MTB frame sizing & geometry for a 12 year old
My 12 year old son has out grown his 24” cannondale.
We’ve discovered we both like Bike Park Wales blues 🙂
He’s currently 148cm (i’m 173cm & the Mrs is 152cm so he ain’t gonna be huge).
I’m looking at a Whyte 403 (26”/100mm) or a Commencal Meta HT Junior (27.5”120mm).
He’s already at the upper limit of Whytes recommended 125cm-152cm height range.
The Commencal height range is 140cm-160cm, so he’s bang in the middle.
But, looking at the geometry:
WHYTE: Reach = 383mm, ETT = 540mm, Stack = 539mm, Stand Over = 706mm
COMMENCAL: Reach = 366mm, ETT = 545mm, Stack = 584mm, Stand Over = 615mm(?)
So, the smaller Whyte is longer and lower & the Commencal is shorter & higher.
Does this make a mockery of the height guides? And will the Whyte actually “fit” him for more years than the Commencal.
I know the answer is “go and test ride” – but this is a paperwork exercise at present.
Any input appreciated (i’ve no idea how tall the post man was).Posted 3 months ago
Ask him which he prefers.
FWIW I’m 10cm taller than you and only happy on mountain bikes with 26″ and a short reach by todays standards (400mm to 425mm). I like all my bikes to ride like little dirtjumepers though. haven’t owned longer than a 55mm stem in over 20 years and back then it was only because I didn’t know any better.
sorry. my point is. depending on how his riding comes along. He may never outgrow the 26″ Whyte
The commencal seems very very (like far too) short for a 27.5″ wheeled bicycle. got a link to the full bike geometry?Posted 3 months ago
got a link to the full bike geometry?
its the “junior” size
Its only 17mm difference in the reach.Posted 3 months ago
Its a bit of a void in the market place, most of the kids bikes go up to 24″ and then you get to adult sizes. He’s an inbetweener at present. On paper the Whyte is bigger, but both companies gumpf points him to the Commencal by height. A local shop have the Whyte in so we’ll go & have a look.Posted 3 months agochiefgrooveguruMember
Another is to build one, maybe put 26″ wheels in a 650b frame…
Seems a good idea to me!
If you go with a small 27.5 hardtail frame and fork, shortest stem possible, fairly narrow bars, 26″ wheels and the shortest cranks you can find, then you can gradually upsize it with bigger rims, longer stem and cranks, wider bars. You’ve still only got 1-2 sizes of leeway before a bigger bike is required though.
I don’t generally trust sizing recommendations or standover numbers (the lowest ones tend to be measured just in front of the seat post – where you can’t stand because the saddle is in the way!)Posted 3 months agobrickwizardMember
My son is 11 and also 148cm. he is now riding a small framed Orbea mx27.5 with short stem and seat dropped down. He gets on great with it and his riding has came on leaps and bounds since going onto the bigger bike. We didn’t look at any charts or frame geo we just went to LBS and tried out a few bikes and took the advice of shop.Posted 3 months ago
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