Chain/cassette issues with KICKR core

Hi all. I’m currently using a Trek hybrid bike on the KICKR Core. 9 speed, new cassette and chain. The problem I’m having is the chain/cassette are grinding/clunky on most cogs. In 7th gear the drive train is smooth, but in every other gear it seems like the chain is catching on the teeth of the cogs. The symptoms are noise and a grinding/clunky sensation through the pedals. I’m starting to wonder if the chain is the problem (SRAM 9 speed chain). Or possibly the crank set is worn/bent and therefore pulling the chain out of alignment. Any thoughts?

I’m using ERG mode mostly, so I just leave it in 7th gear where it is smooth. But I’d like to figure out what’s causing the issue.

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Have you adjusted your derailleur the way you would on your bike? There are often slight alignment changes that require minor adjustments.

Or it could be something else. You could put your wheel back on and bring the bike to your shop to check it out for other problems. If it checks out, most likely you just have to adjust the derailleur.


Yes, this. I had my bike maintained by my local LBS and my gears always shift nice and smooth. But as soon as I put it on my trainer I get all kinds of funny noises and slipping gears because they just aren’t aligned the same as my rear tire. I’ve considered hiring Velofix to come to my house and adjust it all with my Core, but they don’t service my part of the city and then I’d have to get it readjusted to ride outside.

Bike mechanics make gear indexing look so easy, but I have yet to figure it out. You could always bring your Core and your bike to your LBS and have them adjust the gearing there and do a nice bit of whole-bike maintenance to-boot.

I had the exact same issue yesterday with a Trek Verve. I took setup to my local bike store and learned my chain was stretched out. Replaced the chain, now it is much better. I can still detect a little noise that isn’t present off the trainer, but only when pedaling at higher power, and it’s significantly less than before.

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@emacdoug Generally there are barrel adjusters that add or release tension on the cable. If you have just returned from the bike shop with a tuned bike you can go through the process of clicking the barrel adjuster +1 / -1, +2 / -2, etc. to improve the indexing on the trainer. Write down how many clicks and in which direction so that when you take the bike off to ride outside you can make the appropriate adjustment.

If you haven’t had a tune-up lately I would suggest checking your chain wear with a chain checking tool and then checking out Park Tool’s video on indexing. Forget the stuff about limit screws - if you already have a cable wired you don’t have to worry about that stuff. I believe the video begins the process with the barrel adjuster full loosened and then you gradually tighten the adjuster to get the indexing right.

Alternatively just bring your Kickr Core to the bike shop and have them re-index for you.


I have been adjusting my derailleurs for years as chains stretch etc. It’s not hard, but takes some practice. If you’re not comfortable with it, a trainer is a tough place to start.


I do all my own repairs, upgrades, etc, so adjusting the indexing is something I can do. I haven’t tried setting it specifically for the trainer. It’s a brand new cassette and chain, so those should not be the issue. I was already planning to replace the bottom bracket and crankset, since they are getting worn out anyway. So I’ll start with indexing and go from there.

Thanks for the feedback.


Good luck. Hope it works.