I have a '77 deluxe varsity which has the tire size 24" x 1 1/4". I'm wondering if I can put any size of 24" tire on the rim, or if I need a new rim. Also: Is it at all possible to put a bigger tire on the frame? I'm new to this, and don't want to buy the parts if they won't fit the bike. Thanks for any help!

nate