Provided because I learnt a lot in the process

  1. My 5yo daughter has started growing out of her Apollo Petal with 14" wheels and an upright position typical of a child bike.
  2. Basic research and measurements lead to the conclusion she might be ok with a bike with either 16" or 18" wheels.
  3. I found a good deal on a used mountain bike with 18" wheels so we tried that first but it was clearly too large for her.
  4. I bought her a Decathlon B'TWIN 500 SPY HERO (although the sticker on hers says 900?!) on 16" wheels, still with a fairly upright position typical of a child bike.

The problem

I'm struggling to adjust it so that it's comfortable for her! Neither of us have the patience for more trial and error, so I'm hoping someone with a bit more experience can tell straight away what the issue is.

  1. A similar bike has a good product video where the actress seems to have the bike adjusted exactly right (link is to product website where video is included among photos, I don't think it's possible to link to video directly and I couldn't find it on youtube or similar)
  2. This is what my daughter looks like on her bike at the moment. Is she just still a little short for it, or is there something I can do to improve her fit?

Things to note:

  • The seat only has height adjustment (I can't tilt it or move it forwards/backwards)
  • I am reluctant to put the seat higher up. At the current height, her heels are slightly off the ground when sat.
  • The stem and handlebars are integrated so also only have height adjustment too. They are nearly at the highest setting. We tried having them lower and it was even more awkward, she was constantly standing up on the pedals.

1 Answer 1


Seat is too low. Problem with kids bikes as they have disproportinaly long cranks (Shes probably half your height, her legs are half the length of yours, yet he cranks are probably 145 vs your 175..... ). It works because kids are disproprtionaly flexible. I would probably try to raise the seat - just 5mm to start with... Thats much easier for me to say than you to do.

From experiance with my boys, you need to get to the point she will ride the bike. Don't worry about fit, its not important for it to be 'correct'. If shes over trying different settings, don't force it on her. Ask her what she wants, put it there and get her riding. If shes over trying new fit, and uncomfortable, give it a few weeks with no pressure. Make sure the rides are short, if she is uncomfortable and you head out on long rides, it will put her off.

As time goes on, you can suggest imporvements to try. if she does not like it (If shes like my boys, she won;t out of spite), put it back...

The goal here is simple - just keep her riding...

  • I'm not ignoring your answer, and I did lift the seat some 5 mm. But somehow we just haven't really happened to go for a ride since the ride in the video. She has not been asking to go but it is hard to tell if that's got anything to do with the faffing about with seats etc. Hopefully you can see why I'd like to test this out properly before upvoting/accepting.
    – pateksan
    Jul 9, 2020 at 1:36
  • I agree, the seat is way too low if she can almost put her heels on the ground. It’s unfortunately very common. As a rule of thumb the leg should be fully extended with the heel on the pedal in the 6 o'clock position. When you stop you should have to get in front of the saddle to reach the ground properly.
    – Michael
    Oct 25, 2020 at 8:29
  • 2
    Just as an observation, the fact that she got out of the saddle at the end to be able to pedal harder backs up that the saddle could be higher.
    – Wilskt
    Oct 25, 2020 at 8:42
  • 1
    @Michael that applies to performance cyclists and most adult cyclists, but I don't think it does with young children. They should be able to support themselves with their feet on the ground (not necessarily flat on the ground) while sitting on the saddle, for safety/practicality.
    – Wilskt
    Oct 25, 2020 at 8:44
  • 2
    @Michael one foot down and tilt the bike slightly to the side, swing your leg over the back? I don't know, I've never had to dismount a bike in the way you suggest. Children can work it out as they get older and more stable, but the average five year old needs to be able to safely touch the ground with the balls of both feet while sitting on the saddle.
    – Wilskt
    Oct 25, 2020 at 15:14

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