Gwin always had his fork slammed on his Treks, with a bunch of stanchion sticking out the top of the crown, but since day one on Specialized he's been running the crowns really high, with very little stanchion sticking out the top of the crown.
Low front end on the Trek:
High front end on the Specialized:
And you can see this in his body position when he rides. When you watch the video, his handlebars just look higher on the Specialized:
The other lesson learned is that having no music as in the Lawlor/Specialized videos is a better choice than whatever that horrible teen bop semi punk emo obscenity was in the Trek video:
So why does he run his bars higher on the Demo? First off, I don't know. These are all guesses and who knows what the real reason is. But that's never stopped TEAM ROBOT before, so here are some uninformed guesses:
He's a brainless gorilla and has no idea what his bike feels like
This one actually seems plausible, because a lot of World Cup guys act like brainless gorillas whose only thought is to crush. The story goes like this: when he got on the Demo that's just where his bars ended up, it felt alright on day one, so he just kept his bars there.
I find this explanation to be unsatisfactory. First off, these guys test stuff all the time, and if this new setup was just by chance, and was in fact inferior to the old lower bar setup, it would have been revealed in the countless tests he's performed for the multiple iterations of Demo 8's he's developed and raced for Specialized. Someone would have mentioned something. Also, even if he is a brainless gorilla, "it feels good" is probably still determined by real, tangible numbers and qualities of the bike, ie low bars felt better on the Session, higher bars felt better on the Demo. If there's a tangible reason that relates to geometry numbers, I'd like to know that reason. So we keep exploring for a better explanation.
The Demo has a lower BB height
Assuming these guys don't have custom frames, the Session BB sits right around 14" stock, and the Demo BB is right around 13.5" (338-353mm for the Demo in it's various adjustable heights, and 356-360mm for the Session). All told that's a range of almost an inch (22mm) between the lowest possible Demo configuration and the highest possible Session setting. If you don't like that and you don't want your bottom bracket to be super low, you can run your fork high in the crowns to raise your BB height off the ground.
Head tube angles are right around 64 degrees for both bikes, though just a hair slacker on the Session, so you could achieve almost exactly the same BB height and head angle on the Specialized by running the fork super high. Raising the fork an inch rakes out your head angle just under a degree, and raises your BB about 1 cm.
This explanation still doesn't answer my questions, though, because it ignores all the other geometry numbers. His BB and HA might be the same on both bikes after adjusting fork height, but his bars are still higher on the Specialized, resulting in a higher stack height from pedals to handlebar, and a wildly different feeling bike. Anyone who was psycho enough to measure and then emulate BB height while going from one bike to the next probably wouldn't slip the little detail that his stack height is an inch or two higher than it used to be.
I'm that psycho, and I wouldn't miss that detail.
This one goes out to all the haters. The argument goes something like this: the chainstays on the Demo were too short, his bike was unstable, so he raised the bars because he was scared. Initially that sort of makes sense, sort of, except it doesn't make sense at all. Short, unstable chainstays would cause a "looping out" kind of feeling when you shifted weight rearward, making you scared or hesitant to shift weight rearward. So to combat this sensation, he would raise his bars to shift his weight rearward?
Probably not. Also, his bars are still high on new bikes with longer chainstays, so yeah that's probably not it.
This is going to take some explaining, but bear with me for a second. Or don't, I don't really care.
In my experience, really stiff forks pair nicely with relatively low front ends, and really high bars only work with softer forks. As a guy who ran really high bars on all his bikes for multiple seasons, this was actually a big lesson for me over the past season. I've lowered my bars a touch and stiffened up my forks on all my bikes as of late.
More on that personal bike/lessons learned theme soon.
The suspension theory makes sense because A) Gwin is famous for running his fork mega stiff, and B) the Demo has a much more linear leverage rate than the Session.
Start with the rear suspension leverage rate: if you have two 8" travel bikes set up with 450 pound springs, and one bike has a more linear leverage rate, the linear bike will feel harsher on small bumps and will blow through it's travel more quickly on big bumps, a "worst of both worlds" kind of situation. With a linear leverage rate you have to choose between harsh small bumps, divey suspension in big bumps, or some compromise between the two. Knowing how Gwin rides (out of his mind fast), and knowing his suspension preference (I don't care about small bumps, just give me the stiffest suspension possible so I can ride through big holes at mach 10), my wild guess is that he's been running a really stiff spring in the Demo, probably a stiffer spring rate than the equivalent spring on the Session, and the small bump performance of his rear suspension is probably less than stellar as a result. Of course the Fox guys can work their devil magic to make the shock have better small bump performance, but relatively speaking it would be worse.
Now throw a super stiff fork into the equation: you can only ride a jackhammer fork if your rear suspension is doing exactly what you want. Said differently, you can only handle one disaster at a time. If your fork is insanely stiff, and it's kind of skatey and unpredictable on small bumps, you need to shift your weight forward to deal with it and you need you rear end to be dialed, predictable, and low stress. If your rear end is extremely stiff, skatey, and sort of unpredictable on small bumps, you need to shift your weight rearward to control that near-disaster. You can't have a near-disaster on the front and the rear of your bike simultaneously and expect to ride it out.
My bet is that Gwin got on the Demo, had to bump up spring rates in the back so he could run the bike through big holes, and to compensate he had to make his fork softer. As a result, he raised his bars. That's my guess, but who knows? The only thing for sure is that, if you read all that, I look like a complete psycho right now.
The linear leverage rate thing isn't my bag, but Specialized has made it clear that they like it on the Demo and it's not going anywhere. The new S-Works Demo carries over a very similar, almost identical, leverage rate from the existing Demo's, so Specialized has committed to their linear spring rate for the forseeable future and that's what Gwin will be working with as long as he's on the Big Red S.
The real question is this: is that a bad thing? Is the difference between the Session and the Demo bad? The big overarching assumption surrounding any comparison of the Aaron Gwin Demo vs. the Aaron Gwin Session is that the Demo isn't working for him and the Session was, thus something was wrong and something needs to be fixed on the Demo.
I'm not sure that assumption is correct. Every internet armchair engineer looked at Gwins results on Trek vs. his results on Specialized and assumed the bike made Gwin slower, and suddenly in 2013 and '14 the broad internet concensus is that the Demo is "more of a park bike" (whatever that means), but most of those people wouldn't know their ass from a hole in the ground, led alone the subtleties of a winning bike setup. It's true that the Demo is different, and I for one don't agree with all of the design decisions, but they are just that: decisions representing the combined preferences and informed opinions of people seeking an acceptable compromise to multiple design challenges. There is no perfect downhill bike, and each downhill bike on the market takes a different angle on meeting the various and conflicting demands on such a bike.
I don't think it's a matter of Gwin putting a bandaid fix on a bad design, as much as Gwin adapting his setup to a different bike. Even in 2011 and 2012 when he was winning every race in sight, I don't pretend to believe that he was on a perfect bike. People assume that the Session was a perfect bike (look at the results, bro!), but I'm positive there were significant compromises made in the design and setup of Gwin's 2011 and 2012 Sessions, but the man is a single-minded freak of nature winning machine and he did what it took every day to make that poor Trek Session his bitch. I have no doubt he is doing the same thing right now with the Specialized people.
I think there are a lot of terrible, unrideable bike designs out there, and TEAM ROBOT is first to call those unrideable bikes out, but from what I've seen and heard I don't tend to think the Demo is one of them. While the Demo wouldn't be my first pick of downhill bikes due to the leverage rate, A) that's my personal preference speaking, and B) if I was winning or losing on a Demo 8, I hope I'd be smart enough to recognize that it's not the bike winning or losing those races.