Hey everyone,
I figured it was time to share a project that’s been quietly evolving over the last 10 months.
I’m Laurent – a mechanical engineer and lifelong bike nerd. Together with my friend and coworker Axel, we’ve been designing and building our own custom enduro frame from scratch.
This started as a passion project. We wanted to build the kind of bike we couldn’t quite find on the market. we’re just two guys who love riding bikes and wanted to make something that is durable, quiet, easy to live with, and above all, fun to ride.
Somewhere along the way, we figured why not give it a name – so we went with Unchained Bicycles. It kind of named itself, really. No chain, no drama – just ride.
🔧 Tech Overview
We were honestly just tired of the usual drivetrain headaches – constantly degreasing and re-greasing chain, bent derailleurs, and constant fiddling to get smooth shifting.
We wanted a bike you could pull out of the garage, check tire pressure, and ride. No drama.
So we went for:
- Pinion Smart.Shift C1.12 with CDX Belt
- Full 7075-T6 aluminum frame – bonded tubes and CNC’d lugs + built-in mechanical fail-safe
- Mid-high pivot
- 170 front and rear travel
- Lab test planned to ASTM Category 5 before it hits the trails
- Mullet or full 29"
- Dual shock mounts - two progressivity settings (air and coil)
- Adjustable dropouts - fine-tune rear center or switch between 27.5" and 29"
- Very low pedal kick-back
- Target weight: ~16.5kg with enduro tires
📐 Geometry & Kinematics
We didn’t try to reinvent the wheel.
We shot for the ballpark of what works – that sweet middle ground where a bike feels alive, planted, and doesn’t fight you.
We’re running a 4-bar linkage because it just made sense for us – it’s simple, proven, and gets the job done without overcomplicating things.
Considering how good modern shocks are these days – and the reduced unsprung mass – we didn’t feel the need for anything more complex.
We’re not sharing anti-squat or anti-rise numbers just yet – because these charts often spark endless debates.
We’d rather ride the bike, make adjustments based on feel, and see if it lines up with our philosophy. Then we will share.
🔭 What’s Next?
Right now, it’s all for the stoke.
But if interest builds – and if our lab + trail testing checks out – we’re open to launching small batch production, potentially in multiple batches.
We're also working on a full-power eMTB version based on the Pinion MGU and a high pivot layout. That’ll come in round two…
Oh yes, some pictures :
We’ll keep updating this thread with CAD, fabrication steps, test rides, etc.
Let us know what you think, and feel free to ask anything.
Cheers,
Laurent
Love to see it!
Splendid. I like the look of the lugs! I'm designing something similar for a uni project. I don't have access to FEA at the moment though. What diameters and wall thicknesses did you choose for the tubes?
You can get a student version of Ansys Workbench for free with a University email.
Definite learning curve with the software, but it’s probably the best FEA program out.
I've been using the free version of fusion, unfortunately I'm not a student yet and the free version doesn't do FEA
1.5 steerer tube to adjust reach and head angle?
You've already done CAT5 testing? Or is that currently underway?
We are currently on manufacturer selection phase (for CNC for our 3 prototypes (one for Axel, one for me and the other for torture), then we will test it ourselves and then CAT5 testing in Germany. Hopefully, within the end of summer.
Not planned for now. Not excluded though!
This looks really good, excited for the MGU version, or check the Intradrive GD8
Why the truss rear triangle and not tubes if I may ask?
Ease of manufacture.
@Lolo.ch Do you have a delivery date for the first prototype?
Really curious about your built in mechanical fail-safe, is it specifically to mitigate risk of the adhesive bond failing?
Looks sick, looking forward to the updates!
For wall thicknesses- try to get your hands on an older enduro frame- cut it up, measure tube thickness/shape/size, then back out the tensile strengths- ie if the frame is 6061 and you're using 7075- and you have a ballpark figure. Can easily measure steerer tubes as well.
FEA is hard and an incorrect assumption at the beginning can mean the results are trash... Good to verify your FEA loads/assumptions on an existing product.
Cool project- love to see it!
For the front triangle we wanted it to be stiff in all directions. For the rear triangle, truss ss and cs can be optimised to get the compliance we want.
As for the prototypes. We are aiming middle summer.
We are sure that the glued bonds are enough to keep up with high loads and fatigue stress. We are helped by people working in the field.
With regards to the mechanical failsafe – it’s simple, low-cost, and adds peace of mind when you’re dropping into gnarly features. Hopefully, we’ll never need it… but it’s there, just in case.
Some technical details will follow later.
Magnifique Laurent!!! Vivement la bête en vrai
))
That sir, is a big yes. Excited to see this project going. Bien joué Laurent 🙂
Here’s a quick update:
The design is 95% complete — just a few small parts left to fine-tune. The finite element simulation is done and looks promising. Some shapes had to be optimized to reduce stress concentrations, and we’ve achieved a solid safety factor (to be confirmed with real-world and bench testing, of course).
The rear triangle has been tuned to deliver the compliance we’re aiming for. That compliance will be adjustable thanks to an interchangeable bridge on the chainstays.
We’re super excited and can’t wait to see the prototype come to life!
We made it!
Follow us on Instagram
Thanks for your comments.
Nice
Make a bike check so this can be bike of the day!
Beautiful!
Any reason why you guys didn't go with an Effigear? Get a high pivot placement without an idler
In fact there are two models of Effigear. The one you mention has an offset output shaft. We didn’t go with this one as we wanted to be able to tweek the anti squat value by placing the idler where we want.
The other one, the mimic, has only nine gears and can only downshift if we release the power.
However we are not closed to test it someday.
When will your page go live? Would love to see where you guys are situated. Its a lovely bike and i would love to see one
Congrats! Bike looks amazing!
Ive always wondered, does cleaning the truss rear triangle become a pain in the ass? How much mud and dirt gets stuck in there?
We’re currently working on the website, but our main focus is on testing for now. We expect to launch the first batch by mid-next year, or sooner.
We are based in Vevey, near Lausanne. Don't hesitate to contact me if you'd like to test it out.
Thanks Steve. This is really appreciated.
To be honest, we haven’t tested it in muddy conditions yet. However, as the pockets face outward, mud thrown by the tire is unlikely to accumulate. If it does, a pressure washer should easily clean it off.
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