Originally Posted by
JayC
This bike is a vintage Santana with 140mm rear wheel spacing. It's 7 speed with a Sachs 5 groupset. It uses Shimano 7 speed freewheels. I believe we have a 34/14 on there now and will be replacing it with a 34/13. If I could find something with a 12 or even better an 11, that would be great ...
Its got a 52 tooth big chain ring on the front.
7-speed choices:
Sheldon Brown
http://sheldonbrown.com/k7.html#8cassettes lists all the choices which Shimano made ... might not all be available.
Otherwise (no comment on quality levels)
SRAM's PG-730 at Nashbar is 12-32
Nashbar has "MTB" 7-speed freewheels 12-28 and 13-32 and "road" ones 13-24 and 13-32
Loose Screws has Sunrace 13-24 and 13-28, as does Biketoolsetc.
these are all in the $30 or less range, with postage.
eBay may have some, too.
I'd go with the suggestion to upgrade to a cassette system, however ... much more flexibility, more cassette choices, AND better rear axle/bearing conditions. You could put in an 8-speed and probably only have to change the chain.
The 52-14 does cramp your top range. 54-13 would bring you up 12% in your top gearing; 54-12, 21%.
I'd expect that the bigger chainring would cost more than the freewheel.