Results 1 to 14 of 14
  1. #1
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030

    Need help on kids bike sizing

    Running into a dilemna.

    My son currently rides a 20" 2009 Trek MT60 ($20 on craigslist, $40 parts to fix) I got him little over a year ago for his Bday, he helped me to the work and he actually does much of the maintaining himself (i supervise/help as needed). Hes now 7 yrs old. Fork though crappy and heavy actually dampens well, previous owner left it outside and was too heavy for bike so forks got stuck partially compressed. So when I went through them and got them working good again, they are nice and soft for my boy. But look like hell with coils external and showing cause boots were shot.

    Bike fits decent, on outer crank arm holes (hate the fraking steel crankset BS) seat is almost up to the hieght above frame (scaled down of course) you see with us adults. TT length is a bit long had to get a shorter stem. FFs TT length is long on kids bikes,lol. Not sure if next year will be last season before he out grows it or not, thinking 2 seasons at least.

    Heres pick from April (kids race thing) before growth spurt that allowed me to move pedals out and seat up much more, 6.5 yrs old. He does ride the easy/green singletrack with me, does very well except uphill climbs( cant blame him for walking, swear his bike weighs almost as much as my 29er)



    OK now thats the backround info. Oh and new son being born any day, so this bike will be kept for him probably but could change with how much better kids bikes are getting.

    Now the issue. I am going to redo his bike over the winter. But cant decide how far to go. Could go all the way with converting to full disc, get some 24" air forks. Already worked out fabbing rear disc mount and having it welded to rear dropout. Base plan is paint job/decals, new hubs for at least 1x8, and tires. Have boots I can cover current springs up with so dont look ghetto anymore. Also crankset, plan to buy a proper sqaure taper crankset and shorten it for him. Dont like bmx cranks rather be able to use alivio (or if i get really froggy a m590) for 1x bashwich.

    But how long do I actually have before he'll need a 24"??? Is it worth doing the build fully (disc brakes,air forks, =$350ish plus work Im doing either way) ????

    Once this part is sorted, Ill start a build thread as plan to start on this build in about ~2 weeks, so gotta figure this out asap,lol.
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  2. #2
    Havok
    Reputation: Jordan300's Avatar
    Join Date
    Jul 2008
    Posts
    209
    I would keep him on the 20" as long as you can. It'll help with his bike handling skills.

  3. #3
    mtbr member
    Reputation: albertdc's Avatar
    Join Date
    Mar 2007
    Posts
    434

    Re: Need help on kids bike sizing

    I don't see the advantage to disc brakes in a bike that size. A good V-brake is plenty powerful to stop the kids. Even out here in Utah with steep and long hills! My son has never gotten fatigued from breaking or been unable to brake hard enough with rim v-brakes. He can skid the rear wheel on pavement at will, let alone on dirt. Disc brakes will likely be harder to modulate on dirt so will be touchier. Also, the inexpensive disc brakes don't have much increased stopping power anyway, from what I've felt, and tend to howl. You'll need a new wheel build if you go disc because you need the mounting tabs on the hubs.

    The fork, on the other hand, could make a huge difference if you are actually hitting trails with it. I imagine it would be a pound or 2 lighter and it would actually work. I'd consider that and save the disc brakes for a different bike when he is bigger.

    Sent from my SCH-I545 using Tapatalk 2

  4. #4
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030
    The disc brakes thing was a "cause I can" thing over anything else. It just made the choice of which hubs I go with since I am changing out the hubs either way at the very least so I can loose the freewheel and go 8 speed cassette. Not to mention hes a kid, he sees disc brakes on a bike he gets excited,lol.

    Doing some further "out of curiousity" reading, found that 26" bikes start at about 12-13" frame size. Means to me I could skip 24" by keeping him on a 20" as long as possible (and increasing gearing over time to build leg strength). Say this because 24" bikes come in a 12-13" frame anyway. At that frame size, to scale, would give him a similar bike feel to me on a 29er, more in the bike instead of on the bike.

