Discs need t oget bigger with cars to spread the heat energy out over a larger surface area - otherwise the pads get cooked. Similarly the mass of disc is important - the same kinetic energy has to be absorbed as heat. So put crudely doubling the weight means half the temperature rise.
What gets omitted in these discussions is that there is 700g of 'disc' available on a rim brake, which is why rims get warm while discs get very hot.
The main advantage of discs is that they stay clean and dry and can have a no-compromise design for optimum friction and heat dissipation without having to hold a tyre as well. This ability to optimise the braking system gives the advantage.
What gets omitted in these discussions is that there is 700g of 'disc' available on a rim brake, which is why rims get warm while discs get very hot.
The main advantage of discs is that they stay clean and dry and can have a no-compromise design for optimum friction and heat dissipation without having to hold a tyre as well. This ability to optimise the braking system gives the advantage.