Bicycle Mechanics - 7sp Cassette question

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RGW
09-23-06, 10:43 AM
I have a 91 Paramount with the shimano 7speed group. The largest cog on my 7sp shimano 105 cassette is 23T. I would like some additional gearing on my road bike but am not sure as to what is the largest cog that the group can take? Does it have to be Shimano?

operator
09-23-06, 10:46 AM
STI? Do you have a long/short cage RD?
RGW
09-23-06, 10:49 AM
Sorry - yes, it is STI, and it is short cage (double up front). Also was considering putting barend shifter on this (currently have downtube shifters). Do I have to use 7speed, or will 8 spped work as well

Retro Grouch
09-23-06, 12:36 PM
I'm not positive about components that old, but modern Shimano road derailleurs will handle a 27 tooth big cog with no problems. Long or short cage usually doesn't matter.

7-speed cassettes come with 12-28 and 13-28 cogs. If it was my bike I'd try one of those. I'm about 95% confident it'll work.

Your freehub body isn't wide enough to handle an 8-speed cassette.
HillRider
09-23-06, 02:06 PM
There was a 13x30 7-speed cassette available from Shimano also. Most of the time even short cage rds will work with them even if their "wrap" won't let you use the small-small combination.
top506
09-23-06, 02:40 PM
I ran a short cage Shimano Light Action RD with a 13-30 with no troubles.
Top
mycoatl
09-23-06, 02:44 PM
Also was considering putting barend shifter on this (currently have downtube shifters). Do I have to use 7speed, or will 8 spped work as well

You likely need to stick with 7 sp because of your hub spacing. However, you can also use a 9 sp casette with one of the cogs removed and run what Sheldon Brown calls "8 of 9 on 7." Check this (http://www.sheldonbrown.com/k7.html) out for more info about this conversion (it's toward the bottom of the page).
HillRider
09-23-06, 06:40 PM
You likely need to stick with 7 sp because of your hub spacing. However, you can also use a 9 sp casette with one of the cogs removed and run what Sheldon Brown calls "8 of 9 on 7." Check this (http://www.sheldonbrown.com/k7.html) out for more info about this conversion (it's toward the bottom of the page).
If you do this you will need 9-speed shifters to index properly and you just lock out one click with the derailleur limit screws.