12 speed cassettes on direct drive trainers

Hi @Tommy_Roenningen
Some of that is expected relative to a road bike. Just as when you ride your mountain bike outside on flat pavement - your lowest gears will be too low to be practical, and when you’re going fast on the flats you’ll spin out your highest gear of 32x11.

First - I’d recommend calibrating your trainer using the Tacx app. Power readings can vary if you calibrate when it’s cold vs when it’s hot. Also - perhaps the cadence RPM’s will be improved?

Secondly - the level of resistance you feel is predicated on several variables - your age, height, weight, but most critically - your Functional Threshold Power number. If the FTP number is set too high - you’ll barely be able to move the pedals. If your FTP is too low - the trainer will not provide enough resistance. You can manually adjust this in the game app, in the Menu settings.

If you set the FTP high enough that your low climbing gears are usable - chances are your top gear will be too difficult. Your speed numbers will probably be unrealistic as well. As long as you’re not doing a race where bizarre numbers would skew the results, it’s probably not doing harm to anyone else.

Lastly - have you tried the off road routes where the increased rolling resistance makes better use of your mountain bike?. We are adding more off-road game features like steering that you might find fun. Be sure to select the Zwift mountain bike in your garage to use the steering feature.


I came across aftermarket 12 speed cassette which is compatible with existing Shimano 11 speed spline. Maybe that might help preserve the existing Shimano 11 speed freehub for trainers using 12 speed drivetrains.

Interesting. I’ve never heard of this brand or product. Can’t speak to how well it may or may not shift with 12 speed SRAM or Campagnolo road drivetrains.

Cramming 12 cogs on the freehub body may leave very little clearance between the derailleur cage and the spokes of your wheel (if you’re mounting this on a bike). If mounting it to a trainer you may have similar clearance problems, depending on the trainer design. Proceed with caution.

I am 2 months into using their 11speed (11-28T) SLR cassette 205gm vs Ultegra 235gm. The cog engagement is near Ultegra but not as fast though it eventually worked.

I am looking at a Sensah Empire Pro 12 speed groupset that looked promising. Until I do, can’t say anything more about 12 speed trainer set ups.

Thanks for the reply Shuji.

Brand new to Zwift and have a question about cassettes and this thread seems on point. Tomorrow I am getting a new KICKR with attached 11-speed cassette. I had thought about dedicating an old road bike I have that I don’t ride anymore but it has a 7-speed rear cassette with 3-speed front cassette. From what I’ve read (the bike is an old Canondale from 2003) this isn’t going to work without a lot of mods and maybe not then. Yes I know I can get a different trainer that allows me to leave the wheel on but I wanted a direct drive. I can use my current Specialized Roubaix Comp with it’s 11-speed cassette just prefer a dedicated bike to use with the trainer. The old Canondale is not going to work is it?

The short answer is it depends on how old this 3x7 drivetrain is. If it was made in the past 10 years, it’ll probably work fine. If it’s 1980’s vintage, then probably no.

It’s from 2003. At worst, it just won’t change gears correctly, right? Can I hurt anything by giving it a try? I won’t damage the trainer/cassette I hope! I might just carefully try to set it up and see what happens. Not sure how easily it would be to get someone at Wahoo to talk to about this.

If 2003, you should be ok. Stack both a 1.8mm and a 1.0mm spacer behind the 7 speed cassette to take up the extra width on the freehub body.

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Little update. A sram nx 12 speed 11-50 cassette will fit straight onto trainer without using xdr freehub.

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As Shuji wrote, it’ll work. See the March 23 post above in this thread: 7 Speed Bike on Wheel-off Trainers:

A post was split to a new topic: Trainer Difficulty vs Gear Ratios

I ordered an XDR hub for my Tacx Flux so I could run my 12 Spd SRAM AXS group on it…6 months later I’m still waiting, they finally have them in stock and apparently it should arrive in June!? Garmin have taken over Tacx and the customer service leaves a lot to be desired here in Australia.

