How do I replace the gears on my Trek?

Well, my boyfriend. He knows a fair amount about fixing bikes. We're going to buy gears from the shop for $40 here but the labor is like $75 and we'd like to see if my boyfriend can do it by himself. He's never switched out gears before but he thinks it'll be easy enough.



My bike was made in the late 80's/ early 90s and has mountain tires--so its not a street bike. The gears being how they are now make it uncomfortable and difficult to ride even just across campus, with minor hills and such. They don't shift very easily and they have a very small range and even the tops of them popped off so they don't work so well.

I love the gears on my boyfriends bike. There are two different levers for them-- one goes up one goes down a notch. Plus they make pedaling and riding a breeze.



So I'm having trouble researching these on the web, they all either talk about the cassette? (I don't know what that is) or they talk about how to change gears when I'm riding.

Can anyone give me a tutorial on how to do it or some helpful links?



Thanks...How do I replace the gears on my Trek?
Here are some good sites to use.



http://bicycletutor.com/



http://www.sheldonbrown.com/home.html



http://www.parktool.com/How do I replace the gears on my Trek?
you may also have to get a longer or shorten the chain _IF you change any gears

BUT

what you say doesn;t make sense

usually mt bikes have super low gears

are they not *shifting*?

if that is the case the gears may not need replacing



wle.
that depends on which ';gears'; you are talking about.



the ';cassette'; is the cluster of gears on the rear wheel. if you need to change out the cassette on a bike that old, i would say don't bother, just buy a whole new wheel/wheel set. pricepoint has good deals right now for wheels that will fit your need (about $90). the cassette would have to be bought separately (about $30), but at least you'll know you are getting reliable components.



you guys could just buy the cassette, the problem with that is finding the proper tools (i've never worked on a bike that old so i'm not sure if the standard cassette remover would work on it).



as far as the levers, it sounds like you are describing trigger shifters (about $80 for the pair).



if this were my regular commuter, i could easily justify completely overhauling the entire thing: new cassette, new wheels, new shifters, and new derailleurs. that would cost about $300 though, at which point you might as well buy a new one (unless you are particularly attached to that one).