Editor’s note: we all want to see our kids riding their bikes, but getting them up and running can be a bit tough since trainers are made for adult bikes. Zwifter Maurice D. recently got in touch with us and asked if he could share a few tips from his experience getting his kids up and riding on Zwift. We found his advice quite useful (who knew a bike setup would work ok just freewheeling?)
Here’s all the info you should need to get your children going on Zwift, even if their bikes are very small.
In the past year our children (a girl and a boy) have both used their Zwift Kids account regularly for sessions ranging from 20 minutes to 1 hour. Styling the avatar is their most favorite business, next to riding the Repack Ridge MTB trail. In total, they managed to use Zwift for almost 15 hours and have reached level 7. Here’s how we did it!
First Step: Get a Free Account
First, you need to arrange a children’s account for Zwift first. Since these accounts are free and not difficult to set up, we’ll assume your child’s account is arranged and the bikes need to be set-up.
This is how the login screen looks when signed into a kids account:
Note: minimum weight is currently 45kg in Zwift settings, which is almost double the weight of our oldest child (8 years old). Luckily the ‘watts” can be manipulated by choosing a bigger wheel size combined with a dumb trainer (more on this later). Here below is the account summary:
Choosing a Trainer that Fits
We place all our children’s bikes on a Kinetic fluid trainer. The good thing is that one can find these relatively cheap secondhand nowadays, as many people have upgraded to smart trainers.
The minimum distance between the two bolts is 12 cm. The bikes we used on the trainer are about 14-15 cm in width. A Tacx Sirius, in contrast, has a minimum width of 16 cm which is a bit too wide for the small bikes.
Although I made a wooden interposer block to fit a small bike, using a dumb trainer that directly fits the width of small bikes is easier. The good news is there are plenty of dumb trainers which can fit small bikes.
Note: I’ve used this fluid trainer with (calibrated) power meter occasionally as a second portable setup. It’s pretty quiet for a wheel-on trainer and definitely not a bad alternative to use now and then. When bought 2nd hand it’s one of the cheapest dumb trainers with the relatively accurate inRIDE power sensor. See Shane Miller’s video about the inRIDE >
We also bought an extension kit to get the fluid brake to reach 16-18″ wheels. But on small bikes without gears, the brake power is too strong for small kids. I wouldn’t buy it again:
The front wheel riser needs a little increased height, therefore we use a small ramp. This ramp can also be used for the front wheel support when steering on the Watopia MTB section (without riser block):
The good thing that I’ve observed is that the rear axle with hex nuts fits directly into the Kinetic fluid trainer. It doesn’t fit 100% perfect, but good enough for children’s bike purpose.
Here’s a look at the small bike (16”) mounted on the trainer:
For 100% correct fit, it’s also possible to buy ‘Axle Nuts for non-Q/R wheels’, for example from Tacx (T1416). But I don’t think it’s really needed to mount a simple children’s bike on a trainer.
Below is an example of a girls’ single gear bike (20”) that we used on the trainer with Zwift. The rear axle has rounded hex nut which also fits onto the trainer. During the indoor session, the bicycle bags were still on the bike! (It’s too much work to remove the bags for a single Zwift session.)
A 20” bike wouldn’t touch the fluid brake when mounted on the turbo. However, as explained before the brake power is way too high for small kids (with single gear bike) and freewheel is the best working option (that we found).
Recently we’ve bought a 24″ Kona MTB. This bike has gears, and again it has hex nuts on the rear axle, which we fit directly on the trainer without too many worries. This 24” rear wheel can be braked with the standard Kinetic fluid brake, although it’s quite noisy as there is some knobby rubber tread on the rear tire. We still use the ANT+ speed sensor as it lets us play with the wheel size to get decent w/kg in-game (whilst minimum weight setting is 45kg).
