I have become quite experienced with cog indexing and derailleurs. I write this to convey that I have assessed and mechanically tuned/indexed the rear cassette with great attention to details. I'm using a new SRAM pg1070 12-28 cassette and new SRAM pc1091R chain and new SRAM RED 53/39 front rings. Shifting is absolutely crisp and precise.
However, I get a slight rub sound in the middle three cogs of rear cassette while in small front ring. Is this typical and I simply did not notice before or should it be dead quiet?
That cassette number you quoted can be 10 or 11, didn't know which one you had.
It may just be resonance. Try just gently lifting the deraileur with your finger, don't allow any sideways movement, just lift it up a little. If it goes quiet, try a little move on the B tension, if that doesn't work then it was your hand damping the noise and it is not rubbing somewhere, it is just resonance. Only real way around it is to change the parameters that set it up, so maybe one more chain link or one less link will shift things up enough to stop it.
Still sounds like hanger needs alignment to me though. What did you use to align it?
You say it is rubbing, is it? Can you see it or does it just sound like it is to you? Can you make it go away in those particular gears by indexing, even if the rest of the cassette won't run properly? Are the pulleys spinning freely? Are the pulley cage bolts tight? Is there play in the freehub bearings? Is the wheel in straight?
Some photos or video may help. These type of problems are a 2 min fix when the bike is in front of you. So something you describe is incorrect or you have left something out of your description.
This post has taken longer to write than your fix would be.......
That cassette number you quoted can be 10 or 11, didn't know which one you had.
It may just be resonance. Try just gently lifting the deraileur with your finger, don't allow any sideways movement, just lift it up a little. If it goes quiet, try a little move on the B tension, if that doesn't work then it was your hand damping the noise and it is not rubbing somewhere, it is just resonance. Only real way around it is to change the parameters that set it up, so maybe one more chain link or one less link will shift things up enough to stop it.
Still sounds like hanger needs alignment to me though. What did you use to align it?
You say it is rubbing, is it? Can you see it or does it just sound like it is to you? Can you make it go away in those particular gears by indexing, even if the rest of the cassette won't run properly? Are the pulleys spinning freely? Are the pulley cage bolts tight? Is there play in the freehub bearings? Is the wheel in straight?
Some photos or video may help. These type of problems are a 2 min fix when the bike is in front of you. So something you describe is incorrect or you have left something out of your description.
This post has taken longer to write than your fix would be.......
Excellent analysis. I will try the RD lift experiment. It is more of a clicking sound versus a run. While on a stand it's not detectable. Therefore, world need to be recorded during a ride. Not possible. I have minimized the noise in volume and to one cog. The middle cog. Not sure of the tooth count. Hanger was checked with a park tool hanger alignment tool. Like I indicated earlier, while in the 53 ring there is no detectable clicking. Otherwise, relatively faint clicking. With all else dead silent I'd like to eliminate the noise. Seems after a fresh chain lube it's almost completely gone. I'm sure those with slight OCD with cycle noises not to mention wanting everything prefect when occasionally exceeding 40 mph highlights the interest.
Just a thought, but since it does not occur in the 53 but does in the 39, is it possible that your chain length is not just right or the spring tension is a bit off on the RD? When you go the 39 the chain tension will definitely reduce a significant amount and it could be allowing the resonance?
Just a thought, but since it does not occur in the 53 but does in the 39, is it possible that your chain length is not just right or the spring tension is a bit off on the RD? When you go the 39 the chain tension will definitely reduce a significant amount and it could be allowing the resonance?
According, to chain length methods, it seems the chain could be shortened a bit. Perhaps, shortening the chain length will resolve the resonance.
That cassette number you quoted can be 10 or 11, didn't know which one you had.
A PG-1070 is a 10 speed cassette, the 11 speed version is the PG-1170. The first two digits is the number of cogs/speed.
For some reason that cassette is advertised all over the place as both 11 speed and 10 speed. Don't know why, it just is, so I didn't know if he had 10 or 11 as he may have ordered according to the wrongly published web ads and never actually looked at the number on the part when it arrived. Some people have no idea if they have 10 or 11 speeds so needed to verify if correct chain was used as it may have been a 10 speed chain on an 11 cluster.
Just a thought, but since it does not occur in the 53 but does in the 39, is it possible that your chain length is not just right or the spring tension is a bit off on the RD? When you go the 39 the chain tension will definitely reduce a significant amount and it could be allowing the resonance?
According, to chain length methods, it seems the chain could be shortened a bit. Perhaps, shortening the chain length will resolve the resonance.
There are more than one chain length method and they are all just ROUGH GUIDES to get you to a STARTING POINT. The lengths these methods give will only give you a length that won't rip a derailleur off or have a slack chain, and only then if you are totally within the recomended configuration for the parts you have. If you have short chain stays, then you are out of spec and need to spend some time to find the best setup. You need to check the configuration across the operating range and size for best operation.
The best way is use an old joiner link and size the chain for maximum length, that is when in little cog/little cog, the two pulleys just clear.the chain and apply some tension. You can then run the system through all gears and test how it runs looking at the distance between the top pulley and cogs in all gears. You can then play with B tension and grabbing the chain links to try shorter chain to see if the cog gap can be made small and consistent across the stack in both rings.and manipulate the deraileur with your hand to change things up if there is a problem. If some gears have a 10mm gap and others 3mm gap, then something may be better.
Once you find your perfect length, fit a new link or joiner pin as you prefer.
With short chainstay bikes like tri bikes, longer chains tend to be better as the lower chain span takes a less crossed path. If you run shorter, the severe cross of the chain can influence how the chain runs through the pulleys and can pull the chain off line to the cogs as it twists it's way through the deraileur cage.
This is why they have minimum chainstay lengths and one of the reasons higher cog counts are harder to engineer. Shimano can no longer run their floating top cog due to this as the wider stack of 11 speed twists the chain on moderate crossed cogs as a narrower chain has less resistance to this, and then looses indexing.
I bet if you put a shimano cluster on there the noise goes away........