Kids bike sizes

General cycling advice ( NOT technical ! )
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warey4life
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Kids bike sizes

Post by warey4life »

My youngest 12 nearly 13 yo daughter is now riding my older daughter's mountain bike which has 27.5" wheels. She is about 4'7 so going by Halfords size chart she should be riding a 24" wheel bike. She's stopped ringing her 24" bike because the seat post is at max height.
I have dropped the seat to its lowest and moved it forward a bit, and replaced the 80mm stem with 35mm stem, and she can ride it comfortably and confidently. She is going on a school cycling trip in France in July and we had to bring her bike to school today so that it could be checked for suitability and that it's safe to ride. The teacher has told her it's too big because it's got 27.5" wheels, despite her being able to touch the ground with both feet while sat on the saddle and being able to easily reach the handlebars.
In my opinion it's a small frame so wheel size is irrelevant. I've attached pic of seat tube size and a pic of her riding it.

I'll be interested to know everyone's opinions.

Thanks 😁
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warey4life
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Re: Kids bike sizes

Post by warey4life »

I thought I'd add, the teacher who said it's too big is an ICT teacher 😀
Last edited by warey4life on 14 May 2024, 8:52pm, edited 1 time in total.
rareposter
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Re: Kids bike sizes

Post by rareposter »

warey4life wrote: 14 May 2024, 7:59pm In my opinion it's a small frame so wheel size is irrelevant. I've attached pic of seat tube size and a pic of her riding it.
I'd say you're entirely correct - wheel size is irrelevant.

Kids that age race 700c (very small frame) road bikes with no issues. Bike geometry is pretty sorted these days so the idea that x age needs 20", y age needs 24", z age needs 26" etc is a bit outdated now.

Plus if you want to look at it another way, plenty of adults ride 16" (Brompton), 20" (Moulton and many cargo bikes, all BMXs) but no-one ever says "oh your bike is too small"!
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warey4life
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Re: Kids bike sizes

Post by warey4life »

rareposter wrote: 14 May 2024, 8:44pm
warey4life wrote: 14 May 2024, 7:59pm In my opinion it's a small frame so wheel size is irrelevant. I've attached pic of seat tube size and a pic of her riding it.
I'd say you're entirely correct - wheel size is irrelevant.

Kids that age race 700c (very small frame) road bikes with no issues. Bike geometry is pretty sorted these days so the idea that x age needs 20", y age needs 24", z age needs 26" etc is a bit outdated now.

Plus if you want to look at it another way, plenty of adults ride 16" (Brompton), 20" (Moulton and many cargo bikes, all BMXs) but no-one ever says "oh your bike is too small"!
Thanks you've made me feel better, and I concur about wheel size irrelevance, I was riding a BMX until I was 20, and I still have two 26ers today!
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531colin
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Re: Kids bike sizes

Post by 531colin »

Don’t ignore crank length.
Back in the day when BMX was fashionable, I used to see little kids riding “full-size” BMX bikes “because they can get both feet on the ground”.
Unfortunately their knees used to come up to their chest because the cranks were far too long.
I don’t think your daughter is as bad as that, but I think you should check that her knees don’t come above her hip joint, although it’s doubtful that she will do enough riding with a school group to do any damage.
From the photo her saddle can go up a bit
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warey4life
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Re: Kids bike sizes

Post by warey4life »

531colin wrote: 14 May 2024, 10:18pm Don’t ignore crank length.
Back in the day when BMX was fashionable, I used to see little kids riding “full-size” BMX bikes “because they can get both feet on the ground”.
Unfortunately their knees used to come up to their chest because the cranks were far too long.
I don’t think your daughter is as bad as that, but I think you should check that her knees don’t come above her hip joint, although it’s doubtful that she will do enough riding with a school group to do any damage.
From the photo her saddle can go up a bit
I did have the seat a bit higher but I was ganged up on by all the women of the house and forced to lower it.

I always say when your crank arm is at 6 o'clock your knee should be very slightly bent, that's how adjust my seat height anyway, unless I'm on my MTB and I need a bit more clearance.

The school cycling trip will cover 80 miles over 4 days so I'll take her out on a few more practice rides yet and check her knee and hip movements.

Thanks for the advice 👍
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pjclinch
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Re: Kids bike sizes

Post by pjclinch »

Wheel size on a kid's bike tends to be to fit the general geometry of the frame, i.e., a toddler's bike tends to have 14-16" wheels because that's what will fit in a frame for someone that small. Frames tend to get bigger in proportion to wheel size but it's not a same perfect linear relationship for all models and it doesn't need to be.