    Damn I swear dealing with kids bikes is more complicated than for us lol cause gotta take into account growth and development when planning. VERY WORTH IT for my boys though!!!
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,491
    Quote Originally Posted by tigris99 View Post
    The disc brakes thing was a "cause I can" thing over anything else. It just made the choice of which hubs I go with since I am changing out the hubs either way at the very least so I can loose the freewheel and go 8 speed cassette. Not to mention hes a kid, he sees disc brakes on a bike he gets excited,lol.

    Doing some further "out of curiousity" reading, found that 26" bikes start at about 12-13" frame size. Means to me I could skip 24" by keeping him on a 20" as long as possible (and increasing gearing over time to build leg strength). Say this because 24" bikes come in a 12-13" frame anyway. At that frame size, to scale, would give him a similar bike feel to me on a 29er, more in the bike instead of on the bike.

    Damn I swear dealing with kids bikes is more complicated than for us lol cause gotta take into account growth and development when planning. VERY WORTH IT for my boys though!!!
    Be careful on skipping the 24. In theory it can be done, but it depends on the child and the type of riding. My son fit perfectly on his 24. I built a 26 XS framed bike with 24 inch wheels and it was just too big.
    He was too big for the 20 inch and needed to move up and I'm very happy we went with the 24 and sold the XS 26. That said, if he was just riding around on the street it would have worked, but jumping and learning general bike handling skills like manuals, bunny hoping etc... a 24 inch was just better.
    The frame size number mean nothing. Specialized 24 come in 11 or 13, and Marin frames tend to run small compared to Specialized.
    Last edited by TwoTone; 10-09-2013 at 04:08 AM.
    13 Lenz Lunchbox punkass

  6. #6
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030
    didnt know that, I knew the bigger tires would make things more difficult but a guess the couple inches on the TT and things like that would make the bike too big. Guess Ill make that call when the time comes. We ride XC so some of the more advanced stuff will be up to him if he wants to not something im pushing for though.

    What age/height did your son need to move up to 24" ? I did find several 24" bikes that are worth the money as long as hell be riding it more than 1-2 years,lol.


    Update: Found a sizing chart for kids to get an idea, oddly enough his inseam is just into 20" bikes..but hes been on this bike for a year. Guess he was a little small for it at the time but seems hes built same as me, longer torso shorter legs. Which would be why for me I ride 18-19" frames but im 6'1", guess hes going to be the same, which means I got 2-3 seasons before he needs to move up.
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    1,519
    For the money you're thinking of spending, hook that boy up with a decent 24" ride that you can upgrade over time. FWIW, I spent about 400 on a brandy new disc-ready Hardrock that's a really nice little bike. I also picked up a really sweet used 24" FSR Spec DH bike for about the same. You'll get your kid on better bike faster and cheaper if you buy something complete. Likely you'll be end up with a much better platform for upgrades too.

  8. #8
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030
    Really not spending that much, and forks im getting 24" air forks, so can move them up if i buy a bike without them when he is ready.

    Thing being he is DEFINATELY not big enough for a 24", barely big enough for his 20". He only just turned 7 lol.

    But being all the recommends for 24" when it comes times, and sizing info I read, got 2-3 years before hes ready for 24" so plenty of time to have funds for that. Really im not spending alot on this, dont need xt hubs and things like that,lol. Hubs i can find for around $30 a set, tires $30-40, and so on, $400 max including air forks for the build as im doing work myself from start to finish included adding the rear disc mount and paint.
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  9. #9
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    1,519
    Just saying - $400 buys a nice bike that's ready to roll. Your plan sounds like it could get pretty time consuming and expensive, and unless you've got a lot of past experience working with bikes (including building wheels), you're likely to run into some major hiccups along the way, and very likely end up with a bike that works nowhere near as nice as one you could buy off the shelf. Far as 7 being too young, my kid started riding a 24" for DH when he was 6. IMO, I'd just let him ride that bike the way it is for the short time it's going to take for him to grow into a 24" and put your effort into making that next bike really sweet instead.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,491
    Biggest problem with this thread- referencing age instead of height. When talking about kids and bikes age mean absolutely nothing.

    My son was 9 before moving to a 24inch bike, but he is short for his age.

