Cassette compatibility

[nscrbug]

Is your crankset double or triple, and how many teeth in each ring? A RD has a maximum cassette cog it can handle as well as a maximum tooth difference (add differences in cassette large-small and chainring large-small). Tooth difference defines the amount of chain that the RD can wrap up.

It's a compact 50/34. Yes, I was basically told the same thing by a LBS...that my current 6600 SL RD is maxed out with my current 12-25 cassette...so it would not be able to accommodate a 27t or 28t cog. However...when I do the formula you provided above, I get a maximum difference of 29...so now I'm confused...

[aicabsolut]

The Ultegra RD will probably work. A Dura-Ace 7800 RD will not work well with the 11-28 spread, but for some reason the 105 and ultegra ss RD are a bit more friendly to larger gear spreads with a compact. However, your chain might be a bit short now...

[lo123]

It's a compact 50/34. Yes, I was basically told the same thing by a LBS...that my current 6600 SL RD is maxed out with my current 12-25 cassette...so it would not be able to accommodate a 27t or 28t cog. However...when I do the formula you provided above, I get a maximum difference of 29...so now I'm confused...

My LBS said it'll work and that's Ultegra 6600 SL with compact crankset. And it does work. Actually, LBS owner, a female(!), has the same setup on her Madone 6.2

Like I said, it does need more frequent tuning, but I'm learning how to do that myself and hubby does it for me now, so I don't have to go to the LBS.

[nscrbug]

Thanks to everyone for the advice!!! I've decided to go with the 6600 12-27 cassette...which should work with my current 6600 RD...or so I was told by yet another LBS that I stopped in at over the weekend. So now I'm just shopping around for a good price on one. Oh...and I was told that I'd likely need to replace the chain (even though it only has 300 miles on it) since it probably wouldn't fit with the wider tooth range on the new cassette.

[aicabsolut]

Thanks to everyone for the advice!!! I've decided to go with the 6600 12-27 cassette...which should work with my current 6600 RD...or so I was told by yet another LBS that I stopped in at over the weekend. So now I'm just shopping around for a good price on one. Oh...and I was told that I'd likely need to replace the chain (even though it only has 300 miles on it) since it probably wouldn't fit with the wider tooth range on the new cassette.

Have you thought about trying a 12-27? That would probably fit easier with your current chain...though can't really tell till you get it on there. Just don't cross-chain in the big ring too much.

[nscrbug]

Have you thought about trying a 12-27? That would probably fit easier with your current chain...though can't really tell till you get it on there. Just don't cross-chain in the big ring too much.

Yup...in my last post, I stated that I decided to go with a 12-27. Now I just need to find one for a good price.