What’s the difference between a triathlon bike and a time trial bike?

At first glance, it’s pretty difficult to know exactly what the differences are between a triathlon bike and a TT bike, which is one made specifically for cycling time trials; however there are a number of things that set them apart, mostly concerning geometry, build and fit…

Bike geometry

As with many things bike-related, the question isn’t as straightforward as it first seems: this is because a lot of bike manufacturers will offer the same bike for both triathlon and TT’s that can be adjusted (through fit and removal/addition of accessories) to suit the riders’ preferred event. Canyon, for example, offer their Speedmax bike for both triathlon and time trials.

“There is basically no difference, the TT version comes without the bottle and speedbox and a different stem cap to fit the frame/stem junction better,” says Canyon’s Jack Noy.
“As a rough guide, world tour setups will likely be more aggressive- while they look to maximise speed and power output. Generally a TT in a world tour will be less than one hour, whereas a triathlete will have other considerations such as comfort and how sustainable the position is for the four-plus hours in the saddle they need to endure for an iron-distance race.
“Of course this can vary massively from rider to rider- some world tour riders may have a less aggressive setup than a pro triathlete depending on their preference and personal biomechanics.”

Dedicated triathlon bikes often have a steeper seat tube angle, which pushes the hips forward and saves the hamstrings for the run. TT bikes have to adhere to International Cycling Union (UCI) rules, which requires that the saddle nose must be 5cm from the centre of the bottom bracket.
Bikes that fall within the UCI’s rulings previously had to adhere to the 3:1 rule, meaning that no part of the bike can be any more than three times longer than it is wide at any point. These rules have been relaxed from January 2017, however, which means the line between tri and TT bike may be blurred even more in the next few years.

There has recently been a boom in totally non UCI-legal frames thanks to the continuing popularity of multisport events. Notable examples include the Cervélo P5X, Diamondback Andean and Dimond Marquee, all of which were recently put head-to-head in an exclusive 220 test.

Due to the huge amount of R+D that goes into them and the specificity of these bikes, the cost can be high (up to £13,500 in the case of the P5X) which is another reason why bike brands will often invest in developing a bike that can be used for both triathlon or TT.

CERVÉLO P5X

The geometry of Cervélo’s P5X completely does away with UCI regulations, with extreme aero shapes in the frame, a ‘beam’ design and various add-ons specific to triathlon.

A triathlon bike that doesn’t have to adhere to UCI rules is designed to be as aerodynamic as possible, but the rider may seek a less aggressive position on it to cope with the demands of running after the bike leg. In contrast, a UCI-legal bike can only be as aero as the rules stipulate, but a TT rider will seek the most aggressive position that their biomechanics will allow.

Bike build

This is perhaps the most obvious, visual factor that sets a tri bike apart from a TT bike, as tri bikes will more often than not have additional storage boxes and equipment needed to tackle a triathlon, either integrated or added on as aftermarket products.

Time trial riders will usually require a small amount of nutrition and two water bottles, assuming they are well-trained; whereas in long distance triathlons, even the pros will get through a considerable amount of food and fluid to fuel themselves for an all-day event.

The Canyon Speedmax used by Jan Frodeno at the 2016 Ironman World Championships with added tri-specific accessories (top), and the version used by the Movistar pro cycling team for world tour events (bottom)

Tri-specific accessories vary greatly between bikes, depending on how the bike is built and what the athlete prefers to use. Many more high-end triathlon bikes now come with top tube boxes and hydration systems bolted and slotted onto the frame, and integrated solutions in other areas of the bike for storing tools in case of a puncture.

Bikes that don’t come with these accessories as standard will have space for the rider to attach their own; a standard set-up will see a triathlete attach a top tube bag for nutrition storage and a bag behind the saddle for tools and inner tubes. For longer races, hydrations systems can be added to the front end and additional water bottle holders to the saddle rails.

Bike fit

In a time trial, a cyclist’s only concern is getting to the finish line as fast as possible, leaving them completely spent after an all-out effort when they get off their TT bike. A triathlete has the run to deal with afterwards, which often means a more forgiving set-up. A triathlete will generally want their forearms wider apart on the aero extensions, and bent at a slight angle at the shoulder down to the elbow. Having the seat tube on their tri bike further forward also puts less pressure on the hips and hamstrings.

The add-on accessories needed to tackle a swim/bike/run race and achieving a position that helps the triathlete to save their legs for the run are the things that ultimately set apart a triathlon bike from a time trial bike; and it goes without saying, it’s always worth getting a professional bike fit to optimise your own position if you’re looking to buy your first tri bike.