quick brake calipher question
 

when cleaning the brake calipers on my trek 1000 i lost the small plastic casing that goes around the spring so the spring does not rub against the actual metal. how important is this part? while looking at other bikes i noticed that they did not have this part. is it worth replacing?

I would'nt worry too much about that. Some brake calipers dont even have those little plastic pieces you speak of. Just polish the contact area where the brake spring end rests/slides and it should be okay.

An occasional drop of oil or chain lube (don't ask what kind, please!) will help, too.