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  1. #1
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    basement built gt fatbike!

    hello all, Ive been jealous along time of all you fat bike people..but no more! I recycled my old gt borrego frame. I cut most of the rear end off, extended the seat and chain stays with another frame and brazed them on, I made the seat and chain stay yokes out of the left over seat stays. I made a quick jig in the basement and reassembled the old girl. I bought some tires and rims and a fork and now I have my very own one of a king fatbike!
    these first pics were before paint and not quite finished welding yet, no disk brake tab.
    basement built gt fatbike!-sspx0627.jpg

    basement built gt fatbike!-sspx0628.jpg

    basement built gt fatbike!-sspx0629.jpg

    basement built gt fatbike!-sspx0632.jpg

    basement built gt fatbike!-sspx0633.jpg

  2. #2
    workin' it Administrator
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    NIce work! Sleeved the dropouts over the old ones? The BB widening is quite impressive I must say.

    Good on you to recycle so well!
    Try this: HTFU

  3. #3
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    here are some pics of the gt finished with new paint. and the chain, seat stays are sleeved it made the most sense to me at least.
    basement built gt fatbike!-img-20111112-00088.jpg

    basement built gt fatbike!-sdc13004.jpg

    basement built gt fatbike!-img-20111112-00091.jpg

    basement built gt fatbike!-sdc13005.jpg

    basement built gt fatbike!-sdc1300069.jpg

  4. #4
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    Cool. Nice job.

  5. #5
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    I love it!! Wonderful job. Now go ride the bejewbus out of it.

    Just curious, what's the idea behind the spokes?

  6. #6
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    Good ob on the BB shell. What spindle did you use?

  7. #7
    ride more
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    Wow, that's really cool.

  8. #8
    All fat, all the time.
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    Cool project!
    Those spokes are craaaazy! I love it.

  9. #9
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    Wow that's some serious work, great result! Congrats.
    Jason
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  10. #10
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    I always prefer a home-brew

    How does it handle?

    (Added some rep to you)
    As little bike as possible, as silent as possible.
    Latitude: 57º36' Highlands, Scotland

  11. #11
    Geordie biker
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    Superb, love these self builds
    2014 milage so far - 2,485
    www.ukfatbikes.co.uk

  12. #12
    That Unicycle Guy
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    I can't quite make it out but is that 4 pairs of twisted spokes on the front with the rest strait?

    buy a pack of 50 spokes for the twisty pattern?

    whatever your reasons great job.

  13. #13
    A Surly Maverick
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    Great build, well done
    A Fatback'd Lefty for who life IS a Beach

  14. #14
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    I am similarly in the middle of a standard steel hardtale to fatbike conversion;
    BB widing???EXTENDING

    Good start you have, following Intended purely as constructive criticism -
    Looks like the new fat setup gave you around 67-68° of head tube angle (and even slacker seattube). Unless you get a fork with massive amount of rake, the fork trail is probably much too big (100+mm) and it will have some very wierd, querky steering. Keeping most of the original frames seatstays probably somewhat limited the needed changes you could make to the frame geometry. You probably should have increased the angle between the seattube and the chainstays by a few degrees (reducing the BB drop) so that the head tube angles would remain a bit steeper and keep fork trail <90mm.

    Hard to tell from the pictures but is there some crimping of the seatstays where you added clearance bend? My attempt to bend CS and SS in-place were a complete failure, convinced me to just cut them off entirely and start fresh. New steel 29er chainstays and seatstays long enough for a fatbike only cost me about $50 total from NOVA. Much easier to get them bent to shape beforehand and then attach to the frame, no sleeve extensions needed.

    Interesting idea on widening the existing bottom bracket shell. What method of welding (does not llook like brazing) and what did you use as a jig for this to keep the lengthened shell strait?

  15. #15
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    Awesome. The triple triangle/fattie combo works very well!
    Look out honey, 'cause I'm usin' technology

  16. #16
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    Twisty spokes! Love it!

  17. #17
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    Quote Originally Posted by GrayJay View Post
    I am similarly in the middle of a standard steel hardtale to fatbike conversion;

    Good start you have, following Intended purely as constructive criticism -
    Looks like the new fat setup gave you around 67-68° of head tube angle (and even slacker seattube). Unless you get a fork with massive amount of rake, the fork trail is probably much too big (100+mm) and it will have some very wierd, querky steering. Keeping most of the original frames seatstays probably somewhat limited the needed changes you could make to the frame geometry. You probably should have increased the angle between the seattube and the chainstays by a few degrees (reducing the BB drop) so that the head tube angles would remain a bit steeper and keep fork trail <90mm.

    Hard to tell from the pictures but is there some crimping of the seatstays where you added clearance bend? My attempt to bend CS and SS in-place were a complete failure, convinced me to just cut them off entirely and start fresh. New steel 29er chainstays and seatstays long enough for a fatbike only cost me about $50 total from NOVA. Much easier to get them bent to shape beforehand and then attach to the frame, no sleeve extensions needed.

