Words: Ryan Williams | Pic Getty Images
In this short article I would like to discuss bike sizing. I’m not going to go into specifics of sizing your bike, but I want you to be aware of the common mistakes, that lead to people ending up on the wrong size bike.
1. “My road Bike is a 56cm so I bought a 56cm triathlon bike”. This is the most common one I hear. The problem here is that there is no consideration in the vastly different geometry between a road bike and triathlon bike and the huge difference in the ideal position on each.
The same rider can something require a different size bike for UCI Time Trial races than they would for Triathlons, even in the same make and model.
In fact, when Lance Armstrong started racing triathlon he used a bigger size bike to allow for a triathlon specific position, over what he had previously used in his UCI road TT races. Though both disciplines use TT bikes, they are different sports and require totally different positions.
2. “My old bike was a small, so I got a small”. There are two main problems with this theory. The first is assuming that all brands are the same
size. The best example of this would be the new Giant Trinity size small in comparison to the small (51cm) Cannondale slice, there is a 20mm difference in reach between the two and even a medium (54cm) Cannondale Slice is still shorter in reach than a small Giant Trinity Pro. Now I’m
not saying that either one of these bikes are better than the other, you just need to be aware that all bike companies size their bikes differently.
The second problem is assuming that your last bike was the right size to start with. It’s amazing the amount of money that people will lay down for a bike without first getting some neutral professional advice on what size bike to buy.
3. “The guy in the shop said it was the right size for me” This one I hear a lot. You have to ask yourself “what’s the assistant’s motivation?” Bike shops are there to sell bikes and if you’re willing buy it, then they will most likely sell it to you, regardless of fit. A lot of the time the shop assistant might not know any better. Questions you should ask the person selling you the bike are “what is their cycling background?” and “why is this one the right size bike for me?” There is a chance you are talking to a guy that only rides mountain bikes or even BMX and simply doesn’t have the skill set to get you sorted on your new race rig. Be well informed before entering the shop and you can tell them what size you need.
4. “A guy in the tri club is the same height as me and he rides a large” Ok, so you need consider the variables here. Though two people can have the same overall height, leg length to torso ratio can vary widely. It can often be the case that the person with the shorter legs needs the bigger bike or a bike with totally different stack and reach geometry. Other things to keep in mind like, rider flexibility, experience and is the guy even on the right bike for him?
5. “I knew it was a bit small / big, but I got it cheap”. Yep, I really do hear this one more than you might think. All I can say is “it won’t be cheap by the time you sell it and purchase the right size bike” don’t compromise on a bike size to save a few dollars. Think of the hours you invest in training and the money you spend entering and going to events, coaching and physio / massage. My advice is to race one less time in the season and the money that you save could be the difference in getting yourself the right equipment.
Ryan Williams has been runs 3D Bike Fit in Western Sydney. He has performed over 1200 bike fits using the Retul system for data collection, of which 90% have been Triathlon specific. His clients range from complete beginners to Ironman and Ironman 70.3 winners and include multiple world champions.