Originally Posted by
johnj2803
I am in the same predicament as the OP... Bt I have a question... If I were to buy new tires do I always have to buy new tubes? Or as long as the tube size and the tires are the same size I can keep on using the tubes that I already got?
Chances are the fat knobby tires that come with your mountain bike have different size tubes than a new Semi-slick or slick tire's tube. You might get away with it, but I wouldn't risk it, plus new tires will be more narrow than the fat knobby tires too!
SO to answer your question, yes, you will need to buy new tubes with your new tire, if your going semi-slick which for a hybrid would be the case.