MotoMatters.com is delighted to feature the work of iconic MotoGP writer Mat Oxley. Oxley is a former racer, TT winner and highly respected author of biographies of world champions Mick Doohan and Valentino Rossi, and currently writes for Motor Sport Magazine, where he is MotoGP correspondent. We are featuring sections from Oxley's blogs, which are posted in full on the Motor Sport Magazine website.
How Brembo is dealing with a half tonne MotoGP bike + rider (under braking)
MotoGP braking g-forces have reached 2g, which makes bike (and rider) effectively weigh half a tonne on the brakes. Here’s what Brembo is doing about it…
How much does a MotoGP bike weigh? The rules state that a MotoGP machine must weigh no less than 157 kilos, including oil and water, timekeeping, camera and data-logging equipment.
Add a rider at around 67 kilos (the grid average), plus riding gear at 11 kilos and 22 litres of fuel at 17 kilos. That makes a grand total approaching 260 kilos.
Now accelerate that mass to around 350kph/210mph and then decelerate it as fast as you can into Turn One at Portimao, or anywhere else where riders apply absolute maximum braking force. At recent MotoGP races Brembo engineers have seen negative g-force figures of 2g, which equates to about 1.2MJ (megajoules) of kinetic energy that needs to be dissipated through the brake system.
This is the first time this landmark number has been reached. The figure of 2g is only reached for brief periods of time, but it highlights the fact that braking forces are reaching rates barely conceivable a decade ago.
If bike and rider reach around 2g deceleration they effectively weigh half a tonne or thereabouts during maximum braking. And most of that force goes through the front tyre, which is useful because it expands the tyre’s usual straight-line contact patch by a factor of four, increasing grip, although in extreme cases the force can collapse the tyre. (By the way, at the apex of a corner the tyre’s usual contact patch is doubled.)
Read the rest of Mat Oxley's blog on the Motor Sport Magazine website.