Paragon Machine Works quick release belt drive rocker dropouts

Paragon Machine Works is testing a “quick release” rocker dropout design for belt drive bikes. Typically, you’d need some sort of tension bolts to push the dropouts away from the bike to create tension in the belt, much the same as with chain-driven singlespeed bikes.

The new design is basically it’s a rocker dropout, but instead of using the threaded bolts to create tension, a quick release lever on the backside pulls things back as it closes.

The toggle clamp is attached to a turnbuckle bolt that allows fine adjustments to get the tension set properly and equally on both sides. On the driveside pic above, it’s closed, which pulls the axle rearward to the preset tension. You’d then clamp the skewer to secure everything into place and go ride.

Yes, it’s the combination of pressure from the skewer and the turnbuckle screws holding the wheel in position. PMW’s CAD designer Jeff Whinney says it only works with a 142×12 axle because the thinner 135×10 QR skewer wouldn’t be strong enough. It’s using Shimano’s e-Thru rear axle, but with a custom titanium nut engraved with their skull logo.

Pic, video and more details below…

Paragon Machine Works quick release belt drive rocker dropouts
Non-drive side shown in open position.

Open, the axle slides forward and creates slack in the belt. Unthread the axle and you should be able to wrestle the belt loose for simpler wheel removal (compared to pulling out your multitool to loosen tension bolts and loosing axle nuts). Besides saving a bit of time, it maintains your tension settings during wheels changes, offering something like set-it-and-forget-it.

If you’re ordering a custom bike with dreams of belt drives spinning in your head, might want to ask your builder about these.

Looks like it got cut short, but you get the idea.


  1. I just finished a belt drive build a month ago using one of Paragon’s slider drop out options. Cool company, great people and very, very nice products.

  2. So, it’s a not-at-all-quick-release quick-release with a cam, huh? It’s pretty. But pretty worthless as a QR dropout. How is it any better than a sliding dropout with an adjuster screw?

  3. >How is it any better than a sliding dropout with an adjuster screw?

    The main advantage is that you can easily reset the tension to exactly where it was. With slider dropouts you never really know exactly where it was at, and you have to remember precisely how much you moved the one side to get the other to work. Another problem with sliding dropouts is if you use disc brakes, as they will cause your wheel to slide in the direction opposite the adjuster screw on the non-drive side.

    This looks like a simple and sleek system that allows for very precise and repeatable wheel changes.

  4. It does look nice, but doesn’t seem all that necessary.

    I’m using normal sliding vertical dropouts on my belt drive Kona A. I do have a 10mm bolt-in hub, to stiffen up the rear end, but I have no problem getting the wheel in and out with the belt tensioned enough.

  5. I think the point is that it uses 142×12 through-axle. which would be nigh impossible to remove with tension on the belt.

    Why you would need 142×12 on a rigid steel rear end? I have no idea.

  6. This is funny I designed something very similar at Uni and it’s sat on my computer as a CAD file ever since! I designed one that would fit to any existing horizontal dropout though, rather than needing a completely custom dropout. Mine looks a little more industrial but does include a thumb screw to adjust the tension of the QR (set and forget). I don’t know how to attach an image to this comment but if BikeRumor would let me I’ll email them an image of the assembly for them to publish…..?

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