A Piece of a Bigger Puzzle - Testing Specialized’s Gen1 Proto DH Bike 13

The Specialized Gravity Team has been at the center of attention thanks to the prototype bikes they've piloted to numerous World Cup victories over the past couple of seasons. Specialized has spared no expense or effort developing their next downhill bike, and they've done a good job of keeping details about it fairly under wraps. 

We've been dying to swing a leg over one of the team bikes. At the beginning of the year, when spy shots started circulating of the #2chains proto, we asked Specialized what it would take to ride the bike (this was obviously before the very production-looking bike was a thing). It was an ambitious ask, and Specialized politely said no, citing that the current race bike was reserved for Finn, Jordan, and Loïc. 

What they did offer was the chance to ride the first prototype bike. Hesitant to ride a bike that felt seemingly irrelevant as it had been replaced, we realized that the first bike likely held a lot of the secrets as to what Specialized was chasing with this whole project. Plus, who wouldn't want to ride such a rare machine? So we said yes, and here is what we uncovered. 

Highlights

• Frame material:
  • Front triangle: aluminum lugs, carbon tubes
  • Rear end: carbon seat stay, CNC aluminum chain stay
• 203mm rear wheel travel // 200mm fork
• Mixed wheels only
• Concentric, adjustable button bracket
• Removable stiffeners at the down tube and upper link
• Reach adjust headset compatible
• 12x148 Boost rear hub spacing
• 62.5-degree head tube angle
• 473mm reach
• 630mm stack height
• 445mm chainstay length
• One size
• Weight: 38.58 lb // 16.13 kg

Frame Details

Frame material—Specialized hand-made these prototype frames in their Auburn (R.I.P.) and Morgan Hill, California, facilities. The chainstay and front triangle lugs are CNC'd aluminum. The carbon seatstay is from Specialized's Enduro model. The front triangle uses carbon tubes that were hand-rolled by Specialized. Specialized chose the lug and tube design to simplify prototyping as they went through various design tweaks. It also created some very boutique-looking race bikes.

Compliance goals—Frame balance has been a key focus for Specialized with this project. They wanted a chassis that worked as a whole unit. The bolt-on stiffeners allowed them to tune frame compliance in different ways. The stiffener on the upper linkage alters the amount of side-to-side movement of the rear wheel under load, while the stiffener on the bottom of the downtube, located below the shock, distributes flex across the entire frame rather than concentrating it at the back end. When flex happens over a bigger area, there's less displacement at any one spot, so the rear wheel moves less and the handling stays more consistent. If you spread the flex to more locations, nothing weird is likely to happen when riding. 

U.B.B. suspension design—It stands for 'under the bottom bracket.' Catchy, right? The design features a beefy chainstay that rotates around an even beefier pivot above the bottom bracket. As the bike compresses, the chainstay pulls on a rod below the bottom bracket, which rotates a rocker link clockwise (when viewed from the driveside). As the rocker link swings forward, it compresses the shock. 

The new prototype bike has a similar layout, but the pull rod is now above the bottom bracket. A.B.B. suspension design? Our best guess is that Specialized made this change to keep from smashing the lower link on things. There is also a second chain enclosed in the frame that connects the cranks to a non-concentric chainring to mitigate pedal kickback due to the now higher main pivot. 

Kinematics—Specialized remained tight-lipped about the kinematics of the bike. What we can gather from the design is that the lower linkage controls the bike's leverage, while the upper linkage controls braking behavior. This separation allowed them to tune the leverage curve to match rider preference without compromising the braking characteristic (anti-rise) they were seeking. It's a clean way to split two things that are usually tied together and make tuning easier. It's also a tidy, low-slung design that keeps the weight centered and the bike stable. We'd be curious to know how the new design affects the bike's center of gravity, since the shock is now higher in the front triangle, but there is an additional drive unit near the bottom bracket.

Test Riders

Jason Schroeder Vital MTB Tech Editor 30 years old 180 lb // 81.6 kg 6' // 182cm Fav DH bike: 2014 Specialized Demo

Ryan Burney Engineer behind Bare Innovation, Vital Contributor 31 years old 190 lb // 86.1 kg 6' // 182cm Fav DH bike: GT Fury (super biased)

What's The Bottom Line?

Jason's Bottom Line

I feel like I'd be dishonoring my position at Vital if I didn't mention how insane it was to ride this bike. It was not lost on me and will stand as one of the coolest things I've done during my time as an editor. I don't have the pace of a World Cup rider. But oh boy, did I pretend I did for the two days I rode the bike.

The first thing that stood out to me was how comfy and safe the bike felt. I stood pretty neutral over the bike, and it didn't take more than a couple laps to begin pushing my pace. As my intensity increased, it became pretty evident that the bike had a lot of potential speed on tap.

