October 21, 2013 at 4:14 pm #94928Keymaster
I imagine that quite a few people reading this have already seen this project we did for Interbike, but we figured this was a good time to complete the details on it. Complete finished weight of the bike was just under 5.4kg, (11.89 pounds)
The frame is a custom handbuilt by Nick Crumpton of Crumpton Cycles. The frame came in at 957.2 grams. Being almost the same weight as a superlight 29er frame which is twice the size, this one could certainly have been lighter, however the goal was not to have just the lightest but something that could truly be race worthy.
The bar/stem combo is a Bombshell handlebar and Enve stem with bonding by Calfee.
Hubs are custom made by Tune. The rear started as a Mag150 and had a new axle and end caps machined as well as the alloy freehub body replaced with a titanium single speed version.
Rims were custom from Velocity based on the tried and true A23 extrusion.
Spokes were custom Pillar Titanium. Bladed profile with beefed up 13g ends matched to custom 13g alloy nipples.
Complete build list below gallery.
Complete Build List:
Frame: Crumpton Custom, 957.2gr
Headset: Kcnc Radiant R1, 46.7gr
Fork Expander: Tune GumGum 8.7gr
Top Cap / Bolt: Fair Wheel 5.9gr
Headset Spacers: Parts of Passion 2.8gr
Fork: Sinz Carbon (175 lbs weight limit.) 462.2gr
Crank Arms: Tune Smartfoot 508.2gr
Bottom Bracket Cups: Extralite PF30 22.3gr
Bottom Bracket Bearings: HSC Full Ceramic, 33.4gr
Chainring: Absolute Black, 36t, 51.4gr
Chainring Bolts: Kcnc SL 4.6gr
Chain: KMC X9SL 194.8gr
Cog: Recon Titanium 13t, 21.1gr (includes all spacers)
Cog Lockring: Far and Near, 5.1gr
Front Wheel: Tune Mig45 Custom front hub, Velocity Custom A23 rim, Pillar Custom Titanium spokes. 438.5gr
Rear Wheel: Tune Mag150 Custom Rear hub, Velocity Custon A23 rim, Pillar Custom Titanium spokes. 544.4gr.
Rim Tape: Rox Superdute 8.1gr.
Pedals: Bebop Titanium, 146.9gr
Brake Caliper: Kcnc V-brake, 84.9gr
Brake Lever: Kcnc Brake Lever, 23.4gr
HandleBar/Stem: Bombshell Carbon bar / Enve Carbon stem, 407.9gr
Handlebar Grips: Kcnc w/plugs, 19.6gr
Saddle: Tune KomVor, 92.1gr
Seatpost: Tune Carbon, 101.1gr
Brake Cable: Kcnc Titanium, 7.3gr
Brake Housing: Aican Bungarus, 12.1 gr
Tire, Front: Tioga Powerband Kevlar 1.85. 267.6gr
Tire, Rear: Tioga Powerblock Kevlar 1.75. 301.7gr
Chain Tensioner: Custom, 14.6gr
Tubes: Eclipse, front 40.7gr, rear 41.1r.October 23, 2013 at 3:14 pm #94973
What is the mechanism to tension the chain?Nothing ventured nothing gained!October 24, 2013 at 12:17 am #94974Participant
I’m quite intrigued by this bike. I love the idea of a lightweight race based bmx, takes me back to my teenage years. The frame is stunning as I would expect of Crumpton. The choice of chainring is interesting but there again I’m biased in that department. I would still choose a fibre-lyte single ring, however. Is there something special that I’m not aware of with absolute black chainrings? I’m really not too sure about the handlebars, the narrow section where the stem meets the bars at either side looks to be a weak spot? What I’m very intrigued about is a Mig45 front hub on a race bmx, not too fragile? Despite these small things, still an amazing build.October 24, 2013 at 4:24 pm #94979Moderator
What is the mechanism to tension the chain?
I’m not sure what exactly you want to know, but looks like vertical drop outs to me."Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.October 26, 2013 at 10:34 am #94980
Ypsylon, thanks for your response. I noticed that there are allen bolts behind the rear axle. Was wondering if when tightened they pulled the rear wheel back to tension the chain. Some motocross bikes used such mechanisms in the past.Nothing ventured nothing gained!October 28, 2013 at 6:13 pm #94983Keymaster
Ypsylon, thanks for your response. I noticed that there are allen bolts behind the rear axle. Was wondering if when tightened they pulled the rear wheel back to tension the chain. Some motocross bikes used such mechanisms in the past.
It’s a BMX chain tensioner that we modified a bit. You’re right, it’s a washer with a bolt that tightens against a plate that is braced on the back of the horizontal drop out. Very similar to what some motorcycles use. They come in a few different types and shapes but they’re all pretty much the same concept.October 28, 2013 at 10:58 pm #94984
Thx for clarification Emiliano!Nothing ventured nothing gained!