[Closed] Misaligned rear derailleur

Back to the shop!

Bought secondhand, so no dice.

Looks like the dropout was slightly misaligned when they built the frame, as the axis of the axle socket is correct but it isn't perpendicular to the dropout.

I think I could bend the dropout by bolting M12 threaded bar into the axle socket and using that as a lever. Problem is the rear triangle is very stiff so I'm not sure how much force it will require.

Is it a Direct Mount hanger (which won't work with SRAM derailleurs), or a regular one?

If the axle fits correctly right now, bending the dropout won't solve anything; the only thing that should bend is the hanger*, assuming it is the correct one.

*except if it is a Syntace X-12 hanger, which is not designed to bend.

I have two bikes with SRAM GX and they both have this misalignment.

I have checked with a mech hanger alignment tool and they are both aligned with the wheel.

As long as the jockey wheel bearings are okay there isn't a problem with shifting.  When they wear out there is though

I've just noticed this same issue on my brand new arkose which has been having jumping gears around 2nd/3rd from new.... no bashes or bent hanger.

Think it's a trip to the store which is bloody miles away.....

Thanks for the input.

@otsdr It isn't a Shimano direct mount hanger. I'd bend the hanger if I could, but it's about 5mm thick dog-leg shape and when I tried that it was really difficult to budge it, then it snappthat's)

I reversed the axle in the hanger, mounting it outboard, to demonstrate that the dropout isn't perpendicular to the axle. However the socket.

@Paulwf My mech socket isn't aligned with the axle, so the jockey wheels don't align with the cassette or the wheel. I started out with a Park Dag-2 alignment tool but the thread on that is a different diameter to the socket in the hanger, and it requires more clearance than I have. It did confirm the misalignment of the hanger and helped me break it.

My other GX bike has clearly aligned jockey wheels and cassette.

From previous experience of bent hangers, I'd expect skipping gears from this.

@Mikertroid Interesting. Shop should have picked this up on setup. If the hanger is bendable that's a quick fix; although if the underlying issue is the dropout it's a warranty issue. Takes a bit more work to prove that though.

I've reached out to the manufacturer to see what they think.

Another way of fixing it would be to shim the mech hanger, about 0.8mm higher on one side than the other. Not sure how to make such a shim though. 3D printing? 🙂

Why say "reached out" when contacted is much more succinct and far less pretentious?

Why be pedantic when pernickety is a much more fun word?

@giallo...

Took it in and a bent hanger was discovered. All sorted now.....

Get yourself one of these. It is, quite literally, my favourite tool in the garage and worth the money (although I'm sure I paid half this from Wiggle!)

Quick and easy to use. You could always make a ghetto version (it's hardly a high-tech piece of kit), but I've got this one and it works well. It's amazing how many bikes get bought to me for gear adjustment that don't need any cable adjustments - they just need the mech hanger straightening. Even new bikes too - the last one was a brand new Cube road bike brought round last week, which was miles out of alignment. The owner was getting really annoyed that he couldn't set it up properly but five minutes later, it was sorted and working perfectly. I barely had to touch the barrel adjustment.

I had this prob when going from 9 speed to 10 spped on an old On-One Scandal.  The dropout forgings/machinings were clearly (if you looked at them hard) not quite vertical - they were pointing slightly inwards rather than straight down. This wasn't a problem with 9 speed, but with 10 speed it was impossible to set the gears up - new derailleur, new hanger, but if it was rignt on the small cogs it wasn't on the big ones.  A slight bend to the mech hanger cured it.

Some modern frames have really chunky mech hangers built into bolt-on dropout things.  This probably helps with shifting on 10 speed and up. As long as it is built straight in the first place!

@bigyinn Reached out and contacted is one letter and I don't value a letter. You've used 66. Maybe better to save them on the grounds of economy. 😀

@daern Thanks for the suggestion, I'll get one of those.

Misaligned mech hanger is the biggest cause of shifting problems in the workshop. Just because the frame is new don't expect the hanger to be straight. Probably 90% of new bikes we Pdi need adjustment with the alignment tool.