Boxerworks.com

I was under the impression that the 70 -73 SWB sub frames were shorter than the LWB sub frames.

However, looking about at realoem I see the same part number for the sub frame regardless whether it is a /5 or a /7.

Is there a difference in the sub frames?

Jim

It's the swinging arm length that's different.

There are pictures about that show an extra bit welded in to the early LWB versions.

Interesting, so how can you tell if you have a Short or Long wheelbase swing arm?

Maybe you can see the images here on the MOA forum:

https://forums.bmwmoa.org/threads/short ... st-1049013

fwiw, who knows if any ol' /5 has its original one on it after all these years.

www.realoem.com wrote:01 33 17 1 231 010 REAR WHEEL SWINGING ARM, BLACK (to 01/73) 4.72 1 $381.07ADD
*FG R50/5 2 906 304 / R60/5 2 947 966 / R75/5 2 997 986 :
01 33 17 1 231 220 REAR WHEEL FORK PRIME COATED (to 01/73) 4.91 1 NANLA
01 33 17 1 240 459 REAR WHEEL SWINGING ARM, BLACK (from 01/73) 6.90 1 NANLA

https://forums.bmwmoa.org/threads/measu ... lwb.36690/

bmwmoa.org wrote:The R100 shaft (granted this is a newer model than yours) measured about 10-3/4", the R60/5 measured 9-1/2". I've seen some LWB bikes and the extended tube weld is obvious...

Not all /5 machines were short wheelbase. The changeover happened early in 1973 but the change to the /6 model didn't happen till October for the '74 model year. Strangely the rear subframe was changed in 08/71... whether that had anything to do with the longer wheel;base, I know not but significantly the pannier frame fitting (which would be affected by changing the length of the subframe) specifys long or short wheelbase.

Rob

There is a visible weld on my late '73 (74-model) R90/6
As stated here some /5s where lwb as well

hal wrote: ↑Wed Jun 12, 2024 6:14 am There is a visible weld on my late '73 (74-model) R90/6
As stated here some /5s where lwb as well

Similar on my December 1974 and January 1975 R75/6 bikes. Visible weld.

The attached BMW service bulletin from January 1973 might be of interest...

It shows the parts necessary to convert short to long wheelbase and confirms that the rear subframe is, indeed, different...
Rob

Sports character??? Ya, right.

Bulletin should have read: "We are experimenting with a longer wheelbase to try to quell the disconcerting wobbles many clients are complaining about before we get our asses sued to hell."