Many years ago, (when I was 11, now 17), I got a bike for my birthday/Christmas combined present, I got a mountain bike. It was good for what it was: V-brakes, 21 gears, front suspension etc.
So, I enjoyed the bike for about a year, then decided the forks weren't great, and that upgrading them would make everything much better. Now, knowing nothing about bike geometry, I fitted some longer forks. Lovely, I could go over all sorts, land jumps and the front wheel always stayed attached to the ground. Being young and adventurous, I started doing drops - onto concrete. Needless to say the wheels that came attached to a £150 bike didn't hold up particularly well.
So, a little re-speccing later, the bike got some new wheels. These were heavy duty jump wheels that are designed for grown men to jump off stuff. A 13 year old would be fine. Due to the different hubs, I also had to fit a new rear cassette, and all the deraileurs and shifters that come with.
Seeing they were disc...