Pinkbike takes a close look at Trek's carbon-framed Session 9.9 downhill racer and its special Fox Hybrid Air 40 RC2 fork and custom-tuned RC4 shock. Is this the fastest off-the-shelf production bike ever produced?
Aaron Gwin's Trek World Racing Team 9.9
You're looking at Aaron Gwin's Trek Session 9.9 carbon downhill race bike, the very bike that he rode to victory at the Mont Sainte Anne World Cup just two races ago. That race also happened to be the 9.9's coming out, as well as Aaron's first race aboard the new machine, having thrown a leg over it only a short time before heading to the Canadian round of the World Cup. Not a bad debut! While the 9.9 is almost identical to the Trek World Racing aluminum team bikes, it should really be thought of as an entirely different animal from the 2011 Session 88 platform. That isn't solely down to its carbon construction - for about a year and half now the team has been riding a version with a slew of changes, including big modifications to the new bike's geometry and suspension layout that greatly effect its performance. Oh, and the new carbon frame happens to be about 800 grams lighter than the 2011 aluminum team frame to boot, with the complete production version of the 9.9 projected to weigh in at around 35 pounds. Pinkbike photographer Ian Hylands sat down with Aaron for a few minutes at Mont Sainte Anne and asked him a few questions about the bike:
This video tells Gwin's incredible story aboard the Session 9.9
First Look at Trek's Session 9.9 Production DH Racer
The 2012 Production Session 9.9 in all its glory. While any new downhill bike stirs up the rumors, Trek's new carbon Session took speculation to a new level. Forums were filled with wildly different details of the new machine, but everyone seemed to agree on one point: it would be made of carbon. Then, at the Mt. Sainte Anne round of the World Cup series, the carbon Trek made its public debut as Gwin rolled out of the pits for his first practice run aboard the new Trek. The internet immediately went into overdrive, with photos of it popping up worldwide on mountain bike websites. At that point, little was known about the new bike, beyond that it was obviously made from carbon and that it would be called the Session 9.9. Pinkbike spent the last four days in the Austrian Alps with Trek, learning about the Session 9.9 and about the technology that Trek used to construct the new chassis. The 9.9's carbon frame includes an impressive range of geometry adjustment - the very same setup the the Trek World Racing team is using - and a new quick-change leverage-rate feature that tunes the suspension to better handle square-edge bumps on a race track and to hug the ground - or to pop better and pedal firmer for pedal-heavy tracks, or sessions in the bike park. The production 9.9 sports Trek-developed proprietary Fox suspension, including a radical Fox Hybrid Air fork that uses an air-assist spring that you'll find only on the 9.9, and a custom shock tune that is currently used by the TWR team.
Our goal was to create a bike that any rider could use on the World Cup circuit and not be held back. We feel that the stock Session 9.9 will actually outperform many factory race bikes, it's that dialed, off the shelf.- Jose Gonzalez, Trek suspension engineer
Trek Session 9.9 Details
From a distance, it would be easy to mistake the new carbon frame for the aluminum model. It follows the same lines and basic layout. Trek claims that not only is the frame 800 grams lighter than the TWR aluminum frame, but it also performs even better in strength and stiffness testing.
The new carbon frame features new bolt-on fork bumpers to keep the frame from being damaged during those inevitable crashes that every downhill bike sees, and they also serve double duty as the entry point for the internal cable routing. Both the rear brake and derailleur can be run through the frame, making for smoother lines and a setup that is less likely to be damaged in a crash. The Session 9.9 still gives you the ability to route both shift and brake lines externally as well, making it easier to replace or shorten them if the need arises. Trek created what they call 'MicroTruss' housing guides and according to Trek, the MicroTruss system is lighter than standard cable guides and also makes the frame stronger. Aaron's bike, pictured above, is fitted with a standard Cane Creek headset, while production models will be equipped with Cane Creek's adjustable AngleSet that allows riders to tweak the steering geometry to their liking.
