Triathlon bikes, time-trial bikes, popularly known as TT bikes, have aerodynamic and geometric advantages that make them faster than road bikes.
TT bikes are designed to make riders faster. The most significant difference is the design, or geometry of the frame of each bike. The seat tube is closer to vertical than a road bike. TT bikes have a steeper angle of the seat.
The steeper geometry places the rider’s hips over the crankset which engages their quadriceps more for increased power. With the purpose of going faster, the steeper angle also allows the rider to ride at a faster rate because you can bend your body down lower which reduces wind resistance.
Are TT bikes really that fast and worth substituting your road bike with?
When a body’s center-of-gravity is positioned with most of the bodyweight placed directly at the top of pedaling stroke, we can achieve the highest efficiency in weight transfer to the pedals. This posture minimizes bodyweight dispersion at the saddles, reducing “wastage”.
However, there’s a downside to this posture. When applying this method of weight distribution on a road bike, this posture becomes forward-heavy and is very demanding on the upper torso and arm muscles, causing pre-mature muscle exhaustion and eventually leads to numbness and pain in the arms, shoulders, and neck.
The most effective way of dispersing this forward-heavy weight is to transfer it through the skeleton structure directly onto the bicycle, removing the need for upper body muscles to support it. This is when the elbow support on a TT bike comes into play.
Although the elbow support is commonly being referred to as aero bar, the true purpose of it is to disperse forward-heavy weight from the shoulders directly onto elbow pads, preventing upper body discomfort. Coincidently, this provides an aerodynamic advantage with reduced frontal wind-drag when the elbows and arms are tucked-in in front of the body, hence the name aero bar.
With the higher pedaling efficiency and lower wind-drag benefits, the TT bike is definitely a faster bike on straight roads.
Now one would ask, what’s the purpose of road bikes then? With the TT bike posture, the upper torso is in a similar posture as performing elbow planking – the arms and elbows are placed parallel and close to each other. There are two major disadvantages to this: lack of agility in bike handling and delayed braking response.
When the elbows are pressured against elbow pads, this truncates the arm movement connectivity between forearms and shoulders. Bike maneuvering is restrictive as the forearms have a lesser steering range, instead of relying on tilting or leaning the body onto the sides to steer the bike. This way of steering is less accurate and has limited range when reacting to bad road conditions or other rider’s sudden changes in a paceline.
Another safety concern is the brake levers are located at the sides of the handlebar, not at the ends of aero bars where the hands are placed. This requires riders to reposition their hands to operate the brakes, delaying the braking process and risking a crash into riders at the front.
TT bikes are faster when traveling on roads that are reasonably flat, fairly straight, and have good surface conditions. However, they are not suitable for group rides and riding on hilly or winding routes due to a lack of steering accuracy and delayed braking response. In contrast, a road bike will be the better performing all-rounder bike in comparison to a TT bike, giving the rider a better chance in tackling a wider range of terrain and road conditions when out cycling with friends.