Derailleur moves beyond largest cog

[Emanresu]

Bike ran perfectly a couple of month ago when on tour. It was reassembled on my return and have just taken it back out to check all is well for the next trip. Chain is now coming off when on highest gear. Tried indexing it but no change. On the lowest gears it jumps off the first cog onto the second and third cog.

Pic of the set up showing the derailleur beyond largest cog. Second pic shows on lowest gear and the chain seems twisted. What to check next? Hanger?

 

[Paulus]

It does look like the rear mech is bent inwards a touch, it should be horizontal to the cog the chain is on.
It could be that the hanger has taken a whack. Check the alignment before you start fiddling with the indexing.

 

[EckyH]

Second pic shows on lowest gear and the chain seems twisted. What to check next? Hanger?

That's a good idea.
It's relatively easy if you have the right tool for that: a derailleur hanger alignment gauge.
If you don't have such a tool but the rear wheel of that bike and a second rear wheel with 10mm axle (eg. quick release axle) and the standard thread on the axle, then it is also fairly simple. Remove the rear derailleur, screw in the axle of the second wheel and measure the distance between the two rims around the full circle. Then you can carefully(!) align the hanger with the second wheel. Of course both wheels need to be true laterally for that.

Good luck.

E.

PS: On your picture the chain is on the smallest cog and the highest gear.

 

[Andy in Germany]

I'd go with the hanger; if I had a bike on the stand with a mech looking like that I'd assume the hanger had taken a whack; it's easily done if the bike falls over.

 

[Ming the Merciless]

The derailleur (and chain) in second shot should drop down in a nice straight vertical line below the cog you have selected. Either hangar bent or the derailleur cage is bent or both. Hard to tell from photo, but does look as though hangar is bent inwards.

Usually best to remove the hangar if flying etc and reattach at destination / home. Then also put spacer between dropouts if you've removed wheel for travel. You may have done this anyway.

 

[Emanresu]

Another pic looking down (up as the bike is upside down). There looks to have been damage to the pulley supports. Assume this bend is not by design?

 

[EckyH]

Assume this bend is not by design?

That's what I thought when I saw your third photograph.
There are also gaps between the pulley cage and the body of the derailleur.
In my opinion that indicates that the bent cage is more likely the culprit than the hanger.

If you have got a vice and some soft (eg. wood or aluminium) vice jaws you could try to straighten the cage plates.

E.

 

[Emanresu]

Usually best to remove the hangar if flying etc and reattach at destination / home. Then also put spacer between dropouts if you've removed wheel for travel. You may have done this anyway.

B**ger. No I didn't so lesson for next time.

If you have got a vice and some soft (eg. wood or aluminium) vice jaws you could try to straighten the cage plates.

Checked the SRAM service page and they state the outer cage plate (bent one) is not serviceable. Have a 2 week tour coming up so looks like I'll have to get a replacement as I don't want to be stuck in a remote part of Italy waiting for a part. (Been there. Done that. Don't want to do it again). Any recommendations for SRAM parts?

Appreciate the help and the knowledge here. Second time I've had to rely on the accumulated knowledge so many thanks .

 

[Cycleops]

If the derailleur has had a hit that's bent it that much the hanger would also have suffered as well most likely. You might get away with using a derailleur alignment tool to straighten it but if not it's a replacement.
Park offer the tool but you can get something similar from the EvilBay for twenty notes.
SJS have a good selection of hangers.

 

[Ajax Bay]

Have a 2 week tour coming up so looks like I'll have to get a replacement. Any recommendations for SRAM parts?

Think you'll have to replace. Always remove the RD and just tape it between a seat stay and a chain stay (can leave the chain in situ).
RD must be a SRAM.
"SRAM Exact Actuation. Available in 9 and 10 speeds for both road and MTB (shifter lever ergonomy differs for flat MTB and drop road bars), and in 11 speeds for road only."
https://bike.bikegremlin.com/1339/bicycle-rear-shifter-compatibility/

 

[ColinJ]

If the derailleur has had a hit that's bent it that much the hanger would also have suffered as well most likely. You might get away with using a derailleur alignment tool to straighten it but if not it's a replacement.

I wouldn't risk it... See below!

Unbolt the rear mech, wrap it in bubblewrap and attach it to the chainstay. Get spacers from your LBS to insert between the dropouts to stop your frame or forks getting crushed.

A Scottish lad arrived on one of our training camps in Spain with a hanger bent by baggage handlers. He straightened it out but it snapped off in the middle of his first ride, resulting in his mech going into the back wheel so he ended up with a broken hanger, broken mech, broken chain, and broken spokes ...

He was damn lucky because:

• Between us, we had enough tools and know-how to bodge his bike into a singlespeed to get him back to the hotel
• Great ex pro Robert Millar was staying at the hotel
• He was the same size as RM
• RM had a collection of superbikes with him to test for Pro Cycling magazine (Pinarello, Colnago, Bianchi etc.)
• RM lent him a different superbike every day in return for a mini-review!

 

[bikingdad90]

Also, it might just be the angle of the picture but is your chain threaded correctly? Should it not go in over that top pulley wheel in a C shape as opposed to an I?

 

[Emanresu]

Derailleur wasn’t removed for the flight so chain wasn’t displaced. It was fine before with a crisp change before it was handed over to Porto Airport baggage handlers. My fault for not RTFM. New one ordered. Now poorer and wiser.

 

[T4tomo]

• Great ex pro Robert Millar was staying at the hotel
• He was the same size as RM
• RM had a collection of superbikes with him to test for Pro Cycling magazine (Pinarello, Colnago, Bianchi etc.)
• RM lent him a different superbike every day in return for a mini-review!

I'd have happily walked home knowing this

 

[Paulus]

Derailleur wasn’t removed for the flight so chain wasn’t displaced. It was fine before with a crisp change before it was handed over to Porto Airport baggage handlers. My fault for not RTFM. New one ordered. Now poorer and wiser.

You are the first person to have the ham fisted baggage handlers at an airport to of done a rear mech or other component in when the bike rattles off onto the conveyor belt, then onto a trolley and finally into the hold of the plane.