The field of aerodynamics is especially important for triathletes, as it is one of the primary determiners of speed on the bike. But what is aerodynamics, hoes does it affect us as triathletes, and how can we get more aerodynamic on the bike?
The Science
How aerodynamic (or aero) an object is refers to the ability of air to pass over and around the object. Think about fast moving objects such as racing cars, planes and high speed trains, they all designed to cut through the air as efficiently as possible. Whether it’s the pointed nose of a jet fighter or the elaborate wings of an F1 car, these are tapered, smooth shapes which encourage the air to flow around them as easily as possible.
How aerodynamic an object is can be measured with CDA (drag coefficient), and extensive testing is carried out to find the best way to achieve this for objects in different fields. Generally speaking, the smaller, narrower and shorter an object is, the faster it is. Concord was incredibly fast, but also a very impractical design. The cockpit and cabin were all incredibly cramped, as they made compromises in other areas to optimise performance. The result of this is that they had a high performance aircraft which was expensive and uncomfortable.
Why aero matters for triathletes
When you are riding a bike, it is very easy to hit 10KPH, in fact many children can go that quickly. When it comes to hitting 20KPH, this takes a bit more effort, but it achievable by most people for sustained periods. Hitting 30KPH however is a huge step up, you will have to be a very fit individual on a road bike to be able to average 30KPH for a sustained period of time. Perhaps not very fit in the content of triathlon, but relative to the general population. As for being able to hold 40KPH or more, this is incredibly difficult. So why is it not four times harder to hold 40KPH than 10KPH?
The issue is air resistance. At low speeds the air does not offer much in the way of resistance at all, but the resistance it offers increases exponentially the faster we go. To reduce the amount of resistance the air provides, we need to try punching the smallest hole in the air we can, and encouraging the air to flow as nicely as we can around us and the bike.
Aerodynamics are incredibly important in triathlon, in fact there is an entire industry around aerodynamic bikes, helmets, wheels, even water bottles. The cleaner our bike is, the smaller hole we punch through the air, the faster we will go.
The antithesis of aerodynamics is someone riding a sit up and beg bike in their everyday clothes, which is designed for getting to the shops or work in an urban environment. In this situation, aerodynamics is at the bottom of your list of things to worry about, but a professional triathlete on one of these bikes would struggle against your garden variety triathlete on a triathlon bike, such is the penalty for poor aerodynamics. So which areas affect aerodynamics the most? Where can we find the most time?
Bike
The shape of your bike frame in of itself isn’t incredibly important, in fact it accounts for less than 10% of the drag created, what’s more important is your body position. Specialist triathlon (or time trial) bikes can help the rider get much lower and narrower than a traditional bike. In most conditions, someone will be 2-3KPH faster on a triathlon bike than on a road bike.
So why don’t people ride around like this all the time? Well, for a start you don’t have access to the brakes in this position, which makes it unsuitable for anything except riding on quiet roads. It can also be more uncomfortable, although it’s not as bad as it looks at first with enough flexibility, mobility and strength training.
The downside is that triathlon bikes start at around £2500. This is a huge investment to make to get a bit faster, and I certainly don’t recommend them to anyone in their first year of racing. What I do recommend however are clip on aero bars, which attach to the handlebars of a road bike. These allow you to get into that low, narrow position for a fraction of the cost (around £30).
However, you don’t have access to your gears here like you would on a triathlon bike, and you need to adjust the fit of your road bike to get comfortable, moving the saddle slightly further forward. It’s very difficult to get a road bike setup to the point where you can be comfortable both in the road position and on the hoods, so there is a real element of compromise here.
Helmet
An aero helmet is one of the cheapest way to reduce drag on the bike, offering a similar benefit to deep section wheels for around 1/10th of the cost. Most helmets have lots of ventilation holes in them which really badly disrupt the airflow over the helmet. An aero helmet sacrifices ventilation for speed, providing a significant boost to your ability to cheat the wind.
You are still looking at around £200 for most aero helmets, but when you consider that some wheelsets can cost £4000, that’s a steal in my eyes. No matter how fast a helmet advertises itself as being, comfort and protection is still king, and in some very hot conditions you may need something with a bit of ventilation such as a road aero helmet.
Wheels
There is nothing sexier in triathlon than a disc wheel. The visuals, the sound they make, the speed, there’s nothing quite like it. Unfortunately, they are also extortionately expensive, and actually provide a very low return on investment relative to coaching. You don’t need to go full disc, you can simply go for some slightly deeper rims such as 50mm or 80mm.
Wheels make the bike more aerodynamic by allowing the air to flow around the wheel much easier, and using less turbulence by using a lower spoke count. The downside to a low spoke count is fragility, meaning the wheel is more prone to blocking if you hit a pothole. The workaround for this is to make the spokes incredibly resilient, however for something to be lightweight and very strong is very expensive. You can get aero wheels suspiciously cheap online from questionable websites, but they may be a health and safety risk.
Aero wheels are also heavier and will corner poorly relative to road wheels. If you are taking on a very technical course or a mountainous event, you may want to pick some wheels which handle better and accelerate faster.
Due to the price tag, aero wheels should be the last purchase an athlete makes. They should have a top end frame, top end aero helmet, good coaching, a comprehensive hydration system and a good groupset before they start browsing for disc wheels. Yes they look and feel great, yes they will make you faster, but the return on investment on them is very poor.
Hydration systems
I hate to be the bearer of bad news, but keeping your water bottles on your bike frame is slowing you down a lot. Especially if you have a bottle on the seat tube as well as the seat tube.
There are three solutions to this. The first is to have an aerodynamic bottle on your downtime. These are slimline and have a golf ball texture of dimples to help with aerodynamics, however they cannot be refilled while riding, so are only really suitable for sprint events, as they do still create a good amount of drag.
The second option is to keep your liquids between your aero bars (if you have any). This can be keeping a bottle between your bars or having a large reservoir with a straw instead. Removing a bottle from the holder at the front of the bike does take a bit of practice, but the upside is that you can swap it for a new bottle at the aid station, rather than having to refill your reservoir.
The most aerodynamic option is to keep your bottles behind your saddle. Yes this can be a bit cumbersome when you’re new to it, but by placing the bottles behind your saddle they do not interrupt the airflow at all, giving you free speed. This is probably excessive for the newbie triathlete, but definitely something those looking to set PBs should consider looking at, especially over longer distances.
Clothing
There’s a reason cyclists wear skintight lycra, anything baggy will flap around and cause huge amounts of drag. Yes it may feel badass to ride around with your unzipped jacket flapping around in the wind behind you, but it’s the equivalent of having a parachute behind you slowing you down.
A triathlon suit with sleeves is the fastest option, with some (very expensive) suits optimised for aerodynamics. You want it to be snug fitting, as even small gaps around the arms or chest can have a very real impact on your speed. Technically speaking having shoe covers and arm covers will make you faster, but they also increase the chances of overheating and given the time they take to put on in transition, you probably don’t actually gain much of an advantage at the end of the day.
Conclusion
Aerodynamics is a subject you could throw money at forever and never be satisfied. I’m not an expert in the field, but the above should be enough to get you started, and help you get free speed. The difference between two equivalent riders on tricked out time trial bikes with all the gear and someone on a road bike could be up to 30 minutes over an Ironman, so it’s definitely worth looking at. Just remember that the primary determiner of performance is still your legs and lungs at the end of the day.
