DOS

Well it never ceases to amaze me that whenever I am having a mechanical issue, someone else on Bike Forums has had the same problem.

I put a new cassette (SRAM 11-26) on the other day, and I am now getting annoying rumbling/vibration in the smallest three cogs (11, 12, 13). Seems ,according to attached two threads, others have had same problem.

https://www.bikeforums.net/showthread...ette+vibration

https://www.bikeforums.net/showthread...ette+vibration


While both threads discuss possible solutions (tighten lock ring, play with B-tension screw, get new chain) neither comes to definitive conclusion. I have tried the lock ring and b-tension ideas, no luck. My chain is a bit worn -- .75% according to my Park CC3 -- so I will be changing that. But I was wondering if anyone out there had solved this issue definitively since the above posts first appeared.

DeadSailor

what kind of hubs? for example some american classics have shims between the cassette and the freehub body you might be missing

how many speeds? maybe your missing a spacer or have the wrong size spacer before the cassette

also its not really a good idea to use a worn chain with a brand new cassette

DOS

Its not a spacer issue. Its a 9 speed SRAM cassette on a shimano Ultegra hub. The old cassette was exactly the same, no noise. As for chain, I intend to replace the chain but I actually hadn't planned to replace the cassette so hadn't bought one yet. I bought the cassette for a wheel I just built up to use as a spare but decided to put the new cassette on my main set of wheels rather than on the wheel I intend to use only as a spare. I went for a long riode today without much of a problem so perhaps my tinkering with the b-tension screw helped. Will see what happens with a new chain.

Panthers007

+2 It's a rather unwritten rule regards a new cassette (or chainrings) = a new chain. Chains rapidly adapt to their environment. That means stretching and merging to match the shape of the old cassette or chainrings. Running it with the old chain can cause a plethora of symptoms - all pointing to necessity of chain replacement.

The only other thing I can think of would be a problem with the hub. Looks like you have the RD covered. So hopefully you can provide us with a definitive answer to your oft-repeated problem.

Happy Trails!

EDIT - Do make sure the lockring on the cassette is on square and not off-angle. Seen that cause some lovely problems!

merlin55

Chains don't stretch. The chain pins wearing causes them to become smaller in diameter, and the bushing that they wear against gets larger in diameter, thus each joint gets a little loose. Hence the chain become longer from wear, nothing really stretches.

Chains are about half the cost of a cassette. I usually get about 4000 miles from a road chain, and 2 or three times than from a cassette, so every cassettes starts off with a new chain. Chainrings are so expensive these days, keeping a fresh and clean chain reduces wear to the chainrings

DOS

"So hopefully you can provide us with a definitive answer to your oft-repeated problem."

B-tension screw appears to have solved the problem -- or maybe just riding a bit got chain and casette into better harmony. I haven't yet replaced the chain (SRAM PC-991 in transit from JensonUSA as we speak) but have been out on a couple of long rides since my original post with nary a wisper form chain or cassette. The only thing I did was muck with b-tension screw, which at first didn't seem to make much of a difference but apparently it helped. It would be ironic if the vibration comes back once I install the new chain.