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1980 BMW R100T Front Axle

Posted: Mon Aug 21, 2023 7:33 pm
by Blue1
I was wondering how these bushings fit on my front axle?
Does the side with the flange face out, or in against the bearing?

I have a 1980 R100T, any idea what this part is called?
They're kinda worn, any idea what the part number is?

I can't find these answers on MaxBmw.

Re: 1980 BMW R100T Front Axle

Posted: Tue Aug 22, 2023 12:31 am
by melville
Flange goes toward the bearing. This keeps the bush retained by the seal

Re: 1980 BMW R100T Front Axle

Posted: Tue Aug 22, 2023 5:51 am
by Rob Frankham
That drawing is pretty bad. There are parts from numerous different set ups. It originates from the BMW spare parts catalogue and is more or less useless without the parts listings that go with it. It is basically a parts location drawing, not an engineering drawing at all.

The part you are referring to is part No 2 on the diagram and the relevant number for the part associated with a 1980 R100T is 36 31 1 230 322. BMW referred to it as a 'compression ring' (in english anyway). I would refer to it as a spacer.

The most important job of this spacer (well, on the right side anyway) is to set the position of the wheel between the forks. If the spacer is too long or too short, the wheel will be offset slightly to one side (which probably wouldn't make too much difference) and the disk will be offset in the caliper (which will). For this reason, it's important to get the right one, there are a number of different sizes for differnt model/years and wheel types.

It can be fitted either way and it will make no operational difference. If you fit it with the flange inward, the grease seal will, as Mel says, retain it in place when you take the wheel out which is nice. On the other hand, if you need to remove the grease seal you are more likely to damage the seal when you lever it out. FWIW, I believe that BMW practice was to fit it with the flange outwards and that is how it is shown in BMW diagrams. I would suggest that this is probably to minimise pressure damage to the alloy fork leg which it butts up against (again on the right).

Rob

Re: 1980 BMW R100T Front Axle

Posted: Tue Aug 22, 2023 7:44 am
by barryh
I always thought the lip is supposed to go behind the seal as mine came from the factory that way, or the dealer put them in that way when the bike was uncrated. I do see it would work both ways though.

Ideally you would avoid pulling the lip trough the seal to remove the spacer and pushing it back through the seal to replace it but I've done it several times without apparent damage. There is no way I could have removed the seals without pulling the spacers out first.