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Thread: Educate me.

  1. #1
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    Educate me.

    Been single speed on my DJ for a while but am about to convert to BMX cranks and have a few questions. First, I have a 13T cog that came with the Gusset SS conversion kit, will this work with 1/8" chains? Also I've noticed some sprockets have a pretty wide "hub" to them, will this work with Profile cranks or will it throw the chain line off? Thanks for your help, there's just so many different options with chains, cogs, and sprockets and I'd like to minimize the amount of things I need to replace.

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    Since you're using a single-speed conversion, any chain-line issues can be solved by adding or subtracting spacers around the cog. The 1/8" chain should work on that cog.

    What size chainring are you using? A 28t with the 13t in the rear gives a 2.1:1 gear ratio. Personally, I run 2.5:1 which takes more torque to get going, but has a higher top-end.

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    I did many calculations to determine gear inches [ (Sprocket/Cog)x Wheel Dia. ] and based on the few different setups I had available to ride on I determined 56 to be a suitable target and if it's too low I've got a 12T I can use. I do mostly street riding and park so I don't need a high speed setup. Thanks for the info otherwise though. Just ordered an Odessy Burlington sprocket and white half link chain.

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    Quote Originally Posted by Johnny No.5 View Post
    Been single speed on my DJ for a while but am about to convert to BMX cranks and have a few questions. First, I have a 13T cog that came with the Gusset SS conversion kit, will this work with 1/8" chains? Also I've noticed some sprockets have a pretty wide "hub" to them, will this work with Profile cranks or will it throw the chain line off? Thanks for your help, there's just so many different options with chains, cogs, and sprockets and I'd like to minimize the amount of things I need to replace.
    It depends on the bottom bracket shell, but you may need a longer (6") spindle for the bmx cranks.


    see:

    Will a mid spindle fit in a euro BB?Will a mid spindle fit in a euro BB? - Pinkbike.com Forum

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    Damnit, this is getting expensive. $60 for a spindle, wonder how easy I'll be able to sell the stock one? Worst part is that I'll have to wait until I get the crank before I know if I'll need it. My frame (Identiti 666S) has a 68mm Euro MTB BB according to the frame specs.

    Edit: Just noticed that thread is regarding a 73mm BB shell and the stock spindle is 5 5/8, I may be safe right?
    Last edited by Johnny No.5; 02-22-2012 at 12:49 PM.

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    Quote Originally Posted by Johnny No.5 View Post
    Damnit, this is getting expensive. $60 for a spindle, wonder how easy I'll be able to sell the stock one? Worst part is that I'll have to wait until I get the crank before I know if I'll need it. My frame (Identiti 666S) has a 68mm Euro MTB BB according to the frame specs.

    Edit: Just noticed that thread is regarding a 73mm BB shell, I may be safe right?
    See the ridemonkey link inside the PINKBIKE link I posted...

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    So it may or may not work, eff'n eff!

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    Profile spindles only come in one length 5 5/8". It will work on your bike fine assuming you have a frame less than 50 years old. You will need a BMX BB kit that will include the spacers you need to align the chain. With a 13T cog you should get a 26T sprocket or more if want low speed

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    correction: 26 x 13 would be a standard park ratio. For easier pedaling you would want less teeth on the sprocket

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    Quote Originally Posted by Motl500 View Post
    Profile spindles only come in one length 5 5/8". It will work on your bike fine assuming you have a frame less than 50 years old. You will need a BMX BB kit that will include the spacers you need to align the chain. With a 13T cog you should get a 26T sprocket or more if want low speed
    I had to buy a 6 inch PROFILE spindle to use with a73mm wide euro BB shell on my MOB.
    Last edited by cmc4130; 02-27-2012 at 08:25 AM.

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    Quote Originally Posted by Motl500 View Post
    correction: 26 x 13 would be a standard park ratio. For easier pedaling you would want less teeth on the sprocket
    I know some people ride that, but if you agree that bmx'ers invented park riding then the standard gear inches is 55. So 26/12 is closer.

    2:1 is what xc SS riders frequently use.
    Last edited by cmc4130; 02-27-2012 at 08:24 AM.

  12. #12
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    Just going by eye I can pretty safely say I'll need the long spindle to have the arm clear the chainstay. No biggie, my roommate's son is on a BMX team that is sponsored by Profile so I can get it for cheap, it's already on the way actually. Thanks for the help guys. And I already got my 28T sprocket so we'll see but based on my experience with other bikes I'll be fine with that ratio.

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    Quote Originally Posted by Johnny No.5 View Post
    Just going by eye I can pretty safely say I'll need the long spindle to have the arm clear the chainstay. No biggie, my roommate's son is on a BMX team that is sponsored by Profile so I can get it for cheap, it's already on the way actually. Thanks for the help guys. And I already got my 28T sprocket so we'll see but based on my experience with other bikes I'll be fine with that ratio.
    Yep, 28/13 will be golden.

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    Plus it's gonna look sick to boot!!!

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    Quote Originally Posted by cmc4130 View Post
    I know some people ride that, but if you agree that bmx'ers invented park riding then the standard gear inches is 55. So 26/12 is closer.

    2:1 is what xc SS riders frequently use.
    Not sure if there'd be a huge difference to be honest, whatever you prefer I guess.

    I ride a 25 x 12 which comes stock on most modern (post '09) complete DJs. I have a friend who rides a 24 x 11 and about identical to mine so I assume the 26x13 would be also.

    check out the DJs on the bottom of this page: BMXmuseum.com Forums / 24" and 26" DJ/Urban bikes go here.

    i stand corrected Profile does make a 6" spindle btw.. good call

    cheers

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    26x13 gives a gear inch of 52, WAY too easy to pedal in my experience. My current 32x13 makes a GI of 64 which was way harder than I prefer. 56 seems to be my ideal GI, which is about what your 25x12 and my 28x13 provides.

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    Quote Originally Posted by Johnny No.5 View Post
    26x13 gives a gear inch of 52, WAY too easy to pedal in my experience. My current 32x13 makes a GI of 64 which was way harder than I prefer. 56 seems to be my ideal GI, which is about what your 25x12 and my 28x13 provides.
    right on... I still ride a 44x16 on my 20" so factor in the 26" wheels you're probably about right.

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    it is a race setup with the 180 arms though. Depends on what you're gonna ride, I don't pedal much on the jumps and hardly at all in the park. (depends on the size of the drop in) However I also use it for street and I wouldn't wanna go any higher having to climb hills that's for sure

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