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I’m completely new to cycling, so I apologize in advance for the stupid questions I’ll ask.

I will buy a Kickr Core, to use with a Decathlon Triban RC120 bike (Microshift 2x8 cassette, 11-34T, quick release).

Since I will only be using the bike indoors, I think I have three options:

get the Kickr with 8-speed cassette included for €630. Unfortunately the cassette is 11-28, so I’m not sure if it will work with my bike.

buy the Kickr without a cassette (€500), take the cassette from the bike and mount it on the Kickr

buy the Kickr for €500 and an 8spd 11-34 cassette for €15; Shimano CS hg31 / HG41 / HG51 seem to be the only options available but they are marketed as MTB cassettes; will it cause any problems?

What do you think would be the best option, considering I know nothing about bicycle mechanics? I know that the €630 Kickr package includes a 1 year Zwift subscription, but I don’t consider that in my decision, because I think I’ll use Rouvy.

Thanks

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  • Simply put: Just using the cassette you have is the no-brainer, here. No extra purchases, correctly sized chain and it should fit your trainer, plus the best gear range if you are planning to ride longer climbs with realistic trainer intensity in Rouvy, having 1:1 low gear ratio definitely helps over 34/28, but I must admit that this is not as much of a factor as in real-world-riding. All you have to do is plug and play and using the correct (1,85mm, iirc) spacer on the Kickr.
    – DoNuT
    Nov 27, 2023 at 7:39

2 Answers 2

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Road and MTB cassettes at 8 speed are the same. However, if you will only use the bike indoors, just use the cassette you already have. I do not see the point buying the new one until you need to replace the current one. If you truly need another cassette, any 8-speed cassette compatible with the HG freehub body will work. An 11-28 one will most likely work too. But depending on the specific model of the rear derailleur you must check that 28 is in the range for the allowed biggest cassette cog (there is also a lower limit). It most likely will be, but Microshift actually makes multiple 8-speed mosels, although the bigger ones are meant for MTB.

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  • Thanks, I guessed using the bike cassette would be the best option. Now I need to find some video tutorial to see how to do it. Do you have any link? Thanks
    – younggotti
    Nov 26, 2023 at 16:35
  • @younggotti There are many tutorials, you can start here parktool.com/en-int/blog/repair-help/… Nov 26, 2023 at 16:37
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    Won't a chain that works for 11-34 also work for 11-28? It is reducing the range. It is just like he never shifted into the lower gear or two. Nov 27, 2023 at 4:45
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    It will, there will be some unnecessary wraparound, but if it is supported by the RD, which it should be, it will be like using one of the smaller cogs. Nov 27, 2023 at 7:17
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The cassette will work with your bike setup. The chain will be a bit too long. Your chain will definitely droop in the smaller chainring and smaller cassette cogs, but you could avoid those gears. I think shifting might be slightly worse. However, I would just take the offered cassette and try it with your current chain.

It is true that best practice would be to get a shorter chain for use indoors. You would be using quick links to take the chains off and put them on. Again, this might not be necessary.

I have my gravel bike set up for the trainer. The trainer cassette is an 11-30, but the actual rear wheel has an 11-34.

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    As long as the small cog is the same how can the chain be too long? With a smaller large cog he could get away with a shorter chain, but any one that works for 11/34 should also work for 11/28. He is within the range that is supported by the 11/34 chain. Nov 27, 2023 at 4:43
  • Shimano sizes chains using the big ring and big cog. Say the chain is sized for a 34t cog. If the OP goes to a 28t big cog, there’s a bit left over.
    – Weiwen Ng
    Nov 27, 2023 at 12:46
  • @WeiwenNg that's true, but having a little extra chain in the big-big combo has very little impact. Having too much chain in the small cog, however, will lead to some slop. However x 2, on a direct drive trainer, I wouldn't expect even that to be a huge issue (e.g., no bouncing around from rough terrain)
    – Paul H
    Nov 27, 2023 at 18:59

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