jimwebber

I'm using a 9spd XT mid-cage rear derailleur (m772) with 10 speed Ultegra STI brifters (6600) so I can run a 10spd XT 11-32 cassette. I installed a new KMC 10.93 chain and the cassette is new as well. The chain is routed correctly through the derailleur, but it rubs on the little tab halfway between the pulleys in all gears. My guess is that the chain is too long, but I sized it big-big and added two links.

Are there other factors I'm overlooking? Thanks in advance.

jimwebber

One more thing: here's another thread in which someone seems to be describing the same problem.

Weird derailleur grind - Shimano XT RD-M772 Short Cage- Mtbr.com

Homebrew01

Based on a quick internet search, I see a few similar cases. It seems unavoidable, other than trying to bend the tab out of the way a bit, or get a larger diameter lower pulley.
Since the 2 pulleys are a constant fixed distance from each other, chain length will not make any difference 1 way or the other.

Is this your problem ?

https://forums.mtbr.com/drivetrain-sh...ge-621340.html

tFUnK

Can you eliminate it by adjusting the B-screw?

Sixty Fiver

Shimano changed their pulley diameters from 13 to 11 on a number of models, this does not make a lot of sense when tests have shown that larger pulleys are more efficient due to less chain friction.

Without changes to the cage this could cause a little rubbing and swapping pulleys to a larger one will give a little more clearance and smooth things out at the same time.

HillRider

I've got five Shimano and a Campy rear derailleur on my bikes and in my parts box, 7 through 10-speed versions, and none of them have a tab in that location. They are all road derailleurs except for one old STX so that may be why but I see no reason for that tab.

cyccommute 

When I first looked at that picture I was ready to jump in with a caustic comment about the chain being on the wrong side of the tab. But upon further investigation, I found that it apparently isn't. That said, I'm going to make a caustic comment about the stupidity of designers at Shimano. What are they using for brains? Bananas? Overripe mashed bananas? That has got to be one of the dumbest ideas that Shimano has ever come up with and they designed RapidRise and U-brakes! What possible purpose does that tab serve except to have the chain rub on it? If they had put the tab on the other side of the derailer plates, it would never have been an issue.

Stupid. Stupid. Stupid.

jimwebber

Thanks for all of your replies. Yes, my chain looks like the one in the picture. And, it rubs on that tab. When reading about the m772 derailleur, I gathered that the tab was added to prevent the cage from twisting. I don't know if that was an actual problem, but apparently the tab was an attempt to prevent it.

It sounds like my options are to live with the noise, to file down the tab a bit, or to get a larger lower pulley. Has anyone filed down something like this successfully? Also, the current pulleys are 11 tooth. I see 13 and 15 tooth pulleys mentioned online. Any recommendations for where to get these larger pulleys?

One other angle is that I have a new set of XT pulley wheels in my parts bin. I'm wondering if a new set might make a difference. The existing ones don't look worn to me, but who knows.

Thanks again for your input!

PS--I tried adjusting the B-screw, but that didn't seem to affect the noise.

70sSanO

I think the XTR m972 RD doesn't have the bent tab, but it won't be a cheap fix.

John