F.I.S.T. fitters—specifically those with the requisite tools—now have the ability to automatically generate custom geometries for those clients wanting a custom bike. The F.I.S.T. geometry calculator, the latest in a line of tools and engines built for tri bike fitters, has been completed and is open for beta testing. Slowtwitch.com will host and serve the geometry calculator online. The calculator is here.

The calculator generates bike geometry through an online engine that accepts "Stack" and "Reach" as the primary inputs. Stack and Reach are the bike measuring metrics devised by Slowtwitch.com, and which are in common use by tri bike manufacturers and fitters.

What this means, in practical terms, is that a bike fitter who is able to generate the Stack and Reach of the proposed custom bike can, with this generator, find, tweak, design and tune custom geometries for his clients.

Finding the Stack and Reach of a rider's ideal bike is easy to do with the right tools, most notably the Exit Cycling fit bike made by Mandaric Cycling. Stack and Reach are this bike's standard outputs. But stack and reach can also be found using Serotta's X/Y tool. Other fit bikes, such as the Waterford Fitmaster, and the Rob King fit bike, can also generate Stack and Reach.

The F.I.S.T. Tri bike fit system started simply as a way to identify a rider's fit coordinates. The second leg of the system was the introduction of Stack and Reach as metrics to compare and quantify how any tri bike will fit. The third milestone was the fit bike built by master frame builder Ves Mandaric specifically for use with the F.I.S.T. System.

Last year, another milestone was reached when Slowtwitch debuted a database containing the Stack and Reach measures for nearly every tri bike of import to Slowtwitch readers and North American bike fitters.

Today marks the latest milestone. Until now retailers and fitters have not had an easy way to bridge the gap between fit coordinates and the custom geometry that matched those coordinates. The new F.I.S.T. Tri bike geometry calculator bridges that gap, and should open the door to more and better custom tri geometries. As might be imagined, though, the calculator is only as good as the inputs typed into the engine's dialogue boxes (the calculator is designed to faithfully calculate the geometry of the poorly designed tri bike that matches exactly the poorly executed fit session).

The calculator is in "beta," and Slowtwitch welcomes your input. There is a thread established on the Slowtwitch reader forum for suggestions and comments.