Am I an idiot?Cassette vs derailleur??

[spokelacer]

I have just rebuilt a custom Rock Lobster after a bad crash years ago. I am running Record 10 with compact rings. The rear is 13-29. Oddly, the derailleur seems to push up to the chain/cassette and make a rubbing sound. I have built about 50 bikes with Campy ten(I am a has been mechanic). Other than compact, I don't see what is different...

Any advice?

[lhuerta]

...just rebuilt a custom Rock Lobster after a bad crash years ago.

Did u check alignment of ur rear der hanger (with proper tool) after said bad crash? Lou

[Richard]

run the "b" screw in or perhaps your chain is too long.

[Steve in SLO]

Agree with lhuerta and Richards comments. Your chain might also be too short. If it is rubbing the 29 cog, then it is likely too short if it is rubbing the 13, it is likely too long.

[spokelacer]

The frame is aligned, as is the hanger. Actually, the Mavic Kyserium SSL SCs (sorry about the spelling) crushed and the Q fork took the blow, along with my knee. This allowed the frame to survive. The ride in the trunk of a cop car was the worst of it believe it or not.

I am sure the chain isn't too short. I could take out another link. Also the frame has very short stays so any cross chaining is very problematic.

[#campyuserftw]

The B Screw (aka Hidden Screw) moves the RD cage away from the cassette, or allows it to be closer. Check it. Make the cage move away from the 29 until the noise disappears:

http://www.ctownbikes.com/wp-content/themes/patagonia/images/b-screw-adjust.jpg

If the upper wheel of the RD is too close to the 29, the chain will be too close to the 29, causing chatter/noise:

http://www.ctownbikes.com/wp-content/themes/patagonia/images/b-screw.jpg

In the stand, put the RD onto the 29 teeth and pedal the crank. Noise? Is the Alignment of the hangar good? Is the RD set to reach the 13 and the 29 (High and Low screws)? If they are good and you can visually see the chain is too close to the 29, simply adjust B Screw.

[Ralph]

Assuming your compact rings are 34-50 with a 13-29 (32 tooth difference).......that's pushing the capacity of a short cage. A lot depends on the length of the derailleur hanger also. Run the chain as tight as you can in big to big, to pull the upper pulley back out of the way on the small front ring and 29, and also use the B screw.

You can always run the chain so short the big to big won't work, and that will pull the upper pulley out of the way. But I, personally, don't like to do that. Afraid I might accidently shift to that and break something.

There is a good reason why Campy says that combo needs a Med cage. Sometimes it does.

[oldpotatoe]

I have just rebuilt a custom Rock Lobster after a bad crash years ago. I am running Record 10 with compact rings. The rear is 13-29. Oddly, the derailleur seems to push up to the chain/cassette and make a rubbing sound. I have built about 50 bikes with Campy ten(I am a has been mechanic). Other than compact, I don't see what is different...

Any advice?

B limit screw or chain is too long. Just enough for safe big-big combos, no more.

Top pulley hitting largest cog when in small ring.

[oldpotatoe]

Agree with lhuerta and Richards comments. Your chain might also be too short. If it is rubbing the 29 cog, then it is likely too short if it is rubbing the 13, it is likely too long.

Not too short as a too short chain rotates the upper pulley away from the biggest cog.