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  1. #1
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    Project Columbia

    Hey all. Just picked up this 20Ē sized rim MTB for $20 off CraigsList. I really like the frame and needed something to do. Like I said the frame is really cool as it is a tig welded & gusseted os aluminum and square-tubing mixed concept. My plan is to go for a superlight setup replacing steel with carbon and thin-walled aluminum. This is another one of those crazy bikes where they made a great frame then threw a bunch of heavy cheaply made steel components on it.
    I have three things that Iím looking for input and suggestions on. I am looking at replacing the crank, shock/fork, and rims right now and hence my questions.

    1) On the crank, Iím simply going to replace the steel crank with a Sinz aluminum. The current crank is 140mm. Should I go with the same or drop down to a 130 or 135? My son is 7 yrs old. 49Ē tall with an inseam of 20Ē so not really thinking a shorter length crank is necessary unless Iím missing something like ground clearance etc.

    2) I am pondering replacing the fork with a straight fork but havenít given up the thought of another suspension fork. What are suggestions I can go with for each and what is the weight penalty? I didnít seem to find anything that was just a straight fork that would use v-brakes and keep the same frame to wheel axle distance. Any options?

    3) And lastly Iím playing with the idea lacing up some super light rims. Anyone have experience of what hub & rim combinations that came out really light when finished? I have a Shimano Megarange MF-T207 7-speed cluster on the current rim and am thinking of keeping it as the gear ratios are really nice.

    PS. the chainring is a 40T. Stick with the 40T or ???
    Attached Thumbnails Attached Thumbnails Project Columbia-columbia.jpg  

    Project Columbia-columbia-old-crank.jpg  

    Project Columbia-columbia-front.jpg  

    Project Columbia-columbia-stem-bars.jpg  


  2. #2
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    Wow, that looks like quite the little project you have going on! Will you be posting updates as the project moves forward? I'll be interested as I'm in somewhat of the same boat with my daughter's bike. Happy building!

  3. #3
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    Yup! Stay tuned. Some parts are in the mail already. This is going to be fun!

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    Your bike is very similar to my daughter's. She has a 40T chainring with 140mm cranks (looks identical from your pic). Soon as my hubby gives me the ok, I'll be ordering Sinz 120mm cranks, 34T chainring and Sinz BB.

    I already changed the rear from 6-speed to a 7-speed Mega-range. Had to change the shifter too of course and we went with trigger because she could not twist the grip shifter. Just doing that has been a big improvement already.

    This is soooo much fun!


  5. #5
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    Wow! The frames do look a bit similar. Is the KHS aluminum? I only see a couple subtle differences which is the type of butt weld and angles at the head-tube and the location of the rear brake cable bosses.

    I read somewhere that the frames for the Columbia bikes were built by Ironhorse Bikes in Wisconsin. As I inspect the frame I am really impressed at the quality of craftmanship that was put into it. The welds couldn't be more perfect and everything is straight and true. The PO said it was ridden only about a half dozen times which is evident by the amount of tread left on the tires. Too bad they left it outside in the rain and elements. Good thing the frame is aluminum and I can pretty much toss most of the rusted out junk.

    The search for parts has not been super encouraging as I really wanted to put some super light parts on it but am having difficulty locating. For the cranks, stem, and forks I wanted to put something on made of carbon-fiber but have only been able to find aluminum. Not the worse thing in the world but it just would have looked out of this world if I was able to pull it off. Will have to just keeping searching bike shops and the internet. So far I've just had a little time after work to take some measurements and start cleaning up the frame a bit getting all the unwanted stickers, adhesive, dirt, & grease off. The stickers are being stubborn and I will have to go after with some Goo Gone tonight. All the other dirt came off with Simple Green.

  6. #6
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    Quote Originally Posted by Rondo View Post
    Is the KHS aluminum?
    That was my only requirment when shopping for a build. I did weigh it on my bathroom scale when we got home (yeah I know, not the most accurate) and it came in at 24.5 lbs. I didn't think that was too bad and I knew we could lighten it considerably.

    The search for parts has not been super encouraging as I really wanted to put some super light parts on it but am having difficulty locating.
    I've searched high and low for a rigid fork (carbon was my first choice too) with V-brake mounts. Only found a couple and usually the A to C measurement is way off. So far, a mod trials fork is the best bet. But the better ones aren't here in the US, they're in Europe! Grrrrr! LOL!

    Are you going to have the frame painted (or powdercoat)? I've been thinking of having it done.

  7. #7
    jr2
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    I bought my son the same Colombia bike used. His was in VERY good shape and was always garaged. I don't believe the kid hardly ever rode it.