Our daughter uses the MTB on the lowest gear and prefers lower cadences as the brake power is quite high for her. Ideally, she would prefer no brake applied. But my opinion is that she should learn how to ride with a brake applied. Maybe it’s related to low flywheel momentum? As low speed, small wheel size doesn’t create a lot of momentum in the flywheel.
Sensor Pairing
To get an ANT+ signal to the computer a simple speed sensor on the rear hub is used. As the rear hub is pretty big compared to quick release hubs an additional elastic band is used to hold the speed sensor. Note we don’t use the standard ANT+/Bluetooth Power sensor on the Kinetic. Just the speed sensor on the rear wheel.
For ANT+ sensor pairing we use a tire size of 650c, which basically boosts the watts they produce and combined with 45kg weight the in-game w/kg is in the 2-4 W/kg range.
You want to avoid getting flagged by Zwift (the cone of shame!) and wheel size is a variable to play with: smaller wheel will decrease w/kg and a bigger wheel size will increase their w/kg.
Once we use the 24” bike with fluid brake the wheel size could be chosen a bit bigger and for the small bike without any braking (freewheel) the wheel size could be chosen a bit smaller.
Although the small bikes freewheel, our children only spin-out once they do a sprint. During normal cycling, they prefer pretty normal cadences.
The pictures here below show the pairing of the trainer in Zwift.
Selecting another kind of dumb trainer will probably work as well, but never tried.
Phone Mount for Steering
To enable steering in the MTB section of Watopia one of our mobile phones is used in combination with a simple phone mount on the bicycle steer. Important: log out of the Companion app (settings – log out) and log back in again with child’s Zwift account. Otherwise the steering won’t work!
Note: we remove the front wheel riser block for steering, and the phone is not exactly in the middle of the bars, but that works fine for steering. Kudos to Zwift!
Other Considerations
A fan is used to get some fresh air flowing as well. Both our kids seem to like some fresh air from a fan (a Wahoo headwind fan is used on manual mode at lowest intensity setting).
As we ride the trainer as well once our kids are moving on Zwift, it’s pretty handy to have a wireless mouse connected to the computer running the kid’s Zwift session to choose some basic setup choices at the start of the session.
This morning, I had started a long ride already before breakfast. I took a quick break for eating together with the family and after breakfast, our son started to Zwift as well. (He had pointed out yesterday that he wants to ride together again, so I set it all up already before starting my ride.)
You can follow your child in the Companion App, which allows you to see where to go to if you would like to ride together. 
After we met on the track we were riding together for about 30 minutes. He needs to learn to keep pedaling continuously (its really on/off style sometimes). 
The kids really like that we play their music during the Zwift session.
We use a nice playlist with songs for children on the phone and sing together!
That makes the time fly!
Ride On!
My children’s bikes are atrached to a Minoura Mini-Mag turbo trainer.
This trainer is purpose fit for folding bicycles and worked well with my 14″ bikes without additional fitting required.
Hi, will it also fit a folding bike 9″ wheel? thank you
The Kinetic trainers come with end caps that work with the axle nuts when purchased new. You might want to reach out to them about replacements. We’ve been using the Kinetic trainers with the small wheel adapter since my kid was 4. The resistance was never an issue but the height was always a bit sketchy with getting on and off (which kids do a lot of). The rock and road is a bit worse in this regard than the regular version. While not nearly as cost effective, a wheel off smart trainer is definitely safer as it eliminates the… Read more »
Maurice – Thanks for taking the time to put this together. Great photos!
For really young kids who are fine freewheeling, you can just adjust a pair of training wheel so the rear wheel is off the ground. Then you can add a speed sensor.
I’ve also used this training wheel method when transitioning my kids from a strider bike to a bike with pedals. I let them ride stationary so they can focus on pedaling and build some muscle memory. Then I jump straight to riding without training wheels (so they don’t forget the balancing skills they’ve mastered on the strider bike.
Bkool dumb trainers work well with small wheels as they’re not fixed-height.
