Forum bmwbike.com

My rear bushings are shot on my R51/3 Plunger. The replacement bushings I received are a type of gray nylon/plastic, which would replace the old type of bakelite bushings. I am wondering what is the best procedure to replace them. Pound out the old bakelite ones and just press the new ones in, or should the new ones be glued or epoxied in? Any help or tips would be great... Thanks!!!

Hello Stacey, I did reply to your bushe problem during the site down time so it was lost, in my experience you may find that the holes in housing tend to become a bit oval, usually more so at lower end. This makes it more difficult to fix. Someone suggested using bronze for bushings and that is what I have done by making a bushe with a much smaller i.d to allow it to be bored out true as it takes on shape of any out of true in hole. Hope you are are lucky and don,t have this added hassle. Good luck, Regards Geoff in OZ.

Hello Stacey

The question of rear suspension bushings was raised on the /2 list, Mark Huggett responded with this answer

"Please note that these where never brass. These bushes have been made
out of pertinax since 1937 and this material is specified on the
original technical drawings. Obviously sombody has made your bushes out
of brass or bronze. Seiwert in Frankfurt has made these out of
plasticccccccccccc. The pertinax bushes are pressed in to the alu
housing and then honed to fit. Pertinax absorbs oil and grease and has a
high abrasion resistance. That is why it is ideal for linear bearings.
Very often the linear bearing drys out if insufficiently lubricated and tends
to clamp the suspension tube."

I used the pertinax bushes and honed the internal diameter with a small brake cylinder hone. It was quite time consuming however the results are good. The bronze bushing may be better however there are no machine shop facilities in my area so the pertinax bushes suited me.

Ben

Thanks Geoff + Ben for the response, I guess I am still uncertain on what I should do... I have the new plastic bushings which must be the ones from Seiwert in Frankfurt.

Should I:
1) install the new plastic ones (and should these be epoxied in)
2) get a machine shop to make up a set of the pertinax kind
3) get a machine shop to make up a set in bronze?

Thanks! Stacey (I guess this project is going to be little more involved than I thought)

Hello, I'm going so late, but, in my experience, broze was really good, because the holes ussually are not perfect and they need to be rectified.
And glue may cause damage if plastic parts don't work rigth.
I has changed 4 rear bushings in bronze and its really perfect, may be In my mind, pertinax was right when the bikes was new or holes are perfects.