I got a full group of the new Sram red this past February. I had it put on my 2010 Supersix frame and road it for 4 months. Then I bought an Evo frame in July and had it built up with the same new Sram red group. About a month ago I discovered that, when loaded hard, my rear derailleur was throwing the chain off the bottom pulley, towards my back wheel. The bike would still pedal just fine - it would chatter but since I usually ride with head phones I hadn't noticed. After I realized it was throwing my chain, I looked closer and saw that my chain, when running next to the pulley, had worn down the teeth on the bottom pulley and had ground a chunk out of the derailleur cage.
I took it in to my local bike store and the mechanic said that my rear derailleur hanger was loose, and he thought this must be why it was throwing my chain. But then I looked at my 2011 Supersix, and the rear derailleur hanger was loose on it also.
So my guess is that there must be some problem with the rear derailleur that makes it throw the chain, and that the chatter, over some months, caused the derailleur hangers on both frames to work loose (I'd ridden my old Supersix for 18 months with an old Sram red rear derailleur and the hanger never came loose, and the Evo frame was brand new).
My local bike store guy is saying I should just get a new pulley, but the pulleys for the new Sram red only come in sets and they cost $140 for the set. Also, this doesn't seem like it would solve the problem.
Anybody had the same problem, or have suggestions? Would this be warrantied by Sram?
Sram may take care of the pulley If the shop installed the group, they ought to go to bat for you. It would be good for them to accurately check the hanger alignment as well.
The mechanic from my local bike store didn't mention that the derailleur hanger alignment was off (and I think he knows his stuff because he used to travel with pro teams).
And the fact that it shook the der hangers loose on both my 2010 Supersix and now the Evo makes me think it's gotta be a problem with the derailleur.
Does this make sense?
And the Evo was brand new - it had just been stripped. And it was built up by a good mechanic who's been working on bikes for 30 years and I think he would have checked to make sure the hanger was not loose. And the hanger on it came loose within 4 months.
Wouldn't that bee too weird a coincidence?
Rick wrote:I can't imagine how a derailler could make a hanger come loose. Those things should be screwed and loctited securely.
More likely you really did have two hangers come loose from faulty initial installation.
glowder wrote:The mechanic from my local bike store didn't mention that the derailleur hanger alignment was off (and I think he knows his stuff because he used to travel with pro teams).
Based on the failed attempts to fix what is a straight forward fix (i.e. properly align hanger, apply loctite to hanger fixing bolt, check der cage alignment) I suspect your "mechanic" was actually just touring with the team not actually wrenching.
But the more I thought about this, the harder time I have invisioning exactly how a chain gets thrown off a bottom pulley at all. It seems virtually impossible. But maybe I am just not seeing it. Can you post a picture of the situation ?
The design of the SRAM RDs seems to make it far easier for the chain to derail from the lower pulley than with other brand's RDs. Even without a bent cage or hanger, when the shifter gets operated without turning the pedals the chain can easily come off of the lower pulley on a SRAM setup, whereas this seems to rarely happen on other brands (or, at least, on other brands, the chain finds its way back on by itself as soon as you turn the cranks, whereas with SRAM the chain has to be helped back into position manually).
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