Originally Posted by CargoDane

I run 180 mm on the back and 203mm on the front. And I use Saints DH brakes. Now, granted, they'd probably be overkill for a normal length bike, but as mine (the Omnium) is longer than a normal bike, if I do an endo, it is me going over the handlebars landing on the cargo platform, rather than the entire bike endoing.

What is also a tad ridiculous is that the 203mm disc takes up just under half of the diameter of the front wheel (front = 20"). The front brake is ridiculously powerful - especially with weight on the bike (because a lot of that extra weight is taken by the front wheel, increasing grip). That's how I like it. You can never have too much stopping power. Assuming you can modulate said power.

Physics will tell you that a larger diameter rotor will be more powerful. It's not simply a matter of heat dissipation as a certain someone claims. It's about leverage.If it was about heat dissipation, they could just make the, say, 140mm rotor larger inwards, even make them completely solid, thus giving more area and more mass to the rotor. That's not how disc brakes works.

On the back, though, I don't need a 203mm disc. A 160mm would probably be plenty of braking power, but I decided that it's only a little bit more weight to have a 180mm .