There are a few things that immediately come to mind looking at the failure photos.
1) Compared to cage u joints the bits are small yet rpm will be about the same meaning heat loads will go up faster if lubes or bits fail.
2) The paralever (or equivalent) doesn't exist in (most) cages and between it and the fact that its a bike with a very different suspension and axle location method from a cage, also much shorter than most cages, it is likely the vibration modes of this system are very different.
I'd bet a few bucks that a serious vibration analysis of this design will show that some dimensional combinations, perhaps in conjunction with certain road surfaces, produce a vibration that pounds those rear bearings to death, exacerbated by their fairly small size.
It should not be difficult at all to make these bulletproof but the designers need to do the homework- no doubt guys who design these systems for a living can look at these failures and have a pretty good idea what's killing them, might or might not match mine.
This looks like something that might happen if one were to drop it into 1st or 2nd going 50+ and then drop the clutch. Seen it before.... teaching my 16 yo daughter how to drive a stick
Interesting thread...Over at my normal hangout..ADV Rider..35-40,000 miles is all we expect out of driveshafts..just too many of them die around then, no one get's too suprised by it....yes it's bs..but whaddya gonna do?
I have been repairing them with servicables..simply centering the u joint on a lathe then welding a washer over the cap..
maybe an exchange repair service is in order (if there is not one already)....have a couple refurbished and ready to ship....RT owner sends his in for an exchange....just thinking out loud here....BeemerBoneYard and FleaBay do not have driveshafts for the 10+RT....but many others....
2015 BMW S1000R - Duke - Black Storm Metallic
2013 BMW R1200RT - Sassy - Fluid Grey Metallic
Go back and look at the photo where the joint is all apart. Notice the one leg of the cross piece that has worn tapered almost like it was in a crude pencil sharpener.
That wear took a lot of miles. I found the same type of wear on Voni's R1100RS. The insidious thing was that there was no discernible vibration at the riders seat/bars/pegs. Then one day seemingly all of a sudden it got ugly - bang!
Having had my hands on several driveshafts with shot, but not yet exploded U joints, I have concluded that they don't last forever and ought to be periodically examined/inspected by hand. Yes - taken out and manipulated to look for any binding, or any detectable play in any axis for either the front or rear joint.
I guess it varies with the type of bike, rider and riding that is being done; but at what mileage would you recommend they be examined, etc?
Last edited by easy; 09-27-2013 at 07:00 PM.
On Oilheads, the first several failures I heard of happened between 125K and 200K so I used to say start checking at 100K. Then I started hearing about 75K, 50K, 37K etc.
There are variables: how heavily or lightly loaded the bike is - heavy load means less angular deflection (good) but arguably more stress due to the load (bad).
Phasing: there is a right way and wrong way to phase paired U joints. They come out of the factory every which way. The manuals don't prescribe the correct way either. Improperly phased U joints add considerable stress to the joints. So for optimal life they ought to be phased correctly.
BMW has made some changes. I'm not sure but don't think the latest shafts can be changed. The R11xx shafts can need to be properly phased.
On our bikes I am certain the shafts are correctly phased because I did it, and I know how we load and ride the bikes. So I am comfortable having gone in once to not do it again until 100K miles. But then, every 24K or so until I am tired of it and just replace the shaft.
This advice would, of course, be of no help to the guy or gal who got the shaft so to speak at 30K miles.
Interesting thread.....there have been some comments about how the destroyed u-joint looked. I have seen this many times on equipment and barring something out of the ordinary- like on a brush hog, letting grass and debris build up and the heat baking the u-joint, it's 9 out 10 times a lube issue in the joint itself. Classic example is when pick-up truck makers eliminated locking hubs on the front axle- and grease fittings on the front wheel drive shafts. Do the u-joints come from the factory with a grease fitting?
My point being is that a u-joint was spinning all the time- and there was no way to lube it. Sure it had support and the wear is/was worse when there was a 4X4 load actually on it. The first CV-joints that I remember in regular automotive us was in the small for Bronco- front drive shaft. Owners of these shafts suffered loss from theft more than mechanical failure....the "new" CV joints were not properly serviced (due to being new) and the ball part went bad rather quick and they were very costly back in the early 70's.
Bearings need grease or lube especially needle bearings under high load/torque.
When those tiny needles in a u-joint start to wear out, the end comes soon. Do you ever remember a car going by with the "odd squeak"?
Without a new u-joint the shaft ends up looking like the picture.