Carbon rocker link: The 9.9's front triangle, seat stays and the one-piece HexMC EVO Link are all made from carbon. (The swingarm is still a welded aluminum part). The red link is said to be both lighter and stiffer than the original welded version, and the main pivot bearings have been moved inboard into the frame as opposed to pressed into bearing journals within the link itself. Fox Racing Shox puts a huge effort into dialing in Gwin's suspension to his exact needs, whether that is custom valving (his tune comes stock on the Session 9.9) or special low-friction seals. Aaron's custom-tuned Fox RC4 damper sports a sticker with his initials - a clear reminder as to who it belongs to. The TWR shock tune on the 9.9 is a great example of racing improving the breed. Aaron uses it to win World Cups, and then we get to take advantage of it.
Although the Session 9.9's basic suspension layout looks quite similar to the previous model's, changes to the pivot locations have altered the leverage rate. The main swingarm pivot is still in the same location relative to the bottom bracket, but both the EVO Link rocker's shock pivot and seat-stay pivot locations have been changed slightly. Trek has also altered the length of the swingarm's 'Full Floater' extension at the lower shock mount. Why? Trek is adamant that the suspension's leverage rate plays a much larger role in allowing the bike to carry momentum over rough ground. The new design features a slightly flatter rate through the middle of the stroke - where the bike spends a lot of its time - which allows the rear wheel to react quicker to abrupt impacts that try to suck your speed away. In simple terms: the rear wheel can move out of the way faster if the suspension uses a flatter leverage rate, and the faster the rear wheel can move out of the way, the more momentum the bike will carry. That flatter rate also adds an extra 10 millimeters of rear-wheel travel, upping the total amount to 210 millimeters. It isn't quite that easy though, as there is always a trade-off from one realm for improved performance to another. In this case, Trek World Racing found that the flatter rate didn't hold the bike up quite as well in the corners, especially at the speeds that they hit them at World Cup races. The answer was simply to tune the Fox RC4's compression adjustment to better hold the bike up in its travel, which is an ideal solution given that the TWR team found that they had to set their compression settings quite light on the original design. The result is that the new bike allows riders to use a wider range of adjustment on their shocks.
The new Session makes good use of Trek's Active Braking Pivot (ABP) out back, that keeps the suspension active and tracking the ground while the rider is on the brakes. ABP works by minimizing the angular change in the tire's contact point through the rear axle in relation to the ground as the suspension cycles. The smaller the change between the two, the less effect braking will have on the suspension. The rear end also features 12 x 157 millimeter spacing, referred to by Trek as 'ABP DH Convert'. Now, before everyone gets up in arms about another new axle standard, it needs to be said that the system is easily converted to fit standard 150mm hubs simply by swapping out the hardware with some included parts. Trek's wider, 157 millimeter axle spacing nests into a small shoulder which automatically aligns the through axle with the dropouts and hub. (Same as the 142/12mm hub design). The system lets you easily center and install the rear wheel without struggling to align the axle with the hub. Easier is better, right? If you want to use standard-spaced, 150-millimeter rear wheels, just install the standard dropouts and you're set.
Trek is well aware that there are many different crank options on the market for downhill use and didn't want to limit the choices by building the new Session frame with a Press Fit bottom bracket shell as on their other carbon models, so you'll find a standard, threaded 83mm bottom bracket shell that will accept any downhill crankset on the market. The frame's ISCG-05 chain-guide tabs are machined into the threaded- aluminum bottom bracket insert to ensure perfect alignment.
