I have a Univega via carisma hybrid bike. I bought it used recently and I am guessing it is mid-1990's. It has a triple crankset with shimano exage deraillers and 7 speeds in back. 700c wheels. A link on my chain broke and my bike mechanic explained if the new chain skips he will replace the cassette. He has a new replacement 12-28 7 speed shimano cassette. Hes prepared to put this in if needed. Im wondering if i will lose any easy gear with that replacement cassette, i dont know what the bike has now (its with the mechanic now.) Is there a 7 speed cassette with an easier gear i should consider. I know about the Shimano megarange but since i have a triple up front that doesnt seem like a good idea (34 is probably too big considering the triple up front?) I need to ride up steep hills, what cassette should i tell the mechanic to install if he has to put in a new one?
The availability of 7 speed cassettes may be limited at some shops... our local co-op carries a good selection as I am the guy who helps with the parts orders and make sure we can service 7 speeds as there are still a bunch of them out there.
12-28 should offer a nice range with a triple unless you really need a stump pulling low gear... you might be able to install a smaller inner chain ring to offer a lower gear but would have to know what crank you are running but if my specs are correct the Charisma came with a 28/38/48 crankset which is typical for hybrids.
If the cassette choices are limited you could customize the 7 speed by swapping out the 28 for a 30, 32, or 34 tooth cog if you can find a salvageable cassette to provide a donor cog or might look at upgrading your crank to an mtb crank that will handle a 22-24 tooth granny and with a 44 tooth big ring you would not be losing much off the top.
I got the bike back. New chain, new cassette (12-28, repairman said old one was 11-28), and he had to put new used derailler because mine was bent/damaged. The shifting is noticeably smoother. It's a noticeable improvement on the bike.