brucem76 Posted December 23, 2015 Share My LBS (which is awesome, and has given me brilliant service) took a look at my rear derailleur, which has been shifting really badly, and advised that it needs to be replaced entirely. I'm happy to do it if necessary, but feel that derailleurs have many parts and are very serviceable - it's also an XT Shadow Plus, which I've really enjoyed - how often does a derailleur get so badly damaged that it's not fixable? Link to comment Share on other sites More sharing options...
dirtrider Posted December 23, 2015 Share unless it has gone into your wheel and you ripped it from the derailleur hanger not likely but it is possible . Link to comment Share on other sites More sharing options...
AlanD Posted December 23, 2015 Share Only if youve crashed and really bent and broken it. Bad shifting can be other things like worn cassette or chain or even bent RD hanger. Strange that they say the whole thing must be replaced. Did it suddenly shift badly? Link to comment Share on other sites More sharing options...
brucem76 Posted December 23, 2015 Share It started shifting really badly, and then it hopped off the smallest cog, and locked up - I couldn't turn the pedals at all - I assume that could have bent it badly? Link to comment Share on other sites More sharing options...
DJR Posted December 23, 2015 Share Post pictures please. It will be easier to give you an opinion. Generally speaking, Shimano derailleurs cannot be rebuilt or repaired much. The jockey wheels and cage plates can be replaced or bent back, if damaged. The rest of it not. A single crash against a rock can damage a derailleur beyond salvage. If it gets caught in your wheel it can be bent so badly that you can do nothing with it. If it has seen lots of dirty mileage and the linkages are worn, it is time to replace. Make sure your derailleur hanger is tight and straight and that the derailleur is tightened properly to the hanger. Sometimes the play(and sloppy shifting) comes from this and the derailleur itself is fine. Also check / clean /replace cables and housing before making the final call on the derailleur. Often something as simple as that is behind poor shifting. (Not that I doubt your LBS, I just mistrust them all and prefer to look for myself) Pete the Pirate, Amberdrake, Jakkals77 and 2 others 5 Link to comment Share on other sites More sharing options...
AlanD Posted December 23, 2015 Share Post pictures please. It will be easier to give you an opinion. Generally speaking, Shimano derailleurs cannot be rebuilt or repaired much. The jockey wheels and cage plates can be replaced or bent back, if damaged. The rest of it not. A single crash against a rock can damage a derailleur beyond salvage. If it gets caught in your wheel it can be bent so badly that you can do nothing with it. If it has seen lots of dirty mileage and the linkages are worn, it is time to replace. Make sure your derailleur hanger is tight and straight and that the derailleur is tightened properly to the hanger. Sometimes the play(and sloppy shifting) comes from this and the derailleur itself is fine. Also check / clean /replace cables and housing before making the final call on the derailleur. Often something as simple as that is behind poor shifting. (Not that I doubt your LBS, I just mistrust them all and prefer to look for myself)Agree with all of that. Good point all round. ZakAttak 1 Link to comment Share on other sites More sharing options...
AlanD Posted December 23, 2015 Share It started shifting really badly, and then it hopped off the smallest cog, and locked up - I couldn't turn the pedals at all - I assume that could have bent it badly?Could be possible. Can you send some pics? Link to comment Share on other sites More sharing options...
ZakAttak Posted December 23, 2015 Share Stretched Cable? A stretched cable could also cause the Deraileur to shift badly... Oops, as DJR mentioned... Edited December 23, 2015 by Buzzman Link to comment Share on other sites More sharing options...
brucem76 Posted December 23, 2015 Share Thanks - helpful to know - as I said, LBS has always been awesome, I trust them. Was just surprised. Will post pics when I get it back. Link to comment Share on other sites More sharing options...
DJR Posted December 23, 2015 Share It started shifting really badly, and then it hopped off the smallest cog, and locked up - I couldn't turn the pedals at all - I assume that could have bent it badly?The hanger is made of a softer alloy than the derailleur. It is designed to bend or break before the derailleur to prevent damage to the more expensive derailleur. (It is easily damaged by something as minor as the bike falling over) It sounds to me like a bent hanger might be behind it shifting badly and then going off the small cog. If the chain just got stuck between the cog and the frame, it should not damage the derailleur. It then obviously also could not have gotten into the spokes and bent that way, being on the far side of the cassette. Generally, the chain coming off the small cog should not cause serious damage to the derailleur, but it might have damaged the chain. Check for bent links. * Look at derailleur and hanger from the back - it must be 100 % straight / parallel with the wheel, both in up/down and front/back dimensions. Put a ruler next to it - it will make skew things easier to see. Replace if bent. As an emergency fix it can be bent back (Google how to, it is tricky)* Feel with your hand if derailleur moves normally in and out. (Best done with chain removed)* Wiggle derailleur by hand, is there play anywhere? Try see where it is coming from. In the derailleur or where it attaches?* Is any part of the derailleur visibly bent? Often the cages bend first and the jockey wheels are not parallel.*If all seems normal, then set up the derailleur from scratch (first stop screws, then tension screw etc. You'll have to Google again)*Still no joy, get professional help (Ok, I mean bike mechanic help.... These things have driven me slightly mad in the past) Hope Santa gives you a new one if it is really stuffed! Edited December 23, 2015 by DJR Odinson, JXV, AlanD and 3 others 6 Link to comment Share on other sites More sharing options...
Rapunzel Posted December 23, 2015 Share all of us want things fixed 100% first time so it is understandable that a bike shop would play safe if they're not certain and rather replace the suspect part. Paul Ruinaard 1 Link to comment Share on other sites More sharing options...
JXV Posted December 26, 2015 Share Good advice from previous posters but unless I missed it nobody has mentioned the metal link piece between the bike's hanger and the derailer's shifting mechanism on the Shadow + RDs. This is also designed to bend before the main mechanism and is easily replaced at much lower cost the the whole RD. Mine got bent - hanger was still straight but I had shifting issues and I could see the RD cage was not parallel to the cassette ..... a new link sorted it all out. I actually bought 2 and the spare went in my backpack alongside the spare hanger that lives there. Good luck...check it out carefully before forking out for a new RD. Link to comment Share on other sites More sharing options...
Onlybikes Posted December 26, 2015 Share In my experience just about every bike shop will try and avoid replacing the RD . They would of surely checked minor things like a bent hangar or bent link like the last post suggests. Cables and the likes would definitely be second in the list to check. so I am pretty sure that your LBS is not trying to do you in. Just ask for the old RD back, this way you can salvage a few spare parts that are left on that mech Link to comment Share on other sites More sharing options...
porqui Posted December 26, 2015 Share If there is excessive wear in the joints where the pins are you can throw it away but this rarely or ever happens but possible. Link to comment Share on other sites More sharing options...
Mojoman Posted December 26, 2015 Share My old GT has its original XT derailer that has done many thousands of K's (well over 20k) No Issues. Just replace cables and outers once a year or so and occasionally dribble some oil onto the moving parts and pins etc. But on another bike I mangled a derailer in the spokes. Replaced the hangar and cage but it was never the same again. Would sometimes just shift when it felt like it!I wound up forking out for a new one after a couple of weeks of headaches... Edited December 26, 2015 by Mojoman Link to comment Share on other sites More sharing options...
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