To determine the length springer front end you need, you can put a block of wood under your frame and get it level, or sitting exactly how you would like. You can slide a broomstick through the neck of the frame and line it up to the axle location of your front wheel and measure to get an idea of what length springer you need. For many springers, the length is measured from the underside of the bottom triple tree to the center of the axle.