R26 driveshaft shimming

[BSA Bob]

Apologies, there's already a thread on this but I wasn't able to put up a post to continue it.
The distance between the driveshaft flanges on my R26 is 37mm. That's a lot. If I put 2x 3mm shims in that doesn't leave much contact area on the driveshaft & flange splines. I'm thinking of just using 1x 3mm shim. Any opinions?

[BSA Bob]

[Taz]

Hi Bob.

I might be mistaken, but according to my memory the distance between those two flanges should be 31-32mm, when the flange plates are parallel (both wheels on the ground, rear wheel pressed down accordingly)...so those 37mm of yours seem way to much, readjusting the flanges might be required...but owning only an R25/3 I don't have the knowledge to help you here...maybe one of our English speaking R26 riders can corroborate the 31mm mentioned above and shed some light on the procedures necessary to correct this....


The shims are meant for the thinner "rubber starfish" to keep the distance while at the same time allow for larger deviation angles the swingarm suspension makes possible compared to the plunger suspension.

All the best, Ute

[rolf.soler]

It should be 30 + 1,5 mm when the flanges are parallel, meaning the bike ist on both wheels and someone is sitting on the seat. Measure in the middlele of the flanges, i.e. over the axis.See also repair manual, page 40
It that distance is too long, you probably have no distance ring at the front end of the cardan shaft, just under the flange at the front of the shaft - there are distance rings in various thickness, 2 or 3 mm (or more, but not much), they go over the toothed end of the front shaft end UNDER the flange, bring the flange more forward
If you measure properly (flanges parallel, with weight on the bike) you approach probably the 31,5 mm, if it is a bit more, use the proper distancers, if it is much more, there is something more wrong

[BSA Bob]

Thanks for these quick replies.
I've measured the 37mm distance with the swingarm parallel & the faces of the flanges parallel to each other.
You're right that the manual says the distance should be 30 +  1.5mm. I've measured without any distance rings behind the driveshaft flange. There are new rubbers & a new Hardy disc.
I measure the length of the splines on the flange & cardan shaft at about 16mm. So if I put 2 x 3mm distance rings on that only leaves 10mm contact length for the splines.
I think I will assemble everything with a 3mm   distance ring & see what happens & repeat my measurements. Perhaps the problem's between my ears, it has been known to happen.
By the way, how tight should the castle retaining nut be? https://bmw-einzylinder.de/forum/Smileys/my/huh.gif

[rolf.soler]

The one on the cardan shaft "normal" tight, as the flange is held by the splines. However, the one on the gearbox flange VERY tight, 140 Nm (12-15 mkg in manual = 117-145 Nm, or 87-108 lb/ft), this one sits on a conus, the woodruff-key is only for positioning and pulverized if the flange is not pressed on the conus

[BSA Bob]

Thanks Rolf.
I'm glad I don't have to tighten up the gearbox flange, I don't think I'd have the strength for it these days.

[rolf.soler]

The power is not the question, with a long torque-spanner. The problem is to fix the gearbox and the flange so that 140 Nm torque can be applied, and turn the crown nut...some special tools are almost mandatory