At its core, the Purple Pie combines three elements that define how it rides: large tires, a steel frame and a Pinion gearbox. Together, they form a system focused on durability, consistency and control across a wide range of terrain.
A different approach to drivetrain design
The Pinion gearbox is not a feature choice for us – it’s a design decision.
By placing the gearbox at the center of the frame, mass is kept low and centralized, chain wear is dramatically reduced and shifting performance remains consistent regardless of conditions. No exposed derailleur, no compromised chainline, no tuning required mid‑trip.
This setup allows the Purple Pie to focus on reliability. Long rides, bad weather, extended trips – the drivetrain stays quiet, protected and predictable. It’s a system designed to work every day, not just on perfect ones.
Asphalt, gravel, forest roads or light singletrack – the Purple Pie doesn’t ask what surface it’s on. It simply keeps moving.
Built around real tire volume
With clearance for tires up to 55 mm, the Purple Pie embraces tire volume as a foundation, not an accessory. Larger tires are central to how the bike handles uneven surfaces, carries speed over rough ground and maintains comfort on long days in the saddle.
The geometry complements this approach. Steering remains precise and responsive, while the overall feel stays calm and grounded when surfaces deteriorate or loads increase. This balance makes the Purple Pie equally comfortable covering distance or drifting off into less defined routes.
Made to last, built by hand
Every Purple Pie frame is built by hand in our own workshop in Saxony.
That means we don’t separate design from execution. Tube selection, alignment, welding and the placement of every mounting point are part of one continuous process. Each joint and connection is considered not just for strength, but for how it contributes to long‑term durability and ride quality.
The result is a frame that is robust without feeling overbuilt, and precise without becoming precious. A bike meant to be used, loaded, ridden and trusted.
Built to get lost – and to get home
The Purple Pie is ready to write its own story.
Not because it demands adventure, but because it enables it.
It’s quick when efficiency matters, stable when conditions worsen and dependable when the ride turns into something longer than planned. The kind of bike that supports curiosity rather than controlling it.
Whether the route is mapped carefully or made up along the way, the Purple Pie is designed to keep going – quietly, reliably and without fuss.
| Geometry | XS | S | M | L | XL | XXL |
|---|---|---|---|---|---|---|
| ST Length (mm) | 450 | 480 | 510 | 540 | 570 | 590 |
| TT Length (mm) | 519 | 532 | 545 | 561 | 576 | 594 |
| Reach (mm) | 374,2 | 378,2 | 377,6 | 382,7 | 383,8 | 389,9 |
| Stack (mm) | 540,3 | 554,4 | 583,9 | 602,1 | 628,5 | 647,5 |
| HT Angle (°) | 70,5 | 70,5 | 70,5 | 71,5 | 71,5 | 71,5 |
| HT Length (mm) | 120 | 135 | 145 | 160 | 190 | 210 |
| ST Angle (°) | 75 | 74,5 | 74 | 73,5 | 73 | 72,5 |
| CS Length (mm) | 440 | 440 | 440 | 440 | 440 | 440 |
| BB Drop (mm) | 72 | 74 | 72 | 72 | 70 | 70 |
| Wheelbase (mm) | 1031,8 | 1034 | 1040 | 1042 | 1052 | 1064 |
| Fork Length (mm) | 405 | 405 | 405 | 405 | 405 | 405 |
| Fork Offset (mm) | 45 | 45 | 45 | 45 | 45 | 45 |
| Max Seatpost Insertion (mm)* | 241 | 271 | 271 | 301 | 331 | 351 |
| Wheel Size | 650B | 700C | 700C | 700C | 700C | 700C |
* Max seatpost insertion +5 mm / min. seatpost insertion 120 mm
At Sour, framebuilding is not a black box.
t’s a controlled, repeatable process where design decisions become physical structure.
Every frame is fabricated and welded in‑house, in our workshop in Saxony. This proximity between design and fabrication is fundamental to how we work. Tube selection, alignment, joint preparation and welding are not separate steps handled in isolation — they are part of a continuous process, informed by both engineering intent and hands‑on experience. Building frames ourselves means we take responsibility not only for how a frame rides, but also for how it is made.
How we see Steel
At Sour, steel is not a stylistic choice.
It’s a design decision.
We use steel because it allows us to define frame behavior precisely — under load, over time, and across a wide range of riding conditions. Material choice, tube selection and heat treatment directly influence how a frame transfers forces, responds to repeated stress and ages through use.
All Sour Bicycles frames are made by hand, one-by-one, in our own facility in Saxony, just outside of Dresden. We use custom tubing designed and drawn for our frames, it’s a multi-butted heat-treated CrMo steel that’s ready to stand the test of time. All our steel is produced from a partially recycled product and drawn by one of the worlds leading production facilities in Taiwan, the beating heart of the worlds bicycle production.
Our dropouts are designed in-house in Dresden and cast made for us.
The seat clamp is designed in-house as well and is integrated into the frame. Should it ever fail, the frame can be professionally modified to use a traditional clamp, if repair of the original clamp is not possible. We have never seen one fail.
By The Numbers
Headtube: 44 mm upper and lower
Pinion Smart.Shift Gearbox Frame Bridge
Axle: 12mm x 142mm thru axle
Seat post: 27.2mm
Brake standard: FM160 Direct
Wheel size: 700C/29“
Tire clearance: up to 55mm
Tubing: Custom drawn, multiple butted, partly heat treated SOUR CrMo (we love steel)
Bonus facts and features:
Fender and rack mounts
Recommended tire size 45mm – 55mm
Two water bottle mounts inside frame, a third bottle mount under downtube
internal brake hose routing
Business Fork
The Business Fork is our carbon gravel and adventure fork designed for all the adventures, big and small!
We designed this fork in-house and worked with our long-term production partner in Taiwan to make it. We have tested this fork at EFBE in Germany and pass their Tri-Test with flying colors!
Specs
Maximum Tire Width: 55mm
Axle to Crown Length: 403mm
45mm Rake
Tapered Steerer Tube 1½” – 1⅛”
Thru-axle 12mm x 100mm
3 Cargo Cage Eyelets on Fork Legs
Internal Dynamo Cable Routing
Flat-mount Brake Mount 160mm
Fender Mounting Possible
Weight With Full Steerer and Axle: ±565g
Brake Mount Thickness: 35mm
Below are the frame weights for each size of the Sour Purple Haze. These weights do not include powdercoating, but please keep in mind that your chosen powdercoat may be heavier than the average coating we use. Fades, gradients, and metallic colours can weigh more than single solid colour powdercoat. If you are interested the final weight, please get in touch. Weights are averaged over three frames per size. We apply a wax coating on the inside of the frame for rust prevention, this will also add a small amount of weight.
Purple Pie Frame Medium = 2795g ±50g
Small Parts: Bolts, rear axle, brake mount, derailleur hanger= 160g
Included with your frame
Included with your Purple Pie frame or frameset is all the grommets and small parts to run any cabling you wish (as longh ist it’s internal lol) You get a rear thru-axle of course, and if you’re ordering a frameset, you get a front axle with your fork as well. Headsets are only included if you add one to your order.
A Pinion‑equipped all‑terrain bike, built with intent and designed for long routes, loose plans and real use.