The static geometry did make me wonder if the bike would feel small. Especially after seeing Loïc tower over his bike like a bear on a unicycle for so many years. I sort of assumed it was going to fit like a smallish size large. However, that wasn't the case. The short chainstays never felt too short, and the higher-rise bars helped compensate for the modest stack height. I think the head angle being quite slack, matched with a little bit shorter reach, placed me more over the bars without feeling like I was getting thrown over the front. The overall fit was very neutral and blended well with how composed the bike rode. I didn't need to be in any unique positions to compensate for tendencies the bike had. 

Which brings me to what stood out the most about the Specialized proto: its ability to get out of the way of compressions and remain fairly active and very consistent during heavy braking. This allowed the bike to ride within a tighter window of dynamic geo, avoiding ever pitching or drastically tossing my weight around. A sensation that only elevated my confidence with each additional lap. It also reminded me of Santa Cruz's V10 in its ability to be mid-travel and still offer a solid platform to push against. It created a nice blend of remaining stable when blasting through compressions, but also responsive enough to ride with intent. 

I wouldn't say the bike completely eliminated bumps like a high-pivot bike might. But the feedback from impacts wasn't to a degree that was fatiguing or unsettling. Rather, it gave me insight into how the bike was reacting to the ground. The stiffness of the frame was likely a factor that added to this sensation. The frame felt stiff at slower speeds, but became increasingly more stable as I went faster. It was an interesting sensation because as I hit things harder and drove more energy through the bike, the more comfortable it felt. I never noticed any wind-up in the frame, and the rear end never kicked out.  
 
We didn't need to ride the bike for everyone to know it's fast and capable. We already knew that coming into this test. But it was pretty cool to realize that you don't have to be Loïc, Finn, or Jordan, or have fancy electronic suspension parts to benefit from what Specialized has created. I'm sad that this exact layout isn't going into production, but I'm sure the new bike will carry many of the same traits. And the good news is that a production version is surely coming within the next year. I look forward to when that happens and getting to see how Specialized chose to evolve or maintain aspects of the prototype in the production version.

Ryan's Bottom Line

On most bikes, you know you’re getting close to the limit of how fast the bike can be ridden when your vision starts to blur from the chatter and you’re getting rattled around so much that you're just hanging on for the ride. This bike pushes that point higher. Everything is calmer and more controlled, so it’s easier to reach that limit and actually stay there without putting yourself in too much danger. It doesn’t feel sketchy when you’re pinned. It feels like you’re in control.

The back end grips terrain without dulling feedback, so you always know where the tire is and how much grip you have. The frame's compliance takes the chaos out of rough sections and lets you focus on speed instead. That smoothness is paired with a chassis that’s predictable and neutral, never doing anything weird or unexpected. It holds lines well, the rear wheel never steps out on you, and it drives through corners, letting you pump all the way through.

Another thing that sets it apart is how the chassis feels like it stiffens as you get deeper into the travel. Early in the stroke the frame is comfortable and compliant, but as you push deeper it stiffens up and feels more stout for g-outs and big holes. My guess is that most of the flex is coming from the small seatstay early in the travel, and as the suspension compresses the angle between the seatstay and chainstay increases, creating a larger triangle and a stiffer structure. The rear end doesn't do anything weird as the large chainstays keep the wheel pointed in the right direction and prevent any rear-end squirm. Whether that’s exactly what’s happening or not, it feels really good when charging in a race run or just pumping and playing on a park day.

The geometry isn’t as "modern" as some longer race bikes. The shorter rear center and moderate reach help you stay centered and in control when braking in the steep chunk. It's difficult for the rear end to rise under braking because the body position the bike puts you in keeps your more over the rear wheel, fighting much of the brake-related rise. You don’t get pitched forward and forced onto your hands, and you’re not running out of arm travel in the steep sections. Like other low anti-rise bikes, you can brake later into corners, but with this bike you’re not thrown into a push-up position which reduces fatigue. Its moderate size keeps it maneuverable, but in fast, open sections you’ll have to work a bit harder to keep it stable since it’s just not as long as some of the others out there. Because of that shorter wheelbase, you also can’t be as reckless in loose corners as some of the longer bikes let you get away with. There’s a smaller window where your body can be before you lose grip on either the front or rear wheel. So if you come in too hot or lean too hard, you’re more likely to break traction and slide out relative to the longer bikes. This isn't a problem, most bikes are like this, it's just a note that comes up once you have ridden some of the longer bikes out there (and yes, those have their own compromises). 

This bike’s biggest advantage is how easy it makes going fast by taking the edge off rough trails. If your average speed down a track goes from 20 mph to 20.2 mph because of this, that’s a massive time improvement, and I think this bike does exactly that. It takes the edge off and in doing so gets out of your way of going faster. Because of its geometry, it’s not the most stable bike out there, but good riders can keep a bike stable at speed, it just takes some experience. The tradeoff is sharper handling and the ability to put the bike exactly where you want it and it will fit into most corners without feeling too large. Plus, the bike never feels too cumbersome, which is a win for those who will ride the bike park... It's still fun to ride at the bike park and isn't boring.  It raises the speed limit of your trails via frame compliance, allows you to brake later, carry more speed, and never do anyhting weird so you can fully trust it. It's really good. I like it.