Frame Geometry and Fit
As I alluded to at the outset, fit on the Session is a topic worthy of some discussion. To put it briefly, the bike feels really small. The last Session I rode was a size Medium, but this time I bumped up to a size Large. The Large Session has a reach of 426 mm and an effective top tube length of 539 mm. To give some perspective on that, my Canfield Jedi (a Medium), has a reach of 419 mm and an effective top tube length of 584 mm. As another point of reference, a Medium Specialized Demo is right in line with the Jedi: 420 mm reach, 596 mm effective top tube.
In other words (and at the risk of stating the obvious), the Session feels really small because, by the numbers, a Large Session is about the same size as many other companies’ size Medium.
An exception to this is the Santa Cruz V10 — the Session 9.9’s sizing is pretty similar to that bike, and interestingly, they’re both pretty long in the chainstays. Many companies tout their short chainstays, but Trek has always bucked that trend; the Session has 445 mm chainstays, which are some of the longest on the market.
Those long stays have a pretty significant impact on how the bike rides, but in terms of geometry and numbers, it mostly means that the wheelbase on the Session isn’t actually all that short. While the cockpit of the Session feels really small compared to a Jedi or Demo, the wheelbases between those bikes are roughly comparable. The Jedi, with its super short stays, has the shortest wheelbase despite having an effective top tube length that’s almost three inches longer than the Session.
The Session does come equipped with Trek’s Mino link, which is a swappable chip in the rear linkage (similar to that used by a few other companies) that’ll change the head tube angle by about .5° and change the bottom bracket height by about 10 mm.
The head angle on the Session, in low mode, sits at 63.6°, which is pretty middle of the road by modern DH bike standards. Interestingly, even in low mode, the Session’s bottom bracket sits at a relatively high 356 mm — about 14 mm higher than a Demo, and higher than most other bikes on the market. I’ll get into how that affects the bike in the riding impressions below.
Frame Features, Weight, and Construction
As one would expect of a high-end carbon bike, the Session 9.9 is impressively light; a Medium weighs in at a bit over 34 lbs, which is fairly absurd, especially considering that the wheels and drivetrain aren’t particularly light. The frame also gets a bunch of nice touches to keep everything stiff, clean, and running smoothly.
The Session is built around Trek’s ABP (Active Braking Pivot) design, which involves a pivot concentric to the rear axle. The idea is to keep braking forces neutral so that, when on the brakes, the rear suspension remains active. The system bears some similarities to a Split Pivot design insofar as there’s a pivot at the rear axle, but the rest of the suspension linkage is quite different than, for example, a bike like the Devinci Wilson that uses a Split Pivot rear end.
With the exception of the rocker arm and some hardware, the Session 9.9 is carbon front to back; the front triangle and both stays are carbon. Cable routing on the bike we rode was internal and quite clean, with the forward cable ports being integrated into fork bumpers, but the frame also has “microtruss” attachment points for external routing on the top of the downtube. As with most modern carbon frames, the Session 9.9 has integrated rubberized frame protection in the usual spots (underside of the downtube, and in chain slap areas).
The pivots are running on sealed cartridge bearings as is fairly standard among DH bikes. The rear shock is a “full floater,” meaning that the shock attaches to the rocker arm at one end and the chainstay at the other. This offers two advantages — the front triangle can be made lighter since it doesn’t have to include a shock attachment point, and it gives Trek a little more leeway in creating the leverage ratio that they want.
I rode the Session 9.9 back-to-back with a Devinci Wilson Carbon and a Rocky Mountain Maiden. The first and most noticeable thing about the Session, especially compared to those two bikes, is that it’s pretty damn light.
Coming in under 36 lbs with pedals in a size Large for a completely stock build is ridiculously light for a downhill bike, and the lack of heft is noticeable on the trail in all the ways that you’d expect. The Session is easy to push into corners and maneuver in the air, and particularly for smaller or lighter riders, it takes less work to yank the bike around in technical spots.
The flip side of the low weight, however, is that the bike also got kicked off line a bit more easily. A bit more time to dial in the suspension might have improved this, but I had the suspension set up very similarly the the Wilson I was riding, and the Wilson felt a bit more planted in high speed chunder.
I also noticed that the Session wasn’t quite as stiff as some other DH frames on the market, presumably because the frame has been pared down to save weight. Standing in the lift line and pressing sideways on the bottom bracket yielded some pretty obvious flex, while doing the same with a number of other bikes didn’t reveal much at all. On the trail, I can’t say that the added flexiness made a huge difference — I could feel the rear end wiggle on hard hits sometimes, but it wasn’t particularly problematic. That said, bigger riders who are putting more force into the bike or anyone who’s overly concerned about frame stiffness should take note.
But weight and flex quibbles aside, the Session is undeniably fast. If floats through chunky terrain impressively well, and I was actually pretty surprised at how little the bike would hang up in holes. Whether it was an excavated series of brake bumps, a big messy pile of roots, or just some ledgy rocks that I picked a crappy line through, the Session handled it all with impressive grace and more importantly, without losing momentum.
A lot of this I attribute to the long chainstays – that extra length means less of my weight was hovering over the rear axle, and it also meant the axle path was a little more inclined to allow the rear wheel to get out of the way of obstructions. It was interesting switching from the Session to the Rocky Mountain Maiden which has chainstays that are almost an inch shorter. The Maiden tended to hang up in holes and didn’t carry speed through rough patches that the Session glided over relatively effortlessly.
Some might expect that the longer rear end would make the Session a handful in corners, but for the most part, I actually found the opposite. The longer rear end meant my weight was much more centered on the bike, and it was easier to maintain traction on the front wheel. Rather than having to consciously keep my weight forward, I could ride in a more neutral position and still keep the front end hooked up. In a few tight situations, the longer rear end maybe took a little more attention, but there wasn’t any cornering situation where I came out of it thinking that a shorter chainstay would have been clearly preferable.
The long stays do, however, make the bike a bit less playful – it’s harder to manual than something like the Maiden or a Specialized Demo. I’d also say the longer rear end makes it a bit less interesting on jumps, although the light weight largely makes up for that.
I’ve also heard concerns about the height of the Session – in an age where bottom brackets heights are trending lower, the Session still sits relatively tall. I have to admit that, while the Session didn’t feel like the lowest slung bike I’d been on, it never felt tall while I was riding it. I was actually surprised when I checked the geometry chart after spending a day on it to see how tall the stated bottom bracket height actually was.
If you’re dead set on having the lowest bike on the market, the Session clearly isn’t it. But if that isn’t a chief concern, I never found the Session to feel top heavy, nor did I find it difficult to settle it into a corner. And, of course, there’s all kinds of tweaks that can be done to the setup and suspension to dial in the bike’s ride height.
I did notice that the Trek handled quite well while on the brakes – the ABP design apparently works as intended. The place where this was actually the most obvious in Whistler was actually just under the GLC drop, right at the lift. The runout of that little drop is always a brake bumped, bombed out mess since everyone is on the brakes as they come back into the lift line. That area is always brutal on the hands, but the Trek was pretty smooth through it, and stayed active even when I was dragging brakes through the holes.
NEXT: Some Comparisons, Bottom Line