I got a Giant Contend 1 2023 the other day, but am having issues with the chain skipping under very moderate load with the Zwift hub one. If I peddle gently it’s fine, but above say 150W it constantly skips.
I have videos, but think I can only upload photos here. Basically there’s a clicking noise and the idler moves. When I peddle it just constantly jolts as it skips. I had a hybrid bike on there before with zero issues. The hub one is only 9 months old and this new bike is brand new, so I think I’m looking at some kind of rear derailleur adjustment? I’ve had a fiddle, but have got no where. I tried adjusting the rear barrel from one extreme to the other, to no effect. I also have tried different gears to make sure the chain is properly aligned.
Any help much appreciated as I know nothing really about bikes.
The pictures don’t show it but for the rear derailleur adjustment you’d be looking for the rear derailleur pulleys to be perfectly aligned below the cog - all in a straight line, so you would look from behind the bike and get your eye down to where you can see the chain connecting from the cog on the trainer to the upper pulley on the derailleur. You also have the option of taking the bike and trainer to a bike shop for adjustment if you can’t work it out. They could tell you if it’s an adjustment problem or something else.
The old hybrid bike - when’s the last time you replaced its chain? Every chain wears (slowly) over time, and if that chain’s stretched beyond is useful life - that means the distance between each roller on that chain is longer than it was when it was new. A clapped out chain on a new cog / cassette will wear out that cog within a a very short period of time because metal will wear on metal.
For your hybrid bike - you may want to take that to a local shop and ask them to measure the chain wear with a tool. They may recommend that your chain, the cassette cogs and the chainring on that hybrid all should be replaced.
Chains are a wear out part and need periodic replacement just like tires and brake pads. If you replace a chain before it’s well and truly shot, you prolong the life of the (more expensive) cassette and chainrings.
My hybrid had less than 100 miles in it when it went on the turbo. My understanding of a Zwift cog is it is built to last and shouldn’t wear like a normal cassette? The chain could have worn in the last 9 months, but surely not to the detriment of the cog?
Chain and cog (like casettes) wears down together.
The chain elongates between the links because of wear and grinds this elongated spacing into the cog (cassette).
If you put in a new chain, its spacing does not match with the worn cog and the chain skips.
You most likely need a new cog.
I hope zwift will offer the actual gearwheel which built in the cog as a replacement part.
How frequently are you meant to replace the chain to avoid damaging the cog? I’ve not been riding a lot on the turbo. Only just gone over 2k miles. Surely you shouldn’t have to replace the Zwift cog along with be chain!?
Depends on you chain care routine and the oil you are using.
You should measure chain elongation from time to time with a chain wear gauge/tool.
So you can change the chain before it elongates much and damages the cog.
A well serviced ultegra chain lasted 8000km on my kicker core with a cassette and with a dedicated trainer bike on it.
I expect the cassette to survive three to four chains, so 24000 to 32000km.
The chain on a zwift cog should last even longer because you are not shifting it and there is no cross chaining between the cassette and chain rings.
Have you adjusted the cog to the new bike?
Afaik you can adjust the chain line on the cog.
You’re meant to shift gears to get it aligned so there is no rattling. I’ve tried a few different gears, but doesn’t seem to help the issue.
Given the miles I’ve done is it not more likely the rear derailleur is not properly adjusted? Or would that not account for this?
Derailleur adjustment could certainly explain it. I’d be a little surprised if it were chain wear given the amount of use you describe but it’s possible and something to check. Drivetrain wear can be accelerated by dirt, the rider’s power, lack of lubrication, or low quality materials. Mechanical issues like this are hard to accurately diagnose without getting your hands on the bike. A bike mechanic could probably figure it out in a few minutes.
No it would not. You can’t assume that the derailleur should be adjusted the same for both the cassette and the cog. There’s no guarantee that the position of the cog on the freehub will perfectly match one of the sprockets on the cassette. Minor adjustment may still be needed. You can also remove the cog from the freehub and install the cassette from the rear wheel on it. Again derailleur adjustment might be needed but presumably the chain at least fits cleanly on that cassette since both are new.
