Geometry and fit for 24" kids full suspension bike.- Mtbr.com
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  1. #1
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    Geometry and fit for 24" kids full suspension bike.

    So the little 20" has gone down a storm (He's been riding it for about 18 months now) I think a 24" wheeled full suspension bike is on the cards for his next ride. This time round, with him being older, and his riding coming on way too much, i think it's going to be more important that the bike as a whole has a bit more thought going into the geometry etc.. Not that the 20" didn't work, it appears to be fine, but would an 8yr old know a good, from a bad bike? I think not. I struggle and i've ridden quite a few!!!

    So where on earth do you start? I'd like this bike to last 2 years of riding, but with average growth rates that means the rider will have changed size approx 5". So what do you do about fit? am i just to take a few educated guesses? Copy whats already out there? (i doubt it, i've seen what some manufacturers produce) Make a scaled down version of what adults ride?

    Anybody with any experience (or none!) care to chip in, i'm all ears.

    I'm at a bit of a loss for a starting point, so to get me some practice on bikecad as much as anything else i've drawn up a few bikes. Numbers on the downtube are suspension travel in mm. Ive drawn them all with the same 35mm stem and bars, I've found it hard to get reliable info on whats actually fitted to some.

    Geometry and fit  for 24" kids full suspension bike.-commencal-clash.jpgGeometry and fit  for 24" kids full suspension bike.-kona-process.jpgGeometry and fit  for 24" kids full suspension bike.-marin-hawk-hill.jpgGeometry and fit  for 24" kids full suspension bike.-norco-fluid-24.jpgGeometry and fit  for 24" kids full suspension bike.-propain-yuma.jpgGeometry and fit  for 24" kids full suspension bike.-transition-ripcord.jpg

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    I'm new to Bikecad, can anybody tell me why i have a random blue line starting at my BB?

  3. #3
    pvd
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    Full suspension is generally a terrible choice for a small kid. Better to get larger wheels in place. I'd even go full rigid with a fat front tire. Waaaaay faster and easier.

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    Afore mentioned lucky child (not my son but my mates) will already have a Hardtail, and a BMX as well probably! I sort of agree that suspension maybe isnt ideal, but, the 20 wheeled full suss works so well under him. And more importantly he just always wants to ride his little 20 full suss. So in that respect its an unmeasurable success. He just loves to get in the woods and shred his little suspension bike, whilst bigger kids (us!) ride our full suspension bikes. So maybe faster, maybe easier without suspension. But that wont matter if hes not loving riding it, and not out riding. And of course my mate likes to spoil him!

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    pvd
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    He's not spoiling the kid. He's hobbling him. Saw a kid out on the trail the other day on an uber-fs kid bike. It was killing him. What a shame. It's too bad your bros don't know about bike setup.

    I've written on the subject a bit. Still looking for a new grom to build for. Maybe by spring.

    Again, your ability to use CAD is really holding you back with bike design. You're going to need to put some real work in if you want to made any decent bikes.

    Kids bikes | Peter Verdone Designs


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    Quote Originally Posted by pvd View Post
    He's not spoiling the kid. He's hobbling him. Saw a kid out on the trail the other day on an uber-fs kid bike. It was killing him. What a shame. It's too bad your bros don't know about bike setup.

    I've written on the subject a bit. Still looking for a new grom to build for. Maybe by spring.

    Again, your ability to use CAD is really holding you back with bike design. You're going to need to put some real work in if you want to made any decent bikes.
    We are all entitled to our opinions, I get it, you dont think kids should have full suspension. However, it would be very dull in this world if we all were the same.

    Still looking for a new grom to build for Sorry, I dont know what you mean?

    Instead of always being so negative, Id love it if you were to tell me more to help me with what I could be gaining from using CAD more. Like I said in my post. Im new to it.

    Its too bad your bros dont know bike set-up Again, Im starting to sound stupid, but I dont know what you are getting at?

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    Sorry, on my phone I missed you had a link and an image.

    Can I ask why youve got such short stays? The rear seems exceptionally short in comparison to the front? This is only going off what seems average in an adult bike?

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    Quote Originally Posted by pvd View Post
    ... I'd even go full rigid with a fat front tire....
    we all know. you never shut up about it. go crawl back into your hole...


  9. #9
    pvd
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    Quote Originally Posted by Cord View Post
    The rear seems exceptionally short in comparison to the front?
    The proportions on this bike are in line with how an adult rider will use a mountain bike. If I were modeling an exact fit it may change slightly. If you are looking at commercial bikes, you're making a mistake. Production bicycles are generally terrible geometrically, especially kids bike.

    I'm trying to help you here. You need to listen.

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    Quote Originally Posted by pvd View Post
    You need to listen.
    I did listen, and then read, hence why i asked about the short rear end?

