Specialized's designers had one goal in mind when they starting working on the next generation of the Demo: create the world's fastest downhill race bike. “More R&D, more engineering, and more research has gone into this bike than any other bike we've ever made,” says Brad Benedict, Specialized's mountain bike product manager.
That's a lofty statement, but four years of athlete input and constant refinement adds up. Aaron Gwin, Troy Brosnan, and Loris Vergier all provided input during their stints on the Specialized DH team, and now feedback is being delivered by Loic Bruni and Finn Iles.
Demo 29 Details
• Wheel size: 29"
• Rear wheel travel: 200
• Aluminum frame
• 62.7° head angle
• 12x148mm rear spacing
• 450mm chainstays
• Sizes: S2, S3, S4
• Price: $5,000 - $6,500 USD. Frame only: $2,500
All of that input has culminated in the bike pictured here, an aluminum, 29”-wheeled machine with 200 millimeters of travel. It still uses a Horst Link suspension design, but significant changes have been made to alter the bike's ride characteristics in order to meet the needs of elite racers.
The Demo Race 29 is priced at $6,500 USD, and is spec'd with Öhlins' DH38 fork and TTX shock, SRAM X01 DH drivetrain, and Code RSC brakes.
There's also an Expert 29 model for $5,000 that comes with a RockShox BoXXer Select 29 and Super Deluxe coil, along with a SRAM GX DH drivetrain and Code R brakes. The frame only with an Ohlins rear shock is available for $2,500 USD.
Where's the mixed wheel size option? That's a good question, especially since that seems to be the setup Finn and Loic prefer – Loic's piloted his race bike to three World Cup victories so far this year. When the Demo was being developed, the UCI rule that stipulated riders had to be on equal sized wheels was still in place. That's no longer the case, hence all of the experimentation. On the topic of a future mixed-wheel option, Specialized's answer is, “We'll see.”
Designing the Demo
Specialized's impressive in-house machine shop allows them to quickly create frame parts in order to test ideas out in the real world, like this custom link for Loic Bruni.
In order to achieve that goal of creating the fastest bike possible, Specialized's designers worked on improving three main areas: momentum carry, braking, and comfort.
Momentum carry refers to the bike's ability to maintain its speed, even when it's being plowed through rock gardens or braking bumps. Making the switch from 27.5” to 29” wheels was an easy first step, but creating a big-wheeled version of the previous Demo wasn't going to be enough. The Horst Link suspension layout was completely re-designed in order to improve the bike's axle path, anti-squat, and anti-rise numbers - more on that stuff below.
During the development process, Specialized's engineers employed a number of tactics in order to quantify what test riders were feeling out on the trail. Those tactics included the use of pedals with sensors installed in them that measure the forces reaching a rider's feet, and a floating brake apparatus that made it possible to experiment with varying amounts of anti-rise.
The new design is no longer one-sided, and the shock is situated as low in the frame as possible. In addition, the main pivot no longer rotates around the bottom bracket – instead, it's located just in front of the top of the chain ring. It's a layout that's intended to help minimize the amount of side loading on the shock, and the fact that it's now trunnion mounted allows for an increased amount of bushing overlap.
Refining the Demo's suspension kinematics may have been the main goal, but Specialized's designers didn't overlook the important frame features for a DH race bike. The rear brake line is internally routed, but there are also cable guide mounts on the outside of the frame that make it possible to run it externally as well. The Demo uses a 12x148mm rear hub, rather than the 12x157mm that's more commonly found on downhill bikes. That allows for a slightly narrower rear end, and it also means that the rear wheel from a trail bike will work in a pinch. Other features include a threaded bottom bracket, a rubber downtube protector, and the raised chainslap guard that first showed up on the new Stumpjumper. Axle Path
Previously, the Demo's rear wheel began moving forward relatively quickly after encountering a bump, much to the consternation of a certain Pinkbike commenter
. The new suspension configuration addresses this trait, made it possible for Specialized to give the bike a more rearward axle path, although we're talking about a few millimeters here, as opposed to the more dramatic rearward axle paths found on high-pivot bikes. Going that route was considered but then scrapped due to the extra complication and drivetrain drag that it would have incurred.
