On Thursday, November 16, 2017 at 11:38:40 AM UTC-8, David Scheidt wrote:
Tosspot wrote:
:Why do they have holes in them?

:Car discs don't, motorbike discs don't, aircraft discs don't. Why do
:bicycle discs have them?

Lots of high-performance car brake rotors are drilled or slotted.
Slotting is more common on better stuff, holes can crack. They serve
a couple of features. One, people think they're cool. two, they
allow the gasses that come off brake pads somewhere to go (this is a
non-issue with modern pads, but it was a problem in the dark ages).
Three, they give water somewhere to go. Four, they improve cooling
(increase surface area). five, the clean pads, and reduce wear.

BTW, I have found that flaming skulls work better than lizards or space aliens. https://ep1.pinkbike.org/p4pb5960033/p4pb5960033.jpg
https://i.pinimg.com/736x/a8/a5/8f/a...2ba6b94a8f.jpg

-- Jay Beattie.