So I'm having a problem with a new 2012 Sram Red Rear Derailleur. I'm running an 11-26 cassette and when I shift to the low 3 cogs (21-23-26?) the derailleur doesn't seem to have enough tension to properly align itself for smooth running. I've got a 2011 Red Rear Derailleur that I've been swapping back and forth in the stand that I can get to run perfectly and I have them setup nearly identical, which makes sense given it's supposed to be the same derailleur in a different shape.

Now before you start questioning the installation, I've confirmed that the hanger is straight with a Park hanger gauge, the RD limits are set correctly, and the cable is properly seated and cinched tight. I can get the 2011 derailleur running great, so what gives? Do I have a faulty 2012 derailleur? Anybody had issues with the 2012 stuff yet? Anybody had this issue with older red stuff? I've been through 3 different Red groups on various bikes over the past 4 years and never had setup issues like this.

Is the cable on the correct side of the pinch bolt? Is the housing seated properly in the housing stops? Is the housing the correct length?

What cassette? Is it properly installed on the free hub?

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- Cable is on the correct side of the pinch bolt.
- Housing seated properly
- Housing correct "long" length with smooth curve
- New Sram XG-1090 cassette torque to specs

control your derailleur hanger

I dont think you can adjust the tension/spring. I had a problem with a Shimano 105 FD. It wouldnt spring back to the inner position. A little well place race oil, and some movement of the FD solved the problem.
If your FD is new I would sent it back if it wount spring back to the inner postition, and you can move it with your hand ( that way you are sure its not the adjuster screw or cable that prevents it from moving).

B-screw adjustment?

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Wow, that sounds very odd. The only time I've ever had issues with the RD shifting to lower cogs is when I didn't route the cable correctly from where it exited the barrel adjuster on the RD itself to where it cinched in the pinch bolt. But if your sure this is right (it may be different from 2011 Red routing, I'm not sure), then it just sounds strange! I can't imagine a faulty RD; I mean there's very little to go wrong.

Good luck

Derailleur hanger is confirmed straight. I have a DAG-2 as part of my tool set.


The FD is running great, the RD is the problem


B-screw is adjusted according to the manual, with the top pulley resting 6mm away from the 23t cog.


Yeah this is a weird one. I've seen the same issue you speak of when routing the cable improperly, but I'm sure the cable is correct. The 2012 routing is pretty much the exact same as the 2011, they just shaped the 2012 version a little differently so the cable rests a little neater (more aero?). This type of indexing performance usually says bent hanger to me, but my gauge says the hanger is dead on and the old RD runs great. Seriously considering sending this thing back and just keeping the old derailleur that works.

Brought the bike to my favorite shop this morning with the 2 derailleurs in hand just to get a second opinion to satiate my curiosity. Showed them the 2011 RD running smoothly - cool. Pulled that RD and took out the hanger gauge to verify the hanger was straight - check. Put on the 2012 RD and verified the limits were properly set and the cable was seated corrected - yup.

And still having issues with smooth running on the low 3 cogs. After seeing the RDs run back to back with the same setup, the guys at the shop were equally stumped. They wanted to tinker further and suggested replacing the derailleur hanger anyway. I don't really like having other people work on my bikes so I gave them a tip and left it at that. Ordered a couple hangers from Parlee just to be safe.

So long story short, I'm sending this thing back. The 2012 offers (IMO) no improvement over the 2011 RD aside from the pulleys which are definitely less noisy. In my case, it's worse. Aside from the graphics not matching the shifters and FD, the 2011 black RD probably looks better on my bike anyway.

That's fine that the derailleur didn't work for you, but why bring it in to a shop if you wouldn't let them try their hand at fixing the derailleur for you? That seemed like a big waste of time....

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I didn't buy the derailleur from them so it wasn't really their problem to fix. It was more of a take the bike down to see what the shop guys thought before I send the derailleur back. You've heard of a second opinion?

The consensus was that there was a problem with the derailleur, it simply isn't indexing properly. The evidence is pretty obvious when I've got a 2011 RD running perfectly and the 2012 does not. If both derailleurs were running funky then I would agree with you that something needs to be fixed.

Shit happens, so do manufacturer's product anomalies. I hope the replacement works like most everyone else's.

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Yeah I'm certainly not angry or anything. I like Sram a lot, just trying to figure it out. I've had a few issues over the years, but my experience has been overwhelming positive with Sram. I love the new FD and shifters.

Just get another one, the SRAM derailleur cage can be defectively yawed/crooked and cause problems.. the quality control is just not great.

Which chain are you running? My LBS and I set up my new Red using a KMC chain and had a similar problem when changing down in the smaller cogs of the Red cassette. No amount of tinkering with the limit screws or B tension screw could solve the problem. Switching to the 1091R (?) chain that came with the gruppo sorted it all out.