Does it make sense for mountain bikes to have the same size rotor in the rear as in the front? If you look at other wheeled vehicles, such as street bikes, they have two massive rotors in the front and one tiny little rotor in the rear. Cars are the same way - some (cheaper) cars only have drum brakes in the rear. So why do so many mountain bikes have matching rotors front and rear? Is there an actual reason for this? I'm thinking of downsizing the rear rotors on both my DH and trail bikes, but wanted to hear some arguments for or against this idea first. Discuss.