    If i scale up your 24" using what looks like end of bars to seattube centre line as a base (550 dim'n on your drawing) which on my 27.5" bike is 615. this gives me ratio 1:1.116


    Using 1:1.116 :-
    front centre scales from 663 to 739, my actual is 734mm.
    Horizontals handlebars from BB 388 to 433, my actual is 432mm.
    both have 65 head angle
    your seat angle is effective 74.5 mine is 74

    So far these numbers all seem to stack up, and my bike looks very much like a scaled up version of yours.
    However, your chain stays scale from 345 to 385mm. Mine are actually 435, thats a fair old difference.

    I've ridden hardtails with short chainstays and really didn't get on with them, (this may have been the whole bike, not just the short rear) felt skittish and uncontrolable on the brakes, not stable at speed, and as if i was actually sat on the rear axle when trying to climb. Hence why i asked why you chose such a short rear, what do you think it adds to the bike?

    For the record the short chainstay bikes i rode were a Stanton switchback at i think 410mm and a custom built thing that i think was 405 or something. Also an Intense spyder full suss which i think was 415mm.

    Just looking at your page on kids bikes, i presume the gold hardtail is 1 of your frames? That clearly doesn't have 345mm chainstays, they look more like 400?? Why the longer stays on that bike?

  11. #11
    pvd
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    The Podracer is a very old build. I don't build like that anymore. Everything has changed.

    I suggest you stop reading about bike design in PinkBike and do more measurements and drawing. Study the subject. You're really not in a place to see the points as your drawings aren't very good yet.

    https://www.peterverdone.com/bits-of...-framebuilder/

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    Are you a politician? You should be, you are amazing at not answering questions! Quite a skill you have there.

    Would you care to enlighten me on what is wrong with my drawings?

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    Uggghhh. I hate people who make stupid comments about what others build their kids. We get it, you dont want to spent money on your kid, good for you.

    Anyway, Im no designer but my 8yo has gone through a few fs bikes. Hes currently on a Rocky Mountain reaper with 26 wheels. I would look at that geometry and the suspension is the most active for light light riders from the other ones weve tried.




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    Geometry and fit  for 24" kids full suspension bike.-img_5447.jpg

    This is my kids build, I can take actual measurements for you, the RM site has some wrong


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    Thanks, I appreciate an actual positive response to the topic.

    I think 26" is just going to be too big, but i'll have a look at the site. If the geometry makes no sense i shall ask. I see the seat is fully down, is this for descending, or just to reach the floor? If it's the latter, then are the handlebars not to high with it being so tall at the front? Approx how tall is he?

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    the 24" reaper has fairly long chainstays (to accommodate the swap to 26" wheels), which makes it a bit tough for people of wee stature to pick up the front. i'd build the rear relatively tight (24 specific) and design around a 26" fork (because functional 24's are relatively nonexistent), so he can swap to a mullet configuration when he gets a bit bigger.

    also: it may be a regional thing (north shore / whistler), but i see heaps of wee rippers on small wheel fs bikes that in no doubt benefit from that bit of rear cush. i've certainly witnessed it w/ my kids. obviously wasn't always the case, but there's actually a pretty decent selection of fairly well sorted full squish options these days.

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    When I first started I did wonder about future proofing and making the rear 26 capable. As you said, that will make the rear too long. Im not going down that road. Axle to crown on 100mm travel 26 forks isnt to big, thats what I think Ill be using.

    Im with you on small full suss bikes. The 20 I made with really light damping in the rear shock does work, especially now hes put a bit of weight on. In fact, he rips on it.

  18. #18
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    Geometry and fit for 24" kids full suspension bike.

    Quote Originally Posted by Cord View Post
    Thanks, I appreciate an actual positive response to the topic.

    I think 26" is just going to be too big, but i'll have a look at the site. If the geometry makes no sense i shall ask. I see the seat is fully down, is this for descending, or just to reach the floor? If it's the latter, then are the handlebars not to high with it being so tall at the front? Approx how tall is he?
    The seat is slammed for descending. My son is 51 tall. For climbing the seat post is about 5ish extended. Fork is set at 140mm from the stock 120. My thinking on 26 wheels is that itll help him plow through stuff and get rolling faster like 29 wheels do for me. Also the tire selection is soooo much better than 24 tires.


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    Quote Originally Posted by pvd View Post
    You're really not in a place to see the points as your drawings aren't very good yet.

    https://www.peterverdone.com/bits-of...-framebuilder/

    If you are going to tell people that their work isnt up to scratch, then you should first make sure that you yourself are whiter than white. I opened the link and was confronted with this abomination of a drawing. Geometry and fit  for 24" kids full suspension bike.-screen-shot-2019-10-15-17.10.22.jpg

    Really, i mean REALLY? Jesus wept, i'd done better in high school, and that was before i started tech drawing. I don't even know where to start, but i'll try anyway as you clearly need some help, and unlike you, i'm willing to actually tell you something that may help next time you do a drawing.

