Why do some forks and frames have brake rotor size limits?

On Mon, 13 Nov 2017 10:10:05 -0800, Joerg
wrote:

On 2017-11-12 17:46, John B. wrote:

[...]


As an aside, I just measured the front discs on my wife's Honda Jazz
(I think it is called a "Fit"in the U.S.) and to my horror I find that
they are only 240mm (9.4") in diameter. As the nominal weight of the
car is about 1100 Kg (2400lb), as opposed to (probably) an all up
weight of less then 250 lbs for a bicycle, it is obvious that they
can't possibly be large enough to be safe. And Horrors, there isn't
any room to fit larger :-(


Of course, you didn't bother to measure the rotor thickness and didn't
notice the fact that it is rather solid.

Whatever are you talking about? Does the thickness of the disc matter?
If so why are bicycle (and motorcycle) disc such puny little things
hardly thicker then a piece of paper?
--
Cheers,

John B.