Had that same problem, changed everything. Got new rings problem solved. Had at least 15k on the front chainring. It had a noticeably different tooth profile when placed next to a new chainring
Just noticed that after the second jump in the video when I stopped pedaling, the chain had fallen down to the small ring.
The chain falling off the big ring is what the “jumps” are. When the chain “jumps” in your video, the rear derailleur tension pulley is suddenly rotating rearward to wrap a bunch of chain. The chain isn’t moving to a smaller cog in the back, so the only way slack this slack could have been introduced to the chain is if it’s bailed from the big ring.
That’s what I’m thinking now, has to be slipping off the large chainring. This has been going on a few weeks but only this morning got around to making a video. Only way the jockey pulleys can kick like that is slack in the chain, and it’s not coming from the cassette so must be up front.
I did eyeball the hanger. Looks straight to me but I wouldn’t be able to tell if it’s off a mm or 2. And there is absolutely no lateral movement of the chain on the cassette cogs which is what I first suspected.
That’s what I’m thinking now, has to be slipping off the large chainring. This has been going on a few weeks but only this morning got around to making a video. Only way the jockey pulleys can kick like that is slack in the chain, and it’s not coming from the cassette so must be up front.
I did eyeball the hanger. Looks straight to me but I wouldn’t be able to tell if it’s off a mm or 2. And there is absolutely no lateral movement of the chain on the cassette cogs which is what I first suspected.
Are you using a quick link for the chain? If yes, did you replace when swapping to the new chain?
I did eyeball the hanger. Looks straight to me but I wouldn’t be able to tell if it’s off a mm or 2.
It is hard to eyeball. Just to rule it out you want to get your hands (or someone else’s hands) on an alignment tool.
The alignment tool is nice (I have one) but if you can’t afford one you can take the rear derailleur off, then take the front wheel off, put one end of the skewer through the hanger and then the wheel on outboard side of the hanger. You can then use the front wheel compared to the rear wheel to see if the hanger needs aligning.
I got that from somebody here, can’t remember who.
That’s what I’m thinking now, has to be slipping off the large chainring. This has been going on a few weeks but only this morning got around to making a video. Only way the jockey pulleys can kick like that is slack in the chain, and it’s not coming from the cassette so must be up front.
I did eyeball the hanger. Looks straight to me but I wouldn’t be able to tell if it’s off a mm or 2. And there is absolutely no lateral movement of the chain on the cassette cogs which is what I first suspected.
Are you using a quick link for the chain? If yes, did you replace when swapping to the new chain?
^^^ this - if you have a quick link that installed upside down it can cause a skip at high power. If you have wipperman link the jellybean shape should be facing down when it is on the bottom side of the chain ring.
I can get up over 500W without jumping on the small ring.
It’s a Shimano ultegra chain and I used the new quick link that came with it, arrows pointing in the right direction. Honestly I much preferred when they used a pin.
I like the idea of checking the hanger by hanging the front wheel, I’ll try that tonight.
Shopping for a new 52T ring now, good god it’s expensive in Canada. $240 for my 6800 crank. I can get a whole new RC-800 for $360. Or, just go with a new 105 R7000 for a little less than the cost of a new ring. I do miss the days of cheap Shimano components from the UK.