Disc Brake Thermal Imaging

Today I attached an infra-red camera to my bike, pointed it at my front brake, then rode down a hill, deliberately dragging the brake the whole way.

Notable things include:

• The camera unfortunately doesn't embed the scale in the video, and it auto-ranges to the highest and lowest temps in each frame, so you can't tell what the absolute temperature is.
• Occasional pauses in the video are where the camera recalibrates itself.
• Different materials radiate heat differently, so you can't directly compare the apparent temperature of different parts of the bike.
• At the start, I had been standing at the top of the hill for a minute, which was long enough for one side of the tyre to absorb heat from the road. This is why one side appears slightly orange as I start the descent.
• I start dragging the brake at around 0m40s.
• By about 1m00s the rotor is much hotter than anything else in the picture.
• I come to a complete halt right at the end of the video.

And here's a second video from a short while later showing much quicker heating from hard braking to stop at a junction. At the start, you can see that the caliper has warmed up a bit compared to the first video:

The brake caliper is a Hope RX4, and the rotor is a Shimano RT81, which is one of the ones with an aluminium core.