Lower Fork Oil Leak - Bottom Tubes

[RoryW]

Morning All - New to the forum so Hello ! I have been rebuilding my 79 R100RT over the last two years. During its history a PO has fitted latter forks from an 81-84 R100RT (it now has the Brembo braking system). It looks like the PO used "liquid metal" or something similar to seal the bottom metal disks which sit behind the large circlip at the bottom of the fork tubes. Despite trying all the normal specialist suppliers and even BMW main dealer no one can identify a part number for the O ring needed. See picture with o ring circled. Has any body else found a solution to sealing the bottom of the tube or the part number for the elusive o ring ? Thanks in anticipation - Rory.

[Rob Frankham]

Nope, I have various parts lists going back to 1981 and none of them refer to an 'O' ring at that location, which is strange... I have to say that I was always told never to disturb that bottom end of the fork because it wasn't necessary and I don't think I've ever found the need to. It's also apparent that new sliders come with the bottom base already installed... but that doesn't help you, of course since you are addressing a leak from there. I can only suggest that you measure the 'O' ring seating area and buy by size. You could, of course, try talking to the recognised parts suppliers and see if they've ever hit this issue but, to my mind, measuring up and getting a few rings of the right diameter and various thicknesses would probably be the quickest way to go.

Rob

[RoryW]

Thanks Rob, tried all the usual specialist suppliers non had any information on the o rings - I think your pragmatic approach is best, will try to take some measurements. I guess I just need the OD and ID dimensions. Cheers Rory.

[Rob Frankham]

OD and thickness, the ID takes care of itself

Rob