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Changing cogs on Campy cassette?(4 posts)

Changing cogs on Campy cassette?BikeRider
Sep 22, 2003 12:24 PM
I have a 12-25 all steel MK-2 cassette. Would replacing the 23-25 connected cogs with the 23-26 cogs from a 13-26 work? I would like to have a 12-26 cogset. Would this mess up the shifting?

Thanks for any info.
won't be perfect...C-40
Sep 22, 2003 3:42 PM
The shifting will not be perfect, but I can't predict how bad. Campy cogs have letter designations that indicate their compatibility. The 12-25 has a 19A-21A that is supposed to work properly with a 23A-25A. The 13-26 cogs have the suffix C.

Personally, I wouldn't spend half the price of a new cassette to get only one tooth lower. It's only a 4% change. At the low end, a 2-3 tooth difference is needed to be significant. The 13-26 is really for folks that spend a lot of time in the lower gears and believe that an 18T cog is valuable. I've done a lot of mountain climbing lately and never noticed a need for an 18.
Should work fineKerry Irons
Sep 22, 2003 4:51 PM
How would your derailleur "know" what gears were below the 23? Since the Campy 13-26 set uses the combo you're proposing, it should work just fine on a 12-26. As noted by another poster, one tooth doesn't make much difference (3 rpm at a 70 rpm climbing cadence). Ask if you really need the 12, and maybe next time you should just get the 13-26. Except in a racing situation, you can tuck and coast just as fast or faster than you would pedal a 53/12 (34 mph at 100 rpm).
The chain knowsStmbtDave
Sep 26, 2003 8:53 AM
The derailleur won't know but the chain will. The suffix designates the shift ramps and you won't get a smooth shift. I've tried this before and it just doesn't turn out 'Campy'.