On Sunday, October 22, 2017 at 9:06:05 AM UTC-7, 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 the water mist system yesterday -- if mist is two inches of rain in 24 hours and howling winds. It was like riding in a disaster film with the sheets of rain and all the branches and leaves flying around. My lowly 160mm cable discs were screaming, but they stopped just fine. This time of year, braking force is second to traction. The best brakes in the world don't mean a thing when you're sliding around on leaves and needles. Today was wet but no rainfall and oddly warm. I ended up putting my rain jacket in my jersey pocket. Tons of blow-down, and soon will have piles of leaves in the bike lanes. Wanna know what happens to separate cycle tracks when the leaves fall? This: https://bikeportland.org/wp-content/...aves-path1.jpg

-- Jay Beattie.