    Interesting idea on widening the existing bottom bracket shell. What method of welding (does not llook like brazing) and what did you use as a jig for this to keep the lengthened shell strait?
    grayjay good eye on the the head tube angle! unfortunately, dislexia kicked in and I reversed fork length numbers from 447 to 474. so now my bike rides like a dh bike with long travel its alittle sluggish on hill climbs and I have to man handle it a bit in some corners, but over all the bike rides awesome. I have well over 700km's on it.

    When I did the b.b. I cut off pieces of another b.b. I then used an old steel b.b. cup and threade the two together. The drive side was a bit of a pain, because of the fixed cup lip you can't thread it thru to the other side, so I had to grind down a b.b. tool to fit thru the bb shell and used a non drive side cup and threaded it backwards.

    almost all of the welding was done with a 110 flux core welder. I did braze the seat and chainstays together I had to extend them. My next build Iam going to buy two 29er frame sets from henry james, one for me one for thew wife.(she doesnt know yet she hates bikes)

    the crimping on the seat stays I think youre refering to the bends ridght above the tire, if so I tacked a piece of steel (5.5" wide gives me lots of tire clearance) between the stays and pulled them back together. I did have to put some clearance dents in the chainstays so the cranks wouldnt hit all is good now.

    I hope I answered your questions. sorry for the run on.

  18. #18
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    Quote Originally Posted by ericpulvermacher View Post
    I can't quite make it out but is that 4 pairs of twisted spokes on the front with the rest strait?

    buy a pack of 50 spokes for the twisty pattern?

    whatever your reasons great job.
    Im a bit on the cheap side I try to recycle all of my old parts. The rear spokes were to long I thought I had the right length, they were not so I twisted them. The front similar issue I only had enough to do partial build with either colour, so yes there is a twisty cross in the front. The front is being rebuil I found the rest of my black spokes.

  19. #19
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    Wow, that’s some serious backyard engineering going on there. Really now, your home-fatty ROCKS!!! I wish I had a welder… and a die grinder…*and a lathe… and a CNC machine…
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  20. #20
    That Unicycle Guy
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    Quote Originally Posted by angryx View Post
    Im a bit on the cheap side I try to recycle all of my old parts. The rear spokes were to long I thought I had the right length, they were not so I twisted them. The front similar issue I only had enough to do partial build with either colour, so yes there is a twisty cross in the front. The front is being rebuil I found the rest of my black spokes.
    Cool, I have also used some "creative" spoke patterns in the past to re-use spokes. I can understand why you are re-building the front but the twisty cross does look really cool.

  21. #21
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    Quote Originally Posted by Leopold Porkstacker View Post
    Wow, that’s some serious backyard engineering going on there. Really now, your home-fatty ROCKS!!! I wish I had a welder… and a die grinder…*and a lathe… and a CNC machine…
    thanks Leopold Porkstacker, only specialty tool was the welder, everything else was done with a 4.5" angle grinder. needless to say all of those tools what be great to have.

  22. #22
    will rant for food
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    Quote Originally Posted by angryx View Post
    thanks Leopold Porkstacker, only specialty tool was the welder, everything else was done with a 4.5" angle grinder.
    I admire resourceful people, good job
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  23. #23
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    Thanks drewdiller, Ive always made do with what I have, it doesnt help that I'm impatient and want things done asap

  24. #24
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    Quote Originally Posted by angryx View Post
    Thanks drewdiller, Ive always made do with what I have, it doesnt help that I'm impatient and want things done asap
    Oh I don't know. I told myself I was going to slow down on my next frame build, and I slowed down too much. Work how you work best.
    Disclaimer: I run Regular Cycles (as of 2016). As a profiteer of the bicycle industry, I am not to be taken very seriously.

  25. #25
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    That is awesome. Next step "leaking" photos to show GT is releasing a fatbike to make everybody freak out.

  26. #26
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    That's fantastic! well done, makes me want to fire up a welder and try.

  27. #27
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    thanks, I was out on a ride with my fat bike the other day, and I found my next project. I came across some junk dumped in the 4x4 pits and in that junk was a womens specailized hardrock sport frame...the wife is super happy(not really). cant wait to start hacking this one apart, I might actually buy some frame pieces and do this one properly.

  28. #28
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    hahahaha! I love fatbikes! I went for an urban ride the other night, just cruising downtown watching the crackheads and the rest of my towns finest. then I spotted the four sets of six stairs in a row and thought to myself I can ride up those and I did I giggled like alittle school girl after each set and rode around looking for bigger sets. way to much fun more fun than I ever had on my trials bikes and less painful.

    I went for my first mud ride lots of fun here are some pre cleanup pics...
    basement built gt fatbike!-sdc13007.jpg

    basement built gt fatbike!-sdc13008.jpg

    basement built gt fatbike!-sdc13009.jpg

    basement built gt fatbike!-sdc13010.jpg

    and still lots of tire clearance

  29. #29
    Ancient Astronaut
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    Proper!
    Now add some bird feed and you will have the coolest Chia fatty.

    Cool job.

  30. #30
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    I think you need fenders/mudguards

    (Settles back to see what will get modified by angryx - this should be interesting)
    As little bike as possible, as silent as possible.
    Latitude: 57º36' Highlands, Scotland

  31. #31
    wheelmanron
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    I haven't seen twisted spoke wheels since that frame was new! Let me guess-the spokes were 6mm too long?

