Joined: Feb 2012
Posts: 19,353
Likes: 5,471
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Unless you're using a NuVinci hub. Then the gear ratios come from a pair of disks with a third disk between them. As the central disk touches one (the drive disk) at it's outer edge the central disk angles so that the driven disk is contacting the central disk at the inner point. This is one type of traction transmission. Andy.