What happened to my new sram red rear derailleur?

Discuss light weight issues concerning road bikes & parts.
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by glowder

My apologies but i couldn't figure out how to post photos on my computer so I'm starting a new thread on this with photos through tapatalk.

Just to recap - I discovered my rear derailleur was throwing my chain off the pulley. It's ground down the lower pulley teeth and chewed a groove in the cage. The derailleur was new with a group from February 2012. It was on my 2010 supersix for 5 months then on my Evo for 4 months. Both frames, it turns out, have loose der hangers. This seems too unlikely a coincidence and I think it must be the derailleur.

I'm going to ask sram to warranty it but would still really appreciate input.

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by HammerTime2

I'm not saying this is the cause or a contributor, but you might want to clean your chain and pulley wheel teeth (and probably your cassette teeth and ...).

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by glowder

The chain was brand new 4 days ago, and the derailleur was cleaned like new - you're just seeing the junk I picked up after riding the last 3 days in Central Park here in NYC where the weather has been nice but the park is still pretty messy after the Sandy storm.

The other photo I posted didn't show up, but you can tell from this one how ground down the teeth on the lower pulley are, especially compared to the upper pulley. And the groove I mentioned on the cage is above and to the right of the pulley bolt in this photo - it's immediately next to the pulley on the wheel side and you can see where it catches the light.

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by madmole

Pulley bolt doesnt look like its through properly, you can normally see the end of the bolt flush on the other side. That will allow too big a gap between side plates and chain can run between plate and pulley, wearing teath and plate

Be aware the top and bottom pulley bolts are NOT the same length or size and if they were swapped round this could be the result

The red cage seems very sensitive to bolt tension and spacing of all, when I swapped out my side plates for carbon ones, the pulleys for KCNCs and the bolts for lighter ones I had lots of issues and noise till I got it all just so
Cervelo S3 2011. Blinged 6.718 Kg

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by glowder

Thanks madmole, but I'm pretty sure the pulley bolts haven't been touched, and I bought the derailleur new. I just pointed the problem out to my mechanic last week and he would have had no reason to fiddle with the pulley bolts before that (and I hadn't touched them). I did just check the pulley bolts and they both are snug, so if there is some problem with the length or a mixup between upper and lower pulley bolts then it would have to have happened at Sram.

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by em3

Why are you starting a whole new thread on the same issue???


There are already plenty of responses to this issue in your previous thread? Have you confirmed with a reliable and capable mechanic that the suggestions others already made were actually engaged by your "mechanic"?


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Joined: Fri Jul 09, 2010 9:24 pm

by glowder

I started a new thread because my computer skills are at a 3rd grade level and I couldn't figure out how to post a photo (which Rick had requested) and I had to do it through Tapatalk.

Ive been trying to get as many ideas and as much input as possible because my mechanic who i bought the derailleur from said that he thought it must have been a problem related to my derailleur hangers (on both frames) and that the only reason Sram would warranty the derailleur is just to be nice - I wanted to be able to make a better case than to just plead for Sram's sympathy.

Today I'm going to talk to my mechanic and let him know that others have had similar problems with Sram rear derailleurs, which lead to a replacement.

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by SUCycling88

I've had something similar happen about 2 months after I installed my new Red group. There was no damage to the pulley but it looked like the inside of the cage was delaminating pretty severely almost as if the chain was cutting into it. I wish I saved the picture that I sent to Sram so I could post it. I never figured out the cause being there was no mechanical issues with the bike whatsoever and Sram did warranty it in my case. I'd recommend just having your mechanic call Sram and explain what's going on, however if the hanger was loose (which they will likely ask as one of the determining questions) you may be out of luck.

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