    We have done minimal upgrades at this point. We are waiting for winter to roll in and then we will start the changes. For now we have upgraded the brake levers to Avid Speed Dial 7's. Replaced all of the cables. Upgraded pedals to platforms. Added a Minoura bottle cage to the back of the seat for short rides. Have some new RaceFace Deus 3/4 risers and a new 65mm reach, 40 deg. rise stem to drop on. Am also going to upgrade his tires and those Kendas are bricks!

    I also have my daughters Trek MT 220 24" to upgrade and paint this winter as well. She wants a custom paint job. House of Kolors Pavo Purple and Sunset Pearl Orange $$$ Really!?!?!? Paint job is gonna be worth more than the bike!!!

    Once I have a few more posts I'll drop some pictures on here.
    Last edited by jr2; 10-03-2012 at 09:12 PM.

  8. #8
    jr2
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    Also...

    If you want a lightweight stem without a name tag for $$ savings try these guys..

    crowcycleco.com/bicycle-components/stem/stem-for-1-1-8-steerer-31-8mm-bars-65mm-reach-40-deg-rise.html

    (sorry, you'll have to cut and paste)
    Quality piece at a fraction of the price of name brands.

  9. #9
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    JonnyScotti yeah I found the same problem with the forks! Ugh!!! I actually really like paint that's on it. It almost looks like a powder-coated satin finish. If it were scratched badly then I might think about doing that. I've got a nice vintage Cilo road bike that I'm considering doing that to as its pretty bad but just can't bring myself to doing it yet because of the nostalgia of the bike.

  10. #10
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    Hi Jr2! I hope you find some of this thread useful. I'm not super fast so it may take some time to complete my project too but I'm going to push myself to work on this bike as much as possible. I see that stem in your link and it does look fairly decent. I think I've found something a little lighter though. I'm considering buying this one which is $20 and only weighs 100 grams. Take a dremel tool to the inside and remove some of the excess flashing and you may have a sub 100 stem. 75~90 grams?

    FIXIE ALLOY "SHORT" STEM - RED, FORGED ALUMINUM, fixed gear road bike bicycle | eBay

  11. #11
    jr2
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    I have seen those. Problem I have is -7deg on the stem and the reach. Your going to have to run a pretty tall rise bar to accommodate for that. Real tall rise depending on the kid. I was looking for a taller rise and shorter reach so the bars don't look like ape hangers.

    There are still other options out there though. A ton of bmx type stems but they are all 25.4mm clamp.

    ebay.com/sch/i.html?_nkw=bmx+green+stem&_sacat=0&_odkw=mtb+bmx+ green+stem&_osacat=0&_from=R40

    For me it comes down to usability and cost. He's 6 and growing Fast . I bet he's in a 24" within a year, year and a half at best. His sister is 8 and she's killin the 24". Kids don't have a chance to be small. I'm 6' 2' and Mom is 5' 10".
    Last edited by jr2; 10-03-2012 at 10:26 PM.

  12. #12
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    Had to work a 12 hr. day today which really sucked and I'm totally beat! But when I got home I found my first new hop up in the mail box. $35, only 133 grams, and very pretty!!!
    Attached Thumbnails Attached Thumbnails Project Columbia-carbon-seatpost-27.2-133grams.jpg  


  13. #13
    jr2
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    Very nice....

  14. #14
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    Jr2 I 100% agree with you which is the exact reason I haven't pulled the trigger on it yet. We're thinking alike.

    This is the one I'm considering instead but has a slight weight penalty because of the higher angle and length.

    What are your thoughts?

    Bike Bicycle Fixie +/-30 Degree 60mm Threadless Alloy Handlebar Stem 25.4 Red | eBay

  15. #15
    jr2
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    I like that one better too but, it still has a 60mm reach and only a 30mm rise. Better but, it still pulls the bars away from them and still a bit low. Again, that's all pending on the size of the kid though. I base my opinions on my kids size so to each their own kid! There's no 2 alike.

    I have ridden for more years than I care to admit. BMX, Cruiser, MTB. I spent too much time down over the bars because that's what the times/technology depicted. Today's geometry and COMFORT are a much better option. For me as well as my kids' future.
    Last edited by jr2; 10-16-2012 at 09:30 PM.

  16. #16
    jr2
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    Ya know, you could get that Crow stem down a bit in weight by going with a hollow bolt kit. They are relatively cheap if you save enough on the cost of the stem.

    .ebay.com/itm/320943324813?ssPageName=STRK:MEWAX:IT&_trksid=p398 4.m1423.l2649

  17. #17
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    Hummm.. Now you've got me thinking a little more about geometry. How tall is your little one? I like the idea of the hollow bolts. Ti would be nice too.

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    Oh! That post is VERY pretty!

    I'm thinking about this stem for my girl. My husband is a machinist so I can have him machine off the excess materials... Spank Spoon Stem > Components > Handlebars and Stems > Stems | Jenson USA Online Bike Shop

  19. #19
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    A weight weenies' delight eh? ;-)

  20. #20
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    Quote Originally Posted by Rondo View Post
    A weight weenies' delight eh? ;-)
    Hahahaha! Yup!

  21. #21
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    New derailleur came. Before & after pics. This is the RD-TX31. I believe these were replaced with the cheaper TX35 version but I found this older stock onlne. Notice the size of the extra large pulley wheels for smoother shifting!
    Attached Thumbnails Attached Thumbnails Project Columbia-der-b4.jpg  

    Project Columbia-der-after.jpg  

    Project Columbia-der-369.jpg  


  22. #22
    jr2
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    Quote Originally Posted by Rondo View Post
    Hummm.. Now you've got me thinking a little more about geometry. How tall is your little one? I like the idea of the hollow bolts. Ti would be nice too.
    Whats the latest Rondo?

    My Son is about 49" and 60lbs.. He's got a pretty good reach on him and his torso is like mine "tall" so he's not a small guy.

  23. #23
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    Oh Man, week from hell. Went on a sail trip for a week then when I got home I had a water leak under the house and had to fix. 6ft.x 4ft. hole and a 1" coupler later it's finally fixed. But Iím beat! Oh yeah right before I left on vacation I was in a 5 car pileup accident and my vehicle is now in the shop for a while waiting to get an estimate from the other guys insurance company. Looks like I'll be working from home for a few weeks. Ugh!

    Anyway I thought I would take today off from life pile driving on me and work on the bike a little bit. (My form of relaxation.) I started pulling all the crappy heavy rusted steel components off and work on cleaning up the frame as much as possible. Most of the pieces came apart quite easily to my surprise. Some were even so loose that I could turn by hand. I was blown away by the sealed bearing headset that was on the frame! Wow! A decent component that I will probably leave on the final bike! When I got to the stickers all the fun came to a screeching halt. They peeled off in little chunks the thickness of your fingernail. I finally got them all off but it pretty much took me all day. The logos are painted on the frame and it looks like they did a very high quality job doing it as I couldnít get it off with any type of cleaner I tried. The rest of the from came clean with degreaser, Goof-Off, and widow cleaner. Got the bolts out of the crank arms but the arms themselves seem like theyíre rusted onto the spindle. I lost my puller so ordered one on-line and am now in waiting mode for the tool to arrive so I can continue.

    I got a chance to admire the bike for a little bit. The more I look at it the more Iím really liking it! Iíll probably pick up a little touch up paint to cover the few little nicks & scratches but overall this frame is pretty darn nice. Still canít believe I got the bike for twenty bucksÖ
    Attached Thumbnails Attached Thumbnails Project Columbia-clean924.jpg  

    Project Columbia-clean925.jpg  

    Project Columbia-clean926.jpg  


  24. #24
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    When I saw the first picture you posted, I saw immediate potential. Glad to see youíre stripping it all the way down and starting over from scratch, hard to go wrong on an aluminum frame based kidís bike.
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  25. #25
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    Quote Originally Posted by Rondo View Post
    The rest of the from came clean with degreaser, Goof-Off, and widow cleaner.
    If I should be so lucky someday, I might wish upon a shiny star for the ever-elusive widow cleaner. Thanks for the tip.
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  26. #26
    jr2
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    Way to go Rondo! Now keep us apprised of your changes and take care of yourself after all the wonderful luck you've been having!!

  27. #27
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    Got the crank arm puller tool in the mail and removed the arms without any problems! One of the best tools I've ever bought!

    Now to get the BB out. Drive side came off with no problem. Could have even used a Crescent wrench! The left side had that nasty looking oval threaded cup with the two flat spots. This thing is rusted in place and it's time to buy another tool I guess. For those wondering I did a little mic'ing and internet searching and found I need a Park Tool HCW-15 36mm wrench. Must have called 25+ bike shops in SoCal and no one carries it.

    Here we wait again for the mail. In the meantime I think I'll go outside and install some quick disconnects on the sway bar for my Jeep.

