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My wife has a 2017 Specialized Alibi Step Through. Specs can be found here: https://www.specialized.com/us/en/alibi-step-through/p/154232?color=&searchText=B6617-7402

I have recently ordered a Tacx direct drive trainer. While I should have no problem getting my own bike with a 11-speed cassette on the trainer, I believe my wife's bike will have problems. I'm trying to find the cheapest solution to get her bike on.

I've read the following related posts: https://www.reddit.com/r/Zwift/comments/fgap31/7_speed_cassette_on_a_direct_drive_trainer/

7 speed cassette on a direct drive trainer from freewheel bike

But I still have doubts. First of all, from these posts it sounds like I just need to get a 7-speed cassette with some spacers to fit a 9/10/11 speed compatible trainer. But as my wife's bike has a FREEWHEEL, the hub should not accept a cassette. Please correct me if I'm wrong here.

Also, let's say a cassette and some spacers were really all I needed, and I have my bike shop to adjust the shifting/derailleurs for me to get the bike on a trainer. Do I need to adjust the shifting/derailleurs again if my wife wants to ride outdoors?

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    It doesn't matter whether the wheel you will be removing is freewheel or cassette. What matters is what the trainer uses. Sep 6 '20 at 22:03
  • Return the neo, cough up the extra cash and get the Tacx bike instead. Buy once cry once. Sep 6 '20 at 22:38
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As Daniel Hicks said in his comment, it doesn't matter what's on her bike's wheel. The problem will be that her drivetrain is set up for 7 speeds, and you'll be putting an 11-speed cassette on the trainer. So shifting for her will be rough at best.

With a smart trainer, if you only ride it in erg mode, it doesn't matter what gear you're in. So if there's one gear on her bike that runs smooth when on the trainer (there might be, which would be a lucky coincidence, otherwise you'll need to tweak the barrel adjuster every time she changes between the trainer and the rear wheel), and she only uses the trainer in erg mode and always shifts into that one gear, then you don't need to do anything at all.

The other options are:

  • upgrade the drivetrain on her bike, and it sounds like that will include upgrading the rear wheel. (It might actually be cheaper to replace the whole bike.)
  • change the trainer between an 11-speed and 7-speed cassette every time you swap bikes. I believe that 7-speed cassettes and freewheels all have the same spacing.

One option costs more in money, the other in time and annoyance.

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A 7 speed cassette and a 7 speed freewheel look the same to the chain, so you can fit up a 7 speed cassette to the trainer. and then juggle shims/spacers to get the chainline perfect.

I have an old 80s road bike with two sets of wheels, one is freewheel based and the other is a cassette. Works fine, and friction shifters sort the slight misalignment.

7 speed cassettes are less common, but definitely available. I got one from a popular chinese website, but an LBS should be able to order one for you. Get one with the same 7 cogs, as well as the same large and small sized cog. If the intermediate cogs differ in tooth count, that's okay.

Your other option is let her ride your bike - there may be fit issues.

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    I was contemplating suggesting " Put her bike on the trainer, let it clatter and risk jamming, and she'll likely not want to ride it again" but that's not very nice. You could get her a trainer of her own, but that's going to be expensive. Or just ride on the road like usual - this also gets you places too.
    – Criggie
    Sep 6 '20 at 22:49
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    My wife's bike has 14-34T freewheel. The closest cassette I can find is 12-32T. So I guess I need to adjust shifting every time the bike gets on/off the trainer?
    – LeonC
    Sep 7 '20 at 0:15
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    @LeonC - Why would you need to "adjust shifting"? Sep 7 '20 at 0:28
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    8 speed has almost same spacing as 7 speed, so you can just put on a 8 speed cassette have one unused cog. The chain engages only about half of the cog, so for perfectly adjusting for two tooth difference you'd need a half link. Nobody uses them with derailleurs.
    – ojs
    Sep 7 '20 at 4:43
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    @LeonC no you wouldn't need to adjust the limit screws, provided you get the cassette in the same relative position as the freewheel. This means swapping spacers and shims around till its perfect, and then perhaps gluing the spacers together to make changing bikes/cassette easier. Ojs makes a good point about an 8 speed cassette too - there you'd align to not bother using the smallest cog. Pricing governs that choice mostly.
    – Criggie
    Sep 7 '20 at 10:47

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