As a Bike Fit studio, we love technology and data! That being said, we do appreciate that the amount of data now available to cyclists / triathletes can be overwhelming. Cycling computers now provide an array of information including speed, heart rate, power, watts per kilo and CdA but which of these metrics is important? We often get asked questions by clients based around these metrics such as ‘Will a Bike Fit improve my FTP?’ and ‘How much will a Bike Fit reduce my CdA?’. Although interesting and valid questions, the real question should be ‘What can I do / or will a Bike Fit make me faster?’ Ultimately, speed should be the outcome variable that we are interested in as this is what determines whether you get a PB or win a race.
The dangers of focusing on one metric
That is not to say that other metrics such as watts per kilo and CdA are not important – they are – but none of these should be the sole focus of your racing and more importantly of your training. Let’s start by taking someone who spends a lot of time on Zwift and has become preoccupied with Zwift’s main metric - watts per kilo. Being focused on watts per kilo is great if you are competing in Zwift races and that is your primary goal. However, for the many of us, who use Zwift racing to complement our IRL competitions an obsession with watts per kilo, is not going to do us much good for a number of reasons:
Conversely, focusing solely on CdA values is not a good idea! We regularly see pictures on social media of cyclists / triathletes sat in super aero positions which would be undoubtedly very fast if, and it’s a big if, they can still generate power in that position. Achieving a very aero position often means closing the hip which can make generating the same power output challenging.
Bike Fit as a compromise
This is why Bike Fit is a compromise as we want to maximise both aerodynamics and power output. As such, sometimes your watts per kilo may be lower following a Bike Fit but your speed on the road may actually be higher due to big improvements in aerodynamics. Given how we have to balance these two factors, it is important that you don’t just focus on when evaluating your training, race performance or Bike Fit! Both should be monitored and potentially tweaked in order to optimise the outcome metric we are really interested in – SPEED!
I think the take home message is to monitor metrics such as CdA and watts per kilo but to take a holistic approach which takes into consideration both but doesn’t put an excessive amount of emphasis on either. Although arguably one of the most basic and rudimentary metrics we have, speed (although it can be affected by weather conditions) remains one of the most important to consider when evaluating performance!
If you would like any more advice regarding choosing a new bike please get in touch.