Multiple bikes is a common “problem” for triathletes. An older bike may be relegated to the bike trainer while a shiny new bike is reserved for fair weather and race days. With multiple bikes come some complications; it is common to have one bike that fits more comfortably than another. Different style bikes (road, triathlon, etc.) require different fit parameters, so it is not practical to try to make these feel the same. But for those with multiple road or triathlon bikes, here are a few tips to translate your bike fit to other bikes.
Translate Your Bike Fit to Other Bikes: Before You Begin
Make sure your bikes are on a level surface, and it’s helpful to have the bike secured in a trainer. Match the seat position first and then move on to the cockpit.
Matching seat height is the most important thing to get right, this directly impacts comfort and power, and if it’s wrong, you can get hurt. Pick a point on the saddle surface as a reference point: 80mm back from the saddle nose for triathlon bikes and 120mm back for road bikes is a good place to start. Measure from this point to the center of the bottom bracket (diagonally) and record this value. If the bike you are matching has different length crank arms, increase or decrease the seat height by the difference in crank length to maintain the same leg extension at the bottom of the pedal stroke.
Saddle fore/aft positioning is another important one to get right—this affects weight distribution. Use a plumb bob or a self-leveling laser to measure the horizontal distance from the saddle nose to the center of the bottom bracket. The right tools help here.
Saddle tilt is easy to replicate between bikes—you are likely carrying the tool for that in your pocket right now. Use the level app on your smartphone to record the angle of saddle tilt and simply match that from bike to bike.
The cockpit of road bikes and tri bikes have to be dealt with slightly differently. On tri bikes, use the back of the arm pad as a reference point and on road bikes stretch a long rubber band across the shift hoods, locate it approximately where the web of your hand contacts the hood, and use the band as the reference point.
Matching the horizontal position of a cockpit is fairly straightforward. Measure from the saddle nose to the reference point and adjust the cockpit to match. You can alter the cockpit reach by changing the stem length or moving the arm pads. If you are dealing with a tri bike, after you have matched the arm pad position, measure from the back of the pad to the tip of the extensions.
To match the vertical aspect of the cockpit, you may need a calculator or a pen and paper. Measure from the top of the arm pad (tri bike) or from the rubber band (road bike) to the ground and record this measurement. Next, measure the height from the center of the bottom bracket to the ground and subtract this from the first measurement you recorded. The difference between these numbers is the height of the contact point above the bottom bracket—you can match these by adding or subtracting spacers under the stem or aerobar.
Jon Blyer is one of the co-owners of ACME Bicycle Co., a bike-fitting studio in Brooklyn, New York, dedicated to a fit-first approach to cycling. He holds numerous fitting certifications and is involved with bike fit education through GURU Sports as an instructor in GURU’s fitting academy.