The rear wheel may only move a few millimeters to the rear before heading forward, but it also doesn't move as far forward as before. That means it won't be as close to the seat (and the rider) when the bike reaches the end of its travel, which is an important consideration on a 29er. Anti-Squat and Leverage Ratio
In the past, Specialized's trail and DH bikes have had relatively low anti-squat numbers, and leverage ratios that weren't all that progressive. That's all changed with the new Demo. The leverage ratio is much more progressive, the amount of anti-squat has increased by 300%, and the amount of anti-rise increased by 70%.
Let's start with the leverage ratio. If you follow World Cup DH racing at all, there's a good chance you've seen a picture of the custom links that Specialized's racers were using over that last few years. Those links were designed to give the bike more bottom-out resistance than the stock configuration, which was relatively linear. In other words, there wasn't a whole lot of ramp up as the shock reached the end of its stroke. That shouldn't be an issue anymore, thanks to the Demo's 31.4% leverage ratio progression.
According to Specialized, they didn't specifically set out to increase the amount of anti-squat. Instead, it was a beneficial byproduct of changes to the instant center location and axle path. The amount of anti-squat is now over 100% in all gear ratios, which should make the bike less likely to bob up and down when a rider is really mashing on the pedals.
The amount of anti-rise, the bike's resistance to pitching forward during hard braking, now sits at 50%, which should keep the back end a little more planted in steep sections when the brakes are applied. Geometry
Along with the changes to the suspension, the Demo's geometry has also been tweaked. Any guesses as to what the changes were? That's right, it's longer and slacker... But it's not lower. In fact, the BB was raised slightly to improve pedal clearance – that last thing you want during a race run is to smack a pedal at 40mph and get tossed off the bike.
The reach has increased by 5mm per size, and Specialized has switched over to their S naming scheme. Rather than having a Medium, Long, and X-Long, there are now S2, S3, and S4 size, which have reach numbers of 425, 445, and 465mm respectively. Those numbers are fairly typical, but the one thing that's missing is an option for taller riders. I'd consider a 465mm reach a size large, which means that riders who are over 6' tall or so will likely want something even longer.
The chainstay length has also increased significantly, and it now sits at 450mm vs. the 430mm length of the previous version. The headtube angle is .8-degrees slacker, at 62.7-degrees. There are a number of downhill bikes on the market with multiple axle and shock mount positions, and even the prototypes of the Demo had some adjustment, but there aren't any flip-chips to be seen on the final product, and the geometry is fixed in one position. First Ride
I'm still in the early stages of getting acquainted with the new Demo, but I was able to get in some lap on the new bike at Dry Hill, located in Port Angeles, Washington. It's a classic Pacific Northwest race venue, one that's hosted countless exciting DH battles over the years. The tracks weren't wildly technical, but there were plenty of good corners and short, steep pitches to start getting a feel for the bike. As an added bonus, the dirt was as good as it gets.
I'd been riding an S3 sized Stumpjumper EVO, so I figured it made sense to start with an S3 Demo. Turns out, that wasn't the size for me. It felt like I was perched on top of the bike, rather than having room to maneuver. Once I looked at a geometry chart I could see exactly why - an S3 Stumpy EVO has a reach of 475mm, while an S3 Demo's reach is 445mm. I switched to the S4, which has a 465mm reach and instantly felt much more at home. It was easier to carry speed, and I didn't have to make as many body position adjustments to find the sweet spot when cornering or dropping into steeper section of trail.
The new Demo has a nicely balanced feel to it in regards to both the overall geometry and the weight of the bike. There's plenty of speed on tap, thanks in part to the 29" wheels, but there's more to it than that. On the more chewed up, rooty sections of trail all I had to do was drop my heels and hang on - the bike would plow right through it all without any hanging up or unwanted harshness from the back end. Cornering stability was excellent as well - the longer chainstays and the low center of gravity make it extremely satisfying to really push hard into a bermed turn.
I'll be spending a bunch more time on the Demo over the coming months in order to really dig into its handling characteristics, and to see how that Ohlins suspension stacks up. My first impressions are that Specialized has created a very worthy successor to the previous Demo, one that should meet the needs of everyone from grassroots racers and park rats all the way up to the top pros. That is, unless you're looking for an extra-large frame size.