New mtb disc brakes are a huge upgrade for your bike. They look amazing and are much more better in performance then rim brakes (V-brakes). But you have to spend some money to get the components you need. Check this out to get the knowledge to upgrade your bike with mtb disc brakes.
The most important part is the wheel hub. You need a hub with one of the following mounting standard:
- International Standard (IS) (a six-bolt mount)
- Centerlock (licensed by Shimano)
- five-bolt (licensed by Hope)
- three-bolt (licensed by Hope and another system licensed by Rock Shox)
- there are many other mountings for mtb disc brakes