From the beginning, the Purple Haze was designed to sit confidently between worlds. It needed to be efficient enough for long days on fast gravel, but composed when the route turns rough, remote or simply goes on longer than planned. That balance defines every aspect of the frame – its tubing, its geometry and the way it is built.
Designed with intent
With clearance for tires up to 55 mm, the Purple Haze is made to run volume without apology. Big tires are not treated as an exception here, but as a fundamental part of how the bike works: traction, comfort and control over imperfect terrain, without losing the direct feel that makes covering distance enjoyable.
We do not design our frames around single numbers or isolated features. Instead, we look at the complete system: rider, load, terrain and time in the saddle.
The geometry of the Purple Haze is deliberately balanced. Stable enough to stay predictable when speeds rise or surfaces deteriorate, yet responsive enough to feel engaged on everyday rides. It is not a bike built to impress in a parking‑lot test, but one that settles into its rhythm over hours and days – the kind of bike that fades into the background while the landscape takes over. This approach is also reflected in the tubing. Wall thicknesses, diameters and transitions are chosen for their specific role in the frame. Stiff where forces need to be transferred, compliant where comfort and traction benefit from it. Nothing here exists to meet a marketing target – it exists because it affects how the bike rides, carries load and ages.
Built because we build
Every Purple Haze frame is built by hand in our own workshop in Saxony.
That matters to us – not as a romantic notion, but as a practical one.
Building frames ourselves means we are directly responsible for every decision we make. From tube selection to alignment, from joint preparation to the placement of every single mounting point. When something is added to the frame, it is because it serves a clear purpose – mechanically, functionally or both.
This control allows us to refine the Purple Haze over time without losing its character. The platform has evolved since its first iteration, but its core idea has remained unchanged: a dependable, capable gravel bike designed for riders who value consistency over spectacle.
Made for long routes and open plans
The Purple Haze has quietly built a reputation as a bike that goes places. Not because it demands adventure, but because it allows it. It carries speed well, stays composed under load and remains predictable when conditions change. Fast when the route calls for it, calm when it doesn’t.
It is the kind of bike you take when the plan is loose, the surface uncertain and the day long. A bike that supports the ride rather than defining it. Small detours, big journeys, familiar roads or completely new ones – the Purple Haze is ready because it was designed and built with exactly these scenarios in mind.
| 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
Custom bikes – Painted in Dresden
We love custom colors on bikes. We’ve offered custom powdercoating, done right here in Dresden, since our very frist day of operation.
Every year with have two or three standard colors if you’re not interested in stressing out over the thousands of solid colors, fade, gradients, and pearls… but really, there’s nothing more fun than a frame in your own color!
We have a selection of custom colors, just to keep it a little simpler, but if you’re really looking for super duper custom colors, we’ve got that too.
Click below to learn more about custom colour and braze-on options.
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 in Germany 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 have a replaceable derailleur hanger.
The seat clamp is designed in-house 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
Bottom bracket: 68mm T47 threaded bottom bracket
Axle: 12mm x 142mm thru axle
Seat post: 27.2mm
Brake standard: FM160 Direct. More info here.
Wheel size: Size XS/S 650B ooptimized (bb height), M – XXL fit 700C/29“
Tire clearance: up to 55mm
Tubing: Custom drawn, multiple butted, partly heat treated SOUR CrMo (we love steel)
UDH/Transmission Compatible
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
external cable routing on the downtube for mechanical drivetrains
internal brake hose routing
27,2mm seatpost diameter for maximum comfort
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 Haze Frame Medium = 2195g ±50g
Small Parts: Bolts, rear axle, brake mount, derailleur hanger= 160g
Included with your frame
Included with your Purple Haze frame or frameset is all the grommets and small parts to run any cabling you wish and a derailleur hanger. 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.