Looking at the pic of your daughter on her bike I'd say if there's any problem at all it's she's got the seat a bit low. Bikeability tends to have novice riders set up so they can get both feet down to give them a bit of extra confidence when stopping, but it actually makes a bike harder to pedal. Rule of thumb for saddle height (for a confident rider) is it's typically around an almost straight leg when sat on the seat with a heel on the pedal and the crank straight down at 6 o'clock (one doesn't pedal with the heel there, it's just to set an approximate saddle height, and you need a fairly flat shoe heel to do that).
Putting both feet down stopped and sat on the saddle is actually a bit rubbish to be honest. A rider is typically better off stopping as shown here...

At the cycling club I teach basic MTB skills in we have a 10 year old on a 27.5" wheel bike. She is taller than average for her age but not ridiculously so. Fits her fine because the frame is built for someone her height and 27.5" wheels. Looks to me to be a similar case for your daughter: on a bike that's fine for her.

Pete.
Often seen riding a bike around Dundee...
Jdsk
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Re: Kids bike sizes

Post by Jdsk »

Good advice above.
warey4life wrote: 14 May 2024, 10:47pm The school cycling trip will cover 80 miles over 4 days so I'll take her out on a few more practice rides yet and check her knee and hip movements.
Excellent.

Do you plan to explore getting out of the saddle at stops?

And how are you going to negotiate with the school?

Jonathan
Biospace
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Re: Kids bike sizes

Post by Biospace »

warey4life wrote: 14 May 2024, 8:01pm I thought I'd add, the teacher who said it's too big is an ICT teacher 😀
If there's a list of boxes to tick, I wonder if one states 27.5" wheel size is only for those over 1.5m or similar? If your daughter is comfortable on 20+ mile rides with you then a phone call to the teacher explaining this might could be all they need to hear.

I agree with the sentiments that the saddle could be raised a little, it would be worth checking again just before the trip given the rate of growth at that age. Just check the reach doesn't increase too much, I turned the handlebars round to bring my son's hands a little closer when he first rode a bicycle with full size wheels.

My children are around the same age and they decide on saddle height and reach to the bars - trial and error always works, it's time well spent letting them find out what happens when the riding position is too far from the optimum, with a little explanation from the spanner-man!
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warey4life
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Re: Kids bike sizes

Post by warey4life »

[/quote]
Excellent.

Do you plan to explore getting out of the saddle at stops?

And how are you going to negotiate with the school?

Jonathan
[/quote]

She's fine getting on and off, and we've been down some narrow country lanes and a short distance along the A38, the bike is no problem for her at all.

Thing is, the form the school sent out about the trip just says large road or mountain bike with large wheels, well we've ticked those boxes, but there's been an update today, I asked my daughter to ask if we need to get a smaller bike, and the reply was, it's too late now, her bike has already passed the safety checks and she's been cleared to ride it!?!
I think I'll go and have a word next week.
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warey4life
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Re: Kids bike sizes

Post by warey4life »

Biospace wrote: 15 May 2024, 1:15pm
warey4life wrote: 14 May 2024, 8:01pm I thought I'd add, the teacher who said it's too big is an ICT teacher 😀
If there's a list of boxes to tick, I wonder if one states 27.5" wheel size is only for those over 1.5m or similar? If your daughter is comfortable on 20+ mile rides with you then a phone call to the teacher explaining this might could be all they need to hear.

I agree with the sentiments that the saddle could be raised a little, it would be worth checking again just before the trip given the rate of growth at that age. Just check the reach doesn't increase too much, I turned the handlebars round to bring my son's hands a little closer when he first rode a bicycle with full size wheels.

My children are around the same age and they decide on saddle height and reach to the bars - trial and error always works, it's time well spent letting them find out what happens when the riding position is too far from the optimum, with a little explanation from the spanner-man!
This is all it says regarding bikes. I'm going to take this into school when I take her passport and GHIC card in.
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Biospace
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Re: Kids bike sizes

Post by Biospace »

The teacher has told her it's too big because it's got 27.5" wheels
I suppose this statement can be taken more than one way. If it was nothing more than their personal opinion - compared with seeing other children on their bikes your daughter looked a little small for hers and this was an off the cuff remark - then it's largely irrelevant. If it was said as in "it's too big for us to risk taking you on a school cycling trip" then this is something quite different. I suspect it's the former.

It would be great if more schools were organising this sort of trip, top marks to them for doing so.
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pjclinch
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Re: Kids bike sizes

Post by pjclinch »

warey4life wrote: 15 May 2024, 8:04pm
This is all it says regarding bikes. I'm going to take this into school when I take her passport and GHIC card in.
Any large wheel bike, eh...
So if I showed up on my Moulton (20" wheels" ) I'd be turned away 🙄

I do get the impression that the school has a rather poor understanding of the implications of different bicycle wheel sizes, though to be fair they're far from the only ones and as has been said they do deserve credit for organising the trip.

Pete.
Often seen riding a bike around Dundee...
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