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  1. #1
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    Sons pedals keep hitting the ground

    My son has a 20" Gt Stomper and has a problem with his pedals keep hitting the ground as soon as he leans the bike just a little bit. We switched from the huge tires that were on it down to 1.95 kenda small block 8s. We lost about 2 lbs off of the bike with the tire/tube change.

    Now we are having trouble with his pedals hitting the ground even on the slightest turn. No sure if we should look for smaller platform pedals, or go to a shorter crank. He is very small and just barely fits on the 20" frame, so he may benefit from the shorter crank. I don't want to put the other tires back on because it has helped to improve his confidence just in one ride.

    Any help or thoughts would be greatly appreciated.

  2. #2
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    If he is on the small side of fitting a 20", shorter cranks would likely benefit both the ground clearance and the overall ergonomic fit. For a frame of that size, cranks around 125-135mm are probably appropriate, what length cranks are on it now?
    Only other adjusment I can think of would be to tune the fork for a taller extended height, might help to raise the frame up a bit.

  3. #3
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    First he needs to learn not to have the lean side pedal down.

    My son is short and both his 20 inch, my daughters 20 inch and his 24 inch came with cranks I though were too long.

    Depending on the crank you can send them in to be shortened- what I did for my daughters Shred, or buy shortened cranks- what I did for my son's Marin.

    This guy does top quality work and a few people on here have bought cranks from him.

    SRAM S600 MTB crankarms Shortened

    Depending on the deals you fins some Sinz might end up cheaper. It's been over a year, but I think I paid $55 to shorten her cranks
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  4. #4
    gran jefe
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    A shorter crank is probably the best choice at this point.

  5. #5
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    I get the same thing when I do turns on my stock giant, until I learned a VIP trick to keep the inside pedal in the 12 o'clock position, and the outside pedal at the 6 o'clock position.

    There was a series of video "how-to's / tips" floating on these forums that showed that, and alot more, tips on bike riding. It was really informative.

  6. #6
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    It's really not an issue of him leaning while he is pedaling, it happens even on straight run sections of trails he needs to pedal through. He is 9, but about the size of a 6 year old. He can fit on his 16" bike still, but he is more confident on the 20" so we just adjusted the bike to fit him.

    They are just the stock cranks, not really sure on the length. I will measure them tomorrow morning when we go to ride. I don't think they are worth the money to shorten them, so I may just need to order a set of Sinz cranks. His legs definitely look like they are spinning in some huge circles for his legs so he may benefit from that as well.

  7. #7
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    See chart at the bottom of this page for one guy's take on lengths.
    Highpath Engineering : Crank shortening

  8. #8
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    Thanks for that link. It will me measure my son so I can get the right length or at least close to it.

  9. #9
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    Quote Originally Posted by cboyd1974 View Post
    It's really not an issue of him leaning while he is pedaling, it happens even on straight run sections of trails he needs to pedal through. He is 9, but about the size of a 6 year old. He can fit on his 16" bike still, but he is more confident on the 20" so we just adjusted the bike to fit him.

    They are just the stock cranks, not really sure on the length. I will measure them tomorrow morning when we go to ride. I don't think they are worth the money to shorten them, so I may just need to order a set of Sinz cranks. His legs definitely look like they are spinning in some huge circles for his legs so he may benefit from that as well.
    If that is the case, then yea, I would go with shorter cranks

  10. #10
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    My daughters 20" Hotrock had 152mm cranks on it. Her toe would hit the ground if she had her fit tipped forward at all. I got a deal on som 115mm Sinz cranks on the 'bay. I had to replace the bottom bracket also, because the stock one stuck the chainring out way too far.
    Good thing though. The bearings were toast. I'm amazed the stockers even spun. LOL

  11. #11
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    Are the cranks on the 16" shorter and could you swap them over?
    MTB:
    09 Stumpy Elite
    10 Enduro Pro Custom
    16" HotRock Custom

    Road:
    08 Jamis Xenith Comp
    13 Pinarello Dogma 65.1

  12. #12
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    I measured the way the link showed. It comes up with that he need 115mm cranks. His stock ones are 145mm and his 16" cranks will not swap over. Does anyone have any shorter cranks their kids have outgrown? I can't justify buying a $100 in parts that he will outgrown by the summer.

  13. #13
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    Sinz cranks are ~$45.

  14. #14
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    I havent found them cheaper than 59.99 plus shipping so far unless I go up to a. I also would need a new chainring and bolts since the one on his bike currently do not have a bolt on chain ring. The cheapest I found for everything was 94 plus shipping.

  15. #15
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    Quote Originally Posted by cboyd1974 View Post
    I havent found them cheaper than 59.99 plus shipping so far unless I go up to a. I also would need a new chainring and bolts since the one on his bike currently do not have a bolt on chain ring. The cheapest I found for everything was 94 plus shipping.
    Or get the stock ones shortened for $55
    13 Lenz Lunchbox punkass
    12 TallboyC Frame for Sale-Large

  16. #16
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    Quote Originally Posted by cboyd1974 View Post
    I havent found them cheaper than 59.99 plus shipping so far unless I go up to a. I also would need a new chainring and bolts since the one on his bike currently do not have a bolt on chain ring. The cheapest I found for everything was 94 plus shipping.
    Check out Danscomp and JR Bicycles (mtb sites are usually priced higher than BMX sites for the same stuff). JR has the cranks for 50 and rings for 18. Or you can always shorten the cranks yourself if money is an issue.

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