"Is it better to ride a TT bicycle or a Triathlon bike?" This is a common question among long-distance triathlon enthusiasts, especially newcomers to the discipline.
This guide provides a comprehensive overview of modern Time Trial (TT) and Triathlon bicycles, covering their technical features, similarities, and differences. These machines, built with cutting-edge technology and aerodynamics, are born to race against the clock.
Both Time Trial and Triathlon bikes are designed for speed and aerodynamics. At first glance, they look quite similar, and even on closer inspection, distinguishing one from the other can be difficult. However, when it comes to geometry and saddle positioning, they differ significantly.
UCI vs IRONMAN
The prototype of the new Colnago TT1 with disc brakes | Team UAE Emirates Time Trial bike
The first major consideration is understanding the distinct features of these two bikes. TT bikes must adhere to the strict guidelines set by the Union Cycliste Internationale (UCI), cycling's world governing body. These regulations cover everything from tube width to handlebar length to saddle position. In triathlon races, athletes are not required to adhere to UCI regulations but must follow the rules set by their Federation or the circuit in which they compete. Therefore, while aerodynamics remain crucial in building a triathlon bike, brands can showcase a variety of design solutions, including creative ones that the triathlete cannot alter for race purposes.
Taylor Knibb riding the Trek Speed Concept SLR at the IRONMAN 70.3 World Championship in St. George
Before We Begin: What Is a Time Trial Bike?
The Cervelo P5 of Wout Van Aert of Team Jumbo Visma, in TT setup
A Time Trial bike (also called a TT) is an aerodynamic bicycle made to race against the clock, often on a straight and flat course. Time trial bikes put aerodynamics first. In practice, these bicycles use all the science possible to go as fast as possible: every gram is taken into account, and every angle on every surface is thought about in terms of aerodynamics. Time trial races can vary in length, but at the highest levels, they rarely exceed one hour.
If we consider just the performance aspect, TT bikes offer indisputable advantages, both in terms of aerodynamics and stiffness. It is no coincidence that almost all professional athletes race on a Time Trial bicycle.
What is a Triathlon Bicycle?
The Specialized S-Works Shiv Disc | One of the ultimate expressions of aerodynamics and technical solutions specific to triathlon
Triathlon bikes are specifically designed for triathlon events, where bike courses range between 40 and 180 kilometers. Unlike Time Trial bikes, TRI bikes have no standard UCI regulations to follow. Tri bikes are often engineered for both speed and added comfort, leading to radical frame shapes and unique geometries. For instance, they typically feature a steeper seat tube angle, positioning the rider's hips forward to preserve the hamstrings for the run portion of a triathlon. With the seat tube closer to vertical, the rider’s hips sit directly above the crankset, engaging the quads more and reducing strain on the knees during the power phase.
Time Trial Bike for Long-Distance Triathlons?
Considering the growing popularity of long-distance triathlons like IRONMAN, many triathlon bikes now include geometries designed with dedicated spaces for food, beverages, tools, and spare parts. While road cyclists typically carry items in jersey pockets, an extra water bottle, or even a handlebar bag (in rare cases), triathletes can store their essentials in aerodynamically integrated compartments.
However, there are other technical aspects to consider. A time trial bike may become uncomfortable over long distances. Although both bikes are built for aerodynamic efficiency, the triathlon bike is specifically designed to provide comfort over hours of pedaling, especially for amateurs. The geometry also helps preserve leg muscles for the running course. Both types of bikes feature aerodynamic handlebar extensions, allowing the cyclist to extend their arms and adopt a position that minimizes wind resistance. However, the aero position on a TRI bike is less aggressive, placing less strain on the back and upper body than the position on a TT bike.
The aero position on a triathlon bike is less aggressive than the position on a TT bike
The 10 Key Points to make the best choice
1. Aerobars and Extensions
The technological and aerodynamic integrated handlebar with extensions of the new Felt IA-2
The Aero Bar, the distinctive handlebar for Time Trial and Triathlon, consists of a base—known as the base bar—and the extensions.
Brake levers are mounted on the base bar, while the extensions are used for shifting control. The base bar also serves for climbs, especially steep ones. To achieve the perfect fit, you can adjust the stem length and angle, headset spacers, armrest height, and extension angle.
The extensions protrude forward, and together with the armrests, allow the rider to adopt and maintain a more aerodynamic body position than would otherwise be possible.
Specific regulations limit the reach of extensions and armrests in UCI races. However, outside of UCI-regulated events, this is not an issue.
2. The Frame: Shapes and Geometries
The futuristic Triathlon frameset of the Cervelo PX 2022
Aerodynamics is essentially everything when it comes to TT bikes, while weight is of only secondary importance. For this reason, tube shapes are optimized to be as smooth as possible. These shapes also offer benefits in terms of stiffness, weight, and shielding water bottles from airflow. The geometry of time trial and triathlon bicycles also differs from that of road bikes. The most obvious difference is that time trial bikes generally have steeper effective seat tube angles (approximately 75-78 degrees) compared to road bikes.
UCI rules establish many of the measurements for a TT bike. Beyond these regulations, however, both Time Trial and triathlon bikes tend to have a shorter wheelbase to position the rider closer to the front, short head tubes, and a reduced stack height. Both also typically use shorter cranks, which result in increased power and improved aerodynamics.
