Adding disc brake to a bike without rear disc brake mounts I'm seeking advice on how to install disc brakes on a bike that does not have rear disc brake mounts. The bike I have is the Trek 7.1 FX. 

Does the Trek 7.1 FX have the mount for installing disc brakes?

Which disc brake option is better to go for, mechanical or hydraulic?

Which brands are reliable, or does Trek provides some custom kit?
It doesn't look like that bike includes the caliper mounts, and the wheels hubs do not have rotor mounts.

Converting a bike like this to disc brakes would require custom frame work, a new fork and new wheels (or at least new hubs and a wheel build).  From a financial standpoint it makes a lot more sense to buy a bike already equipped with disc brakes.

This question covers the pros and cons for different braking systems.

EDIT I stand corrected on the issue of 'required frame work' as @cbamber85 mentions below, there is a product called Brake Therapy Conversion Kit available that will allow you to mount disc brakes on your rear triangle.  Looks like the cost is about $150 USD and you would still need new hubs.