Quick Answer: What is the SimWorks Doppo Ronin?
The Doppo Ronin is a TIG-welded Tange Chromoly steel frame and fork, hand-built in Japan by Shin Hattori Works. It is a third-generation all-terrain bicycle designed for 700c/650b convertibility, flat-mount disc brakes, and tire clearances up to 700x43c or 650x55b. The first production batch was limited to 16 framesets worldwide.
Sixteen framesets. That is the total first-run production
count for the Doppo Ronin from SimWorks. Not a typo — not a limited colorway — the entire opening batch of this Japanese all-terrain frame exists in a number smaller than most bicycle shops carry in a single model. When a manufacturer restricts output this aggressively, the frame itself has to justify the scarcity. The Ronin does.
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Doppo Ronin Specifications at a Glance
The Ronin’s geometry has remained largely stable across three generations of the Doppo line, and SimWorks made that a deliberate choice. The frame ships in five sizes — S through XXL — each built around a 71.5° head tube angle (all sizes except XS), 440mm chainstays, and a 70mm bottom bracket drop. These numbers produce a handling character that sits comfortably between a dedicated road bike and a loaded tourer: neutral, stable under weight, and responsive enough for technical gravel.
| Specification | Detail |
| Frame Material | Tange Chromoly CrMo (No. 1–3 tubes) |
| Fork | Doppo Original Chromoly — Offset 49mm, Length 395mm |
| Head Tube | EC 34mm, straight 1-1/8″ steerer |
| Brake Mount | Flat-mount disc, front and rear |
| Max Tire (700c) | 700 x 43c |
| Max Tire (650b) | 650 x 55b / 27.5 x 2.22″ |
| Bottom Bracket | 68mm BSA threaded |
| Seatpost Diameter | 27.2mm |
| Front Axle | 12 x 100mm thru-axle |
| Rear Axle | 12 x 142mm thru-axle |
| Dropouts | SimWorks Original (Paragon 142x12mm inserts) |
| Bottle Mounts | 2 standard + 1 cargo cage (under down tube) |
| Fork Mounts | 3-pack cage mounts, both legs |
| Drivetrain | Compatible with double or single |
| Sizes Available | S, M, L, XL, XXL |
| Paint | NIC Prismatic Powder Coat (Oregon, USA) — Deep Burgundy |
| Built By | Shin Hattori Works, Aichi, Japan |
Where This Frame Belongs on the Road
The Ronin is not a road bike wearing gravel tires, and it is not a touring frame with an identity crisis. The geometry and tire clearance numbers tell you exactly what it is: a machine engineered to spend the majority of its working life on mixed surfaces. The 440mm chainstay length keeps the rear triangle compact and responsive on dirt, while the 70mm bottom bracket drop and 71.5° head angle give it enough trail to carry speed on packed gravel without becoming skittish.
Practical use cases stack up quickly. Commuting on a mix of bike paths and unpaved shoulders. All-day gravel rides on fire roads and forest service tracks. Multi-day touring with panniers or frame bags — the cargo mount points on the fork legs, down tube, and seat stays give you room to carry meaningful weight without routing issues. The 650b conversion option opens the door to fatter tires for softer ground, which makes this frame relevant in regions with clay-heavy or sandy soil conditions where 700c clearance falls short.
The Doppo Original Chromoly Fork — Rebuilt from the Ground Up
The fork included with the Ronin is not an afterthought bolted onto a frame. It is a purpose-built Chromoly uni-crown design manufactured by Tange and co-developed with SimWorks to mirror the rear triangle’s geometry and clearance envelope. The 49mm rake and 395mm axle-to-crown length were selected to match the frame’s head angle across all sizes, producing consistent trail and steering feel whether you run 700c or 650b wheels.
Flat-mount disc brake mounts sit front and rear, and the fork legs carry dual 3-pack cage mounts on each blade. Fender and rack eyelets are present — and positioned deliberately. The crown-mounted fender boss sits recessed, which allows a standard full-length fender to clear a 700x43c tire without custom cutting. The 12 x 100mm thru-axle front end adds lateral stiffness that matters under braking load, particularly when the fork is carrying weight.
Tange Steel Construction and the NIC Prismatic Finish
Tange tubing is the backbone of the Doppo line, and the Ronin uses tubes graded No. 1 through No. 3 from their Chromoly range. These are not budget-tier CrMo tubes pressed into service for cost reasons. Tange is among the oldest and most respected tube manufacturers in the cycling industry, and their steel sets have been the foundation for Japanese framebuilders for decades. The TIG welding is handled by Shin Hattori Works in Aichi, Japan — a small shop with a reputation for clean, precise work on production frames.
The paint finish on the Ronin is NIC Prismatic Powder Coat, applied by NIC Industries in Oregon. Powder coat is inherently more durable than traditional liquid paint — it resists chips, scratches, and UV fade better than most alternatives. The deep burgundy color chosen for this production run has a glossy depth that catches light without being flashy. It pairs cleanly with silver or black component groups, and it holds up to the kind of regular use that an all-terrain tool is supposed to endure.
Frequently Asked Questions
Who builds the Doppo Ronin frame?
The Doppo Ronin is hand-built by Shin Hattori Works in Aichi, Japan. The frame is TIG-welded using Tange Chromoly steel tubes and features SimWorks original rear dropouts developed in collaboration between Shin Hattori and SimWorks’ own welding team.
Can the Doppo Ronin run both 700c and 650b wheels?
Yes. The flat-mount disc brake system and dropout geometry allow full conversion between 700c and 650b without any modification. In 700c the frame clears tires up to 43mm. In 650b, clearance extends to 55mm, which opens the door to tires with meaningful tread for off-road use.
How many Doppo Ronin frames were made in the first batch?
The initial production run was limited to 16 framesets worldwide. SimWorks has not confirmed future restocking dates, making each first-batch Ronin a low-production frame by design.
What type of paint is used on the Ronin?
The Ronin uses NIC Prismatic Powder Coat from NIC Industries in Oregon, USA. The finish is a deep burgundy with a glossy texture. Powder coat offers stronger scratch and wear resistance than standard liquid paint, making it well-suited to a frame intended for daily and mixed-terrain use.
James Hickman is a former USA Cycling Expert coach, Leukemia & Lymphoma Society’s Team N Training coach and Masters category racer with podium finishes in So Cal events.
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