hamcereal

So my chain skips a bunch and makes a horribly disconcerting noise when I pedal with a little more strenuous force.
I have a 3 x 9 setup, and it really only happens when I'm in the middle or smallest chain ring, example: in a low gear ratio going up a hill, or just getting going after stopping at a red light.
It led me to believe my chain was too long (just installed brand new chain), and I've since removed some links, but it still seems to be happening. The smaller the chain ring/cog, the more it occurs.
I've checked the teeth of the cogs on my cassette and they look fine. The bike will ride fine if there's no strenuous exertion on the pedals, I've adjusted the derailleurs, everything shifts properly and doesn't make any clicking noises while I'm riding.
What am I missing? It's a really annoying issue and it's preventing me from really going hard!
Please help!

Troul 

how new are the shift cables & housings? Is the crank deflecting side to side any?

shelbyfv

Classic symptoms. Your cassette is worn and will not work well with your new chain. This is how you know you need a new cassette. You cannot tell by looking.

MNebiker

Just had the same issue. I replace a stretched chain and under load it would skip on the smallest rear cog, even though the teeth looked pretty good. I raised the same question on this forum, changed the rear cassette as advised and all is well.

Bigbus

Did it skip with the OLD chain? If not, do like I did and keep the OLD chain and current cassette as a pair for emergency use. You could always put the old chain back on until you get your new cassette.

79pmooney

My first thought.

+1

This is a bigger issue on the smaller chainrings because of the basic lever principle. You push on a lever the length of the crankarm. You are pulling the chain with a shorter lever. the chainring (of length the radius). The more unequaL the levers are, the harder you are pulling that chain. (I know, we all feel so much more powerful in the huge chainring, but our bikes are simply not impressed.)

New chain skipping on used cassette/FW cogs is classic worn cog syndrome. Cogs get worn far faster by worn ("stretched") chains. Changing chains frequently goes a long ways for extending cog life. (And when new chains stop working, your now collection of slightly stretched chains will work for another few years just fine on that somewhat tired cassette.

Ev0lutionz

Definitely worn cassette. had this earlier in this year and problem was gone after a change of cassette, which thankfully I decided to get as a spare.

hamcereal

Thank you all, I'm relieved to hear you've experienced the exact issue, I'll get a new cassette and report back!

bikebikebike

@hamcereal: Is there play in the derailleur, hanger bolt or jockey wheels?

Mine has similar prob, very low mileage ebike with BBSHD mid drive that wants to shift/jump under load in middle gears.
Replaced chain,aligned dropout, and hanger. chainline is fine
Cassette looks fine, no wobbles in hub. indexed.
Has some hanger bolt play, so I was planning to replace the Acera RD.
Ebay sent a counterfeit, worse than current, so am still trying to source one, but would feel bad if it is cassette.
I really see no evidence of wear on it. ? Don't understand post saying wear may not be apparent.
Cables look good, but if indexing OK, shifts OK when not under ebike load from Overpowered mid drive
could a bad cable do that? Not sure how.

My hunch is it is RD hanger bolt/jockey wheel misalignment that is worse under load, that I can't reproduce while watching it.
Just replacing stuff may get it, but is $$ and inelegant thinking.

bikebikebike

Not trying to be dense, and I get just module swapping as a repair technique.
I was aware of differing things to look for in cassette wear, but was asking about what might be happening that would not be readily apparent.
Modern cassettes have a lot of varying tooth geometry, making things less conspicuous.
Just looking to understand better what the mechanism of failure is.
Bulk module replacement is , um, inelegant,. It at best can exclude components as a cause.
Skips and mishifts may be hard to distinguish and reproduce.

alcjphil

Exactly how much mileage and under what road conditions? Mid drive ebikes put a lot more strain on both chain and cassette cogs resulting in faster wear. If you regularly use the smallest cogs, they will wear much faster than the larger ones. Rear derailleurs on the other hand are not under that much extra stain. A cassette will wear out much faster than a rear derailleur on any bike. A low mileage bike is very unlikely to have worn out a rear derailleur unless you ride almost all the time on wet grimy roads

bikebikebike

less than 500 miles, light use, though ,as I said, the BBSHD is overpowered and capable of 1500 watts (30Ax52v). PO may have flogged it , but the whole bike was real clean.
I use it as a pedal assist at 5A mostly
There is enough side play/wiggle at the hanger bolt to produce jockey wheel side play of 2-3 mm in the affected middle gears. First time I have seen that.
It's hard to reproduce on a stand or riding, since when I'm loading it, I'm not looking down =8() , maybe load changing geometry in that part of the RD range to initiate partial shift?
Cage and wheels straight without play in their joints, cassette spins true, very clean, no play, no conspicuous tooth wear or damage.
I replaced. chain with new Shimano 9speed as the first move. and aligned hanger.
Shimano replacements have gotten real hard to get and priced above MSRP plus shipping, so swapping may just have to be with whatever I can find.
My US sourced Ebay new "Acera" RD was the worst counterfeit I have seen to date. sigh. (not used as replacement )
Thanks for your thoughts

hamcereal

Well, I bought a brand new cassette... Still having the same issue. I'm thinking it must be the freehub... The pawls might not be fully engaging the splines and then slipping. Time to take it apart...

shelbyfv

So it was "skipping" before you put on the new chain? Unlikely that your freehub failed just as you changed some other component. It may be time to visit the LBS.

cpach

It is also possible you have worn chainrings.

It's hard to describe the difference but chain skip feels and sounds very different than (uncommom) freehub slipping.

hamcereal

No, I don't know if it was skipping before I got the new chain. This is a build I made with a group set from a second hand bike, and I didn't use the wheels from this bike because they were in pretty bad shape, so I bought another set second hand.
I've removed the freehub body but haven't had time to inspect cause my kids need me to feed them haha

nickc3

I had same issue - it was the chainrings. which ended up being fairly easily to replace.

hamcereal

So here's some video I took, I'm starting to think more now that it actually could be the chainrings... I hadn't noticed this before, but now the chain has come off the chainrings a couple times...
In the first video @ 1:45 and the second video @ 0:48 are some examples of the issue...

Troul 

Almost seems like the BB has lateral play.

hamcereal

I changed the chainrings, it was the gosh darned chainrings.... 😑 Thanks all for your input!