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  1. #1
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    110mm bmx 3 piece crank? Gearing Recommendations?

    Can you get a 110 mm 3 piece crank?
    Trying to set up a bike for a very young and short 4 year old. 140mm seems too long and I'd like to get somewhere between his current 75mm crank and the one that's on a bike I just purchased for him. Also could use some recommendations/theories on gearing based on the following New Bike specs....

    16x1.75" Tires, 140mm crank, 43T(+/-) chainring (also have 36T), & 16T Freewheel

    His current bike that he's very comfortable on (although he has to peddle 90mph)
    12" tires, 75mm crank, 28T chainwheel, & 18T "freewheel".

    Remember, my goal is to keep him comfortable with the bike, so I'd like to get him geared right between these two bikes. He can get use to the longer cranks gradually is what I'm thinking. Currently I want him to be able to sit on the bike and still peddle without nailing himself in the jaw. Again, get comfortable with the new bike then start standing.

    Thanks for any help.

    Eddie

  2. #2
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    I've never seen anything shorter than 165, so I can't really help you.

  3. #3
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    Well, thanks for listening anyway... all threads that you've replied to!
    Eddie

  4. #4
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    how tall is he? what size is the bike?

  5. #5
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    Easternbikes-
    Thanks for the interest. I'll try and get some measuements tomorrow and get back to you.
    Thanks!
    Eddie

  6. #6
    Senior Member BMXTRIX's Avatar
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    There is one set of cranks that you will hear recommended by more pros than any other... All riders who have to buy their own cranks learn quickly that there is only one type of crank that is truly tried and tested for many, MANY years...

    PROFILE CRANKS

    You can order the crank arms in whatever length you would like, so 110mm is no problem at all. It will just take a while for them to come in. An extra couple of weeks I imagine.

    The cranks are very nice, and when your son outgrows them, you get new crank arms, not new cranks.

  7. #7
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    Easternbikes/BMXtrix-
    Thanks for the info on the cranks. BMX... I'll look into that particular brand.

    Measurements are
    JD is 39" tall with a 15 1/2" inseam (+/-)

    Bike wheelbase is approx 29.5" with standover of approx 16.5" and seatheight of 20.5 +/-

    Probably more than you needed but I'm still learning bikes (obviously).

    After looking at all this it appears that the micros are not a whole lot different in the dim departments.
    I THOUGHT when I put him on this bike the dims would be similar to some I found on the 03 pitboss... but apparently this is a bigger bike (longer wheelbase etc) and closer to micro dims.

    Still need to know if shortening the cranks and regearing makes sense to anyone for this young/short of a rider. Note he JUST turned 4 at the end of December.

  8. #8
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    also you might try mountain bike cranks.

  9. #9
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    Considering the fat that your kid just turned four, I don't even understand why you're going out of your way to buy him three-piece cranks in the first place. I ran one-piece cranks for years without any problems, and if they do break, they're goig to bend, not snap. Save yourself the money and stick with what you've got; considering the rate he's going to be growing at, it's pointless to be buying him a pair of expensive cranks so you can replace the arms every year for about fifty apiece, when you could simply be buying him a new one-piece until he's ready for the heavy duty stuff.

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    Beerman-
    The only reason I'm looking at 3 piece cranks is because I'm of the impression (don't know this for a fact but have been told I take "dust caps" off and remove cranks) that the pitboss bike I purchased has a 3 piece crank.

    If in fact it does, can I still put a one piece crank in it? I'm certainly not adverse to saving some money. So FWIW, I agree with your comments as long as I can use a 1 piece crank.

    Thanks.

  11. #11
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    Actually, you can't use one-piece cranks with that frame, because it uses a Euro bottom bracket as opposed to an American (the Euro BB has a smaller diameter than the American - not large enough for a one-piece to fit through).

    That's too bad, really, because to get new three-piece cranks (which would cost more than half of what that bike costs), you'd also need to get a new sprocket, because the Redline cranks have a built-in spider with a bolt-on chainring.

    Sorry.

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    Do What?
    So, BB means bottom bracket. Is the bottom bracket basically the hole in the bottom of the frame that the "pedals" rotate around in?

    Assuming I've got this correct, then you're saying I'm gonna have to buy both the 3 piece crank and a sprocket (don't really understand the sprocket problem you are describing).

    If the crank is 3 piece, why can't I just purchase different length arms to put on the middle part of the crank I already have? There aren't any 110mm crank arms out there that would work on my crank?

    Thanks!

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    The spindle (the "axle" of the crank) will be a different diameter and design from most other cranks, and the sprocket on the bike currently is built into the right-side crankarm, instead of being separate. And, yes, the bottom bracket refers to the tube that the crank spindle (and the bearings and cups) go through.

  14. #14
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    if you really want a 110mm crank yo would have to get a 1 peice crank.
    last minute breakfest at WaWa......$2
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  15. #15
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    Beerman-
    Quote Originally Posted by Beerman
    and the sprocket on the bike currently is built into the right-side crankarm, instead of being separate.
    If that's the case, then why does the sprocket have the ability to be removed (it has a definite bolt pattern and I got some extra sprockets with it).
    Aren't you saying that the sprocket is built on and therefor not removable?

    BMexican-
    I've already kinda hashed out the one piece crank thing in this thread and I believe, since the bike currently has a 3 piece crank and some other issues that others have pointed out (Beerman?), that I can't use a one piece on the bike. I would like to however find some shorter arms.
    Maybe you know something I don't so I'm all ears.

    Eddie

  16. #16
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    Quote Originally Posted by e.myers
    If that's the case, then why does the sprocket have the ability to be removed (it has a definite bolt pattern and I got some extra sprockets with it).
    Aren't you saying that the sprocket is built on and therefor not removable?
    I'm saying that the spider (the five-spoked piece) appears to be built into the crankarm (at least judging by the picture on the Redline site), and the part that you're referring to is the chainring. A normal sprocket is just one piece, that bolts directly onto the crankarm.

  17. #17
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    Gotcha!
    Now I understand how you're differentiating between the spider and the chainring.
    I apologize for my ignorance when it comes to bicycles (stuff with engines in them is a little different story
    Note that on this bike the arms are annodized but the spider is not. Anyway that I can know for certain whether the arms are removable from the spider?
    I'm gathering from what you are saying, that that MAY give me some more options on crank arm length, correct?
    In "normal" situations are you saying that the chainring bolts directly to the crank arm so that there is no need for a spider?
    Eddie

  18. #18
    Senior Member BMXTRIX's Avatar
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    You know what - check www.danscomp.com under 'cranks'. Then pick out a couple of the crank arms that have built in spiders. There are some by Dotec that are particularly inexpensive. Then call up Dans by phone and find out if you can custom order a specific length for those cranks. If you currently have a square spindle, then there is a good chance the crank arms you receive will fit that spindle and odds are also good that the current integrated spider is 110mm. If you need a new chainring, that is also available on that site.

    If you end up needing a new bottom bracket with a square spindle, once again call up Dans and order it specifically for the crank arms you receive from them. They have several bottom brackets in stock.

    FYI: The bottom bracket on your frame is the tube that is at the very bottom of the two triangles that your cranks go through... The hardware that your cranks ride on which is made up of a couple of bearings and some bearing cups is ALSO called a bottom bracket. This can be confusing to people, so I wanted you to know. If you look at www.danscomp.com you will see photos of crank arms similar to what you already have and you can also look at photos of what makes up a bottom bracket. Most of the bottom brackets sold on Dans also include a spindle which (technically) is actually the third piece of a set of 3-piece cranks.

    Most complete sets of 3-piece cranks include 2 crank arms and one spindle. They also, typically, include a bottom bracket. Check before you buy though and maybe do some measuring of the spindle inside the current cranks on the bike.

  19. #19
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    Thanks again BMX trix. I'll give them a call and see what I can find out.
    Eddie

  20. #20
    Senior Member BMXTRIX's Avatar
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    Eddie, make sure you do some looking around on their website first before you call them and write down products that you looked at and exactly what sizes you were hoping for. Have your entire conversation with them ready ahead of time. Do NOT expect a qualified technician on the phone, just an average joe schlubb order taker who really can only pull up basic information. You may need to dig deeper to get some technical help and it will help you tremendously if you sound like you know what you are looking for and exactly what you want.

  21. #21
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    go to www.danscomp.com for charts

  22. #22
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    Quote Originally Posted by e.myers
    Can you get a 110 mm 3 piece crank?
    Trying to set up a bike for a very young and short 4 year old. 140mm seems too long and I'd like to get somewhere between his current 75mm crank and the one that's on a bike I just purchased for him. Also could use some recommendations/theories on gearing based on the following New Bike specs....

    16x1.75" Tires, 140mm crank, 43T(+/-) chainring (also have 36T), & 16T Freewheel

    His current bike that he's very comfortable on (although he has to peddle 90mph)
    12" tires, 75mm crank, 28T chainwheel, & 18T "freewheel".

    Remember, my goal is to keep him comfortable with the bike, so I'd like to get him geared right between these two bikes. He can get use to the longer cranks gradually is what I'm thinking. Currently I want him to be able to sit on the bike and still peddle without nailing himself in the jaw. Again, get comfortable with the new bike then start standing.

    Thanks for any help.

    Eddie
    ride 28T 10T freewheel, less rotations then a "28T chainwheel, & 18T "freewheel"."

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