Bike fitting is not an exact science. SHOCK HORROR that an International Bike Fitting Institute trained bike fitter should say that! But it’s true. We operate to well researched and well documented principles. But the ‘art’ of a great fit is the adaptation of these to the client and the situation. This is particularly true of a time trial and triathlon bike fit.
Over this past year I have conducted dozens of bike fits, on both triathletes, time trialists and road riders.
Many of the principles stretch across all disciplines such as:
- Cleat alignment
- Knee tracking
- Foot position
- Weight balance
- Contact points, saddles, handlebars and Tri bars
These first three particularly are key to preventing injury and ensuring efficient power transfer to the pedals. Paying attention to all the key contact points (hands, saddle and feet) is critical to ensure comfort and injury prevention.
Bike fitting overview
A good bike fit should walk through the following steps. This ensures the fitter has all the information he needs to understand your goals and any potential limiters or challenges to achieving your position:
- Understanding of your reasons for a fit and previous fit history
- Physical assessment – to review your flexibility and any possible physical limitations to your riding
- Lower body set up
- cleats, shoes and saddle
- Upper body set up
- bars and stem
Getting the optimal fit and position on a time trial or triathlon bike has a number of facets:
- Biomechanical – to ensure the most efficient and maximal power transfer
- Post bike activity – running for instance?
- Physical limiters
For me the starting point is understanding the clients history of previous bike fits. Plus their competition aims and possible physical limitations. This is achieved during both interview and analysis. Following this, the next key part is to understand their goals.
The time trial and triathlon bike fit
Lets take two extremes. Firstly, a rider targeting fast short distance road time trials, say 10miles and aiming for under 20mins. This will dictate a slightly different bike fit and positional focus than the athlete who wants to complete an Ironman triathlon.
As said above, a good fit, for either of these disciplines needs to balance biomechanical power transfer with aerodynamics. Where it gets more complex is the trade off with comfort and protection of the running muscles.
In short distance time trialling, as the position of the picture above indicates, comfort is in reality much lower down the priority list. If you are able to hold a superbly aero position and generate the quantity of watts needed and you can hold it for the approximate race time then goal achieved!
Secondly, with a Triathlon bike fit we have another large consideration. You need to be able to run anywhere from 3-26miles (depending on event length) after the bike leg. So how do we go about tweaking positional set up to achieve this?
Generally I’d be looking in the bike fit process at two key facets. I would also make recommendations about training and adaptation.
1. Back angle. Conventional wisdom looks to set the back angle somewhere between 15-35 degrees. The most extreme 15 degrees (or even less sometimes if the athlete is particularly flexible) being for a short distance time trial position. The most relaxed 35 degrees angle being at the top end of the triathlon position recommendations.
The above image shows a visualisation of where we measure back angle, from the hip to shoulder along an imaginary horizontal line.
2. Hip Angle. We’d look at 40-45 degrees for a time trial bike fit and 45-55º for triathlon, as guidance starting points.
Hip angle measured through the knee, hip to shoulder angle (please note the pedal should be at 12 o’clock for measurement purposes, the above is just a visualisation of an approximation of that measurement).
So how do we achieve these subtle positional differences? Our challenge here is to try to minimise the negative aerodynamic effect whilst ensuring the athlete is able to maintain the flexibility needed to compete their event.
Triathlon bike fit back angle
There are a number of ways to ‘open’ this up. Generally it boils down to two areas:
- The drop between saddle and handlebars. The greater the drop the lower the back angle.
- The distance between the saddle nose and the arm pads.
Through a fit we’d look to optimise the back angle for the athlete. All the time maintaining and delivering a comfortable and rideable position, and enhancing, if possible, his power output.
Triathlon bike fit hip angle
We can affect this in a number of ways, but we’d always be starting at the biomechanically most efficient point and ensure we stay within the researched parameters of angles to prevent injury and deliver performance. Where on this spectrum we sit is the sweet spot.
One major opportunity to look at is to maintain an open hip angle. We can however, still achieve a lower more aerodynamic back angle by looking at crank length. Shorter cranks mean less extension at the top of the pedal stroke and thus a more open hip angle and could well be the key to unlocking performance and aero gains.
Other time trial and triathlon bike fit details
What else would we look at?
- Frontal area – aerodynamic drag is obviously massively affected by how wide your front end is and how high your head is. Generally (and I say this with caution) the narrower you can make yourself at the front the better. The caution comes in trading off head position, a super narrow front end can sometimes force the head to ‘pop’ up like a swan – not ideal!
- Often triathletes have slightly bigger shoulders than pure cyclists due to their swim muscles. This can mean they are either unable, or it’s uncomfortable to go super narrow. This is where some of the new skin suit and speed suit technology can come into play. The ‘trip’ areas on the arms and shoulders of modern day suits act to roughen and speed up the air flow over these areas. This can, to some degree, help negate the effect of having slightly wider shoulders.
If we look at the above image, the air flows nicely past the bars, hands and forearms first hitting the thighs. Only the top portion of air is stopped by his shoulders and head. What the above would mean is choice of tri suit can be critical and the ‘traditional’ no sleeve option may not be the best to use here.
- Helmets – within any bike fit the challenge is trying to ‘hide’ the head from the air, maintain visibility and not over stress neck muscles therefore maintaining a clean smooth air flow. The close-up image above shows what a good head position looks like.
- The helmet smoothly integrates to the riders back meaning air is ‘sped’ along over his helmet, back and out again. There is no ‘dirty air’ that gets stuck on his neck causing drag.
- The rider still has good forward visibility.
- For longer distance racing, the temptation to and need to move the head more during the race can mean that a really long tail helmet may not be the best choice. Maintaining the above head position this longer tailed helmet will work well, but if the rider sticks his head up or turns left or right he will effectively stick up a ‘sail’, slowing him down.
- Below we see a rider in a Giro Aerohead – one favoured by many riders at the moment. This delivers great visibility and aerodynamics. But it reduces the drag ‘penalty’ when the rider moves out of position and can be a great compromise.
The above rider may benefit from a longer tailed helmet to ‘join’ the head to the back, but needs to balance it against his event goals.
Practice, practice, practice!
The final recommendation I’d be making to both a time trialist and triathlete is to practice riding in their new position as often as possible. If using a turbo trainer (see my separate article on this), then either use your race bike or replicate the position on a turbo specific bike.
For the triathlete I’d recommend the same but also at least 2 brick sessions a week, even if one is literally just 10-20mins straight after a turbo session. That time is long enough for the body to adapt from cycling to running and the more you do this the more you will get used to and get through that ‘jelly’ leg feeling when you start the run!
So lots to consider depending on your key race goals. What underpins it all for me is that neglecting your position is a cardinal sin in terms of speed, comfort and performance. You have invested so much in your bike, so much in your kit and so much time in your fitness – the only logical and sensible approach is to invest a small amount in a quality time trial or triathlon bike fit. It’s money well spent!