On Sun, 22 Oct 2017 09:06:07 -0700, Jeff Liebermann
wrote:

On Sun, 22 Oct 2017 08:07:48 -0700, Joerg
wrote:
(...)
The rear is native 160mm and currently has a 160mm rotor. I'd like to
upgrade both front and back to 203mm or 8". Mostly to reduce rotor
heating during long descents.

Have you considered adding a water mist brake cooling system instead?
You already have a battery pack for your lighting and a water bottle.
A small automotive windshield pump and IR over-temperature switch
should be easy additions (famous last assumptions) to your existing
machine. If the brake disks are fairly flexible, they should not
shatter when suddenly cooled. If the brake pads are made to operate
in the rain, a water spray mist should not affect their stopping
power. The water mist might also be useful for keeping the disks
clean.

I did some quick searching for applicable patents, but found nothing
specific to bicycle brake mist cooling. It MIGHT be patentable. I
did find bicycle misting systems designed to cool the rider, but not
the brakes:
https://patents.google.com/patent/US8714464B2/en
https://patents.google.com/patent/US9296001B2/en
https://patents.google.com/patent/US9186691B2/en

I was also thinking that it might be possible to add some vanes to the
spokes near the disk brakes. These would direct additional cooling
air towards the brake disk. However, when I realized that they would
also direct mud and crud onto the disks, I decided that was a rather
bad idea.

Drivel: Here's a patent application for yet another bicycle light.
https://patents.google.com/patent/US20040090040A1/en
The light is simple enough, but the "predicted applications" include
almost every possible bicycle accessory and application. It then
wanders into the realm of barbeques, lava lamps, fireworks, bicycle
calendars, etc.

Years ago I used to see heavy logging trucks using a water spray brake
cooling system in the mountains along the central branch of the Yuba
River in California.

But re disc brake cooling F1 car brakes appear to work with the discs
red hot. In the 1,000 degree (F) range. And they use Carbon Fiber
discs too :-) And everyone knows that CF is better.
--
Cheers,

John B.