Chain jumping gears in small chainring

Hello, the title pretty much sums it up. It’s absolutely fine in the big dog, and is also behaving in the lowest 2 or 3 gears when in the small ring.

As I understand it, the chain is under higher tension in the small ring, so it could highlight a wear issue… but I wouldn’t expect the chain to jump down and back up as a result of wear. My chain is past 0.5 (but not at 0.75), and I’ve ordered a new one. However I’m wondering whether I need a new cassette too, or have I done something wrong in setting up the shifting?

lets see some pics of the teeth,… if they look like shark fins you need a new chainring.

I’m almost ashamed to post these pics, but just got back from a ride and it’s pretty dirty. I usually keep things pretty clean. Included the cassette and front ring for reference even though it behaves in the big ring.




Two things:
First, shoutout for calling your big ring the big dog. I’m going to start using that terminology.
Second, put your chain in small-small and take a photo of your drivetrain. It sounds like it could be a chain length issue.

I think you’re probably onto something @SeanHurley - it’s very slack in the 39/11.

Small ring - 39/11

And for ref…

Big dog, big cog :dog: - 53/11

hmm, that actually looks about as slack as it should be in small-small.

I have seen some pretty extreme derailleur positions on other people’s bikes in big ring/big cog combo that made me question if my chain was too long. Arghh - now I really don’t know. I’ll see how it runs once my new chain arrives.

Chainrings are a bit toothy, could be tolerance stacking, every part is worn so together it is a problem, a new chain will buy some time but I would consider changing the chainrings as they also appear to be a bit wallowed out where the chain rollers sit as do the smaller cassette cogs. the new chain may work initially but you will eventually be in a vicious cycle until you change them out all new

Worth checking derailleur hanger alignment with a gauge if you have not done so already?