Zwift Cog skipping under moderate load

I am using the Bait-and-Switch Jet Black model Zwift Hub One that they sold briefly last year.

The cog has started slipping horribly when I go over 200 watts or so, and if I come out of the saddle it really struggles (I have to be ‘smooth’ with it, no sudden torque). Forget about a hard sprint.

Nothing on the bike has changed, and everything is clean. Is there anything I should try to fix this?

If the chain is coming off the cog, I would check it for wear, or install a new chain, inspect the cog for any damage to the teeth, and make sure the derailleur is adjusted properly. If the freehub is slipping while the chain remains in place you should probably contact Zwift support. You could remove the freehub and see if it has a broken pawl or some other internal failure. If you search the forum for “broken pawl” you will find some reports about that.

Hi @Zach_Johnston. Thanks for sharing your concern with our community. I’m Juan from Zwift. Paul’s suggestions are excellent. You should adjust the rear derailleur. Check your bike’s manual for the location of the barrel adjuster for the rear derailleur on your bike. Turning the barrel adjuster adjusts the tension on the cable that connects the derailleur to the shifter on the handlebar.

If the issue persists, the best way to move forward is to contact us. Please attach any images or videos that may better illustrate the problem. If necessary, we can replace the Cog. The Zwift Support team will be happy to help you.

1 Like

Sounds like a worn chain (and worn cog).
Or broken freehub.

Chains will wear out over time and grow in length as a result. Using a chain wear indicator tool will give you an objective measurement of how badly a chain has lengthened. See this excellent video from Park Tools.

It’s good practice to use a wear indicator tool from time to time and replace a chain before it prematurely wears out your rear cog and front chainrings too.

I read the issue as that the resistance is giving way when a hard burst of power is put down, not to do with chain slipping or skipping. But, it’s not clear at this point.

Awesome, some barrel adjustment alleviated some but not all of it. Ill get a stabilized video of it and send it over to get an opinion on what it could be.

This is a relatively new (four month old) chain, so I am hoping to discount that as a possibility. Its rocking outdoors and performing fine, so Im looking more towards the Hub One as the issue.

Correct. Im a decently strong sprinter and go for green jerseys all the time. So once this issue started appearing, its particularly prone to happening during a 10-30 second sprint like you find on Watopia or during racing.

It was NOT an issue during the first couple of months on it and is not an issue on the same bike outside, but Im using a different cassette then obviously. So I turn to the cog.

You might be right. Or not. But you’ll never know by guesswork. This is why I recommended you get a tool so you can take an objective measurement.

My background is a race team mechanic. We’d routinely scrap chains after two weeks of stage racing because strong riders will wear chains faster than an average recreational cyclist. Sounds like you are a strong rider. Not sure how many miles you pile on in four months, but it’s not the age of the chain you should worry about. It’s your mileage and how much hammering you put on that chain.

1 Like

So it is the chain skipping teeth on the cog, not something going on with weird resistance (lack of) changes at the hub/trainer?