- Jul 23, 2005
A 29t cog will require two more inches of chain than a 25t cog ...Bob Weight said:I have a road bike with Campy chorus Gruppo which has a 12-25 10 speed cassette and a compact crank. My buddies tell me that a 12-29 will make it a lot easier to climb the mountains where I live. Will I have to also change the rear deraileur and chain?
Having a long cage rear derailleur on a road bike will mostly be cosmetic -- if your current setup is already optimized with regard to chain length, then adding four more links could result in the lower portion of the chain sagging at times ... THAT would be unacceptable on a MTB but would be less critical on a Road bike unless you are riding across a section of pave ...
That is to say, you don't have to change to a rear derailleur with a longer cage, but I would ...
Generally, regardless of the cassette I plan to use (I have 12-23 to 11-34 cassettes which I use on my Road bikes), I usually buy/use a rear deralleur with a long cage because it gives me the option to install a wheel with a larger cassette & I don't mind dragging a couple of extra inches of chain around when I am using a cassette with a smaller largest cog.FYI. You can simply replace the cage on your current rear derailleur with a longer one; but, it's probably less expensive to simply buy a long cage Veloce rear derailleur to replace the short cage on Chorus rear derailleur with a longer cage ...
It is my understanding that the cages on Shimano & Campagnolo rear derailleurs are interchangeable (i.e., same size shaft & the registration groove is in the same place ... MAYBE NOT!) ... I HAVEN'T TRIED INTERCHANGING/TRANSPLANTING CAGES FROM ONE (e.g., Shimano MTB rear derailleur) TO THE OTHER (i.e., Campagnolo short cage Road rear derailleur).