Absolutely dispairing and about to bin Kickr Core

Hi all, hoping you can help. For three months I used a Tacx Flux wheel-on with zero problems. I then ‘upgraded’ to a Kickr Core. I have always had a horrible grinding noise and feeling when in the highest gear on my 8-speed mountain bike. I took the bike and trainer in (a ballache) to a local reputable bike shop, who says that they adjusted the deraiileur and made some tweaks and that it was all working ‘perfectly’. They charged me £15 there was that little to do. I’ve just got it all back and the highest gear is doing exactly the same thing. I’m absolutely dispairing and thinking of cutting my losses and selling the Kickr and going back to the Flux. Does anybody know what might be going on here? Could it be me ‘seating’ the bike on the trainer wrong or something? I’ve used the exact same adapter configuration as the shop… Thanks.

Video: you tube dot com /watch?v=DBQJ1z-gfgY&feature=youtu.be

Hi @Kane_Fulton, did you get a new cassette when you got the Kickr Core, or is it the same one from your MTB wheel? If new, did you get a new chain too? It sounds like you might have a bad combination of new cassette with an old stretched out chain. Did the bike shop check your chain wear?

Hey Mike, I used the casette from my mountain bike (which I should add has only been used indoors with Zwift and the Flux for two months) on the new Kickr Core. The shop said that they checked everything and couldn’t find any problems, save for a kink in one of the cables that was preventing gears from changing fluidly (which has now been fixed).

It could be alignment of the cassette and derailleur. It shouldn’t be, assuming that you have the same generation of cassette on the bike as on the trainer – 11 speed on both, or 10 speed on both with the same spacer on each, etc. But it could be.

But also, that chain looks awfully long to be used in that gear combination – small ring on the front and small cog on the back. [And that combination, cross chaining, is not meant to be used.] The derailleur’s jockey wheel looks close to the cog, If you’re getting some contact between the cog, the chain, and the jockey wheel, that would make a noise similar to what I’m able to hear on the video.

There are plenty of good videos on chain sizing. Here’s a search:


He says he did take both.

My money’s on the QR skewer being too loose or tight, putting the alignment out.

did you put a spacer on the hub when you put the new cassette on?

the reason i ask is that i have a kickr, and everything i read said it needed a spacer for a 9-speed cassette. i tried it with the spacer, but everything was out of alignment and i had grinding noises. remove the spacer and voila! everything works as expected!

your mileage may vary, but that’s my story :slight_smile:

@Dan_Dube Wow, going to try that now! It’s an 8-speed… but no harm in trying it. Thanks to everyone for the messages so far, I wondered if I’d put the skewer on wrong - but how do you even manage that? I’ve tried it in both orientations, with and without springs, tight and loose - and the friction/clanking remains.

The KICKR Core is 11-speed compatible. Your eight speed cassette calls for a different spacer on the Core’s hub than an eleven speed cassette would. Here’s a recent thread on the subject:

I bought and set up a Kickr core today. Bought new 9 speed cassette to match my indoor bike that had been used on a wheel on trainer…
added the spacer before fitting the cassette and had to do a little bit of cable adjustment but all was fine other than the two smallest cogs feel very ‘bumpy’.
I’m going to take the cassette off of the bikes wheel and instal that to compare the two…

Let me know how you get on Andy. I’m really close to just selling it and going back to the Flux. I’m not a racer or watt-hungry person - I just want to ride around and keep generally fit. I though the Core would be superior but I didn’t get the annoying chain ‘bumpiness’ that you describe with the Flow and that was 1/3 cheaper…

Kane, so the update is as follows;
I checked I had installed the new cassette correctly and I had. Derailier was in good alignment so the bumpiness was definitely NOT a trying to change sprocket issue.
So I took off the new cassette ( a genuine Shimano 9 speed) and put on the old cassette from the wheel. :slight_smile:
Had to adjust slightly the cable but all is good and the ‘bumpiness’ on the smallest two gears is no worse than the rest of the cassette now. There is definitely a very slight bumpiness across the whole cassette but I think I am only noticing this now due to how smooth and quiet the trainer is.
I’m no expert but suggest that maybe it’s that the chain and original cassette are worn equally and adding the new cassette into the equation had been the issue.
Hope this gives you some pointers on how to proceed. My experience (15 minutes set up ride :slight_smile: ) of the wheel off trainer is enough to know I won’t be going back to my Tacx vortex anytime soon.


Cheers Andy that’s really useful! Going to go back to the bike shop and see what they can do with fitting a new chain and casette and go from there :slight_smile: nice one.

When i got the Core i’ve placed a new 9 speed cassete and chain and I got always that bumpiness in the last cog. Im using the standard 9 speed spacer so all should work fine but in fact last cog is not an option to use.

Kane make sure your spacer is the right one for 8 speed. At the most only the last cog should find some bumps.