How fast could I go on my bike?
You think you’re fast, you know you could be faster, but what is the fastest speed physically possible?
here you are, speeding downhill like your life depended on it. Crouched over the bars, white knuckles gripping the drops, you look down at your bike computer and you see the figure click up to 70kmh. Oh yes, you’re really flying now. But before you can gain any more speed, the road sign signals a junction ahead and you squeeze the brakes to bring you safely to a halt.
But what if that junction wasn’t there? What if there were no obstacles or bends or dogs wandering into the road, and the slope was as long and smooth and steep as you could possibly wish for? How fast could you go then? Let’s begin to answer that question by looking at what’s holding you back.
Life’s a drag
‘That would be terminal velocity,’ explains Rob Kitching, founder of online aerodynamic outfit Cycling Power Lab. ‘In cycling terms, this is the point where the joint stopping forces of aerodynamic drag and rolling resistance equal the forces provided by gravity and power output.’
How much impact gravity has depends on the severity of the slope. ‘If you set the slope to infinite – in other words, a wall – there’d be no load on the tyres or the bike’s structure,’ says Ingmar Jungnickel, R&D engineer for Specialized. ‘Effectively that would make both redundant and you’d be skydiving.’
Or more technically ‘speed skydiving’, where the goal is to achieve and maintain the highest possible terminal velocity. Drop a human out of a plane belly down and they’ll reach speeds of up to 200kmh; head first and we’re talking 250-300kmh; head first and wearing specialist streamlined apparel allows for speeds of up to 450kmh.
‘But that’s not cycling, so let’s ignore that and use an actual road,’ continues Jungnickel. Scanning the world’s streets, Baldwin Street in Dunedin, New Zealand, holds the dubious honour of being the steepest road on the planet at 35-38°, depending on who you believe.
‘On this road’s gradient – but