Chain slipping on smallest cogs (bigger chainring, new chain)

Question

I recently switched my SRAM 1x12 Eagle SX drivetrain from a 30 to 34 direct mount Chainring. I also bought a new chain to accompany with it. Chain length was measured as the sram service manual advices. Put the chain around the largest rings and have 4 links overlapping.
The cassette has around 700km.The previous chain had around 0.5% procent wear.
When going into the highest gear and one cog beneath it by chain slips when applying pressure. The other gears work fine.
I degreased the new chain upon arrival since it was very sticky and applied dry lube after washing off the degreaser and drying using a towel.
I read online and some advice the cassette need to be replaced but after 700km to me that would be really strange. Could the chain slippen have something to do with the derailleur height? Which might be different since my chainring has chained or is this not correct?
I assume a larger chainring does not have impact on the left/right adjustments of the derailleur?
Another option I was thinking about was wiping as much dry lube of the chain applying wet lube.

Nathaniel Hoyt · Accepted Answer

You can play around with chain-wrap and cable adjustment all you want but this problem is 99.999% of the time caused by wear on the cog's teeth. Ask your LBS if they can sell you only the cogs you need. It may seem like the cassette isn't old enough to justify being worn out, but that's a 10 tooth cog you're talking about, a tiny piece of thin metal responsible for handling all those watts we put down! ;) Plus, considering you made the switch to a larger chainring, I get the impression that you were doing a considerable amount of riding in your highest gear, accelerating the wear it experienced.

Correct answer by Nathaniel Hoyt on February 17, 2021

Cyclist · Answer

I have also had this problem several times. Both methods were needed for my road bike after I took a tumble.
I have found that it could be caused by a few different things:

Could be a very slightly bent derailleur hanger

How to fix it:
You can try to fix this by bending it back but be warned! Most derailleur hangers are aluminum and break/snap very easily!

It also could be a minor limit screw adjustment

How to fix it:
Try undoing the limit screw one quarter of a turn at a time till it shifts smoothly. Make sure there’s not too much tension in the cable as to prevent the derailleur from reaching its limit screw
Hope this helps!

Chain slipping on smallest cogs (bigger chainring, new chain)

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