get some new sprockets, 15-41 maybe? then compare the old sprocket to the new one and see the difference. if you dont think the old one is worn so bad but the new stuff on the shelf till its time. not like they are gonna go stale so just put 'em on when you get the time. but if you get new sprockets get a NEW chain to match. get a good, not cheapo special, o or x ring chain and keep it well lubed.