Demystifying speed

“Of all the equipment on your bike, your legs are the most critical component… The bike typically makes up 30 percent of your total aerodynamic resistance, less than 15 percent of your total bike/rider mass, and 0 percent of the power generation.”

The above quotes are from aerospace engineer Jim Gourley’s book ‘Faster: Demystifying the Science of Triathlon Speed’, which crunches the numbers and adds a thick scientific veneer to many of the themes advanced (by a non-scientist) on this blog. According to his calculations, a 1 pound weight reduction is worth just 2.5 seconds on a 1-mile climb at a 7% gradient (the useful rule of thumb in the book is that a 10 watt ‘savings’ in power is worth just 40-60 seconds over a 25 mile distance). That carbon seatpost is just not going to do it.

Still, a 10+ pound weight reduction in the rider starts to add up to appreciable gains, especially on steeper climbs where gravity exerts a greater force. Wafer-thin climbing whippets have a distinct advantage. Which is why power to weight ratios have become all important for pro racers in grand tours. No longer can power be dramatically increased through doping. Weight has to come down. Which is why Chris Froome looked like he was suffering from an eating disorder rather than a course of EPO.

Crunching the numbers says that dramatic weight loss is the way to go for faster climbing, but don’t try it at home. Gourley recommends a power meter as a training tool and a way of measuring (and improving) efforts on the bike. “Given the choice between a new set of wheels and a power meter, skip the cosmetics and work on the engine. Get the most speed for your dollar. Remember the difference between a fast-looking bike and a bike that actually goes fast.” Build up the power of that engine first.

'An x-ray on top of a pair of thighs' (picture from The Guardian)
‘An x-ray on top of a pair of thighs’ (picture from The Guardian)