Joined: Feb 2012
Posts: 19,361
Likes: 5,498
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
Var 171 measures set back from the vertical line extending up from the BB's center to the seat tube's center. This is the short side of a right triangle. The vertical is the long side and the seat tube is the hypotenuse. From these you could derive the angles but this set back, for a certain "frame size", could be directly transferred to a drawing (and therefore establishing the seat tube angle). Here's a shot of my 171 and it's horizontal scale. Andy