    It's like saying I'm 45 what size should I ride?
    13 Lenz Lunchbox punkass

  11. #11
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030
    ya your right, age for bike doesnt really mean as much, like saying cause your 45 you belong on a _______ (fill in smart ass comment :P )

    based on inseam and chart I found, his inseam is about 22" = just into a 20" bike. not sure accuracy of that chart though.\

    New I was thinking about this the wrong way. Bike size needs to be done same as if it was me.

    So fix the question to make more sense:

    What height/inseam are we talking needing to go to 24" ?
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  12. #12
    mtbr member
    Reputation: tigris99's Avatar
    Join Date
    Aug 2012
    Posts
    1,030
    Oh and the thing of not spending so much on this bike starting to lean more and more that way. The build itself I can do, not a problem, but being not an expert serious time will be involved, maybe some wasted funds too.

    Maybe hub change rear for weight/gearing (so I can put 8s 12-34 cassette), still do the paint work, ditch the disc brake idea and all that goes with it. though i guess they do make the "megarange" freewheel to give him better low range. Instead get some speed 7 avid levers make his life easier. And tires and forks. Forks just because I can buy a non-air 24" when the time comes and just transfer the forks. Then at least hes on good forks from now on.

    Sound a bit more "sensible"?
    Trek Marlin 29er

    Like It, Love It, Want Some More Of It!

  13. #13
    mtbr member
    Reputation:
    Join Date
    Jul 2011
    Posts
    3,491
    Quote Originally Posted by tigris99 View Post
    Oh and the thing of not spending so much on this bike starting to lean more and more that way. The build itself I can do, not a problem, but being not an expert serious time will be involved, maybe some wasted funds too.

    Maybe hub change rear for weight/gearing (so I can put 8s 12-34 cassette), still do the paint work, ditch the disc brake idea and all that goes with it. though i guess they do make the "megarange" freewheel to give him better low range. Instead get some speed 7 avid levers make his life easier. And tires and forks. Forks just because I can buy a non-air 24" when the time comes and just transfer the forks. Then at least hes on good forks from now on.

    Sound a bit more "sensible"?
    That's what I'd do. I put a mega range on my daughters bike and it helped a lot along with trigger shifters.

    The only other suggestion I have is some shorter BMX cranks like Sinz if you're keeping 1x. For some reason it seems every kids bike comes with cranks that are too long.
    13 Lenz Lunchbox punkass

  14. #14
    mtbr member
    Reputation:
    Join Date
    May 2007
    Posts
    213
    My 6 year old is on a 24". He's now 137cm tall and the saddle is up a few cm from the bottom. The only issue with the fit is the tt gets longer as the saddle gets higher, so I'll have to turn his post around next time it rises. Not done much off road riding yet but he likes it when we do so I've ordered some pads for him ( pea gravel everywhere here that's spits you off, I think scabbing up every week may put him off for life!!)

    His bike has got cable discs on and he has no problem with modulating them, they work pretty well. It's also got a 3x9 set up but could probably lose the outer at present. I don't think I'd go 1x9 as it would limit the hill climbing when tired.

    My initial reaction would be to keep your son on the 20" until you know he'll fit on a 24" and just buy a whole new bike then, it'll be cheaper than chopping and changing. I did look at building a 24" but the offer I saw on my sons bike was half the price of what I figured I could build.

    Need help on kids bike sizing-image.jpg
    Rocky Mountain 2003 Hammer, 2009 Vertex 70 RSL, 2012 Element 970
    2012 Wilier Triestina Gran Turismo

Similar Threads

  1. What bike? xs womens frame or a 24in kids bike?
    By chimpwars in forum Families and Riding with Kids
    Replies: 12
    Last Post: 06-03-2014, 04:53 PM
  2. Anybody put an IGH on a kids' bike?
    By bolandjd in forum Families and Riding with Kids
    Replies: 1
    Last Post: 09-21-2012, 08:41 PM
  3. we've seen our kids on a bike, how about your
    By ol-crank in forum Eastern Canada
    Replies: 2
    Last Post: 06-18-2012, 09:56 AM
  4. wicked good deal on kids push bike kids woot
    By MattyBoyR6 in forum Arizona
    Replies: 2
    Last Post: 03-30-2011, 11:48 AM
  5. looking to buy a kids bike
    By jeffggardner in forum Arizona
    Replies: 0
    Last Post: 03-23-2011, 08:26 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •