Bicycle Mechanics - Drivetrain noise - video attached
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I am experiencing some drivetrain noise at higher speed (especially pronounced when bike is in the work stand, not nearly as audible on the road) accompanied by a slight vibration felt from the moment I set the crank in motion.
Sounds like it is coming from the cassette?
The cassette is brand new and just mounted (please excuse my dirty chain...)
The chain is also fairly new. However I do not have my chain stretch indicator at hand to measure it for wear. It shouldn't have more than about 2000-3000 km in it.
See a video with sound here:
Also the pulley wheels are brand new.
Thanks for any insight! :-)
07-22-10, 01:17 PM
Sounds like the B-tension screw needs to be adjusted to me. I could be wrong, but if you just installed new pulleys, if they're slightly larger you'll need to adjust for that with the B-tension.
Take a close look at the chain where it threads between the upper pulley and the cassette. There should be some (not much) space there. If the chain is getting 'pinched' between the two gears (pulley and sprocket) you'll get a sort of grinding/vibration noise. "higher speeds" in this case means simply higher gears, which perhaps means that you're not getting the noise on the larger end of your cassette.
* Also * There is no good reason to run a 2000-3000 km chain on a brand new cassette. You can run new chains on older cassettes, but should always include a new chain with EVERY cassette change. Why add unnecessary wear to your brand new cassette? *You don't need a chain stretch gauge, just a ruler. Although right now you need neither, what you need is a new chain before you put any more damaging miles on your shiny new cassette. :thumb:
Thanks Tunnelrat81 :-)
Is the B-tension screw is the one that adjusts the space between the pulley wheels/cage and the cassette?
It looks to me as if there is sufficient clearing between the cage/pulley wheels and the cassette. The chain moves freely between the cassette/sprockets and the pulley wheels.
The noise was present with the old pulley wheels aswell, I just changed them because they were due.
I agree on the cassette/chain part!
I haven't ridden after mounting the cassette. I have no new DA chain around, so I am set to pick up one tomorrow. The weather is too grim for riding tonight anyway.
Things have gotten uneven wear because I keep moving wheels between bikes all the time.
There should be 1" of free chain between the idler (top pulley) and the sprocket. Otherwise the twom can interact through the chain making a sound similar to what yours, and more important the RD can get pushed back possibly getting damaged or breaking a breakaway hanger.
From sound alone it's hard to tell, and I wish you'd moved the camera in for a closeup of the RD and cassette, but the RD does look kind of high, though that could also be camera angle.
How's this video FB?
I tried to get up closer.
I'd say there's enough space between the cage and the sprockets, or should there be more?
Looks too close but can't be sure. Anyway it's easy to tell. Turn the pedals as you did and while turning push the RD down at the lower pivot. If it improves you have your answer straight from the horses mouth.
Thanks for the tips FB.
I tried moving it down while turning the cranks, increasing the distance between the pulleys and the sprocket, but the vibration was still present. I will install a new chain, I guess (premature) chain wear can the root of the vibration.
By chance I located a KMC XL10 chain that I had purchased long ago, and replaced the chain with it.
There was definitely some stretch in the old chain, visible as I lined it up with the new one.
I also played around a little with the B-tension screw, moving the derailleur up and down relative to the sprockets. However no position proved to lessen the vibration. Perhaps now less audible, it is still felt in the pedals.
So.. new cassette, pulley wheels, chain. Only thing not replaced in the drivetrain now are the chainrings on the crankset. However when I turn the pedals, the frequency of the vibration indicates that this is a problem with the rear part of the drivetrain, unrelated to the chainrings.
Note that the crankset inc. BB is recently dismantled, cleaned, lubed and mounted together according to manuf. recommended torque. Bearings rotate smoothly.
Problem remains unsolved.. :-)
Is it possible that the trim is off enough for the chain to be brushing the adjacent sprocket.
I thought about that aswell - you are talking about the cable tension, right?
I'll perform a visual check of that tomorrow, but I have adjusted the derailleur so that it changes gears without hesitation in both directions. Thus it should be correctly positioned.
Thanks again for the input!
Did you mount the cassette yourself? Was it tightened to the specified torque (Important! 40Nm is fairly tight)? If it is a Shimano cassette did you remember to include the 1mm spacer behind the cassette?
I am currently also trying to find a solution to my noisy drivetrain. Good luck!
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