breakdown of a wheel?

[Bman]

howzit guys

 

So your mtb wheel as it stands ready to ride on on your bike consists of? And if you were to have a buckled rim and were upgrading your rims cause you cant just get one you would need to change? Would the hubs and what ever else they consist of be affected by rim? Can these be interchangeable? Have XT hubs which been told are pretty good so can i keep those and out them into new rims, or do rims come with these? Whats the build up and how hard is it to get all together?