Some of the 9.9's most interesting technology is hidden within the frame. Like all top carbon frames, the Session frame is built using a bladder - a lightweight inflatable balloon is inserted within the frame to apply pressure to the layers of carbon as they cure inside the mold. A rubber bladder cannot apply even pressure to tight and or complex-shaped sections within the frame. According to Trek, instead of adding extra carbon to reinforce these trouble spots, it uses a proprietary low-density, ultra-stiff material inside the frame to evenly pressurize these areas from within. Interestingly, Trek claims that this method, referred to as 'InTension', actually results in tube sections that are four times higher in flexural strength and eight times as stiff. InTension helps build a lighter, stronger carbon structure by replacing inner layers of carbon with a material that fills more volume, but with significantly lighter weight than a carbon-only structure. Presently, the Session 9.9 is the only frame in Trek's lineup that currently uses InTension, but Trek is so pleased with the performance that it is likely to be found on other models in the near future. Photo by Sterling Lorence
The Secret of the Session 9.9's Suspension Tune
World Cup Suspension: The Session 9.9, along with the aluminum Session 88, comes equipped with a custom tuned Fox RC4 damper that was developed by Fox and the Trek World Racing team. Listen to Jose Gonzalez, Trek's top suspension engineer, explain the shock's inner workings in the audio below. Photo by Sterling Lorence
Found only on the Session 9.9 and developed by Trek's Southern California suspension lab, Fox's Kashima coated 40 Fit RC2 Hybrid Air fork makes use of a lightweight titanium coil spring and an air-spring, combined to allow riders to tune their spring rates more precisely. Instead of having to swap out the coil spring for the lighter or heavier option, you can simply add or remove air pressure via the Schrader valve atop the left fork leg. Jose Gonzalez explains how the system works in the audio below. Photo by Sterling Lorence
2012 Trek Session 9.9 Specs
Session 9.9 Frame:
• Intended use: Downhill racing • All new carbon frame • Carbon EVO Link and seat stays • 210mm of rear wheel travel (up 10mm from last year) • Tapered 1-1/8'' - 1.5'' head tube • Frame is approx. 800 grams lighter than the TWR team's aluminum version • ISCG-05 chain guide tabs • 12 x 157 ABP DH rear axle spacing (slotted 150mm rear end for easier wheel alignment, can also accept standard 150mm wheels) • Internal or external cable routing for both brake and derailleur • Custom Fox RC4 shock with TWR tune • Adjustable geometry allows head angle range from 62.5 to 65.4 degrees • Revised suspension rate for great square bump performance
Session 9.9 Parts Spec:
Frame - OCLV Mountain Carbon w/ InTension main frame and seat stay. Carbon armor, ABP DH, Full Floater, E2 tapered head tube, HexMC carbon EVO Link, 210mm of travel Sizes - sm, m, l, xl Fork - Fox Factory Series 40 Fit RC2 w/ Hybrid Air and Kashima coating, 203mm of travel Shock - Fox DHX RC4 w/ custom TWR tune Color - Carbon Smoke Shifter - SRAM X0, 10 speed Rear Der - SRAM X0 Cassette - SRAM PG-1070 11-26, 10 speed Crank - SRAM X0 DH Carbon Chainring - 38 tooth Pedals - Wellgo MG-1 Wheelset - DT Swiss 240s 20mm front hub, 12 x 157mm rear hub, DT Swiss FR 600 rims Tires - Bontrager G4 Team Saddle - Bontrager - Evoke 4, titanium rails Seapost - Bontrager Rhythm Elite, 31.6 Handlebar - Bontrager Rhythm Pro Carbon Stem - Truvativ Holzfeller Headset - Cane Creek AngleSet Brakeset - Avid Elixir X0
2012 Trek Session Geometry:
Between the Session's Mino Link system (rotatable chips used to attach the seat stays to the EVO Link), the Cane Creek AngleSet headset that comes stock, and 12mm of adjustability in the Fox fork’s axle-to-crown length, The new Session has over 28 different geometry settings. This unique combination of adjustability gives you 1/3 of a degree adjustments at the head tube, and bottom bracket adjustments down to the millimeter. Excessive? Certainly not considering the bike's intentions as a top tier race machine. It should also be stressed that although using a combination of the Mino Link and AngleSet allows you to select a head angle between 62.5 to 65.4 degrees, the Mino Link's prime intention is to tune the suspension (by varying the leverage ratio to either devour square edge impacts or to pop, enabling the rider to clear rough sections easier, while the AngleSet and axle-to-crown length are used to compensate for the geometry changes made by altering the Mino Link.
