Zwift Hub + Cog with a flattop chain, not feeling great

Is anyone else running a Zwift Hub + Cog with a flat top chain? I just got an Apex AXS groupset installed on my bike and after a virtual club race last night I’m feeling/hearing vibration/resistance through the bike when going over 200watts and at changes in elevation in Zwift and the ERG mode is reacting and applying more resistance.

Zwift says that the flattop chain is supposedly compatible with their Cog, but I’ve heard conflicting info from some folks saying that the larger roller size on a flat top chain makes these two pieces of equipment incompatible. Seems to me like I’ll just have to go back to swapping cassettes on the Hub when my girlfriend and I are both using it, which is kind of why I was stoked about the Cog in the first place.

Anyway, has anyone had any luck in getting this to work or am I wasting my time? Thanks yall!

This is well short of what I have wanted to do on this topic, but for a primer:

This shows the typical roller size and that of the SRAM Flattop chains. 0.25mm larger which is evident on the left side. The right side is a SUPER ROUGH estimate using the same 0.25mm delta between the centers in height, and then the overlap along with the bottom gap height.

The “real” thing to do here is get the sketch profile of a typical 14t cog and see how the SRAM roller sits in that for tooth contact and expected gap at the bottom.

It’s possible we are talking small enough differences that it won’t matter in practical terms. We know people mix these and claim they work. But I still expect there is enough real delta here that it’s less than ideal and might lead to issues in at least some cases.

I got the dimensions from this site and have not validated them for accuracy via other channels yet:


This going to be very helpful for me. I was thinking about the Cog to run shimano 12-speed as well as SRAM 12-speed flattop.

In my experience rival axs was not super smooth or quiet on the stock sram cassette either. If it doesn’t bother you too much I highly doubt it would damage the chain.

I don’t have any personal experience with the cog so take my advice with some salt.

Does the chain wrap smoothly around the cog? Does it take any extra finegaling to get it seated in the teeth?

I’ve used the flat chain on random cassettes and have had any issues with it. The issue with the flattop chain is the top rear derailleur jockey wheel. It doesn’t like narrow wide jockey wheels.

Check that you have the connector link installed correctly.

Any updates? I’m curious.