Bike trainer for kids bike - need recommendations

Hello TR hive mind,

My 12-year old son is planning to enter his first season of bike racing this year. We bought him his first “race” bike, a Fuji Ace 24. It’s a sturdy little guy, 2x7 gearing, and should be a little rocket under him. That said, we can’t get him outside to train, as we’re in the middle of winter, and it’s snowy.

I’d like to get him hooked up to a trainer, but his bike doesn’t have the skewer type axle that I’m familiar with. My current smart trainer (Cyleops Magnus) is a wheel-on, with trainer skewer. Instead, his wheel is secured by hex nuts. (My apologies for not knowing all the technical terminology associated with bikes…yet!) See below:

What options do we have to get this guy on a trainer to get some work in?

Many thanks in advance!

Tacx sell axle adaptor nuts. Have to check if your son’s axle is the right thread diameter and pitch of course.

These do not fit all trainers though due to their shape, it would not fit on a Decathlon trainer I had. but obviously suited to at least (some) Tacx trainers.

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My Cycleops Fluid works with my kids bikes and it has the hex head bolt (no skewer).
The “clamp” fits around the bolt snugly

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Looking at the pics of the hex heads, I wonder if my KK would fit right over them. It comes with 2 sizes of attachments.

Interesting challenge. Wonder why they went with Hex nuts?

I’ll try to see if my Magnus fits over the hex heads. I haven’t measured as of yet. Calipers should give me this info pretty easily. I haven’t tried this option yet, because I didn’t want to get the hex stuck and risk damaging my trainer.

The TacX adapter looks promising - I am thinking we’ll get him his own trainer (mostly so I don’t have to disconnect my bike from the trainer all the time).

Many thanks for the brainstorming!

Ping Tacx and others they’ll let you know what products support what wheel size.

My 13yo sons bike has 650 wheels and I’ve got him on my Tacx Booster. Five minutes adjust to switch my bike for his.

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If you have access to an Ace Hardware, or similar store, go there and find their metric nut section. I suspect an Acorn Nut might work for your needs.


Take one of the existing axle nuts with you to confirm the proper size and thread pitch.

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YES! This looks promising! :+1::+1:

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I’ve used my son’s bike (a 20" trek) with an elite elastogel and it works fine with no extra additions (the trainer is like the elite qubo where the rider weight helps the tire make contact with the roller). Just my experience!

How about getting him a set of rollers?

One other thing to watch out for on the trainer is how far you can adjust the resistance unit upwards. My daughter has 24" wheels (540) and I had to move my unit (Elite wheel-on) up to its maximum to make reasonable resistance with the wheel.

I definitely considered rollers. However, he’s a new cyclist, and the challenge of getting on/off rollers outweighs the benefit at this point. I also considered the travel rollers that are available on the market, but the $400 price tag turned me off.

This is why I think a simple trainer will help fuel his interest without breaking the bank (if he loses interest).

Trainers can be pretty tedious however , unless you are going to get him Zwifting which might appeal to the video game driven youth culture.
Rollers would present him the challenge of mastering his bike handling and there’s no better time than when they are young to acquire this skill.
I am of the mindset to get kids mastering the art of riding and let the fitness take care of itself.

My son used a Cyclops Fluid 2 with his Pinarello Speedy (kids road bike), and it worked fine – Cyclops has an adapter thing for smaller diameter wheels.

I had him on my rollers for a little while, but neither he (nor his mom) was very happy with that.

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I raced BMX from age 5-15 very competitively. Had many roller sprint sessions. Always scared the crap out of me, but it definitely helped with bike handling.