Cranks for 134 cm tall kid who races XCO & Marathon- Mtbr.com
Results 1 to 10 of 10
  1. #1
    mtbr member
    Reputation:
    Join Date
    Sep 2018
    Posts
    4

    Cranks for 134 cm tall kid who races XCO & Marathon

    Hello everyone.

    This is my first post here

    Just bought my kid, 9 years old, an Orbea Alma which came with SRAM X1 Eagle DUB Carbon Boost, 170mm. The cranks are too long for him.

    The saddle is set at maximum height, his leg is almost 100% extended when pedal is down.

    You can check the video below to see how his pedaling looks, in my opinion he bends the knee to much and when in climbing position he hits his chest. Also, he moves his knee to the side when pedal is up.



    I am looking for a 150 mm crankset that is not too heavy, I want to keep the bike around 9.5 kg.

    I have 2 options:

    https://www.federleicht-bike.com/en/...bel-150mm.html
    Very expensive, very light

    https://www.vpace.de/produkt/max-kinderkurbel/
    Not so expensive, not so light


    Any ideas? Any other brands that have kids products? I've looked for some aluminium cranks that could be cut up and found nothing suitable.

  2. #2
    Student of the Bike
    Reputation: CBaron's Avatar
    Join Date
    May 2004
    Posts
    773
    I just recently built up a hardtail for my 10 yr old. Based on some recommendations in this forum I went with the SR Suntour Zeron in 152mm. I was more concerned with accessibility and price than weight. But once I weighed everything, we did drop a few grams with the new cranks/BB.

    https://www.srsuntour.us/collections...nt=45338041742

    IMHO, based on that video, I'd say you sons seat needs to come up possibly 1/2 in higher with that setup. (but I'd prefer to see him actually riding it to make a better judgement)

    Cheers,
    CJB

  3. #3
    mtbr member
    Reputation:
    Join Date
    Sep 2018
    Posts
    4


    The one with the orange bike. Does this video helps? I suggest a 0.25 playback speed

    The bike is a little too big for him, but I plan to keep it for two years.

  4. #4
    Student of the Bike
    Reputation: CBaron's Avatar
    Join Date
    May 2004
    Posts
    773
    I take it back. After watching this video a few times, it looks like his saddle is much closer to where it needs to be. I'd still prefer to see him just casually pedaling by in front of me (in the street). But when you slow this video down and watch his form, it doesn't look like he's throwing his knees to the outside, and his leg extension at bottom of stroke is very decent. That being said, with the addition of shorter cranks, his seat will have to come up the corresponding change in crank length.

    Thanks
    CJB

  5. #5
    Moderator Moderator
    Reputation: 2melow's Avatar
    Join Date
    Jan 2004
    Posts
    2,793
    That's a lot of bike for a little dude! I'd go 140mm if it was my kid so he could sit and spin better.
    Front Range Forum Moderator

  6. #6
    mtbr member
    Reputation: ladljon's Avatar
    Join Date
    Nov 2011
    Posts
    391
    I'm 5ft=152.4cm very happy with 135mmCranks for 134 cm tall kid who races XCO & Marathon-dscn3367.jpg
    Tread killer....

  7. #7
    mtbr member
    Reputation:
    Join Date
    Sep 2018
    Posts
    4
    Quote Originally Posted by 2melow View Post
    That's a lot of bike for a little dude! I'd go 140mm if it was my kid so he could sit and spin better.
    Yes it is. But imagine he races against 9-10 years old kids with 29ers.

    Here is another video of him sprinting:


  8. #8
    mtbr member
    Reputation:
    Join Date
    Nov 2011
    Posts
    600
    If you're not sure on crank length, consider tossing on a square taper BB temporarily and experimenting with cheap cranks of different lengths before you go for something more expensive.

    I put $30 152mm Suntour cranks on an old Trek before spending more on Trailcraft cranks for my main mtb and another set of 155mm cranks for my bmx bike.

    At this point I'm all in on shorter cranks - it's a little easier on the knees, you get more ground clearance to avoid pedal strikes and it lets you run the seat higher leaving room for a bigger dropper post.

    I'll probably be sticking with 130-140mm cranks for my kids when they're that age.

  9. #9
    mtbr member
    Reputation: ladljon's Avatar
    Join Date
    Nov 2011
    Posts
    391
    He is wasting a lot of energy.....with shorter cranks, he could be pedaling a harder gear. I ride with my 29er friends all the time.....no trouble staying with them on 135mm cranks.
    Tread killer....

  10. #10
    turtles make me hot
    Reputation: NYrr496's Avatar
    Join Date
    Sep 2008
    Posts
    11,014
    I like turtles

Similar Threads

  1. Replies: 13
    Last Post: 10-03-2017, 12:41 PM
  2. Does anyone know of any telemetry from XCO races?
    By l'oiseau in forum XC Racing and Training
    Replies: 4
    Last Post: 08-11-2017, 11:01 PM
  3. Replies: 22
    Last Post: 12-24-2011, 04:47 PM
  4. Cross Check....58 cm or 60 cm???
    By endure26 in forum Surly
    Replies: 5
    Last Post: 12-24-2007, 12:22 AM
  5. 170 cm cranks killed my knees. Road Bike
    By The Goat Killer in forum Riding Passion
    Replies: 19
    Last Post: 11-11-2005, 08:57 AM

Members who have read this thread: 3

Posting Permissions

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

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.