F.I.S.T. Bar to Head Tube Calculator

Even if the fit is performed correctly, pitfalls loom. You must have the tools to accurately find the stack and reach of the bike that fits under the rider. The fitter is required to account for the stem length, stem pitch, height of the stem clamp, headset upper stack, spacers under the stem if any, and of course the choice of aerobar. He then must have an accurate way of generating the stack and reach measures, using either a fit bike (best is the bike made by Exit Cycling) that accurately generates these values (taking into consideration negative reach if applicable), or he must use an external tool, such as Serotta's X/Y tool.