What's the difference between a triathlon bike and a road bike?

It's the frame geometry that makes a triathlon bike different to a road bike as the aim is to get your upper body lower and further forwards. This not only makes you more aero but also opens up your hip-leg angle to make it easier to run off the bike.

However a road bike will not get you round the course as quickly as a triathlon bike.

On the bike leg, about 75-80% of the drag comes from you rather than the bike so it’s vital that you’re in the most aero position possible. Tri bikes are designed to help you become streamlined by positioning your torso level with the ground. Manufacturers give tri bikes a steeper seat angle (angle between seat tube and an imaginary straight line where the top tube meets the seat tube) than a road bike. Essentially, they move the saddle further forward in relation to the bottom bracket.

• Frame angles A road bike has slacker frame angles than a tri bike and a higher front end. This gives you a more upright ride position until you shift to the drops and really bend your upper half over.
• Frame tubes Taking their design cues from the pro peloton, which has some strict equipment rules, most road bike tubes don’t slip through the air as well as those of triathlon bikes. Some manufacturers are now offering more aero road bikes, though; Cervélo’s S series and Felt’s AR series, for instance, are designed to reduce drag.
• Seat post: Connects the saddle to the bike. Is clamped into place at the top of the seat tube, but can be moved up and down to adjust height and allow for riders of different sizes.
• Stem: Connects the handlebars to the steerer tube of the fork. This connection means that, when you turn the bars, the front wheel turns.
• Hoods/shifters: If you’re ‘on the hoods’, you’ll be riding with your hands resting on the rubber covers on the shifters. Traditionally, on UK bikes, the right brake is the front and the left is the rear; the right shifter controls the rear derailleur and the left controls the front.
• Brakes: Almost always, on road bikes, side-pull caliper-style.
• Rear derailleur: Moves the chain up and down the cassette.
• Tops: When you’re riding with your hands on either side of the stem, it’s called riding on the tops – a very popular position for climbing.
• Drops:The part of the handlebar that curves downwards. They allow the rider to assume a more aerodynamic position.
• Tyres: For road bikes, usually in 23/25mm varieties. Essentially, goes round the rim and inflated to provide a comfortable ride. Come in clincher, road tubeless and tubular styles, depending on what sort of wheels you have.
• Frontderailleur: Moves the chain between the two front rings
• Wheels: Tend to be more durable and bulletproof than deep-rimmed aero wheels, so will usually feature a minimum of 20 spokes and minimal rim depth.
• Spokes: Joins the hub to the rim. They pull the rim inwards at high tension, which makes the wheel extremely strong. If one loosens or breaks, it can imbalance the whole wheel
• Bullhorns: Usually have small brake levers mounted on the end. (With electronic you’ll also find shifter switches.) Can be used when riding along or, more commonly, when out of the saddle to gain leverage.
• Extensions: Hold onto in order to maintain control when you’re in the aero position. If they have electronic shifters, you have buttons; traditional bar-end shifters are levers at the end of the extensions
• Arm rests: Pads to rest your lower arms/elbows on when you’re on the extensions.
• Rim: The edge of the wheel. The upper part of it is the braking surface, where the brake blocks squeeze the rim in order to slow down. The inner part connects the spokes to the hub.
• Cassette: These days usually 10 or 11 cogs mounted on the freehub of the rear wheel, but can be as few as eight or nine on older bikes. Shifting between sprockets changes the effort needed to move the bike.
• Aero wheels: Though shallow rims pictured here, these are wheels that have added carbon sections to improve aerodynamics. Can come in a a variety of depths, most commonly between 35-90mm.

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Why are deep-section aero wheels faster?

• Integrated brake: Most commonly found on tri bikes, the brakes are integrated into the fork at the front, and hidden under the bottom bracket at the back to improve the aerodynamics of the bike.
• Forks: Connect the front wheel to the handlebars. The steerer tube at the top of the fork goes through the head tube of the bike and is clamped by the stem, which allows you to turn the front wheel with your handlebars.