3. Wheels: High Profile and Disc
The EF Pro Cycling Team testing the Vision high-profile and Disc wheels on the Cannondale SuperSlice Evo, featuring a special Rapha x Palace color combination for the 2022 Tour de France
As with the frame, aerodynamics is critical for TT and triathlon wheels. In time trials, solid rear disc wheels and front wheels with very high rim depths are commonly used, as well as low spoke count wheels, such as three-spoke models. However, front disc wheels are generally allowed only for track use. But the track bikes are another story—you can read about it here.
A balance must be struck between using high-profile, aerodynamic wheels and managing the negative effects they can have on handling in windy conditions. In general, the higher the rim profile, the more aerodynamic the wheels are, helping them cleave through the wind—unless there is a side wind. In that case, the high rims can act like sails, making the bike harder to control. For this reason, many professionals keep a variety of wheels to choose from depending on the race and weather conditions.
4. Aerodynamics
Sam Long is in the typical aerodynamic position on the Trek Speed Concept Disc
While the aerodynamic position (achieved by aero handlebars spacing the arms) is most important, the position of the brake levers should not be overlooked. In general, when fitting a TT or triathlon bicycles, all contact points must be considered: pedals, saddle, forearms, extensions (in the aero position), and hand placement on the base bar.
On time trial bikes, aerodynamics takes precedence over comfort. In a time trial, a cyclist aims to go as fast as possible from point A to point B, even if it requires a slightly contorted position. For this reason, the setup places the rider further back, with low handlebars and a greater distance from the saddle to the handlebars. In triathlons, where races can be very long, comfort becomes the priority. Cyclists adopt a less compact, more relaxed position.
5. Riding Position
The riding position in TT and triathlon is very similar. In both cases, the cyclist aims to reduce the surface area exposed to the wind. Imagine a wind tunnel: the goal is to minimize resistance while maximizing power output. In time trials, this position is more extreme than on a triathlon bike, particularly for longer triathlons. In both disciplines, cyclists strive to stay low in front. A short head tube helps the chest drop, creating a more aerodynamic posture. Some even recommend using a smaller TT frame to achieve lower elbow and shoulder height.
6. Brakes
The aerodynamic fork with disc brakes and Shimano Dura-Ace Di2 braking system, from the Canyon Speedmax CFR
Until recently, bicycle manufacturers struggled to find aerodynamic ways to hide rim brakes within the fork or under the bottom bracket. This often led to compromised braking performance or complicated maintenance (or both), which was accepted for the sake of aerodynamics.
Today, many triathlon bikes are transitioning from traditional rim brakes to disc brakes for improved control in variable conditions. With hidden wiring, disc brakes can also enhance the bike's aerodynamics.
It's therefore too simplistic to say that traditional brakes are always more aerodynamic than disc brakes; it depends on how the components integrate within the overall system. Better braking performance, especially in technical races, can help you pedal faster. Being able to brake later and more safely ultimately improves average speed.
7. Hydration and Storage
The new Argon18 E-119 Tri Plus, with integrated hydration and object storage solutions
For TT races, athletes can often manage with one or two streamlined water bottles. However, in longer triathlon races, having a reserve of hydration, nutrition, and even some gear on board is essential. The bike section offers the best opportunity for athletes to focus on fluid and calorie intake.
On aero bikes, solutions are designed to store water, food, and gear in ways that are easily accessible to the athlete and do not compromise aerodynamics.
8. Drivetrain
The carbon single chainring on the Pinarello Bolide TT of Filippo Ganna | Team Ineos Grenadiers
Time trials often take place on flat or undulating courses, allowing riders to optimize their gearing for maximum advantage.
This typically involves using large chainrings (up to 60 teeth) and widely spaced cassettes. The former optimizes the chainline, while the latter helps riders modulate cadence more precisely—critical when pedaling to the limit.
9. The Saddle
Given the aggressive nature of the Time Trial riding position, choosing the right saddle is essential for comfort and injury prevention.
For this reason, it's beneficial to consider a saddle specifically designed to reduce pressure on soft tissues in the aerodynamic position, as it allows you to shift your hips forward and generate more power.
A saddle with a relatively long carriage also provides greater positional adjustability, which can be useful if the bicycle's seatpost is limited to a fixed position, as is the case with some older Time Trial bikes.
10. Tires
Tire aerodynamics is also a crucial factor in achieving the fastest setup. For time trials, optimizing tire width is essential to maximize performance.
In general, this means choosing a tire slightly narrower than the rim's outer width. For example, if your rim has an outer width of 28 mm, a 25 mm tire is likely the best aerodynamic choice.
Conclusions: what bicycle is suitable for Triathlons?
Time trial and triathlon bicycles can both be used for triathlon races. However, if the bike course is long, particularly in a 70.3 or full IRONMAN, a triathlon bike will provide much more comfort and additional space for hydration and nutrition. Furthermore, while TT bikes keep the cyclist in an extremely aerodynamic position, triathlon bikes offer the best balance between aerodynamics and muscle preservation for the run.
The choice is yours—just remember, the goal is to beat the clock!
