Tuesday, 12 January 2010

Bending the wind

Thinking of how powerful brakes are (see past blogs) reminded me of Bill Lomas saying how much the streamliner on his Guzzi affected braking points

Over 60mph most of a bike’s power is being used to push the air out of the way, so when you roll off the throttle the giant airbrake that is the rider quickly slows the bike. Unless you've a full streamliner fairing

The air around us is easy to forget, even when it lifts you and 150 tonnes of Jumbo up, up and away on your hols. Whatever you're doing now, there's a tonne or two of air weighing down on you, its molecules pulled down by gravity.

This is of great interest to F1 car-bores, because you can pinch this weight as ground effect to make Jenson and Hammy look like passengers in a giant Scalextric set. No good for bikes though, because the direction of the downforce changes when you lean over. Didn't stop MV trying in the 70s, mind..


  1. Nice post, for people that spend so much time with face in the breeze it is surprising that bikes really are the definitive blunt instrument in aerodynamic terms. For the speed merchants out there also worth bearing in mind that those forces are proportional to the square of the speed, double the speed - quadruple the drag.


    This also reminds me of a roadtest I read in the 80's of a unitrack GPz1100 which stated that at three figure speeds the wing mirrors folded down to provide aerodynamic downforce. Still not sure whether I believe this, I rather suspect imaginative Kawasaki marketing compensating for poor mirror design but hell, what do I know. Anyone else know about any weird or bizarre aerodynamics that have gone into production bikes?

  2. Well Cyril Green had something to say on the matter: http://tinyurl.com/yzm6ue3