Recently I’ve had discussions with athletes about getting aero. Specifically Road vs TT bike, aero tubing vs none and aero bar set up. Much of this will be of use to anyone setting up their bike for racing Triathlon for the first time and it may provide some food for though for those more experienced triathletes. This post will start with the basics of Road vs TT bike. A follow up post will look at aero bar set up.
Road vs TT Bike
In general aero tubing has been the domain of Time Trial (TT) bikes though recently manufacturers have been offering aero road bikes which have aero tubing and internal cable routing (gear and brake cables run inside the frame (and out of the wind).
When it comes to TT bikes, in my view, the aero tubing is pretty irrelevant. When comparing a bike in a wind tunnel without a rider it may make a difference but once the rider is on board the biggest factor for wind resistance is the ridings position on the bike. This is where TT bikes come in to their own and something that generally a road bike can’t offer without compromises on how the bike rides.
The top picture is my attempt to show a rider in a typical position on a road bike. I’ve circled the key point here which is the angle of their torso to their leg. I’ve noted it when the pedal is approximately at 9 O’clock as it changes through the pedal stroke.
The bottom picture shows the same rider on the a TT bike. NB the angle is the same. By having a steeper seat angle (and pushing the saddle forward if necessary) you can effectively rotate your body bringing your shoulders down, your backside comes forward relative to the bottom bracket keeping the angle at the hip the same. This means you increase how aero your are without major changes to the angles of your body. A TT bike allows this whereas a road bike it can be very difficult to do. Requiring forward pointing seat posts (where the post has a kink in it angling it forward) and short stems. This can be a big compromise. Aero road bikes don’t seem to offer this steeper seat angle (I’ve been in the market for one recently so have been looking and actually decided against getting one).
If you were getting a bike made up you could get a frame built with standard tube but a steeper seat angle which would give you a great position on the bike.
Though I said aero tubing will be marginal in it’s benefit for (free)speed you will almost certainly get it if you buy a TT bike.
Remember, you may have the most aero position in the world but if you can’t maintain this position for extended periods then all the benefit could be lost by sitting up. So make it as comfortable as you can and ride in this position regularly as the more you ride it the more comfortable it should become.