You spend thousands on wheels, a helmet and a race suit, then ride on tyres that steal several watts at each wheel. Rolling resistance is the cheapest aerodynamic gain in triathlon and one of the most overlooked. The gap between the fastest and the slowest tyre is measurable, and it is measured in watts.
What it really costs
Independent lab testing is unforgiving. The difference between a fast and an average road tyre is roughly 6 to 8 W per tyre, so 12 to 16 W for a pair. The reference point on the road is a measurement in which a 0.9 W advantage per tyre translates to 5 to 7 seconds over a 40 km time trial. Scaled up, a 12 to 16 W pair works out at 30 to 60 seconds over that distance.
That is less than parts of the marketing promise, but still a lot. Put it in training terms. Generating an extra ten-odd watts of power takes weeks of work. A similar advantage on the flat can be bought by fitting better rubber. This is not an argument for ignoring training, it is an argument for not throwing away the watts you have earned on the wrong tyres.
Tubeless won, and the numbers back it
For years the fastest option was a tubular with a latex inner tube. Today tubeless leads, and 28 mm has become the new standard. A good clincher with a latex tube gives up anything from a fraction of a watt to about 2 W against the same tyre run tubeless. The gap grows at lower pressures, though in practice latex stays close behind.
A wider tyre can be faster because at lower pressure it deforms less over road imperfections and damps micro-vibration better, so on real tarmac it rolls more easily. Hence the trend of 28 mm displacing 25 mm for training and most races. The condition is having rims and a frame with room for it. The exception is a pure time trial on smooth surfaces, where a narrower tyre can still claw back something aerodynamically.
Below are figures from Bicycle Rolling Resistance. They cover a single tyre at a test speed of 29 km/h and a load of 42.5 kg. Treat them as a reference for comparison, not as the loss at race speed.
| Tyre | Width | Power loss (per tyre) |
|---|---|---|
| Continental GP5000 S TR | 25 mm | about 10.1 W (CRR 0.00303) |
| Vittoria Corsa Pro TLR | 28 mm | about 11.1 W (CRR 0.00333) |
| Vittoria Corsa Pro Speed TLR | 28 mm | about 6.7 W (CRR 0.00201) |
In dry racing the fastest options today are the dedicated time trial models. The Vittoria Corsa Pro Speed TLR leads, with the Veloflex Record TLR and the Continental GP5000 TT TR behind it. These tyres give up the fewest watts, and the price is much less puncture protection. Save them for race day rather than training on broken tarmac.
Speed against durability
This is where the grown-up conversation starts. The fastest race tyres have a thin tread and little puncture protection. Time trial models can be a few watts quicker than the all-round competition, and they wear out sooner. The GP5000 S TR is the all-rounder: barely slower, considerably tougher.
A practical strategy for the season looks like this:
- For training: an all-round, durable tyre. A few watts more resistance, but no sessions lost to roadside repairs.
- For racing: the fastest time trial model, fitted a few days before the race and checked on one shakedown ride.
- Tubeless always, with good sealant, if the wheels allow it. A small puncture seals itself.
Before you replace anything, set the pressure
The fastest tyre badly inflated is money wasted. Too much pressure bounces you over rough surfaces and genuinely slows you down, while too little increases deformation and puncture risk. Start from the manufacturer’s recommendation for your weight and tyre width. Then make small downward corrections on rough tarmac. Harder on a smooth track, softer on a coarse road.
It is the cheapest optimisation in triathlon. It costs nothing and it can hand back several watts.
More on this: Disc Wheels in Triathlon: When They Pay Off. Racelify lists cycling events with dates and organiser links.