    Font size is clearly to large, not just from an aesthetic point, but from a technical 1, it clashes with several other dimension and extension lines.

    All extension lines should have a gap between themselves and the component

    Angle dimension crosses the dimension line
    Angle dimension line does not have arrows

    Dimensions should ideally all be read from one direction, 2 if that is not possible 699 or 996 ? which leads to the next point

    Avoid confusion at all costs, the handlebar end / stem centre who know what all those lines are pointing at. In my country thats technically known as " a dogs dinner"

    Centre lines of axis should be dot dash not continuos

    Circle centres should be a small cross, with a gap before line continues

    Multiple dimensions from same extension line should be inline e.g. 671, 513, 438

    Some systems allow colour, this is clearly a case where is should have been used, extension and dimension lines need differentiating from component.

    Your welcome.

    Quote Originally Posted by pvd View Post
    It's too bad your bros don't know about bike setup.
    I didn't quite catch the derisive undertones when i read this first time.

    My "Bro" has been heavily involved in the design and more specifically testing and feedback of all the Nukeproof models.

    So far they've been a bit of a failure

    3 EWS World titles
    EWS under 21 world title
    Irish National championship
    2nd 4cross world championship
    4th 4cross world championship
    6th DH world championship
    2nd masters EWS

    That was just the Mega.

    Multiple top10 finishes and wins at UCI world cup
    3rd junior overall UCI world cup

    for the DH bike.

    I can't be bothered to list the success of the various Intense bikes he's been involved in.

    And he personally has a set of rainbow stripes for DH.

    I'll be damn sure to tell my "bro" he doesn't know anything at all about bike set up.

    Thank you soooooooo much for cheering me up today, it is always a pleasure to converse with you.

    Back to the sunbject at hand, could you now tell me why you changed from long to short chainstays on your 24" kids bikes? I am GENUINELY intrigued as to why.

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    Hi Cord

    I meant to bring my CAD file into work to get you a drawing of the small 26" hardtails I did, but I forgot.... Will try and remember tomorrow but currently a bit flat out on work stuff. Can also get the height / inside leg etc of the current user if you want to get a benchmark and look at a photo of their riding position.

    We did a family mtb holiday in Verbier last summer. It was really interesting watching kids in the bikepark - suspension definitely saved some from getting spat if they didn't land things perfectly. And we both know the type of riding that your "customer" will do :-)

    My kids definitely benefited from the move to short travel 26" forks asap - way more use than a big tyre (they were doing techy XC stuff with us from an early age as mum was an ex-elite racer).

    I spoke to Craig about heat treatment. It was a place in the Midlands - we think alloyheat.co.uk

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    Quote Originally Posted by Loadsled View Post
    The seat is slammed for descending. My son is 51 tall. For climbing the seat post is about 5ish extended. Fork is set at 140mm from the stock 120. My thinking on 26 wheels is that itll help him plow through stuff and get rolling faster like 29 wheels do for me. Also the tire selection is soooo much better than 24 tires.


    Sent from my iPhone using Tapatalk

    Thanks for the sizes, good to get some data. Tyre selection, what a brain fart, i never even considered that.

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    Quote Originally Posted by pvd View Post
    You're really not in a place to see the points as your drawings aren't very good yet.

    https://www.peterverdone.com/bits-of...-framebuilder/

    If you are going to tell people that their work isnt up to scratch, then you should first make sure that you yourself are whiter than white. I opened the link and was confronted with this abomination of a drawing. Click image for larger version. 

Name:	Screen Shot 2019-10-15 at 17.10.22.jpg 
Views:	31 
Size:	88.7 KB 
ID:	1286893

    Really, i mean REALLY? Jesus wept, i'd done better in high school, and that was before i started tech drawing. I don't even know where to start, but i'll try anyway as you clearly need some help, and unlike you, i'm willing to actually tell you something that may help next time you do a drawing.

    Font size is clearly to large, not just from an aesthetic point, but from a technical 1, it clashes with several other dimension and extension lines.

    All extension lines should have a gap between themselves and the component

    Angle dimension crosses the dimension line
    Angle dimension line does not have arrows

    Dimensions should ideally all be read from one direction, 2 if that is not possible 699 or 996 ? which leads to the next point

    Avoid confusion at all costs, the handlebar end / stem centre who know what all those lines are pointing at. In my country thats technically known as " a dogs dinner"

    Centre lines of axis should be dot dash not continuos

    Circle centres should be a small cross, with a gap before line continues

    Multiple dimensions from same extension line should be inline e.g. 671, 513, 438

    Some systems allow colour, this is clearly a case where is should have been used, extension and dimension lines need differentiating from component.

