairly common on GS/GSA but almost unheard of on an RT. The GS has a great deal more suspension travel so the angle of the shaft has to change with it.

A shaft likes to be straight.

Engage humour switch!
 

:whistling: ... :laugh:
You don't get off that easily !

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That is a relief as I didn’t really want to replace the shaft but getting the right lubricant is clearly something that would be prudent as, whilst I may enjoy putting the shaft in and out repeatedly, reducing the risk of shaft failure is a better way forward. Given that the chances of the shaft having been slipped out and relubed is minimal I will grasp the mettle, clean it up after checking that is has a smooth action and apply some of the Castrol paste before pushing it back into position and then fiddle with its nuts.

Double entendres always aid a good post.