Originally Posted by
FastJake
BSO mountain bikes may still use 1" threaded headsets on the really bottom end ones, but as far as quality MTBs go they all switched over around the early 90s. I've had a couple MTBs from 1993 and 1995 with 1 1/8" threaded headsets, so that's something to look at too.
As far as all quality MTBs going to 1 1/8 in the early 90's, lets not forget the Trek Bontragers that kept Keith's 1 " head tube until the last 2 years, 1999 and 2000. OTOH my 93 Barracuda came stock with a 1 1/8 threaded RS Mag 21