    Btw. the front Zoom fork shocks for 20" wheel seem quite heavy and I'm looking for some simple straight forks with v-brakes to replace and lighten up the front end a little. I'm open for suggestions if anyone knows where I can find some? All I'm finding on ebay is either too short ,or for center-pull ot side pull brakes.

    I have a pair I could use but not sure the geometry is right. The Zooms measure from axle to first bearing 14" but the straight pair I have measure from axle to first bearing 12". A 2" difference. Not sure if that is going to fly.

    Thoughts?

  28. #28
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    I'll measure the Mozo I just took off my daughters bike against the rigid I put on...

  29. #29
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    Mozo suspension - 13 1/4in
    Rigid - 10 3/4in

    Big difference but I felt the 3+ lb difference worth it.


  30. #30
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    Cool! Maybe I'll give it a shot!

    Thanks for posting that!

    Hopefully my wrench comes tomorrow.




    Btw: What fork is that?

  31. #31
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    Quote Originally Posted by Rondo View Post
    Btw: What fork is that?
    It's a Specialized.

  32. #32
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    WOW!!!! That cup was difficult to break loose! Finally got the 36mm wrench in the mail today. Stupid ebay seller finally shipped 5 days after he was paid! I worked and worked on getting that cup off for about 10-15 minutes. After lots of liquid wrench and a little persuasion it finally broke free. (Remember drive side loosens by turning clock-wise.) Took a small brass brush and a rag and air gun to clean out the threads.

    Now onto BB sizing. Looking at 113mm or bringing in the chainring a bit by going 108. I buy VP alloy hollow spindle bottom brackets at a weight of right around 200 grams. Also you can find titanium crank arm bolts on ebay for about 10 bucks!
    Attached Thumbnails Attached Thumbnails Project Columbia-bb-finally-out.jpg  


  33. #33
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    Had just enough time after work tonight to install the titanium hollow spindle axle.

    About 150g. vs. 400++ that came out of it!
    Attached Thumbnails Attached Thumbnails Project Columbia-bb-hollow-ti-spindle.jpg  

    Project Columbia-bb-hollow-ti-hollow-spindle.jpg  

    Last edited by Rondo; 11-14-2012 at 09:56 PM.

  34. #34
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    Dang, that's a ton of weight saved!

  35. #35
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    Ok looking for opinions. I put together a Sinz crank & chainring, and BBG bashguard with blue bolts. Iím liking it!

    What Iím not sure about is the Odyssey BMX seat and carbon seatpost. Just not sure itís doing it for me. I have another seat setup on my titanium bike (gold post) which is a pivotal and is super light, (less than half the weight of the carbon post) and looks pretty good too but am worried about too much red, which is the color I would get.

    The stem and bars are carbon and I thought they would all tie in. My wife thinks the seat is ugly, maybe I should just find another butt-rest???
    Attached Thumbnails Attached Thumbnails Project Columbia-chainring-en.jpg  

    Project Columbia-chainring1-en.jpg  

    Project Columbia-seatpost-possibility1.jpg  


  36. #36
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    The question I would ask myself is, will the child like it? How important is comfort over weight savings in the saddle for a child?

  37. #37
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    That's a good idea. I'll have both on hand so he can see which one HE likes best!


  38. #38
    jr2
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    Hey Rondo... what happened? What's the latest?

  39. #39
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    I've had to back burner this project for a bit. Will get back to it when I'm not working 7 days per week.
    Last edited by Rondo; 05-15-2013 at 11:43 AM.

  40. #40
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    Ok back on the bike. Seems like Iím making this thing into something it wasnít meant to be and am having a little difficulty finding the right parts but am going to keep trying till I hit a total dead end.

    So hereís a question. Iím thinking about getting Shimano mtb XT disc hubs and lacing them up to 20Ē rims and going with hydraulic disc brakes. I believe the hubs have 9mm axles while the axles that are on the rims now are 3/8Ē. Can I use the XT hubs on this frame and do I need to mod the frame or hubs to do this? Or will the QR skewers work fine in the current frame wheel cut-outs?

    Also, Iím having a little difficulty finding carbon rigid forks for 24Ē wheel with the disc brake mounts. Anyone have a line on them?

  41. #41
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    QR skewers will probably hold the axel in the too-wide dropout OK but if not, you can just fill in the dropout slot with a bit of JB-weld epoxy and then file it to exact 9mm deminsion to get a good tight fit.
    IMHO- hydraulic disks are complete overkill for a 20" kid bike and add considerable weight over using decent V or cantilevers. The frame spacing might also be less than MTB 135mm axel width. I would look at using lightweight 130mm road hubs with rim brakes to save weight and fit in the frame better.

