Got an email this morning from someone who asked why I’d not posted a glowing brake disc photo yet. I did post the odd image of one rotor glowing while the other is not, but if you’re after both lit up nicely, here is Ben Spies in Turn 1.
One of the interesting things about this phenomenon is that not all riders come into Turn 1 with their brakes red hot like Ben’s are. In 2009 when I first noticed this no one’s brakes glowed brighter than Rossi’s. But this this year Rossi’s brakes, while definitely glowing, were not as bright as Ben’s. The Yamaha riders had brighter brakes as a group than any others, though there were exceptions. Aoyama lit them up nicely of the Honda riders, while Casey and Super Sic got a bit of glow working, but Pedrosa and Dovi hardly had any that I saw. I wondered if Yamaha uses some type of disc that affects this, of if Brembo supplies the same gear to all its teams and this is more a difference between riders’ styles.
Another factor that I’d underestimated was the ambient temperature’s influence. During the test sessions on the Sunday and Monday before the race weekend, the wind was considerable and the temperature downright frigid. Thus the riders had very little brake glow the times I went out to check, offering some insight into just how effective air over a hot surface is when it come to cooling it down. As I shivered in the desert and the marshals sheltered from the wind behind anything they could find, the brakes in Turn 1 hardly glowed at all. It wasn’t until the temperature warmed on race weekend that I started seeing bright glows like this.
One thing that has always fascinated me about the Rossi photo from 2009 (see link above) is that the brake rotors are brighter and thus hotter in the few inches behind the caliper. They appear to cool enough in the tiniest fraction of a second after leaving the high friction zone of the caliper that their color changes noticeably. Rossi starts braking at over 200mph and the brake temperature rises very quickly. So maybe he has slowed to around 100mph at the time of this exposure? The rotor is still turning inside the brake caliper pretty darn quickly, and in the time it takes to move a few inches the temperature changes enough to cool from almost white hot to bright orange? Crazy.
This is happening with Ben’s brakes as well. The hottest part of the rotor is behind the front fork, but you can see it if you look closely. There is so much going on that we don’t see until a still image show us, it’s just amazing.
