Setting up Wahoo Kickr Core for different bikes?

If you are mainly using zwift then the zwift cog is what you need

If you use it in ERG mode you'll likely be able to find a gear it'll work for both on one cassette.

Swap her bike to 11 speed if her freehub can take it. Just need a pair of shifters and a RD. second hand that might be about the same as a Zwift Cog. You need the £100 shifters for the cog to really work properly. I ran 10 and 11 speed on different bikes and in the end, standardised on 11 speed, with 1x11 etap on the bike on the kickr (which won’t take a cog). Haven’t regretted it.

Or buy a used 10 speed bike for yourself just for Zwift. Anything cheap will do. Contact points are what matter.

You need the £100 shifters for the cog to really work properly.

You don't need it to work though, it comes with a shift button. For drop bars the play controllers are better but not essential and if you are using flat bars they aren't compatible so you have to use the buttons anyway.

Thanks for all the suggestions. It's probably blindingly obvious that I've never used a static trainer before, so apologies if I'm being stupid, or wilful here.

I should probably have said that both bikes have drop-bars and I haven't got the patience to re-tape bars. So, changing her drivetrain for this is beyond me.

We're on a strictly one-out-one-in policy for bikes (the cargo bike takes up a lot of space in the shed), so I'm not in a position to get a "zwift bike".

I did wonder if we just set it up and see if any of the gears on the cassette the previous owner left on it (10sp) might work with my bike. wasn't sure whether that would work, so I'll look into ERG mode. Might work for me as part of my rehab. Does that mean I can only do cadence-matching work?

We're not planning to get zwift, just use the programmes that come with the wahoo. Does this make the zwift cog a massive waste of money? Or is it just the price of convenience?

Thanks again for all the suggestions.

We’re not planning to get zwift, just use the programmes that come with the wahoo. Does this make the zwift cog a massive waste of money? Or is it just the price of convenience?

If you use the trainer in ERG mode then, as above, you should be able to find a gear combination that works cleanly on the bike that doesn't match the cassette, so you just leave it in that gear and the trainer/software sets the resistance so that you match that power output regardless of what gear you're in.

The only real plus of the Zwift cog would be being able to use both bikes, interchangeably on Zwift, So if you're not intending to use Zwift, it's pretty pointless really. If you discover the subtle joys of Wetopia (sic) I guess you could always get a Zwift Cog later anyway. It'd also be quite expensive if you both wanted to Zwift, there's still - as far as I know - no 'family membership' option, so you either have to have two individual subs or share the same avatar, which might work if you were twins.

ERG mode. Might work for me as part of my rehab. Does that mean I can only do cadence-matching work?

Nope, in ERG mode the software sets the resistance regardless of what mechanical gear you're pedalling so you can pedal at 50rpm or 120rpm and you'll still output exactly the same power. If conputer says 200 watts, it will be 200 watts, if that makes sense. I've never used the Wahoo's native software, so no idea how it works. You can always, fwiw, do a short trial ride on Zwift to see what you make of it.

I suspect a lot of this will make more sense once you've got the Kickr up and running. There are virtual riding options other than Zwift too, notably My Whoosh, which is still free to use, I think.

So, changing her drivetrain for this is beyond me.

Any shop will do this. It's an hours work (external cables). I normally reuse the tape. It's the way I wouldd go. Erg mode is an idea, but if you are used to changing gear when things get harder, and you want light force with higher cadence, you will be changing gears. You can probably get a few gears to shift fine, but one of you will hate it

We've just been through this, considering all options from a static bike but ended up with a second hand trainer and planning to run two road bikes.

However we also ran up against two different cassettes, was planning on converting one bike to match but in the meantime my wife decided that my bike fits with her saddle forward, so for now we've ended up with a seat post each and just swap that.

We have also started with Rouvy after a brief dabble with Zwift as the Duo membership is at lot cheaper.

How different are you in size? It's way less relevant on a trainer as you're riding for shorter time and handling is not an issue. I'm 6', Mrs Hoppy is 5'7" and Hoppy jr is 5'5" all ride the same large Camino with different post/Saddle combos. A junk post with a marker for saddle height has swaps down to a couple of seconds.