Odd noise coming from Dahon rebar
I have a dahon frame and had been riding it for about 300 miles with no problems. The 'rebar' (not the joint with the clasp, but the part that adds structural integrity to the frame) has a black insert in the male part of the joint that looks like a bagel - ie it has a hole in the middle. The female part has no black plastic bits - its just bare aluminium. The black insert looks like some type of hard blown-plastic. This insert has worn more at the 6 o'clock position than elsewhere and this appears to have exposed some aluminium in the female part of the joint. This is causing some nasty sounding grating to come from the rebar as one aluminium part rubs on the other.
I was hoping that someone could tell me if it is possible to replace the black insert. Then tell me if its possible for a non-professional to do this, and if so where I can get the black insert from and how to fit it.
Thanks for any help in advance.