Boxerworks.com

1984 R100S
Many years ago I thought I would install a bigger rear tire....and I did. Now I would like to to go back to standard, as I need to replace the tires. In order to get clearance, I had to shim the wheel. I have the original Shim. I did this over 30 years ago. Is there anything else I need to do besides replacing the shim with the original? Thanx!

No the difference is only 1.6mm but you might have a small step on the rear wheel splines.

Rear wheel drum brake? Wouldn't there also be a possible step in the drum surface?

Kurt in S.A.

I suppose there must be, however small. I guess the brake shoes would soon conform.

I'd leave the spacer for the wider tyre, then the fd/wheel spline connection will remain the same.
I.6 mm shorter top hat will mean that all the drive force will be supported by 1.6mm of spline contact, until the 1.6mm wears back to full spline contact.
It won't break, but....

Hmmm... so is the eventual full contact with the splines, a better outcome? Would leaving the spacer, and using a smaller tire then present an alignment issue?

2mm is nothing regarding alignment. At present with the bigger top hat you have full contact. If you look at your fd splines you'll see a step in the splines from normal wear. That's ok.
With the big top hat left in place, there will be no difference in alignment between the two tyre sizes.
As mentioned it's just not a good mechanical situation to have all the torque going through a small contact area.
Most likely both the fd and wheel spline will yield until full contact is restored.

When the longer 10.7 mm spacer was introduced BMW issued a service bulletin that said maximum wheel offset should not exceed 4mm. You can reduce offset a little if necessary using unequal gaps on the swinging arm bearings.

Why did you leave it there for 30 years?

boxme60 wrote: ↑Wed Apr 10, 2019 4:39 am Why did you leave it there for 30 years?

We'll really, it caused no problems. I thought the bigger tire would provide better grip. But now I wonder if it would handle better with the original size. Now I can't get the Bridgestone S11's (Spitfires) I'm used to. So I have to find a new tire that will fit. The tires that I have on now are 130's so really not really a big tire as Modern tires go.