Thanks Steve! The thing is - I've been witness to this exact argument before on car forums. The boy racers all come in thinking bigger brakes = shorter stopping distances and the old boys quickly put them in their place and point out that basic physics shows that's not the case.
But some people just don't want to listen and feel the need to justify their shiny new thing, even if it contradicts physics.
Logically even, if both brakes can lock the wheels then how can adding more power to the brakes slow you any quicker?! Bigger brakes can't increase the traction at the tyres, so it's just physically impossible. Adding power will just make it easier to lock the wheels and thus less easy to modulate the brakes.
Having made this argument repeatedly here, I'm not saying that larger brakes are inferior, just that you need to understand what you're actually getting them for. Don't buy them thinking they will stop you quicker. Buy them because you want better resistance to heat fade or so that you have to put in less effort at the lever (possibly at the expense of ultimate modulation).
Anyway, it's all not worth falling out over. If anyone wants bigger brakes, buy them - it makes no odds to me.
You are just wrong because you only look at what happens once the wheels are locked and nobody doubts you can't reach that point with a smaller, weaker brake, too.
"Also, with a larger diameter rotor there's more of a levering force, so you probably get a bit more power, which doesn't really translate to stopping you faster, but can make it more likely that you'll lock the rear wheel when you didn't intend to. "Snapper" brakes, I guess."
Quoted from an earlier post of yours. So what are you saying? Sometimes you say smaller brakes are better in some situations (usually you ad a note that you don't want to say smaller brakes are better, but then in fact you say exactly that).
In that quote you admit that there is more levering force resulting in more
power. For my understanding, that is what the discussion was about. And if we'd go into milliseconds, then the less power at the lever will also result in quicker locking the wheel and that will result in quicker stopping, so the larger disc makes a stronger brake, but again: that's not what I wanted to say and not even worth the discussion. The point is that you compare the power of brakes when the wheel is already locked, and that makes no sense.
Of course you can apply more power to the lever to make a smaller brake also lock the wheel (you need more power at the lever because the smaller brake/disc is weaker) but when going seriously downhill that will require more manual power which will lead to less control for steering the bike. Also modulation is more difficult than with a larger disc.
At the same time, modulation depends on the design of the lever unit, so a smaller disc doesn't always mean better modulation and a larger disc dos not automatically result in a "snapper brake".
And again: going downhill one will want a larger brake that gets the wheels close to locking with little manual power necessary at the lever. Stronger brakes.
It is not all about friction, that is a far to theoretical approach.
But even in theory a larger disc results in more braking power.
At some point you came up with rim brakes to show that larger diameter does not result in more braking power. But as you hopefully know, you cannot compare rim brakes to modern disc brakes. The friction is much lower on rim brakes. But if you would use a smaller rim of course the braking power would also be less then with a larger rim.
ONLY when the wheel is locked it no longer comes down to the power of the brakes (better steering control with large discs aside) but to the tires. Anyway, usually one does not brake to lock the wheels.
At least not downhill where you sometimes need to get to close to zero speed quickly and for that you need leverage resulting in more braking power. You don't want to lock the brakes
Larger disc, more power. More power, better control and faster stopping times.
I am now wary of shaking hands with younger blokes who have apparently been taught that bone-crushing handshakes are manly. Fair enough, I used to think the same. So now I warn them before handshaking.
. The 200km until now as been done 100% on the bike park next to my house. But it’s short 200 meter D-
