Jumping gears on SMGT

[Time Waster]

Had it fettled at a local bike mechanic's. He did a good job but middle chainring causes gears to jump on the cassette when I've changed gears post about halfway on the cassette young up the gears. Anyone got a clue what's happening?

 

[Ming the Merciless]

What is happening is that the gears are jumping.

 

[Time Waster]

And anyone else with ideas on causes and solutions?

 

[Arellcat]

If a new gear cable doesn't sort it, and your derailleur doesn't have slop in the parallelogram pivots, it's probably the indexing washers in your bar end shifter giving up the ghost.

 

[All uphill]

Did you have a new chain fitted?

If so it could be that the cassette is worn and needs to be replaced too.

 

[Time Waster]

Everything got replaced at the same time. Chain, cables, cassette, chainrings, but not the shifters or derailleur. Deore I think and still good nick. Jockey wheels too. From what I have read new Everything like that bed's in together. Keeping new and old often causes problems. That's why I don't know why it would be jumping like that. Stiff links perhaps?

Occasionally it's jumping so strongly my feet lose contact with a pedal. I've never gone onto spd yet. Perhaps it's needed with bents. Just needs shoes, pedals and cleats. Shoes are difficult to get right for normal use for me so finding a general use pair that fits my feet and good enough to walk in on tours is probably not easy with a low budget due to lack of trust in getting on with them.

 

[a.twiddler]

Have you discussed this with your local bike mechanic? If he's recently fettled it, he might have a better idea. Might be better to let him sort it if he has any sort of warranty on his work.

 

[Time Waster]

Yes, plan to but I like to read up on possible causes. There's a wealth of knowledge on cycling forums so I thought I'd ask here first. Kind of preparation so I don't sound like I'm completely ignorant off bike maintenance.

In my ignorance I'm thinking cable / cassette interaction, issue with cable somehow, shifters with the indexing, stiff cable links or the rear derailleur are the potential causes. I can't see how long chain length would cause jumping. However my knowledge and experience isn't great so I hoped others on here might have an idea before I go back in with it.

 

[Roseland triker]

Ghost shifting can be caused by incorrectly aligned mech hanger. Worth checking out and see it it's running true with the wheel .
Is the rear wheel in tight on the dropouts?

 

[Time Waster]

I'll check the rear wheel on the dropouts.

Could the hanger get an alignment problem from being stored, moved to a new house then sent to a bike mechanic for new cassette, chain, cables, chainrings, jockey wheels, etc? The mechanic is supposed to be very good and very experienced. He has worked in the area for a council centre, various racing teams and shops over many years. It's why I can't see he would miss it somehow. Although he did say that he's never managed to ride a 2 wheeled recumbent despite trying them many times. So his test ride was a very short, wobbly one with his wife running alongside holding the seat! Possibly didn't get the jumping effect on the stand and the rest ride wasn't long enough to check it out.

I'm going back at the weekend if I can, probably get it sorted out.