I suppose that having spent much of my time in the 70s and 80s building large numbers of time trial bikes with ridiculously short rear triangles, including quite a few with double seat tubes like the RIGI, I can claim to have some experience of the sort of problem that Wayne is experiencing with the chain line on the small ring and the little sprocket. Fortunately the majority of the purist time-trialists eschewed the double chainwheel, so the problem of chain line as Wayne is finding it, was not all that common.There was quite a fashion for pushing high gears on the long straight-out-and-back drag strips, and often riders would fit a 58 or 59 single ring...the largest that I ever fitted being a 66T TA. Such large rings coupled with a very short back-end did give rise to possibilities of the ring rubbing on the chainstay if that hadn't been carefully indented. The other solution that I used more often tan not was to use either a MAVIC or Stronglight sleeve bracket unit - one of those that doesn't use the bracket threads but locks with a couple of external locking rings that bear against the bracket shell. On occasion it was necessary to dismantle these to reverse the axle...but generally the use of such a unit would overcome all set up problems.
The other vary obvious solution is not to use the chain on the combination of inner ring and smallest sprocket...or the reverse! The Mercier company used to publish on the back page of their catalogues, illustrations of goood and recommended gear usage and the opposite..and the two uses of the extremes were always crossed out with large XXXs to dissuade the user from selecting combinations that were known both not to work very well but to also cause problems and lead to faster wear and tear.
Norris Lockley...Settle Uk
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