What new cassette to get for suntour X1 derailleur?
 

i currently have a suntour 5-spd freewheel cassette with a suntour X1 derailleur on a cannondale SM500 (i think the cassette is original, putting it at 20 years old). cassette is worn and in need of replacement. the shifter is 5-spd indexed. what should i upgrade to? would i be better off finding a new 5-spd cassette or should i look for a NOS suntour on ebay? do they even make new 5-spd cassettes? what would be comparable or better in quality?

If you are looking to upgrade, I'd either go friction or swap out the shifter for a 7 speed indexed unit and add a 7 speed freewheel. This will likely require spreading the rear triangle to install the wheel and depending on how often you do that you might want to consider cold setting the frame. 2mm per side in my experience is cake though so 3mm shouldn't be much worse. YMMV though.

i'd prefer not to modify the frame at all. it is aluminum, so i don't know how easy it would be to respace the rear triangle.

In that case, you don't have many options for upgrading as "Ultra" spaced 6 speed freewheels (6 cogs in the space of the normal 5) seem to be impossible to find. Both Harris and Universal Cycles stock a decent range of good quality 5 speed freewheels. You should find something to your liking there.

http://www.sheldonbrown.com/harris/freewheels.html

http://www.universalcycles.com/shopp...&category=1665

Here is one and cheap also
http://www.biketoolsetc.com/index.cg...tem_id=SU-HG5A

Measure the spacing between dropouts first. Sometimes frames were made with 124mm or 126mm spacing even though a 5-speed freewheel was used. If your frame is 124mm or greater, you should be able to use a 6- or 7-speed freewheel (althought it may mean adjusting your hub spacers - i.e. taking a few mm from the non-drive side and putting on the drive side - and redishing the the wheel).