We’ve seen them on the trails at races for a couple years as prototypes, but Sour’s two all-new steel Cowboy Cookie and Double Choc full-suspension mountain bikes are ready for the big time. Pick from the downcountry SRD Cowboy Cookie if you are hitting local singletrack or heading out on bikepacking adventures. Or go all-in on Sour’s SRD Double Choc if you want to take on bigger all-mountain trail rides.
Just act fast, as these are coming only in seriously limited small batches…
Sour SRD steel & alloy full-suspension German mountain bikes
These two Sour mountain bikes mark the official debut of SRD – Sour Racing Development. These are the Homebrew project bikes Sour created for their own team and their athletes. Ever since Sour brought all of their production from Taiwan back to Germany, they knew reduced lead times and shorter development cycles meant they could take on more fun new projects.
The folks at Sour ride a lot of mountain bikes. And one of the first things they did building bikes in Germany, was start tinkering with full-suspension bikes. I actually saw the first linkage-driven single-pivot Double Choc almost 4 years ago.
(Secret insider bike rumor… a simpler, lower-cost single pivot MTB project is still developing in the background of Sour’s workshop, from what we hear.) But it takes a long time to perfect even a classic design, so now Sour are hyped to offer their first two full-suspension mountain bikes to the masses.
Well, a small mass. The two SRD bikes are available to the public in super limited edition batches a few times a year. All, entirely made in Germany, at pretty reasonable prices – compared say to a carbon frameset or something exotic in metal like an Atherton or Frameworks frame.
Sour SRD Cowboy Cookie vs. Double Choc
The Sour SRD Cowboy Cookie is a 120mm XC to Downcountry bike ready for adventure, paired to 120-130mm forks. And the SRD Double Choc is a full-on Trail bike with either 136mm or 148mm of rear wheel travel depending on different rockers, and 140-160mm of travel up front.
Both share the same classic Horst-link 4-bar suspension design – in fact, only the front triangles are different between these two new mountain bikes. They both feature a flip-chip at the lower shock mount that lets riders tweak their geometry: +/- 0.3° at the headtube & +/-5mm in bottom bracket height.
And they’re both entirely made-in-Germany.
Manufacturing & material details
The Cowboy Cookie and Double Choc both match Sour-welded steel mainframes to Actofive-machined seatstays & rockers, literally CNC-machined 600m down the street from Sour HQ. You may notice the similarity with Actofive’s own short-travel I-Train which was developed alongside this SRD project with Sour.
All of these prototypes we see here had chainstays welded by Nicolai. But Sour have their own welded 6061 swingarm in the works now too, which will be ready for this first round of production bikes. Sour were just anxious to get the new SRD mountain bikes out to riders as soon as possible, so we haven’t seen the new rear just yet. Eventually, we hear there will be Sour’s own seatstays too, to help bring costs down.
All elements are designed by Sour, from suspension design to the intricately machined steel bottom bracket clusters holding the main pivot and lower shock mount. Sour makes what they know best – welding butted 4130 steel. Then, they lean on their fellow German craft manufacturers to do what they do best – working the aluminum rear end, rockers, and geometry adjust hardware.
Into the weeds of shared tech details & adjustable geometry
Both custom-butted & heat-treated 4130 chromoly steel frames feature a custom-machined tapered headtube to fit an integrated headset (EC44/ZS56).
They also feature similar custom-machined steel bottom bracket assemblies that fits a 73mm BSA threaded BB, the main pivot, and the flip-chip.
Sour designed the bikes with their geometry in the High flip-chip position. And they deliver the bikes with alloy hardware for the High/Low position – swapping to Low drops the BB 10mm, slackens the head angle 0.6° & slackens the seat angle 0.94°. But they also will offer a Mid chip to split the difference for any buyers wanting a middle-ground geo option.
Out back, the rear ends are all the same, so you get UDH compatibility, a replaceable direct Post Mount 180mm brake bracket, a Syntace X-12 Boost thru-axle, and max 2.5″ tire clearance. Sour recommends 2.2-2.4″ tires for these type of bikes, though.
Both frames also build in a steel seatpost clamp (that Sour says can always be chopped off & replaced with a conventional clamp down the line if you ever damage it) for a 31.6mm seatpost. Cable routing is external on top of the downtube, but of course there’s internal dropper routing, too. The frames come standard with 1 set of downtube water bottle bosses, plus a set of braze-ons above the shock for a tool carrier. Optional additional cage mounts under the downtube and toptube bag braze-ons are also possible.
Sour SRD Double Choc 136 or 148mm steel mountain bikes
With a 64.5° headtube, Sour designed this bike for all-mountain riding, or even the bikepark. You pick the rear travel you want based on how you plan to ride it – 136 or 148mm with one of two rocker links. The Double Choc comes in three stock frame sizes (M-XL). It features a lower toptube for extra stand-over clearance, with a pair of gussets to support the extended seattube, and still plenty of room for long travel droppers.
- Headtube: EC44/ZS56 tapered, with additional gussets
- Wheelsize: 29″ (M, L & XL)
- Fork travel: 140-160mm, with 44mm offset
- Shock: 210x55mm shock dimensions
- Drivetrain: 1x-only, 34T max chainring, UDH & SRAM T-type compatible
- Weight: 3480g, raw medium frame including linkage, bearings & all hardware (+50-200g for powdercoat paint)
Sour SRD Cowboy Cookie 120mm steel Downcountry mountain bike
While the almost-enduro Double Choc was the first full-susser to come out of the SRD workshop, this Cowboy Cookie was really SRD’s first racing mountain bike. But not for XC racing. Instead, Sour created the Cowboy Cookie to have an efficient-pedaling ultra-distance bikepacking racer. Designed as a short-travel trail bike or long-travel marathon bike, it combines a smooth ride over any terrain with expedition-ready durability.
Sour athlete Quinda Verheul has put the new Cowboy Cookie through the ringer. She’s raced the new bike in loaded bikepacking races from the mountains of Morocco to the deserts of Death Valley to the rocky, rainy terrain of the Scottish Highlands. Sour gave her a prototype last year and told her to go break it. She hasn’t yet.
With a 65.5* headtube, the Cowboy Cookie comes in four stock frame sizes (S-XL) with progressive, but all-day stable geometry.
- Headtube: EC44/ZS56 tapered
- Wheelsize: full 29″ for sizes M, L & XL; mullet with a 27.5″ rear wheel for size S coming in late 2024
- Shock: 195x45mm metric
- Fork travel: 120-130mm, with 44mm offset
- Drivetrain: 1x-only, 36T max chainring, UDH & SRAM T-type compatible
- Weight: 3180g, raw medium frame including linkage, bearings & all hardware (+50-200g for powdercoat paint)
Sour SRD MTB: Cowboy Cookie & Double Choc – Pricing, options & availability
As part of the SRD program, both the Sour Cowboy Cookie & Double Choc are strictly limited editions. Sour will offer 20 of each new SRD mountain bike at a time, in 4 time slots over the year. That means that pre-orders for each set will open on 4 Jun, 23 Aug, 17 Oct & 18 Feb 2025. In each pre-order window, once 20 of each bikes sell, you’ll have to wait 3 months for the next slot. Sour will deliver frames 10-12 weeks later. That is, the first buyers now should have their frames at the end of August, in time for autumn adventure races?
Both new SRD bikes are offered exclusively as frame-only for 3500€, without a shock (including 19% German VAT). Sour is happy to set you up with a Fox or Manitou shock too, depending on how you plan to ride the bike and what you are looking for. Then, you can coordinate complete bike builds with your local bikeshop.