MINO LINK RACE - big bumps, super fast, steep, maximum square edge absorption
MINO LINK PARK - maximum pop for jumping, higher BB for super rough and rocky, fast-pedaling courses.
*size medium, applies to both carbon and aluminum models
Behind the Scenes with Trek's 9.9 Development Team
Pinkbike photographer, Ian Hylands, was on hand when the first Session 9.9 prototype was being built for testing a year ago. The photo above shows it being assembled for the very first time in Whistler, with test and development rider Andrew Shandro being the lucky pilot. This prototype was painted up to look like a much less interesting aluminum frame so as not to arouse any suspicion from casual observers. The ruse worked, with Trek spending much time on Whistler's trails, dialing in the settings, geometry and learning about how the new bike performed without anyone noticing.
Andrew up to speed on the early prototype Session 9.9. At this point it still wasn't a given that the bike would ever see production - Trek was still evaluating the possibilities of a carbon framed Session and whether it made sense or not. They obviously came away from the test happy, as a lot of effort was then put into further development.
My first impression of the bike before before I had the chance to ride it was how incredibly light it felt. And once I got the chance to actually ride the 9.9 it blew my mind how fast and stable it felt. I was little skeptical at first, I thought it might feel too light, but it was the complete opposite. The bike is an absolute weapon on the trail, light, fast and stable. The characteristics of carbon are amazing, the bike floated over the terrain and took the harshness out of the trail.- Andrew Shandro, Trek test rider
Aluminum Session gets the same treatment:
While the carbon Session 9.9 is no doubt the king of the lineup, the aluminum models will certainly appeal to more riders due to their more cost conservative construction. Less expensive won't mean that they'll lack any of the bells and whistles though, and the aluminum frame will feature all of the same geometry and adjustments, internal or external cable routing, as well as the 12 x 157 ABP DH Convert rear axle spacing. The top of the line aluminum model, the Session 88, will even come equipped with the same custom TWR tuned Fox RC4 rear shock. The aluminum models should be popular with many privateer racers who will use the left over money that they would have otherwise spent on the Session 9.9 to travel to races and pay entry fees.
Availability and pricing:
Unless you're Aaron Gwin, or another member of the Trek World Racing team, you'll have to patiently wait until this coming October before you are able to throw a leg over your own Session 9.9. Pricing is yet to be decided upon, and while the new carbon bike certainly won't be inexpensive, Trek has been very forward in making it clear that the Session 9.9 will be priced quite competitively.
Lighter, faster, stronger? That is always the goal, isn't it? The new Session 9.9 is simply stunning in more ways than one. Not only does the bike obviously perform well, with Gwin taking it to the win on its debut race, but the production version should also build up to a lightweight bike around 35lbs. Trek has taken a shot at producing what they feel is simply the best off-the-shelf race bike available. And although we have yet to ride the new machine in anger, we're willing to bet that they have succeeded. The 9.9, along with the aluminum version, make use of the same suspension dynamics, same geometry, and even a Fox Racing Shox custom shock tune, that were developed for the Trek World Racing team to allow you to go faster. In what other timed action sport can you go out and purchase equipment that rivals what the professionals use? You or I will never sit in a Formula 1 car, straddle a MotoGP bike, or be able to get our paws on the same machinery that James Stewart uses. But we can jump on a bike that is very, very similar in spec, and exactly the same in geometry, to the one that Aaron Gwin has been absolutely dominating World Cup downhill racing aboard. You may never win a downhill race, or even want to enter one, but you do have to admit that it is pretty damn cool.