On Thu, 16 Nov 2017 07:47:19 +0100, 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?

https://www.ebay.com/sch/Honda-Motor...i.html?_fsrp=1
https://www.boschautoparts.com/en/au...c-brake-rotors
http://www.aerobrake.com/?gclid=EAIa... AEgLxKfD_BwE
--
Cheers,

John B.