EVERY BIKE SHOP needs a “Fit Kit” as the basis for sizing and fitting, regardless of what other bike fitting tools or systems are used.
The Fit Kit System is based on the fundamental premise that anatomical proportions provide a reliable, predictable guideline to selecting a bike size, and establishing an INITIAL riding position, and a STARTING point in the process of fitting a bike for a cyclist.
The primary anatomical measurements are F.I.T.A:
- Foot length
- Inseam length
- Torso length
- Arm length
Additional measurements can include femur or lower leg length, and shoulder width.
The two primary outputs of the Fit Kit System are a projected bike length or reach, comprised of the effective top tube length and stem length, and a seat height range.
The proprietary data used in the Fit Kit Sizing Calculator is not a formula based on mathematical algorithms, but is research-based empirical data gathered from measuring thousands of cyclists.
You can read more about the early history and development of the Fit Kit System here:
The projection of bike length based on the anatomical (hard) measurements can be refined by taking into account a “soft score” derived from responses to 4 simple questions:
- Riding Style
- Pre Existing Conditions – physical issues or injuries that place further constraint on the riders positioning.
The projected seat height range and frame size is not based on a proportion of the inseam length, like the well known “Lemond Method”, but takes into account foot length as well, which is an integral part of the length of the lever from saddle to pedal. A specific seat height is not prescribed due to variations in shoe, pedal, cleat, cleat position and pedaling style. However a starting point is suggested which can be further evaluated and refined.
The Fit Kit™ contains the measuring tools, data calculator (slide chart or app) and worksheets to obtain the measurement and soft score information, and project the bike size and initial set up position.
Using the Fit Kit Systems S.T.A.D.T (seat tube angle determining tool) uses the relative proportions of femur and tibia to overall inseam length to project the steepest recommended seat tube angle.
As the collective knowledge and understanding of cycling bio-mechanics and performance factors has increased over the years, the use and application of the Fit Kit System has evolved. It is used most commonly and accurately now as a Sizing System, to ensure a rider is buying / renting / riding a bike of an appropriate size, with sufficient allowance for the bike to be adjusted (fitted) to suit the rider.
Digital sizing systems assess body joint angles to determine a suitable frame size. These systems require investment in an adjustable size cycle, video or motion capture technology and associated software, and frame finder software.
The Fit Kit™ is an analog system of tools and data that is high quality, low cost, portable / storable, reliable and easy to learn to use. This system can also be used in conjunction with digital sizing systems to establish an initial position on a size cycle.
The Fit Kit has been in use for over 30 years by bicycle retailers and fitters around the world. It is simple. It works. Every shop should have one.