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SRAM SX Eagle 12 Speed Rear Derailleur failure

Had a disaster on the trail today. Luckily I wasn't go faster. Was slowing down and moving into lowest gear ready for a long, steep climb. Suddenly there was a lot of noise from the rear end and the pedals seized up. I quickly pulled to see what was wrong. It wasn't good!! :-/

The eyelet that mounts to the hanger had snapped off, allowing the derailleur to move up and get mangled around the seat stay dragging the chain into the wheel spokes. So the derailleur is toast. Chain is also badly twisted so will probably need a new one + the seat stay paint has been badly scratched up. Bit of a disaster.

Was wondering if anyone else had had issue with this part? The eyelet on the derailleur just totally failed. A bit of it was left but I was able to snap it off really easily like it had become extremely brittle. Not impressed with this component. I've had gear hangers fail but never seen this before. The hanger is actually fine. One of the only bit in the area that survived unscathed ironically.


  • dabberdabber Posts: 1,917
    I had my SX12 RD explode when I was riding on a trail at the end of last week. The trail had quite a lot of forest debris and a piece of wood/branch had caught in it.
    The jockey wheel cages had seperated and one of the jockey wheels was about 2 metres away. Fortunately I wasn't too far from home and walked back.

    I had planned to replace the SX RD sometime in the future and replace it with a NX.
    However, there were no NX available anywhere at the moment.
    I was aware that it was possible to replace it with a Shimano and I bought a SLX12.
    Fitting was easy although I needed to add another link to the chain. I had a new spare chain so that was no problem.
    So, I'm running.... Shimano SLX with SRAM shifter, NX chain, SX chainset.

    It works fine.The SLX RD is far better quality that the SRAM SX.
    “You may think that; I couldn’t possibly comment!”

    Wilier Cento Uno SR/Wilier Mortirolo/Specialized Roubaix Comp/Kona Hei Hei/Calibre Bossnut
  • reaperactualreaperactual Posts: 1,183
    edited August 2021
    I've no first hand experience of the SX mech but have read quite a few times this kind of thing has happened.

    The SX is low end, cheap and weak as it's made of plastic. As above upgrade to something better and at least the hanger should fail before the derailleur does.

    Regardless of which derailleur, it's still unlucky it happened, sympathies. 🙄
  • steve_sordysteve_sordy Posts: 2,438
    edited August 2021
    That is spooky! My 12 speed mech broke in two yesterday. It was a Shimano XT mech. It was a young pine sapling trapped in the mech that caused the damage. That stuff is very bendy, won't break, but cuts easily. The complete mech arm snapped off just below the clutch housing. In the pic below, there is nothing left of the mech after the hinge you can see at the bottom. The fracture runs through one of the studs pressed into the alloy to take a screw (1 of 3) that secure the clutch housing. The gasket that keeps the clutch clean was exposed and damaged.

    The two jockey wheels were still between the sides of the mech arm. No damage that I could see to the mech hanger. I'll find out when the new mech goes on. Trailside, I tried to set up single speed, re-using the same rivets, but that lasted about 3 mins before the chain just fell onto the trail. It was only 2 miles back to the car! The chain is now in two pieces and has a very stiff link in the middle of the longer section. I hope I can get that moving easily again as the chain is hardly worn.

    There is a bike shop (with a full workshop) at the trail centre so I asked for a Shimano XT 12-speed mech. He replied that he couldn't get one until Jan'22, but that he had a SLX that has just come in. "I'll have it", said I. What about a 12 -speed chain? "Only got KMC, all sold out of Shimano and SRAM, don't know when we will get some more." I know the guy and that he was not snowing me, so I said I'll have one them! I suspect that I may (accent on "may") have been able to find something cheaper on the internet eventually, but I wanted something now, not in 3 weeks time!

    In my opinion, SLX is the sweet spot on the weight vs cost chart, so I don't mind, except that it would have been nice to keep my new bike up to spec.
  • dabberdabber Posts: 1,917
    Hi Steve. With all this rain there's loads of forest debris washed into all the trails near me. The ironic bit with my RD failure is that I'd actually been doing a bit of trail clearance on the trail that bit me. Must do better next time.
    “You may think that; I couldn’t possibly comment!”

    Wilier Cento Uno SR/Wilier Mortirolo/Specialized Roubaix Comp/Kona Hei Hei/Calibre Bossnut
  • dogboy73dogboy73 Posts: 440
    As advised above think I'll avoid a direct replacement. I'll go for something better as I can't believe the way this thing failed and the subsequent damaged it caused. I was only on a cycle path at the time. I was about to head up a steep, paved path on my way to a local trail center. It just gave up on me as I was changing into the lowest gear.

    Was going to drop it into the bike shop Monday. But we've just gone into full lockdown in the area here in Australia. So might not be open. Might just order the bits myself and try to install. Shouldn't be too difficult to do I guess. Just need the new derailleur, new chain, new gear cable. That's about it hopefully.
  • dogboy73dogboy73 Posts: 440
    ........ Back on track. Went for a SRAM GX derailleur. Hopefully this one holds up better than the last one! :smiley:
  • steve_sordysteve_sordy Posts: 2,438
    I posted my Shimano XT mech failure (after only 350 miles or so) and to my astonishment three other guys posted with the same failure mode. I had a really good look at the mech when I got all the bits back and I could not believe it but that part of the mech is plastic!
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