  32. #32
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    Quote Originally Posted by Velobike View Post
    I think you need fenders/mudguards

    (Settles back to see what will get modified by angryx - this should be interesting)
    I definately need to build some fenders, Im going to pay my old sign shop a visit and try to pick up some cut off's of either aluminium or lexan and go from there....or just use some 2liter pop bottles glue them together ahahahah no I wont.

  33. #33
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    Quote Originally Posted by wheelmanron View Post
    I haven't seen twisted spoke wheels since that frame was new! Let me guess-the spokes were 6mm too long?
    you sir are correct and must have built some wheels yourself.

  34. #34
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    dude, you are my hero today, cheers

  35. #35
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    Quote Originally Posted by Saddle Up View Post
    dude, you are my hero today, cheers
    thanks!

  36. #36
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    I love this build. I just got my TIG welder today and I got intentions of doing this to some of my bikes.

    Can you explane the BB a little more for me.
    2013 mongoose Fat bike
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  37. #37
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    @bighit,
    first remove existing bb from donor frame, cut the neccessary amount of of both sides left/right hand thread...dont mix them up, that would suck alot.

    reassembly, I used an old steel nondrive side bb cup, because it can be threaded thru both cups...this is done to keep all pieces square.

    The drive side is alittle more difficult, because of the lip on the driveside cup.
    to remedy this I took my bb tool and ground it down until it fit thru the shell now thread the nondriveside cup backwards into the frame being extended, the piece you cut off the othe bb should thread on by hand.

    Tack it all together first and try your bb for fit.if all is good weld away.

    I'am currently working on another frame, I will be doing the bb differently.

    this time I'am going to cut the bb in half and put my extending piece in between the
    left and right sides. when its all welded back together in the frame it should have alot more strength.

    I will post pics of the bb when get around to that part of the build.

  38. #38
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    That's a big issue for me. I am using the old school press in BB. Most of them don't go to 100mm so I got to find out if any bmx bb will. I am only running a Single speed so it is not so bad. If I can't find an old school solution I can put a new school 100 bb on it.

    Thanks awesome work. I love the sleeve dropouts ides. I extend old school kickstands that way.
    2013 mongoose Fat bike
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  39. #39
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    Cool build, OP. To add to the BB discussion.... New 100 bb shells are under $10, and $12 will get you a cup and cone 100mm square taper BB, or there are several modern 100mm BB's. If you widen an existing BB shell for the same reason most of us build our own frames, that's one thing, but their is no way it is saving you money. add in the cutting and welding consumables even if you son't value your time and you can justify buying the BB shell for less....

  40. #40
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    the cheapest bb shell I have found is henry james for 14.00$. The only reason I did any of this was out of boredom and curiosity, I wanted to see if I could do it and if the cheap flux core welder would hold the frame together.

    Ive been riding the bike since september in all conditions, and havent had any issue's.

  41. #41
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    As I said in the fatbike thread I really love your fatbike. Good to see how you recycled the old girl like this!
    2011 Quiring 29er Steel Hardtail
    2009 Gt Peace 9'R SS
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    1997 GT Zaskar
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  42. #42
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    I have a 1973 Fuji road bike frame or a Raleigh skyline frame (both are road frames) that is already bent in the seat stay that i could modify. i'm thinking i might buy a pugs front fork but i think i might like a shock fork...

    anyone tried to do this from a road frame? Im thinking i could weld and add metal tubes to the seat stay and chain stay to make that wider. I suppose if i am doing that, then i might as well mod the fork (if not a shock fork).

  43. #43
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    surly pugsley fork wont fit, old road frames are 1" head tube pugsley fork 1.1/8
    you really should start with a mountian frame, a road frame probably is not the best choice
    to try and modify into any kind of mountian frame.

  44. #44
    Muskoka
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    Awesome! Where there is a will there is a way
    https://picasaweb.google.com/113125576961447749127

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  45. #45
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    Quote Originally Posted by angryx View Post
    surly pugsley fork wont fit, old road frames are 1" head tube pugsley fork 1.1/8
    you really should start with a mountian frame, a road frame probably is not the best choice
    to try and modify into any kind of mountian frame.
    valid point. well, off to craigslist i shall look. thanks

  46. #46
    WAWE
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    That's b i tchin!



    edit: b_it_ch is a censored word? ...seriously?

  47. #47
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    thanks! thats funny you here that word all over television these days.basement built gt fatbike!-sdc13035.jpg

  48. #48
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    Quote Originally Posted by angryx View Post
    thanks! thats funny you here that word all over television these days.Click image for larger version. 

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    Good to see your homebrew fatbike still going strong! How many miles of abuse has it seen?
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  49. #49
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    The bike has been ridden just about everyday since I built it. I used it all winter to commute to work everyday. Now that the weather is nice I average about 300km a week off road riding. I beat the crap out of this bike, just to see if I can break it...so far no luck! I guess you can weld a frame with a flux core mig.

  50. #50
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    Outstanding!! +Rep for you sir

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