Mountain Bike Swingarm Mod
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  1. #1
    Join Date
    Dec 2015
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    Southeast,Florida
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    Mountain Bike Swingarm Mod

    I have a Mongoose 29" mountain bike Ledge 3.1 model I think.Thing came stock with 2.10" wide tires and tire to swingarm clearance was .050" each side.Rubbed swingarm in a few spots when new but I trimmed the tire and managed to mount the wheel straight.Replaced stock tread with new 2.10" wide and the issue comes up again.Time for some rat rod style modding.
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    Rear jig to hold arms,some 2 x 4 alum tube with plates on the side tapped for 3/8-16 bolts to simulate axle width.Sorry for limited view.
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    Turned down some alum tube for front jig;offending parts removed.Kept some of the original tube on pivot cylinder knowing that stainless would be used and wanting to keep distortion to a minimum
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    Keeping in mind sprocket to swingarm clearance,scrap solid SS316L replacement and welded up.
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    1/4" to spare each side of tire now
    Used 316L filler for this project ,308 filler would have been a better choice since the swingarm was probably chromoly.But didn't have a small enough size available I felt comfortable using.

    Would also like to add this bike was a Walmart special,something I think maybe Mongoose lent their name to but not much in the way of engineering.Having owned a Mongoose 20" bmx bike in the mid 70's this one from 2012 has no comparison to it.
    Imagination is more important than knowledge. - Albert Einstein

    I wanted a mission and for my sins, they gave me one. - Captain Benjamin L. Willard

  2. #2
    Join Date
    Oct 2011
    Location
    Jacksonville Florida
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    2,359

    Re: Mountain Bike Swingarm Mod

    So is that solid bar that you welded to the tube? Why didn't you just get a tire that fits?
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  3. #3
    Join Date
    Dec 2015
    Location
    Southeast,Florida
    Posts
    48

    Re: Mountain Bike Swingarm Mod

    Quote Originally Posted by SquirmyPug View Post
    So is that solid bar that you welded to the tube? Why didn't you just get a tire that fits?
    Yes solid bar.Too lazy or whatever to bother with bending and cutting tube to shape.
    This is a 29" mountain bike with the smallest width tire available 1.95" and that would only add 1/10 of an inch more clearance per side.
    Imagination is more important than knowledge. - Albert Einstein

    I wanted a mission and for my sins, they gave me one. - Captain Benjamin L. Willard

  4. #4
    Join Date
    Apr 2016
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    CA
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    Re: Mountain Bike Swingarm Mod

    I like the use of the jigging.
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  5. #5
    Join Date
    Mar 2011
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    Bilbao, Spain
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    625

    Re: Mountain Bike Swingarm Mod

    I am all for function before looks... but in this particular case, I am not that sure about how that assembly is going to FUNCTION. Try it out, let us know. Wear a helmet just in case.

    Mikel

  6. #6
    Join Date
    Dec 2015
    Location
    Southeast,Florida
    Posts
    48

    Re: Mountain Bike Swingarm Mod

    Quote Originally Posted by N2 Welding View Post
    I like the use of the jigging.
    It was a necessity,without it a lot of time consuming checks of angles and measurements.

    Quote Originally Posted by Mikel_24 View Post
    I am all for function before looks... but in this particular case, I am not that sure about how that assembly is going to FUNCTION. Try it out, let us know. Wear a helmet just in case.

    Mikel
    Works great,wheel lines up true,plenty of sidewall to swingarm space and swingarm has less flex than before.No it won't win any beauty contests......well maybe for originality.This bike is not really used for mountains or hills I just like the rear suspension for jumping curbs etc. saves the rim and frame.I'll keep an eye on it though,as I stated non use of 308L filler on a Chromoly Steel(or any steel for that matter)parent metal to stainless steel parent metal is susceptible to hot cracking on the steel side of the weld.At least that's what the books tell me.

    As for a helmet I appreciate the concern but I have never worn one while riding a bicycle.Old school here,I remember back when some of BMX tracks didn't even require a participant to wear a helmet.Some states it is mandatory on public roads.Just can't ride a bike in Florida state parks without one

    Motorcycles a different story I consider it a must have almost like shoes.
    Imagination is more important than knowledge. - Albert Einstein

    I wanted a mission and for my sins, they gave me one. - Captain Benjamin L. Willard

  7. #7
    Join Date
    Jul 2011
    Location
    Western Washington
    Posts
    3,667

    Re: Mountain Bike Swingarm Mod

    a bicycle may be slower than a motor bike. but you falling down isn't the biggest concern as to why a helmet is a good idea. It's other nimrods not paying attention and hitting you that you should be concerned about. but to each their own.
    There are no problems. There are only solutions. It's your duty to determine the right one.

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