Recently listened to the excellent podcast from Michael Liberzon on scientifictriathlon.com which addressed many common questions I get from athletes on bike selection. Here are some takeaways:
Almost everyone will be more aerodynamic than on a TT (or triathlon) bike than a road bike.
It is not the bike itself that is more "aero". It's the riders position on the bike that makes a TT bike more aerodynamic.
Using an athlete who rides 200 W in an Ironman, the time savings from upgrading to a triathlon bike will be around 17 minutes. In a half-Ironman, you will save around 8:30-9 minutes, 4-5 minutes in an Olympic distance triathlon and 2-2:30 for a sprint race.
See AlsoHow to Get as Aero as PossibleThe aerodynamic savings will be less for slower athletes (because they are moving slower through the air) but they are on the course for longer so still results in significant overall time savings.
Triathlon bikes are comfortable while adopting a more aerodynamic position, and road bikes are comfortable in a normal upright position. Aerobars on a road bike can put you in a more aerodynamic position but it may not be as comfortable as a triathlon bike geometry.
When buying a new TT bike, make sure the bike you are buying is adjustable. The co*ckpit should be easy to adjust and have a broad range.
Only on very hilly course will a road bike be an advantage. Most times the weight advantage (road bikes tend to be lighter) will be overcome by the speed of a TT bike on the downhill and flat sections of the course.
On a very technical course you might consider a road bike with aerobar extensions.
When should you get out of the aero position when climbing hills? Liberzon suggests consider sitting up around 17-18 km/h. Any lower and the additional power you can produce sitting up outweigh the aerodynamic loss of an upright position.
Practice training grabbing bottles, your race setup and holding that position (no point getting a bike for an aerodynamic position and never be in that position).
So we've established that a TT bike will be faster than the alternatives regardless of speed during a race. But what about some more practical considerations? What should you choose if it's your first bike and triathlon or you're not even sure triathlon is your thing?
I have both a triathlon and road bike and prefer to train most of the time on the road bike. It's more comfortable in the hills and rough road especially and gives me the same training effect (legs are turning the pedals!). I ideally suggest switching to a TT bike a few weeks before an important race to get used to the position. More important if preparing a longer distance (harder to stay in position for long periods).
So, if you just have the budget for one bike initially, I would go for a triathlon bike, if you live in a mostly flat area. If you have hills everywhere and rougher or more technical terrain to train on, consider a road bike with aero bar attachments to start off with. At the beginning of your triathlon career it's more important that you enjoy training than squeeze every last second out of a race. If you take this option, there really is no excuse for not using aerobar extensions. At around $150 it's usually a fraction of what you paid for your bike and with some tweaking you should be able to find an aerodynamic position close to what you can find on a triathlon bike. Enough to make a significant difference in any case.
