Blimey! Thanks. Loads of good advice. The problem here is that certainly sidecarpro or a number of other stockists will send from China, but things can disappear into Customs here, eventually to reappear a long time later, accompanied by a bill of arbitrary and sometimes astonishing size. Good idea to talk to a suspension specialist- I've done that before for fork springs, rebuilt shocks etc.
I see though that equivalents should be possible. The question I still ask is, for example, were I to build a machine with specifically sized shafts, is there a convention which dictates the internal size of the seal, eg. 38mm for a 40mm shaft? Or, maybe, do I buy based on the exact measurement of the shaft? I was wondering whether there was a percentage 'nip' for want of a better word, which is always applied?
Or, maybe I think too much.....
there is - hence my suggestion to go to Trelleborgs site - they make seals for all applications.