BMW Poor Engineering; an opinion

Some ideas on poor BMW Engineering used on their motorcycles.
These are things that occur with too great a frequency on bmw motorcycles for them to be considered normal ware and tear, or are 'required maintenance that should not be!

Click on a topic, or scroll through.
The clutch spline
The Paralever U Joint

The clutch spline

BMW motorcycles use a dry clutch system very much the same as BMW cars and most other motor vehicles. The engineering is well understood and has been in use for many decades! Normally it is highly unusual for the clutch to require regular maintenance other than adjustment and replacement when the friction material wares out.
Unfortunately on BMW motorcycles the spline on the gearbox input shaft and the clutch friction plate fails on some bmw motorcycles and is a required maintenance item $$$! Regular lubrication of the spline has been a required maintenance item on older BMW motorcycles. Some dealers are now telling customers of current BMW motorcycles that lubrication for the clutch spline 'would be a good idea'! Without lubrication on older models the BMW motorcycle spline wares - eventually the clutch center strips out leaving the bike stranded.
Similar lubrication requirements are made for other driveline splines on BMW motorcycles - suggesting the same design methods are in use for these splines. If the BMW car clutch spline can be made without requiring regular (and expensive) lubrication and remain reliable why cannot the same engineering methods be used on BMW motorcycles?

The Paralever U joint

diagram of two U joint alinment.
The propeller shaft used on a normal motor vehicle is similar to the bmw motorcycle Paralever drive shaft in engineering terms. It has 2 U joints; one at each end and a spline on the shaft to allow for a variable length. The bmw shaft incorporates a rubber shock absorber.
A U joint when rotated at an angle produces a speed variation between input and output depending on the angle of input to output shaft axis and the angle between the U joint yoke and the plane where both input and output shafts axis lie. The second U joint can be placed so that the first U joints' speed variation is cancelled by the second U joint speed variation. Both U joints must have the same angle of input to output shaft.

The Paralever has a high rate of failure of the U joint on the Paralever particularly on high power K1200 models and on long suspension travel GS models. Possible sources of the failure are

Angular displacement by misalignment (some people are now checking their 'new' motorcycles and finding them miss aligned!)
Angular displacement caused by the shock absorber so that the cancellation of the speed variation is not effective
Lack of lubrication
too much angle between input and output shafts

Rumored corrective actions could be;

correct alignment - and marking the shaft so alignment is easier
fitting new U joints with lubrication fittings that are lubricated once a year
reduce the angle between the U joints shafts

Design wise the U joint should be looked at as old technology and possible redesign using constant velocity joints (no speed variation and larger angles tolerated between input and output shafts). If the U joints are retained the rubber shock absorber should be removed from the shaft and placed elsewhere in the driveline so misalignment of the U joints is eliminated from this source.

Comments? all welcome just e-mail me at Yahoo.

If you quote me I would like an acknowledgment. Dated 8 May 2003.

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