SWB = Short Wheel Base, LWB = Long Wheel Base
The question keeps coming up “What is this long wheel base and how do I know if I have one?” A very good question and the answer is simple. When BMW came out with the /5 series in 1970, the bike had some stability problems. See my page on wobbles for more info on this subject. In the middle of 1973 production, BMW started using a longer swing arm to get more wheelbase and therefore more stability. It worked. If you inspect the swing arm (drive shaft housing) you can see what you have. The difference isn’t subtle.
This rough sketch shows three types of swing arm used on the bikes. The upper one is a SWB from 1970 to mid 73. The middle one shows a piece that is “welded in” to make it longer. The text is in error, the 74 had the weld and it was 75 and on that was “finished.” The bottom is a “finished” LWB swing arm.
A SWB swing arm
A mid 73 LWB with the welded in 2″ piece.
The 75 and later type LWB.
The result of the longer swing arm is a BMW motorcycle that is far more stable. One could load it up with more junk and still not wobble. The price paid is much slower handling. The SWB is better for solo sport riding. The LWB is better for two up touring with luggage. It is certainly possible for the LWB to wobble, but is less likely.