Bicycle Mechanics - Rear Derailer Pulley Wheel Rumble....

I am finishing my Scott CR1 build and almost have it dialed in...

The pulley wheel (lower jockey wheel) rumbles when in the lowest gear (34/29)...

Any suggestions to fine tune it...

The rear derailer is a Record long cage...

Thanks...

Adjust the B-screw maybe? With that large of a cog on your cassette, there's a good chance that the jockey wheel is rubbing on it if you left the default B-screw adjustment in place. Chances are, you'll need to screw it all the way in to remove the rubbing. I had to do the same to get a Shimano road derailler to clear a 28 tooth cog.

2001 and later Campagnolo uses an A-tension screw, which works opposite of the B-tension screw found on Shimano. http://sheldonbrown.com/derailer-adjustment.html#btension

I don't know much about Campagnolo drivetrains, but are you sure you're not exceeding the max cog and/or the max capacity (or whatever Campagnolo calls it) by too much? Is the upper pulley bumping into the cog, causing the lower to rattle front-to-back? Adjusting the A/B tension will help but only to so much of an extent if the specs are being exceeded.

The lower jockey wheel? One of the jockey wheels is fairly well located and the other floats a little. I can't remember at the moment which is the more loose of the two. The other thought is that the bushing or pin is worn out so that it CAN wobble and create a rumbling sound. Even though it is meant to float side to side a little it's not supposed to wiggle in angle more than a few degrees.

Finally if it's the metal bushing then grease it. I know they say you don't but they can get pretty darn sticky and hold a lot of muck if you don't. The white ceramic bushings I don't grease.

The upper pulley floats to line up better with the cogs.

Gotta love BF...

Even with all the characters in the other forums, I can always count on Mechanics...


Although not solved, playing with the "A-screw" and the limit stop, it is better...



It looks like the chain and lower pulley do not line up...

As the chain comes onto the pulley the chain is just slightly to far to the outside (or pulley to close to the wheel) so is 'jumps' every few links causing the rumble...

Gotta love BF...

It looks like the chain and lower pulley do not line up...

As the chain comes onto the pulley the chain is just slightly to far to the outside (or pulley to close to the wheel) so is 'jumps' every few links causing the rumble...
Check your derailleur hanger alignment. If the hanger is bent a bit to the inside it could cause the mis-alignment you are seeing.

Also, it's possible the derailleur cage itself is bent.

Check your derailleur hanger alignment. If the hanger is bent a bit to the inside it could cause the mis-alignment you are seeing.

Also, it's possible the derailleur cage itself is bent.

+1
I have one of those derailer hanger alignment bars but don't use it much. I think you can eyeball it pretty well.

Once past the first pulley the chain should be routed by the cage. I'm betting the cage itself or the pulley bolts are tweaked. Unless the hanger is WAY off and the chain line is pulling the chain off the pulley.