freemti

I've been googling this question of mine and have yet to find an absolute answer that would allow me to say "yes this will work" and actually order the components, I want to add a rear cog like a SRAM 11-34 for a pending touring trip across some serious hills to my current compact double campy equipped bike.

I ran across the above statement by a fellow on some other bike forum, he certainly seems to be saying it is possible. I realize I need a long cage dérailleur and the listde SRAM cog, but that is fine compared to the large amount of $ I would have to spend (crankset, BB, FD) to go all triple just for this one tour.

Barabaika

The 34 rear cog won't work well with the Centaur rear derailleur.
The SRAM cassette won't fit the Campagnolo hub.

You should try the 13-29 Campagnolo Veloce cassette. I suspect that you can successfully change the 29t cog to a 30-31t one.

freemti

I have a SRAM 11-28 cassette on my present all campy bike, so I assume he is talking the campy version of the approriate SRAM cassette. I'll have to look.

I am still puzzled by this question since "official" specs say a max 29 tooth rear cog for the medium cage derailleur. OK I can undestand that, but they also say the same thing about the long cage deraillier albeit that the long cage is specifically meant for their triple crankset offerings and therefore would need a biiger capacity due to the small inner ring. However, is there some other physical reason why I cannot at least go to a 32 tooth rear cog with either the long or medium cage derailleur? Staying with my compact double in the second case and going triple in the first.

I'm thinking not, but then I am not a bike mechanic. Another piece to throw into the puzzle is that I've done this on my older bike, but with with Shimano 105. Again compact double with a 12-32 MTB cog on the rear and a medium cage RD, my LBS didn't even have to change the chain, but I did have to stay away from usng 50-32 which I wouldn't use anyway. If all I have to do is to avoid certain gear combination and I can do what I want for my trip, I'll be happy. It will all come off when I get back, I don't need it for my regular biking chores, just touring.

SweetLou

Chain capacity and max cog are two different things. Chain capacity is how much chain the rear derailer can take up. Long cage is needed for a triple because of all the extra chain when running small/small. If you use a short cage, it will work. But, you won't have enough chain for the big/big.

Max cog is how big of a rear cog you can use. This has to do with derailer clearance. If the max cog is 27 and you run with a 34, then the derailer will hit the cog. I'm not sure about Campy, but Shimano is pretty conservative with its max cog. A derailer that says its max is 27 can run a 28, probably a 29 and maybe a 30.

HillRider

I would approach this far differently if I had to use a shortcage rear derailleur with a triple. I would ALWAYS size the chain to allow big-big. Not doing so can cause a tremendous amount of damage if you suffer momentary brain fade and try to shift into that combination.

What you give up is the ability to use small-small without the chain going completely slack. A mistaken shift to that combination will be a nuisance instead of a mechanical disaster.

freemti

Man this bike wrenching research is hard stuff! If it is true that even a campy long cage RD will not handle a max 32 and I need to get a RD anyway, how about I get a SRAM X.7 long cage which absolutely says I can go to 34 max? Throw in a ShiftMate to keep the indexing correct, slap on a SRAM PG-970 9 speed remembering to adjust the limit screw or slap on an IRD 10 speed 11-32 with no adjustment needed?

Bonus question: I have Zipp team CSC wheels with a SRAM 11-28 cassette so I think I have a shimano compatible hub/freewheel and not a campy one?

SweetLou

That's correct. I wasn't trying to imply setting up the chain in this manner. I was just trying to explain chain capacity.

I_bRAD

I bet if you kept your rear intact and got a triple crank you'd be really happy.

freemti

And you'd be right, but the wife would be less happy after I plonk down the cash for a new crankset, FD and BB to go with it. Of course I have to spend on the RD anyway, but I could keep my existing 11-28 cog and rely on the 48-36-26 triple up front to give me the low gear inches I'm looking for.

I'm still hoping that I can do this without a huge cash outlay, say ~$250 for the new cog & RD -vs- $500+ for a full triple-ectomy

I_bRAD

250 now, but a crankset lasts way longer than a cassette and you wouldn't have to switch it out every time you want to hit the hills.

Booger1

For 1 time only deal,You can get a Shimano Mnt crank,BB,and Der for about $50.I just looked at the flyer today and the crank is $7...YES,$7.Certainly not the best,but I bet you can't break it with 1 tour.It will have 44-34-24 chainrings or thereabouts.