Jones Steel Diamond Frame with Unicrown Fork

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Steel Diamond frame and Jones unicrown fork (frameset)

This is the Jones geometry (and superb handling) as a traditional diamond frame. This, being easier to build, costs less than the Spaceframe version, and while it doesn't offer the same compliance, the seat and seat stay tube dimensions have been carefully selected to both improve the ride and reduce the weight.

Construction: The frame is TIG welded 4130 chromoly with a butted down tube. The cable guides and bottle bosses are brazed on. The latest versions (above) have a clear powder coating, over the decals, on top of the tough powder coat paint finish for appropriately rugged good looks. A full range of frame-fitting bags are available for bikepacking and touring capabilities and the 4130 Cro-Mo butted Unicrown forks have custom mounts for the Tubus Duo low-rider racks.

The fork has clearance for 29 X 2.55, 29+(3) and 26 X 4.8 fat tires.


 The fork is compatible with 135mm front hubs such as the Jones 135/142-F. These hubs have very wide flange spacing that allow for a very stiff and strong front wheel. Fork not compatible with 135mm rear hubs or front hubs with rear hub specs.

 BB is 68mm wide

 Frame include a Bushnell featherweight EBB, one derailleur hanger, one singlespeed dropout insert, bolts and cable clips.

 Bottle bolts, hanger nut and bolt are stainless steel.

 The Jones unicrown fork uses standard 1-1/8" headset.

 Seat post size is 27.2mm

 Seatpost clamp size is 31.8-32mm.

 Rear tire clearance up to a 29 x 2.5" on a 50mm wide rim.

Our blog has more frame information and some bikes that Jeff and our customers have built:

Frame and fork details


Singlespeed with 29" wheels

Singlespeed with fat front wheel

Bike pack and camp

Why this bike? It's a high performance non-suspension bicycle... instead of designing the bike for XC-racing like so many unsuspended bikes. I wanted this bike to be better for technical and distance riding... Since this bike is not designed around a suspension fork I'm able to do much more to improve the handling. By designing the frame and fork together and considering the larger wheels I'm able to make a bike that rides very differently to a 'normal' rigid bike (be it 26 or 29er) with a short rake fork.

My bike has a slacker seat-tube and a shorter top-tube than 'normal' bikes... the head angle and rake with this wheel size (more rake, slacker head-tube-angle and bigger wheel) determines the trail which helps determine the handling. Slacker angles keep the rider's weight off the hands and makes the front end easy to lift; the center of gravity is moved back and down for more control, with less shock to the upper body, more traction under braking, and a bike that is much harder to endo. This bike feels quick but also has a laid back feel. It's the best handling bike I've designed.

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