Final Drive inner rim on some models and not others?

[jjwithers]

I have a question about the differences in Final Drives.
The early 70's drives have an inner rim that goes around the drive. It lines up with the outside of the brake shoes.

I have a later 70's final drive that does not have the rim.

Is it simply a dust shield of sorts? Any idea why it is on some final drives and not others?


The photos should help illustrate what i am referring to:
This is an early-mid 70's final drive:


This is a late 70's drive without the inner rim:

[Bamboo812]

The early drives with the lip were drum brake only. You can run an disc brake drive on a drum brake bike by installing the brake shoe pin and lever, but not vice versa, unless you grind off that lip. The depth of the splines changed at some point and the length of the front brake shoe pivot pin got shorter when they went to narrower shoes.

[jjwithers]

I had no idea there were narrower shoes.
i did know that the wheel splines are different lengths from /5 to the other models. i didn't know that the drive splines were different too.
Thanks for the info!

[Bamboo812]

Hmm, I may have been thinking of the wheel spline difference. Can you see a difference in the drive splines?

[jjwithers]

I've never seen a difference in spline length in the Drive. I haven't popped enough apart and compared them. I do know that the replacement splines are all one length so I assumed nothing changed on the final drive end.
I do know that the /5 wheel splines are hard to come by and BMW will sell you the /6-/7 wheel splines.

[Texer]

Hi Josh,

Mike here, contacting you because I just read your blog and because I'll be dismantling the front wheel stack on my '70 swb. I know you mentioned the heat and press. My manuals all say heat the hub and pound the stack out with the front axle. Can I ask for the details of how you heated, etc? I'm a bit daunted prior to the job and the heating process is an unknown for me at this time. Thanks -

[jjwithers]

A press or pounding will accomplish the same thing.
I've done both. The first time, i was pounding and I ruined a hub (that was already ruined). i did it as a test so I was prepared to make mistakes. But i ended up pounding it a bit crooked and it scored the inners of the hub.
The second time (different wheel) I pounded it out, and it worked fine (lots more heat). So I got the hang of it...

However, having access to a press, you can do the job MUCH more carefully then pounding. I started to remove a bearing stack and felt it go a bit crooked... so, I backed off, re-aligned everything, added more heat and everything pressed out smoothly.

Hi Josh,

Mike here, contacting you because I just read your blog and because I'll be dismantling the front wheel stack on my '70 swb. I know you mentioned the heat and press. My manuals all say heat the hub and pound the stack out with the front axle. Can I ask for the details of how you heated, etc? I'm a bit daunted prior to the job and the heating process is an unknown for me at this time. Thanks -

[Texer]

Thanks - that's welcome advice and information. I may be able to access a press, so will pursue that first.

[Duane Ausherman]

Do not use a press under any conditions. If done properly, it will come out easily with maybe a couple of taps with a rubber hammer.

We probably did a thousand of these. Use heat.

[Texer]

Is the best (or the only) way to apply heat by torch? I had used my heat gun on engine parts but sounds weak for this application.