8 or 10 Cassette set for Tacx Flux S trainer for multiple bikes

I got a Tacx Flux S trainer and I have two bikes ,

8 Cassettes Claris and 10 cassettes Dura ace TT.

Which cassette set will be compatible for both bikes? Can I get any 10 cassettes ?

Suggestions please.
(I am new to indoor training, question may be basic, but I need ensure that I pick up right parts)

I am not an expert but am pretty certain you cannot use one cassette for both bikes due to different groupsets. You will need an 8 cassette for Claris and a separate 11cassette for Dura Ace if you wish to use both bikes and switch them accordingly. Probably simpler to use just one bike on the trainer.


It is 10 cassettes dura ace , not 11

I have seen this online
’ Shimano/SRAM Cassette Body Compatibility:
This is a standard Shimano/SRAM cassette body. Any 8 to 11 speed Shimano or SRAM cassette can be placed on this cassette body."

Someone in local bike shop also told me that , spacing difference among 8-9-10 cassettes are same

The 8 and 10 cassette will both fit on the same body, but I’m pretty sure the cogs themselves are slightly different widths, not sure about the spacing between them, but I’m pretty sure the 8 speed Claris derailleur is not going to work properly on a 10 speed cassette. Also the chain widths of an 8 and 10 speed are different so the 8 speed chain isn’t going to work on a 10 speed cassette.

I’ve got two bikes I can put on my trainer (a neo) and they are 8 and 11 speed and I change cassettes and also have to switch between through axle and quick release as well. It’s a pain so I very rarely switch and just leave it set up for one of them.


Can I ask the OP why they want to use two different bikes on the trainer? Is this for two different people?

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As David said the issue isn’t getting either cassette to fit in the trainer but trying to make the rest of an 8 speed groupset and derailleur work with a 10 speed cassette (or vice versa).

Same Person. I mostly plan to use 8 cassette one on trainer, and 10 cassette one outside to more comfortable with aero position. However, closer to race weeks, I want o use my 10 cassette TT on the trainer too.

In that case, I would buy both an 8 and 10 cassette and switch cassettes and bikes when you get ready to race.

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One of the local bike shop advised that 8 cassette bike on 10 cassette trainer will work with a little noise and I should ignore last 2 cassettes. So bit confused. changing cassettes are not an easy game for me.

If the LBS says there’s no issue with the derailleur alignment then it’s worth a shot. You could try it and see how well it works and how much the noise bothers you.

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I’m afraid that your bike store is talking nonsense (or perhaps misunderstood you?).

The spacing of the sprockets on your 8-speed and 10-speed cassettes are different. Measure it yourself carefully and you’ll see this.

Your shifters are indexed, meaning that each shift from them moves the rear derailleur a precise amount. This moving amount will be completely wrong if you put the wrong type of cassette on, leading to a horrible experience.

Then there’s the different width chains, which would probably lead to the 8-speed chain getting jammed if you tried using it on a 10-speed cassette.

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If you are only changing them occasionally then I would just change the cassettes when you want to change bikes. If you get the proper tools (cassette lockring tool and a chain whip) then it’s a pretty quick and easy job, but still too long if you need to do it every time. Just make sure when you take a cassette off to put it on the plastic spindle it came with in the box or some string or a tie wrap to keep all the cogs and spacers in order for next time.

I’d never done it before I got a trainer and I’ve only swapped them about 5 times now, but I wouldn’t think twice about doing it on the trainer or replacing a cassette on my bike if I needed to now.

Incidentally I started down this path because when I started indoor training I only had an 8 speed bike and bought an 11 speed bike and wanted to try it before winter was over so went through the hassle and swapped them over. There are other zwifters in the house and all our bikes are different speeds (8, 9, 10 and 11) so now I just leave my 8 speed on there since it’s a MTB and has a quick release on the saddle and everyone can adjust it and ride it.

For me I’ve found it’s mostly about the power/pedalling and not the position, but understand this is different for everyone.

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It’s not as simple as ignoring the last two cogs. An 8spd and 10spd cassette are the same width so you’re 8-spd bike’s rear derailleur is going to shift 8 times across the same width as the 10-spd, it’ll never line the chain up with the cogs and will skip all over the place.

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