    Your welcome.

    Quote Originally Posted by pvd View Post
    It's too bad your bros don't know about bike setup.
    I didn't quite catch the derisive undertones when i read this first time.

    My "Bro" has been heavily involved in the design and more specifically testing and feedback of all the Nukeproof models.

    So far they've been a bit of a failure

    3 EWS World titles
    EWS under 21 world title
    Irish National championship
    2nd 4cross world championship
    4th 4cross world championship
    6th DH world championship
    2nd masters EWS

    That was just the Mega.

    Multiple top10 finishes and wins at UCI world cup
    3rd junior overall UCI world cup

    for the DH bike.

    I can't be bothered to list the success of the various Intense bikes he's been involved in.

    And he personally has a set of rainbow stripes for DH.

    I'll be damn sure to tell my "bro" he doesn't know anything at all about bike set up.

    Thank you soooooooo much for cheering me up today, it is always a pleasure to converse with you.

    Back to the sunbject at hand, could you now tell me why you changed from long to short chainstays on your 24" kids bikes? I am GENUINELY intrigued as to why.

  23. #23
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    Quote Originally Posted by mickuk View Post
    Hi Cord

    I meant to bring my CAD file into work to get you a drawing of the small 26" hardtails I did, but I forgot.... Will try and remember tomorrow but currently a bit flat out on work stuff. Can also get the height / inside leg etc of the current user if you want to get a benchmark and look at a photo of their riding position.

    We did a family mtb holiday in Verbier last summer. It was really interesting watching kids in the bikepark - suspension definitely saved some from getting spat if they didn't land things perfectly. And we both know the type of riding that your "customer" will do :-)

    My kids definitely benefited from the move to short travel 26" forks asap - way more use than a big tyre (they were doing techy XC stuff with us from an early age as mum was an ex-elite racer).

    I spoke to Craig about heat treatment. It was a place in the Midlands - we think alloyheat.co.uk
    No rush at all, work always gets in the way of real life! Height and inside leg would be good. The more data the better!

    Am definitely with you on the decent suspension over a fat tyre any day of the week Like you, this bike is going to get ridden, probably quite hard, on exactly that type of terrain. Thanks for having a word with Craig, I'll get in touch with them and see whats what.

    Cheers.

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    Quote Originally Posted by pvd View Post
    He's not spoiling the kid. He's hobbling him. Saw a kid out on the trail the other day on an uber-fs kid bike. It was killing him. What a shame. It's too bad your bros don't know about bike setup.

    I've written on the subject a bit. Still looking for a new grom to build for. Maybe by spring.

    Again, your ability to use CAD is really holding you back with bike design. You're going to need to put some real work in if you want to made any decent bikes.

    Kids bikes | Peter Verdone Designs

    Little bikes are cool.

    And seeing someone working in 2D calling out people on their CAD skillz?!?
    Now THAT is frigging funny!

    2D is for dabblers and old dudes that got left behind by technology a couple decades ago. Using a computer like a pencil is silly.
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  25. #25
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    Quote Originally Posted by slapheadmofo View Post
    Little bikes are cool.

    And seeing someone working in 2D calling out people on their CAD skillz?!?
    Now THAT is frigging funny!

    2D is for dabblers and old dudes that got left behind by technology a couple decades ago. Using a computer like a pencil is silly.

    The little 20 I made turned out super cool, hopefully the 24 will too. As for the rest .......... LOLzzzzzzzzz

  26. #26
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    Quote Originally Posted by slapheadmofo View Post
    And seeing someone working in 2D calling out people on their CAD skillz?!?
    Now THAT is frigging funny!

    2D is for dabblers and old dudes that got left behind by technology a couple decades ago. Using a computer like a pencil is silly.
    You should click around before you call people out.

    PVD Sopwith Camel | Peter Verdone Designs

    Plenty of 3d on Peter's site on his current stuff.

  27. #27
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    Quote Originally Posted by shirk View Post
    You should click around before you call people out.

    PVD Sopwith Camel | Peter Verdone Designs

    Plenty of 3d on Peter's site on his current stuff.
    He probably should've picked a better example then.
    I have no interest in looking at his site; read enough of his posts here to not care.
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  28. #28
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    Quote Originally Posted by slapheadmofo View Post
    I have no interest in looking at his site; read enough of his posts here to not care.
    truth...


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    Well at least my own personal negative aura seems to have disappeared.

    Been looking at 24 tyre availability. Definitely not ideal. Having a think about 26 wheels, but I just dont think theyll work.

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    24" dhf exo's are out there.

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    yeah, maxxis makes a grip of 24" mtb tires...


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    Plenty places with 24 listed. Not many with any actual stock, Ive only had a quick search tho. Am sure an in depth nibble will turn some up.

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