Shimano Deore LX Rear Derailleur, shifting glitches

[withiniswithout]

Recently when pedaling up steep hills the chain has been jumping and mashing the gears. The chain jumping seemed to occur in gears 5, 6, and 7.

The drive train is all Shimano, a typical 1 X 10 (urban trekking eBike). The chain, ring gear, and rear cassette were all changed in June and there's only 800 km on them.

I thought the derailleur was probably getting worn. It is a lower-end 2017 LX model and it has 20,000 km on it, almost 12,500 miles. The top plastic jockey wheel has significant back and forth play. I haven't been meticulous with cleaning after each ride--often the jockey gears have sludge built up on them--so I thought these might be getting worn and allowing the chain to slip.

I took it to the shop and had the mechanic take a look. He said the play in the top guide wheel was normal. He said the barrel adjuster on the front derailleur was probably too loose and advised playing with this to get the shifting dialed in. I felt a bit foolish as if I were overly concerned about a minor problem. The mechanic's attitude was kind of, "Ah, hell, it's fine. The cable is probably loose." He said there was no advantage to changing and upgrading the derailleur to an compatible SLX model.

Just wondering if the mechanic's assessment was probably accurate. If the derailleur is fine, these are remarkably durable for something with moving parts.

 

[Rás Cnoic]

If you haven't already give the entire drive train a good clean, degrease the chain and cassette check for chain wear. Replace the jockey wheels (Cheap to do) and did you get new cables back in June? Derailleurs do last a long time if looked after, unless they've taken a knock, they are very vulnerable to knocks. How many gears is it? A new Deore derailleur is not expensive, or the new Shimano Cues equivalent.

 

[withiniswithout]

If you haven't already give the entire drive train a good clean, degrease the chain and cassette check for chain wear. Replace the jockey wheels (Cheap to do) and did you get new cables back in June? Derailleurs do last a long time if looked after, unless they've taken a knock, they are very vulnerable to knocks. How many gears is it? A new Deore derailleur is not expensive, or the new Shimano Cues equivalent.

It is a 10 speed, with one gear in front. The chain and cassette are pretty clean. The cables were not replaced when the chain, rear cassette, and ring gear were replaced three months ago. The SLX RD-M675, XS short cage according to an internet search should be a compatible upgrade to the LX model. I would have been fine if the mechanic had recommended putting on a new derailleur and cleaning or replacing the cables, but he said it all looked good. I am conscientious about checking out things like chain jumping because I'm quite vulnerable if the bike breaks down and I rely on a good mechanic to keep things up to spec

 

[Rás Cnoic]

If you have the option of another bike shop or a friend who is local and bike knowledgeable it might be worth them checking the bike and getting some more advice. That original mechanic sounds a bit flippant. There can be cable stretch which can knock the gears out of sync. It's hard to be certain from afar, though it sounds like you checked things out fairly thoroughly.

 

[withiniswithout]

Thanks, I might look for another option. A friend has somebody he goes to that is good. The mechanic and the shop is close to the house and they are really good with many years of experience. But the communication and attention is often lacking. Part of this is cultural. I am an American in Italy, and I'm working with Italians. You get the feeling at times that they err on the side of saving money and getting by.

 

[stompandgo]

Skipping gears mid cassette is a symptom of a loose lockring. Pull the cassette off, clean everything, reassemble, and torque everything back down. If it's a HG cassette, pay close attention to the shift ramps in each cog.