Joined: Jan 2009
Posts: 44,167
Likes: 6,388
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
I don't remember all the details, but I recently replaced the headset on my Twenty with a 1" threadless-type headset. To clamp the stem onto the steerer, I used a shim specifically made for going from 1" to 1-1/8". (1-1/8" equals 28.6mm.)