Originally Posted by
veganbikes
IRD does a 13-24 so that sort of corncob set up that was popular for racing. You can apparently also now build your own freewheel again which was something they did back in the day. However if not running a freewheel as Bill said you will probably have a uniglide cassette and those aren't in existence anymore but you might be able to swap out the free hub body to a hyper glide (I did that once and the hub was used and worked). Your frame might not be spaced right and if steel you can possibly cold set it but if not you really can't.
Get some info on the bike and we can help you out more. If the bike is steel and you are running friction shifters you can respace the frame get a new rear wheel and run more gears. If you space out a steel frame to 130mm you can easily get a road wheel with a hyperglide free hub and you could run 10 speed frictionally without a ton of problem and 9 and below with even less issues. Your derailleur might be able to handle it just fine. I am running an 7 speed RD with a 9 speed indexed shifter.
Right now I'm finding that I'm always in high gear and it doesn't feel high enough. I keep looking to shift up and then glancing down to see I'm already in the highest gear on the bike. I guess I'm just used to riding my MTB which with all the gear on it weighs in at close to 60# and this Giant feels super light to me. It's a Giant Quasar 12 speed indexed from the late 80's. Thanks for your input.