Bicycle Mechanics - 28 cassette with older Ultegra RD?

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john_iverson
06-04-10, 11:43 AM
I currently have an RD6500 RD on a new road build. I've been using a 12-27 cassette w/ no problems but it's pretty clapped out--If I buy a new cassette with a 28 top gear can I expect the same or will there be problems? Mucho hilly near my house so I would love another gear.

Thanks,
John

dwr1961
06-04-10, 04:20 PM
As far as being within the working range of the 6500 derailleur, I'd say it will work. Shimano specifies that a 27-tooth cog is the upper limit for that model, but they're pretty conservative in their spec. My concern have more to do with the entire gear range of the cogset you're replacing the 12-27 with. If you're going to use an 11-28 mtb setup, you'll have some widely-spaced gears on the low end. Also the difference between 27 and 28 isn't all that much. It probably won't feel like an "extra gear" when you're climbing that monster hill.
HillRider
06-04-10, 05:12 PM
It should work. As dwr1961 said, Shimano is very conservative in their derailleur ratings. Shift into your 27T cog. If there is a modest amount of clearance between the cog teeth and the chain or you can tighten the "B-screw" a bit then a 28T cog should also work.