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Project BMX Part 1

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  • #93577
    Keymaster

    I’ve sometimes been asked how we come up with the ideas for our project builds.  Somehow the ideas just seem to find us, and being one who is willing to try most things we play with the idea until it either materializes or it becomes too absurd to pursue anymore.  To show more how the whole process works start to finish, over the next several months I will chronicle a project start to finish and post updates here as it progresses.

    The idea, it has to begin with the idea.  Sometimes I try to give myself ideas by leaving things on my desk or hanging on the wall where I can see it in hopes that at some point the idea comes.  This fails as often as it succeeds, as an example I have a 50th anniversary Colin Lange custom that’s been hanging on the wall for almost 10 years waiting for the idea to come, which it still hasn’t.  Other times it seems to come quick.  The quick ones tend to be the best as everything just seems to fall into place easily and naturally.

    This project is one that came quickly.  A new frame had just shown up and I was trying to come up with a wheelset and found myself frustrated by the lack of light parts for pure race bikes.  Why in the 30 years that I’ve been riding Bmx bikes has the weight of a race bike not changed like it has in other categories of cycling.  Sitting on my desk at that time was a Tune Mag150 hub, that’s when the thought came,  “If this is suitable for mountain biking, why can’t a version be done for bmx?”  So with that thought and the notion of cost be damned, this project to build the worlds lightest Pro XL bmx bike for a grown up was born.

    Keeping motivated can sometimes be a challenge with a long project build so it’s important to feel some progress right away to get excited.  That means this was the time to start, besides it gave me less of a chance to think that maybe this was an absurd idea.  I took the hub in hand, thought for a few minutes and then headed to the work bench to start.

    The first thought was the freehub body, both size and durability were an issue.  As a solution I grabbed a Tune Single speeder hub and removed the single cog titanium freehub body to see how it fit to the 150, the fit was perfect as I thought it would be.  Next the axle length had to be considered, because the 150 uses a carbon fiber axle with press fit end caps, shortening the length would be easy.  The bigger challenge was coming up with proper length end caps to allow the hub to stay without dish and keep a proper chainline at the same time that the overall length was decreased.  I had an assortment of Tune end caps from road and mtb hubs to work with and made up the difference with a fairly minimal custom spacer.  At this point it was just a matter of assembling the hub and checking the dimensions to make sure everything was correct.  It wasn’t.  Measure twice cut once, there’s a reason that’s a good rule, this time at least it was only a $100 screw up.  Double check my numbers, grab another carbon axle and cut it.  Check again to see if it was proper and this time  It was, which meant the hub could be taken back apart and the details could be considered.  Again with durability and performance in mind the skyline titanium pawls were removed and replaced with stainless steel.  The stainless bearings were also removed and replaced with HSC full ceramic.  The last piece was the titanium drive ring.  The stock 24 tooth drive ring was removed and replaced with a custom made steel 36 tooth drive ring, producing faster engagement of the freehub body.  (Special thanks to Jeremy at Alchemy for producing the custom drive ring.)  The hub was reassembled and of course the weight was checked, 146.3 grams, definitely the lightest cassette hub ever made for bmx.

    At this point I sent pics and specs to Harry at Tune to show him what I had come up with and ask his opinion.  He took them over to Uli (owner and engineer at Tune) and together they looked at it and decided that it was a solid start.  The one concern which we all shared was the carbon axle.  Uli offered to produce a one-off version of the hub for me using the changes I had made.  The new production hub was changed to a custom made alloy axle and end caps that did not require a spacer to attain the proper spacing.   This one off hub also had to be reinforced and drilled for the appropriate 32 spokes.

    While making the new rear hub, Uli also came up with a matching Mig45 front hub.  At 60.7 grams the front is heavier than a stock Mig45 but it’s reinforced to handle the rigors of bmx racing.  Remember this is a without regard to budget build so here’s how the pricing breaks down.  The stock Mag150 was $785, the Singlespeeder which was salvaged for parts was another $615, misc end caps for $30, custom drive ring at $60, the extra axle to replace the one I cut wrong added $100 and  4 HSC full ceramic bearings at $90 each puts the retail price of the rear hub at a pretty staggering $1950.  Tune will in all likelihood begin to offer this hub as a stock item, with stainless bearings and without having to use two hubs to build one, the pricing should drop to just a little more than a stock Mag150.

    Of course now that we have the hubs, we have to do something equally special for rims, spokes and nipples.  A couple calls were placed to see what we could turn up and we’ve got what we consider to be worthy components to finish this build, but that will have to wait for another day.

     

     

    #93578
    Chris Rishell

    Been out of BMX for about 4 years now but am very excited to see what else you come up with. Can’t wait for the next installment.

    #93579
    kim neuendorf

    nice .with the new frames ,they are using either 15 mm axles or 20mm ,good time to design hubs with those stiffer axles .sinz makes a 20mm carbon fork

Viewing 3 posts - 1 through 3 (of 3 total)

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