Trainer Cassette

Hi All, silly question for you. I’m looking at moving from 12-25 to 11-25 for some extra speed during sprinting in zwift. Will I need a new chain?

No, but also make sure your trainer diffculty is set to 100% if you are running out of gearing on small end.


As long as your sticking with the same number of gears on your cassette, the chain should be fine.
The chain length should be ok too but sometimes might be a little slack in the 11 gear requiring removing a link.


That’ll add some resistance “headroom” if you’re sprinting uphill – but otherwise, what would it do?

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It shifts resistance so you’ll use more of your smaller gears. At 0% you can use more of the larger gears as you’ll “feel” the hills less.

If the terrain is flat, isn’t 100% trainer difficulty the same as 0% trainer difficulty? If the terrain is downhill, isn’t 100% trainer difficulty easier than 0% trainer difficulty?

Yes, I think so. 100% will represent both uphills and downhills more like they actually are. 0% will basically flatten the hills. You still need the same power but your gearing is different. For example I usually leave my trainer difficulty set at 30% and I can do almost everything in my big ring. If I had my trainer set to 100% I’d need to use my small ring.