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I mistakenly thought the chain had been checked. [Duh.]
Or maybe it has?
But maybe not with a good tool?
It's easy to see why L/L would say the cassette is toast. Those teeth look like they've been peened by the chain. That must have taken some doing.
Hard to imagine the chain is in good shape running over those teeth. Even if the chain hasn't "stretched" (worn) I'd be checking the
inside of the links for cuts from that damage.
If the chain is in really bad shape, and the cassette needs replacing, might the chainring also be
kaput?
I'm surprised the blueing (finish) on the cassette is worn as it has. I'd expect the wear to be more uniform around the whole circumference, not just the high and low points as seen in the pictures. What is not shown, is if the cassette is running true, meaning all the sprockets are parallel and each one is flat. Unlikely the axle is bent, but is it being sat in the dropouts correctly, everytime the wheel is refitted? [
My first ever disc only bike a 2000? Claud Butler Cape Wrath IIRC, left the LBS with me riding it and the front QR undone. I didn't find out until a mile later, fortunately while lifting the bike into my car. Seems the shop closed last November apparently after 34 years.]
The videos were easier to watch (in fact the only way I could watch them) was to download them first from Google Drive, and play them locally on my computer.
I've watched them both about 5 times each, and I am no less confused. The movement down (hard gears to easier gears) seems to be a problem detailed in both videos, but indicated at different positions on the cassette?
Read elsewhere:
"
Poor shifting down the cassette is likely caused by excess friction in the system. The cable tension may be excessive or dirt or other physical impediments to cable movements are present. So start at the beginning and inspect cabling from shifter to derailleur. Disconnect the cable from the derailleur (note whether you've correctly routed the inner cable at the pinch bolt) and taking a section of cabling at a time, manipulate the shifter while holding the inner cable taught with your fingers noting any deviation from perfectly smooth in the cable movement. Worn ferrules or kinks in the outer cable are common points of friction. You've made a lot of changes and if the same cabling was used between shifters, there's lots of opportunity to contaminate or slightly damage the inner cable at change over. Pushing inner cable through the outer moves grease along and abrades the outers' inner liner. If your cable routing is internal and where it exits the frame, if there is a cable clamping mechanism there, make sure that isn't so tight that it's making a dent in the outer cable. Lots of things to look for and excess friction is the number one cause of poor shifting especially down the cassette."
A kink in the cable, or debris somewhere could have explained the issue with the middle gear that wouldn't index correctly, but doesn't explain why a new hanger fixed the problem? As indicated earlier, if indexing for
one is out, it's likely (logically) out for them all.
Doing some purchasing research about 5 weeks ago, I considered upgrading my 8 speed (3x8) which is super reliable, to something like a 3 x 9 or 2 x10. Sunrace cassettes are very attractively priced, so I considered a purchase. Further research suggested by a professional reviewer, the Sunrace cassette produced less reliable gear changes, so it left my shopping list.
Trying to find tht review, my search criteria turned up a number of results relating to the problem identified here. Apparently, the higher/smaller gears are prone to early wear, and prone to skipping, especially on e-bikes. Both Shimano and Sunrace sell these replacement rings in 'kits' for that very reason. Sometimes a move to a Shimano cassette improves things, sometimes (less frequently) a Sunrace cassette improves things. Whatever happens next, I think a new cassette and chain are on the cards for this bike.
Have you checked the wheel bearings are as tight as they should be?
If you have one of these, are you putting it on the right way around?
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This is the WRONG way around as this is the
return chainline heading toward the derailleur.