    THe tourney RD you got is pretty heavy. You could easily save 100+gr with a lighter RD. If only using a single chainring, no need for a long cage RD, a short cage road RC can work fine so long as the largest sproket is not too big for the RD.

    For inspiration on a much-lighter suspension fork, check out my daughters 20" project bike;
    Novara Pixie 20" project

  42. #42
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    If you are using disc brakes on a 24" wheel, you can use 26er forks, the geo may be a bit off. The bike my son had was a 24" Rocky Mountain Reaper, it has disc brakes front and rear, 24" wheels and the forks was a 26er. Come to think of it, his Specialized Gromhit freeride bike also has 26" Marzocchi AM forks. It gets more complicated with rim brakes. Also, I am using bolt on axles on both the Gromhit and his current ride (same fork I used on his Reaper 24). XT hubs can be converted to bolt-on by buying Wheels Manufacturing axles (Front 9mm by 155mm and rear 10mm X 178 (I believe, not 100%)).

  43. #43
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    Here is one company with a 20" carbon disk fork;
    CarbonCycles.CC :: Components :: Products :: Forks - Recumbent / Folder :: eXotic Carbon Rigid Fork for 20 Inch Wheel - Disc Only :: CC-F03-20

    (Same company also has a 24" fork if you want higher AC and to be able to re-use it on next bike when kid grows)

    Still fairly heavy at 750gr, comes with 200 lbs rider weight limit! You could probably cut down and modify a light-weight steel road fork to weigh less for a 20" MTB. Finding a carbon fork that is actually weight-optimized for a sub 100 lbd rider will probably be very difficult.

  44. #44
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    Quote Originally Posted by RSabarese View Post
    If you are using disc brakes on a 24" wheel, you can use 26er forks, the geo may be a bit off. The bike my son had was a 24" Rocky Mountain Reaper, it has disc brakes front and rear, 24" wheels and the forks was a 26er. Come to think of it, his Specialized Gromhit freeride bike also has 26" Marzocchi AM forks. It gets more complicated with rim brakes. Also, I am using bolt on axles on both the Gromhit and his current ride (same fork I used on his Reaper 24). XT hubs can be converted to bolt-on by buying Wheels Manufacturing axles (Front 9mm by 155mm and rear 10mm X 178 (I believe, not 100%)).
    Going from a 20" suspension fork to a 24" rigid form is probably not going to be a huge change in geometry. A 24" bike can be designed from ground-up to have the geometry correct when using a 26" length fork. Just putting a 26" fork onto bike designed for 20" wheel and fork would seriously mess-up the geometry, the head-tube & seat tube angles would be very slack and handlebars would be sky-high.

  45. #45
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    Thanks for the kind responses guys. Although I am concerned about weight it might actually be my second concern. First and foremost is to create a bike that will be safe for my son to ride and something he will be confident in controlling. The bike he has now he has problems stopping so I thought in building this bike the addition of good stopping disc brakes would be in order. ( just hope he remembers not to fully grab the left handle?) ;-)

    Weíve gone pretty fast downhill a couple times and it has freaked him out that the v-brakes donít work to well at high speeds. Me thinks he just canít pull very hard at 6 yrs of age. Heís a really good peddler so the heavier hubs should be ok. I know Iím taking a gamble that the disc clearance might be an issue but only one way to find that out. The bike had a shock up front so itís a little taller than a standard 20Ē fork. Would the 24Ē work?

    CarbonCycles.CC :: Components :: Products :: Forks - Recumbent / Folder :: eXotic Carbon Rigid Fork for 24 Inch Wheel - Disc Only :: CC-F03-24

  46. #46
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    Then there is this too which is a cheaper alternative but not really fond of the M-33 mounts showing on the front of the fork.

    Bloodline 24? Chrome Aluminum Fork Disc Brake Rigid BMX SE Haro Redline | eBay

  47. #47
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    Compair the Axel to Crown length of new fork options to the measured AC length of the bikes current suspension fork when compressed 20%. An additional 20mm of AC length changes the head tube angle by about 1 degree (slacker angle).

    I think the challange is that most any short fork you can find will be designed to take the abuse of a much larger rider performing huge verticle drops, probably 10X as strong as anything a kid can dish out to a fork so correspondingly heavy.

  48. #48
    mtbr member
    Reputation: Rondo's Avatar
    Join Date
    Oct 2011
    Posts
    116
    AC on current 4LB. (shock) fork was 35cm, and with sag was somewhere between 34 to 34.5cm

    The Carbon disc only fork is 33.9 so seems like it may be a perfect match.


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