The Wahoo Kickr Core works as a charm for my son’s Frog 62 (24inch). You have to mount his 8 speed cassette first of course. Wish there was a bigger community for kids on Zwift with group rides, races and audio guided workouts. Would be really cool. Of course they would need to lower the 45kg minimum limit as well.
My son’s Norco 20″ mountain bike has 8 speed cassette as well. Fits just fine on the Flux S. I suppose for direct drives, wheel size don’t really matter as long as the frame clears the trainer and the appropriate cassette is installed.
Elite Aleno Smart is the simplest. Works with 20″ to 29″. No adapter needed. Cheap, less then 200 EUR.
Not so well calibrated. And it is not an interactive trainer. But who cares? The kids love it.
What sensor would I need to buy for my childs bike. I am totally new to all this. We have a standard cycleoops pro trainer. Our triathlon club has just started using Zwift for them to train but I have no idea what to buy to make this ride realistic for him.
At a minimum, I would recommend you need a speed sensor for the rear hub and a heart rate monitor for training (a cadence sensor would be optional but is nice to have for training). I prefer the wahoo fitness brand myself- their speed and cadence sensors have both bluetooth and ANT+ connectivity plus are easy to install. The TICKR heart rate monitor is bluetooth/ANT+ as well and everything integrates nicely with Zwift so that the speed from your trainer’s resistance can be converted to watts. There are lots of other options for speed and HR sensors like Garmin/Tacx, Polar,… Read more »
Can’t seem to get this to work well at all. My son is on a 24″ bike using a Garmin ANT+ speed sensor. We’re using a Cyclops Fluid trainer and no matter how hard he pedals or what wheel size I choose he rarely breaks 1 w/kg. I’ve also tightened the roller on the wheel a number of different ways and no luck their either.
Any ideas?
I have a Sirius soft gel, bought second hand but it doesn’t seem to adapt to a 660 wheel. The extension kits do 610-640 or 690-720. Does anyone have a solution?
This is exactly what I’ve been looking for. We’re starting our 6th week of Covid-19 lockdown here in the U.S. and I’ve been trying to find ways to keep our 7 year old active. She just learned to ride without training wheels last summer but since no streets have been closed off to car traffic in our area and the bike paths have been closed to prevent infection (plus most people aren’t wearing masks outdoors) I don’t feel comfortable letting her bike outdoors. I’ve read through this post several times, and as someone who is not a cyclist or zwift… Read more »
You need a separate speed sensor for the rear wheel. And then don’t tighten the wheel of your child’s bike against the resistance brake on the turbo trainer. If you do want your child to have some resistance then you need to set an even bigger wheel size 700cc 32mm, to make the speed a bit higher; still reading off the speed sensor on the rear wheel, not any sensor on the trainer. They may still be slow even then as they are pedalling against adults. I estimate my seven year old can produce between 30 to 50 watts, which… Read more »
Thanks James! Since writing my question I have acquired and added both the Wahoo speed & cadence sensors which helped some. Sounds like you’re recommending that I should now unpair the kinetic sensor–the app seems to be able to connect to all 3 sensors at once but perhaps that’s unproductive? She does want some resistance (otherwise I could have gone with the much cheaper training-wheels-in-shoes option) so I’ll also try changing to the bigger wheel size.
If you also set the trainer as a tacx on level 4 this will again increase the power from if you set it as a kurt kinetic rock and roll
As a further update in case anyone is interested. I have now fitted the small wheel kit to my kurt kinetic. This fits my 7 year old son’s 8 geared frog bike perfectly. I run it off the rear wheel sensor. He has 20 inch wheels but I select 700cc and 32 mm wheels on zwift as well as tacx trainer on level 4, as it one of the first to come up. My son averages about 130 to 200 watts on the game, as opposed to the estimated 25 to 30 he is actually producing. This means he moves… Read more »
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I am trying to figure out how to get my sons 20 inch bike on a trainer/Zwift. I am looking at a few used options, any chance any of you know if a bkool trainer would be able to fit a kids bike?.