Chain skipping on high gear and torque

Hi All! I have a problem for some time now with my bike (on and off the trainer). The chain skips when I am on relatively high gear (I believe it only happens while on the smallest cog but I am not sure). Mostly it is just a loud “ping” and I loose a momentum when tying to muscle up the small hill, probably when reaching something close to 800 W. My first guess was that this is cassette wear but I changed the smallest cog with the cassette I have on the trainer and the same happened. I was trying to record that on the camera and I actually did it but this time the whole chain fell off - that doesn’t happen when on small ring on the front. Any suggestions what that might be?

Chain ring wear.


Thank you for the reply. The chainring is < 12 000 KM old and I really keep the whole drivetrain clean so I did not consider that…I will inspect is closer.

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Drivetrain wear. Very often that happens when you have a worn cogs (cassette or chainrings) and you buy a new chain. The old chain will fit better into the worn, larger grooves and the new one doesn’t.

If your chain skips in the front, it is your chainrings. If it is in the rear, it is your cassette. If it is both, well, it is both. In your case it is your front chainring for sure, and I’d also replace the cassette and the chain (unless you have changed it very recently). Skimping on one of them, e. g. chain, might mean you have accelerated wear of your new components.


Chain is pretty new (end of May) and was waxed straight away, cassette was changed somewhere in the end of last year. Too bad grx separate chainrings are not available anywhere right now…

I also say front chain ring.

I was skipping for a few months when putting in hard efforts like you mentioned. My initial thought as I was just dealing with it and not doing anything about it due to me not really giving it hard efforts in the time period I was experiencing it, was it has to be the rear cogs somewhere.

But no, it ended up being my large front chain ring.

Looking at your video in slow mo, it seems that’s the case for you too. But its hard to tell unless you’re the one riding it.

Are you running an 11-speed system (that comes stock on the 1x ALR 5 Driftless)? Note the FC-RX600-10, 46t big ring you have on your bike is not compatible with an 11-speed system, while the FC-RX600-10, 30t little ring is. This occurs often when a 1x GRX RX600 set up is being swapped to 2x.

The combo of your big ring and 11-speed chain/rear drivetrain will result in pre-mature wear on the rings, especially the front. Even when brand new, I wouldn’t be surprised if a mixed-speed system set up would result in skipping/chain drops under load on the front, let alone after 12,000 km.

I would recommend snagging the FC-RX600-11 46t ring (Chainring 46T for FC-RX600-11 | SHIMANO BIKE-US) to prevent skipping in the future. It is also backward compatible with 10s GRX, thus the URL.

@shofmeister Nice catch :grinning:, however…I have a ALR 5 Driftless frame but the rest of the components is from the older ALR 4 so the whole drivetrain is 2x10.

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Is your quick link installed backwards/upside down? That will make it skip in the smallest cog.

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Yeah, I have seen topics about that but it was about SRAM powerlink which is directional, I am using KMC link which is not directional.


Thank you all for contributions. I replace both chainrings and I no longer have this issue! It still puzzles me how come it wore so quickly. Hopefully with the waxed chain it will last longer :slight_smile:

I was going to say perhaps look at your cables first @boskidamian but I see you have replaced the rings which has sorted it. If the inners or outers are worn its likely the chain when you change down to the lowest cog actually snags before it gets there and a little bit of torque frees it and it only slips down to the smallest then.

I would check the front derailleur alignment - I destroyed a large chainring because my derailleur got slightly out of alignment (must have taken a knock at some point) and by the time it started showing symptoms it was too late - the chainring was worn to unusable, and must have been surprisingly quickly too. If you have the same problem, changing the chainring may have just temporarily masked it, and be in the process of destroying the new one…