You can buy a 7 speed cassette. You might find a 7 sp with the right gearing would match your 6 speed free hub. You could set or leave the rear derailleur to not use the inner most gear. As your bike has down tube shifters and 6 speed its probably not indexed just friction so no issue. To use a 7 speed cassette on my kicker trainer I had to use a number of cassette spacers to move the cassette out on the hub.

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A post was split to a new topic: Better power readings on the small chainring?

Great post, a lot of stuff in here i did not know about :grinning:

Hi all. Totally new to all this so forgive the dumb questions.

I’ve just bought a road bike with 14 speed shimano gears (7 speed cassette on the rear wheel). It’s a new bike ( Challenge Venture CLR 2.0 700C Wheel)

Looking at getting the Wahoo KICKR Core smart turbo trainer, and I understand it doesn’t come with a cassette. What cassette size should I get with the KICKR that best suits the bike? Do I also need to get a front wheel riser? Anything else (tools for installation etc?)

Many thanks!!!

@Ricky_John: You need the same type of seven speed cassette on the trainer you’ll use with Zwift. You can likely find that at your local bike store where you bought the bike.

The hubs on modern wheel-off trainers like the KICKR Core, out of the box, are set up for the most common cassette/shifter type on road bikes today, which is eleven speed. The number of cogs on the cassette matches the specs of the rear derailleur and the gear shifter up front. You’ll have a seven speed shifter and a seven speed derailleur.

Your seven speed cassette will slip onto the Core hub. The notches that make the cogs line up with each other are all backwards compatible. The one thing you’ll need to adjust is the spacer that goes on the hub first, so that the total width of the spacer plus cassette matches the hub width properly.

Here’s a YouTube video showing the concept and the adjustment that is needed for a seven speed cassette versus what’s needed for an eight, nine or ten speed cassette. Those 8, 9 and 10 speed cassettes will go straight onto the 11 speed direct drive trainer with a simple adapter. For 7 speed use, you need to add a second spacer, 4 or 4.5 MM, and file a couple of small indents in the aluminum spacer. Our local bike shop provided a 4mm spacer for a couple of dollars and we used a 7 speed triple on a 2014 Wahoo KICKR for a long time.


Thanks so much for the info. Really useful.

Do I just need to ask for (or find online) a ‘4mm hub spacer’?

I’m looking online for a 7 speed cassette, shimano, how do I need what ratio to go for, for example 11-28T. Is there something on my bikes cassette or chain that will tell me?

Cheers again!!!

That’s a good question. While any Shimano 7 speed cassette will fit on the hub, the number of teeth on the cogs will have a small but noticeable effect in Zwift. The smallest cog determines the fastest you can go in Zwift at a given cadence (such as turning over the crank set 90 to 100+ revolutions per minute). The largest cog determines how steep a grade you can climb at a reasonable cadence (such as 60+ RPM). Very low cadences (50, 40 …) uphill are harder on the knee, etc.

Zwift offsets that in a big way by having a “trainer difficulty” setting. By default, it’s set at 50%, so that the extreme 17-20%+ grades treat your knees, and your gearing, as if you were actually on 8.5-10%+ grades, and so on. You can adjust that anywhere from 0% to 100%, so you can effectively give yourself virtually very low gears, regardless of the physical cassette on your bike.

The easy answer is to get a cassette just like what’s on your wheel. One point there is that if the chain is the right length on your bike now, and your derailleur works properly across the range of the cassette, there will be no incompatibility with the cassette you put on the trainer. The chain, derailleur and the cassette need to be in “sync” with each other in that the chain needs to be the right length for everything to work properly from the big cog to the small cog. If too short you won’t get on the big cog, and if too long there won’t be tension for the small cog. Also, a much larger big cog could need a longer cage derailleur.

In most cases, there’s enough “slack” that a small change in the cassette won’t make a difference, say from 28 to 30 or maybe 32, or from 14 to 11. Off the shelf, they’re only available in certain combinations.

Sheldon Brown was a guru of bicycle mechanics. He died in 2008 but his web site has remained on line. You can read more about seven speed cassettes here: