Sour Bicycles SRD Steel Full Suspension Review: A Rolling Prototype

Peter Georgallou might be the last person ’round these parts you’d expect to test an all-mountain/enduro full-suspension mountain bike like the steel single-pivot SRD prototype from Sour Bicycles but that’s what makes his review so interesting. Continue reading below as Petor dives head-first and in-depth into a new-to-him world of riding in addition to a preview of some exciting things to come from our friends at Sour…

How we found each other…

I have not owned a mountain bike in recent times. This might mean that I have never owned a mountain bike because a mountain bike, in modern times, is so separate from the uncomplicated machines of the ’90s that I grew up riding. The mountain bikes that I have owned have mostly functioned as off-road tourers. Most notably, a 1998 Specialized Rockhopper (on balance, perhaps the best bike ever made), a Rock Lobster Team Tig 853, a first-generation Surly Krampus, and a slew of other bits and bobs I made myself.

With the exception of the Rock Lobster (a superb bike in its own right), they all made fantastic touring bikes, and I put in many off-road miles on each over the years. But, by modern mountain biking standards, they’re all on the gravel end of the spectrum. The Krampus has to be my favorite to ride now because 29 x 3.0 is exceptionally forgiving as a wheel/tire size so despite road cycling being my first love, and having not grown up riding mountain bikes properly, I can keep up with people on proper mountain bikes by catching them on the uphills.

I guess each of these bikes could be a proper mountain bike (if I was a proper mountain biker), but until just now, I’ve been inclined to keep both wheels on the ground, doing my best to avoid any loss of traction, and—for the most part—stay within some parameters of verticality. This has led to my firmly held belief that Chris and Joergen of Sour Bicycles are either the kind of evil geniuses I’m glad to call my friends or perhaps saboteurs, insiders making a play to take me down one collarbone at a time.

Me: “Of course I’d LOVE to review a bike!”

Sour: “If you could pick a bike, which one would you choose?”

Me: “Hmmmm…I’d love to be the sort of person who could do a worthwhile review of the Double Choc prototype, but in reality, the Bad Granny probably makes more sense because it’s kind of fun and the thing I think I could do the best job of because it’s what I’m closest to? What bike do you think I should review?”

And that’s how I ended up with my first PROPER mountain bike: a big squishy “trail-duro” mountain bike. I’m not even sure what I mean by a proper mountain bike. Perhaps it’s a bike for proper mountains or just-for-fun riding. The bike that I ended up with isn’t even a bike. Obviously, it’s a bike because it has two wheels, and you turn the pedals to ride it, but the bike that I have been riding is a prototype, which is to say that it isn’t a bike yet because it doesn’t even have a name.

It was built under the ambiguous and slightly tongue-in-cheek Sour SRD umbrella (more on that below). It’s neither an enduro bike nor their new race-proven ultra-distance/XC prototype we saw at last year’s Bespoked. It’s something in the middle, for a kind of riding I’ve never really experienced, and which I need to make a six-hour round trip from my house in a car to attempt. Mountain Biking. In many ways, it’s the bike least meant for me, at least on paper, and I’m the rider least meant for it.

What even is it?

My SRD’s life began as a pile of mitered tubes destined to be an iteration of the forthcoming enduro-focused Sour Double Choc during the middle stage of Sour’s onshoring process when tubes were still mitered in Taiwan and welded in Germany. Due to some mis-mitering, the tubeset couldn’t accommodate the tire clearance required by the Double Choc as well as the Horst link, so whatever it is that I’m riding was born.

Geo Quick Hits: Sour SRD Prototype

  • Size: Large
  • HTA: 65
  • STA: 77.8 s
  • Reach: 475 mm
  • Chainstay length: 445 mm
  • Travel: 160 mm front/ 150 mm rear

Chris took one of ten tubesets that didn’t work out as an opportunity to redesign the swing arm to accommodate a simplified single-pivot suspension design with just enough room for a 29×2.5″ tire and some mud clearance. As a result, the mis-mitered tubes could be used to build a fun bike to be given to friends, and after some happy accident, I ended up with one—a steel, single-pivot, long-travel trail bike or, perhaps, a slightly sketchy enduro bike.

SRD (Sour Racing Development) also stands for Stadtreinigung Dresden, Sour’s local refuse collection and recycling company. The twist feels doubly fun as my SRD is made from tubes that were actually repurposed. Given my non-mountain biking background, there may have been some mixup before I took the bike about what a trail bike is for. Contrary to my belief that it’s a bike for riding trails, I found out later that it’s instead a bike for riding at trail centers, which I guess is proper mountain biking.

The Build

The frame is made from custom butted and bent 4130 tubes and cast parts manufactured in Taiwan. The frame was welded just outside of Dresden, Germany. While we discussed a basic bitch build kit as an intro to mountain biking, when I collected the bike it was built with some of the most esoteric, decently high-end made-in-Europe parts out there.

The handlebars and rims were made by BEAST Components, which is also based in Dresden. BEAST is fairly new to the cycling industry but has a long history in composites manufacture with their sister company CarboLife, a world leader in high-end, ergonomic wheelchair rims and whose company director’s (Merko) previous career was in testing for aerospace engineering.

I visited the factory in 2022; the trip felt somehow elicit as I had to be expertly guided there through custom shop Lightwolf Studio’s warehouse, through a back door and some other manufacturing units, and round a corner to where the testing happens before finally meeting Merko there. Testing is a big part of what happens at BEAST; every component they build is built to significantly exceed ISO testing standards and what that means, in my experience, is stiffness.

BEAST Components

The 35-mm clamp diameter carbon risers that the bike came with have an anti-crush zone where they be clamped, as well as a soft, high-friction coefficient lamination on the outside in clamping areas because over-tightening of stem bolts is often a reason for handlebar failure. In this way, the bars don’t move, even with less-than-the-ideal torque, and won’t get crushed with more, so the risk of crush-based failure is mitigated.

In practice, that translated to the bars feeling significantly stiff. Regrettably ill-equipped for the scientific process, I’d estimate deflection over their ample span to be within the acceptable deflection tolerance over the same span for a rolled steel joist designated for constructing a skyscraper.

Obviously, the oversized 35-mm clamp diameter adds significant stiffness more efficiently than it adds strength, but it’s also designed internally to be super strong, which adds further stiffness. I’m not sure how it’s possible to feel the stiffness of a set of handlebars with 160 mm of suspension travel and a big squishy Schwalbe Wicked Will up front, but somehow, it is. On most bikes, the sensation would be unpleasant, but with all that movement going on below, eating anything the trail has to throw at you, the steel-beam-like stiffness feels quite confidence-inspiring and keeps the steering feeling agile and reactive.

It’s nothing about the effects of tires, suspension, and steering geometry, but the stiff bars worked nicely in the context of this bike. The BEAST rims also felt incredibly stiff both vertically and laterally, but again complemented the dynamic handling characteristics of a big squishy bike quite well. They were very light and felt incredibly solid, sustaining zero permanent damage from being repeatedly smashed against rocks when the tires bottomed out. I’m normally a fan of flex everywhere but in this instance, the super stiff BEAST parts kept the bike feeling positive and surprisingly efficient on climbs.


Tires are, for me, one of the most important choices for any build. Most people, including Schwalbe themselves, seem to think that the “G” in Schwalbe’s G series of tires refers to gravel, however, it actually refers to wildman and all round good egg Grant. Grant works for Schwalbe in the UK but in his spare time is also a tire nerd, who indulged me and my fantasies about the kind of riding I might do for far longer than reasonable.

Together, we made a decision about the direction that my riding would realistically take. It didn’t seem appropriate for my skill level to go for an all-in enduro tire like the sticky yet resilient Tacky Chan, although there were points riding through the UK winter that I wished I had. Instead, we chose the faster rolling and much lighter weight Wicked Will Super Trail EVO for the rear with the matching Nobby Nic on the front.

The lightweight, fast-rolling, and surprisingly resilient combo worked for me in two ways: They were light enough in combination with the BEAST rims that it opened up the possibility of long days riding cross country, and they forced me to learn very quickly that on a proper mountain bike, it’s ok not to have traction all the time.


The SRD was my first experience living with an INGRID drivetrain, which differs from running one. The RD-1 rear mech is by far the best-looking out there, but more critically, it’s unfussy about what other parts it works with, meshing equally well with 11—or 12-speed SRAM, Shimano, or even Campagnolo shifters.

(Of note: you needn’t run either, since INGRID now makes their own super simple, super ergonomic, and aesthetically pleasing shifter that works even better. Unfortunately, it didn’t exist when my SRD was built, so the bike came equipped with a SRAM shifter which was fine.)

The shifting itself is nothing to write home about, but it works well every time. You can drop half a cassette at once or make single shifts with the expected precision, and it works, but not as nicely as SRAM electronic shifting. I have never NEEDED anything to work as nicely as SRAM electronic shifting in horrible conditions.

However, I have needed a bike that can be maintained easily by any bike shop without ordering parts; I’ve needed parts to be repairable; and I’ve needed flexibility to run weird combinations of things so that I can use what I have instead of buying something new. These are needs that the INGRID rear mech satisfies, while neither SRAM nor Shimano does.

Looking at a component in isolation, I really prefer the performance of SRAM electronic shifting, especially in wet, grimy conditions, but some people prefer mechanical shifting, and those people prefer Shimano. Looking at buying a $600 mech, I love the idea that individual parts of the mech can be replaced if they get damaged, that it will run with almost any shifter, and that I can swap the cage out to run short or long so it can be used on more or less any bike.

It’s an expensive part, as expensive as an equivalent electronic shifter, and it won’t outperform those shifters, but it may well outlive them. And, because of its flexibility and repairability, it’s likely to outlast them in terms of its usefulness. Aside from that, it’s a looker for sure.

The INGRID cassette is just bonkers. My SRD came with the 10-52 wide range 12-speed version. It weighs in at 356 g and is machined in two parts, a heat-treated steel part for the first nine smaller cogs, and a hard anodized aluminum part for the three largest cogs to save weight. It offers amazing and consistent performance throughout its 520% range. At just over 400 euros it’s not inexpensive, but it’s built to last and offers an insane range for the weight.


I’ve always been a fan of Dresden-based Acto5 and their absurd CNC-machined frames. Conceptually wild and, in the flesh, a sight to behold. I will never need the performance that they offer, so thankfully, they make cranks for fanbois. The SRD came with the classic Acto5 mountain cranks, nice and short in 165—because this bike has all the gears—and long cranks are for flat-earthers.

They look great, and the finishing was fantastic. They’re about as light as I can imagine a crankset being, and they took a number of substantial hits due to my terrible riding and came off relatively unscathed. What more can you ask for from a crankset, and what more can I say?

Bike Yoke Bits

Bike Yoke is a brand with which I was not previously familiar, as they are best known for their droppers, mountain bike specific saddles with integrated suspension, and alternative yokes for rear shocks. I received the Sagma Lite version of their saddle without suspension, which was pretty comfortable. It was more padded than anything I’ve ridden for a long time and quite a bit shorter, as I’ve been riding mostly road-derived saddles forever, and I expect the Sagma Lite to be a little more enduro-focused.

The stem looked incredible in the unique raw forged finish. It weighs just 86 g and is tested to exceed standards for an enduro bike. The top cap, which integrates a bolt, looked great, weighed half nothing, and matched my Acto5 cranks well, although I’m afraid of aluminum bolts, even if it is just to preload the headset.

The real stars of the show were the grips, which were super comfortable, amazingly durable, had integrated bar ends, and were designed to be rotated with wear, which is unusual for lock-on grips. As for the dropper, I fiddled with it a few times at the start but otherwise just got it out of the way so I could ride. The dropper is designed for super quick and easy bleeding, which refreshingly takes significantly less time to do in reality than it takes to watch the 18-second video on their website about it.

There seem to be a decent number of specifically German brands that do a great job of making a good product at a reasonable price point that works well and lasts without feeling the need to update it frequently and whose marketing is more or less just data without a hint of lifestyle or aspiration. Bikeyoke is relatively obscure outside of Germany but I hope that changes, as everything they specced on the bike looked great and was a joy to use.


The bike started life with Berghaus flat pedals, because I felt like that was what I should run. However, a couple of months in I gave up on learning to hop things properly and switched to Hope XC pedals, hoping that they’d help me get some air. In fact, they didn’t as the sensation of jumping through the suspension was completely new, and my poor technique bunny hopping did not translate to a bike with suspension. Regardless, I did continue to run the Hope pedals because I felt more secure clipped in, which inspired greater confidence which in turn improved my riding, even if it was for the wrong reasons.


Suspension is just not something I’ve ever felt that I needed, so this is my first bike since owning a 1995 Pro-Flex 855 that has had suspension, and needless to say it’s a completely different box of frogs. I set the suspension up to the letter of the manual for my weight and rode it for a month or so like that to get used to it. Having never owned a proper bike with suspension and only having ridden one in anger a handful of times, I had very little to compare it to, but I do feel like 160 mm of travel on the front and 155 mm at the back are beyond my riding for sure.

Not knowing anything about it was sort of a luxury because I didn’t have any preconceptions about what it should be like, but also because the DT Swiss F535 does a lot of things, and has very clear instructions which gave me a lot of scope to fiddle around and learn how different things felt, and how that would impact my riding. To start with, I marginally overinflated the shock, but that didn’t feel quite right, so after some research and chats with Chris and Joergan over at Sour, I added some spacers to make it feel a little more progressive, which felt suitable for the kind of riding I was doing.


It’s unfathomable, to me at least, that anyone would need improved performance or reliability than the Magura MT5 brakes offer, however mine came with the Oak Components lever upgrade, which costs more or less the same as the brakes themselves. It’s a little lighter but a lot stiffer and easier to adjust than the original lever, and the one from Oak significantly improves the braking feel in my books, although that is sort of a matter of taste.

The stiffer lever feels a lot snappier and makes the brakes feel much more direct and powerful, whereas the original lever has greater modulation and feels a little more progressive. The Oak lever adds a twizzly knob for adjustment normally reserved for the MT7, so if that’s important to you then the Oak lever upgrade might offer an alternative to a fancier brake set.

The Ride

There were perhaps three weeks after I’d brought the bike home, it sitting in my living room, where I just looked at it a lot, half in disbelief that I owned a real mountain bike and half worrying about not riding it properly enough. After three weeks, I took it out for the first time on a familiar route to try to ride it up and down some sets of stairs or to drop off street furniture to get a feel for it before taking it out on trails.

I find intact collarbones to be both beneficial and desirable in my line of work and as a self-employed person, so I was overly cautious to start with, riding an alien-feeling bike on things that I can’t ride. It’s a good-looking bike with a concise and consistent design language used throughout the frame, with all the castings for the pivot points matching the dropouts and gusset shapes. It looks pretty minimal for a long travel mountain bike.

While I’m not going to pretend to have ridden enough trail bikes or enduro bikes to be able to make nuanced observations about suspension kinematics, I have ridden enough bikes over the past two decades to have a good idea about what worked for me and how the bike felt to ride. It’s a bold move to build a deliciously dynamic and forgivingly flexy steel trail bike in Germany, the heartland of stiffness being touted as the grail of bicycle manufacture in cycling media.

The simple single-pivot design might not satisfy the needs of committed enduro racers or kinematic sniffers, but through well thought pivot points and the mounting of a decent shock, a single pivot offered surprisingly good performance dropping down things and hitting big stuff on the trail.  All the while being simple and, in my experience, maintenance-free with four sealed bearings between the swing arm and the frame.

Having some flex in the swing arm helped significantly with rear wheel traction through berms and cornering at speed without detracting too much on climbs, and the moderate chainstay length (which felt longer than I expected) gave the bike a feeling of predictability and sure-footedness.

At the other end, the font center was moderate and reasonable. It wasn’t the super-hyper-extra-long enduro-specific wheelbase I expected, and while for a minute that was disappointing, the disappointment was only relative to my expectations rather than the reality of riding the bike long term.

While a fairly moderate geometry by 2024 standards didn’t give me the immediate stability bombing down hills, at a speed and level of technical difficulty that I’m uncomfortable with, it made the bike surprisingly versatile, and the sort of bike I’d want to live with rather than ride for a day.

A fairly conservative geometry made (what could have been hard work) the SRD become my new favorite XC bike, my best bike for trail centers, a thing to take on gravel rides occasionally, and a bike with headroom in its capabilities for me to progress to bigger riding.

I’m not sure I know any cyclists or even bike people who could reasonably ride the SRD without having fun. It’s like having a weird friend who your parents accept through familiarity over time, who’s low-key and effortless to hang out with, but who also goads you to climb lamp posts, snort wasabi in the cinema, and get thrown out of the club for dancing too weird on a night out.

These are the types things the SRD did the best: being a mild-mannered jack of all trades happy to show up to pretty much any kind of party it’s invited to, but also bringing the fun in a low maintenance, relaxed, and unfussy way to most situations.

What I used it for

I’d expected to have to make huge efforts to get the best out of the SRD, but what surprised me in the long run the most was how useful the bike became. I started out fairly excited about improving my skills in riding mountain bikes by making an effort to drive to places where there are actually decent trails. It was fun, and I did learn and improve, but the best part was taking time to go riding with friends who I don’t see often enough and almost never ride with.

The geometry was designed around being versatile and fun, with long travel but less ultra-long and ultra-stable than an enduro bike. After a few trips out to various trail-heavy bits of woods, I just started riding it as much as possible on anything to get a feel for it and the way it moves, and in a way, it became exciting for all the right reasons. On the SRD, I could pretty much ride anything that exists locally, which I hadn’t experienced before. A set of steps or a broken slipway, the bit of woods between one path and another or any section of landscaping in a public park.

The lack of anything fun to ride locally and my deep desire to ride the bike all the time instilled a sense of being lost and bored, which seemed to always result in play. I’d cruise around looking for things to ride up, down, off, or onto. I could go out for a ride with no aim and no idea where I was going and have a great time just repeatedly trying to hop over a log or riding down a set of steps fast enough to be able to ride up again on the other side; just playing around by myself, having a nice time.

Because the build, and especially the wheelset and tires, were so light, the SRD was no slouch cross-country; in a pinch, I even used it to cover a gravel event on a harrowingly wet and hellishly sloppy October weekend where it didn’t feel at all like a compromise beyond the reach is a little short.

Overall, I increasingly rode a fairly niche bike relative to my location for normal stuff and having a great time. I was overbiking for sure, but simultaneously, I was pushing myself to ride new things rather than pushing my fitness as I’d expected. I started out locking out the rear shock each time I came to a climb, forgetting to release it for descents, fiddling and fussing with bits and bobs, learning about the gizmos that I haven’t used before but once I’d fiddled enough to get the suspension feeling in tune with how I was riding, I stopped faffing about with levers and adjustment and just rode it without thinking.

With the pivot point inline with the chain I didn’t NEED the lockout at the rear, while it might have saved a watt or two up hills the difference was negligible and probably balanced against the increased off-road climbing performance with the shock active. Through riding it every which way on everything, a bike that I initially found intimidatingly over-specced for my riding became a simple, easy to maintain, solid and enjoyable platform that has proved an invaluable addition to the bikes I already owned.

A gravel bike has become a go-to bike that works for everything, where everything discounts anything that the SRD was designed to do. Having a bike that’s so much further removed from the ubiquitous gravel platform than just a little more tire clearance has not only pushed me to ride more and differently, but it’s also informed the way I ride other bikes by inspiring confidence in more technical riding through practice.

Having come from a road cycling background, “gravel” now is what I had considered “mountain biking” previously, which put me off the idea that I might need a bike like the SRD prototype. I wouldn’t have chosen it from Sour’s lineup had Joergan not pushed me to try it, but now that I have it, I wouldn’t want to return to not having it. Even if I did, it changed how I ride gravel for the better. It took a while to get used to the idea that sometimes, where traction ends, the fun begins, rather than my old road cycling mindset, where traction ends is the beginning of the road to A&E.

Becoming accustomed to riding more dynamically, going full pelt into my own personal unknown, and coming out the other side surprisingly unscathed became—through practice—a matter of course that has brought more play to all of my riding. Gravel became road cycling for mountain bikers and, at the same time, the gateway drug to mountain biking for road cyclists. There is also a simplicity to just making tires and clearances bigger for comfort and traction.

What I learned more than anything else over the last eight months on the SRD is that there is significantly more value in adding a bike that’s designed around riding far more extreme terrain than your current capabilities than there is in adding something tailored towards being a stepping stone in that direction. It’s a psychological plunge into a different kind of riding that lays the groundwork for having more fun in every other kind of riding—but you only get there through exercising the frequently neglected play muscles that form that foundation!

We’re super stoked for the upcoming crop of full suspensions from Sour Bicycles. Watch this space for more updates this summer!


  • Stable but pedal-able geometry
  • Simple and easy to maintain
  • Balleur German-made build kit
  • The friend maker
  • No one has ever heard of it in the UK
  • FUN
  • Surprisingly light
  • Recycled


  • I’m not a confident enough rider to push its boundaries
  • I’d like a little more reach and front center- although that could likely be achieved through sizing up
  • Highlights the inhospitable flatness of England’s southeast
  • The diamond hoax of 1872 and the Bre-X gold fraud of the mid-1990s