MooCow

I recently replaced my Ultegra 6700 10-spd cassette with a new Ultegra 6700 cassette and am having rough noise/feel problems.

I am using:

a 2011 Reynolds Assault wheel,
a recently purchased DA 7900 rear-derailleur,
a Shimano DA or Ultegra chain which shows no significant wear (less than 0.75%)

With the new cassette installed, I adjusted the rear-derailleur tension to ensure it shifts OK on the stand. But when I get on the bike and pedal, it has a rough feel or sound to it. It feels like I would expect it to feel if the upper pulley were dragging along the cassette; and yet, there seems to be plenty of distance between pulley and cassette and the B-tension seems to be fine.

I pulled off the new cassette off and tried two OTHER cassettes I had available from other wheels - used, but in good condition. An 11-23 and 11-25 cassette both feel fine and smooth. I'm beginning to think I bought the "wrong" cassette, but I counted and re-counted to make sure it was a 10-speed and that it says Ultegra.

What could be wrong?

Thanks

FBinNY 

Stupid question. Did you replace the chain?

Running well with used cassettes but not new ones, that's par for a worn chain. Before going crazy try the new cassette with a new chain (save your old one in case it's in fact still OK). You might also check the chain for wear (stretch). A chain worn to where 12" (24 links) measures over 12-1/16" will likely run badly with a new cassette.

It's more serious than a noise issue because a worn chain will very rapidly wear sprockets to match it's wear age costing you a good percentage of the cassette's usable life. Because of this a new cassette should never be run with a more than slightly worn chain.

MooCow

I have a chain wear gage tool, which is designed to check for .75% and 1% wear. My chain shows significantly less than .75%, and I replaced it not so long ago (I can't remember exactly when). Would you still advise to replace the chain and re-check it?

Thanks

FBinNY 

Given that most chain gauges read high, I'm on the fence. If the chain has a reusable connector, I'd buy a new chain just to be sure. It's no waste because you always need chains anyway, so it'll get used. As I said, save the old one to put back on if the new chain doesn't help.

Or better yet, keep the new chain with the new cassette until it passes the old one in stretch, then switch and rotate both chains going forward. I'm a firm believer that rotating multiple chains (up to 3-4) is the best way to squeeze the most miles out of your drive train dollar.

If the chain switch doesn't help, or helps somewhat, ride it as is for a little while and see if things improve as the sharp edges of the new sprocket break in. For all we know that may be the only issue.

MooCow

Thanks very much for your input. I will try the new chain at my first opportunity next week. In the meantime I will use the old cassette and chain this weekend since I need something that works.