“Innovate or die” says Specialized, and it’s certainly not big on standing still. The previous Specialized Stumpjumper FSR platform was introduced for 2008, tweaked for 2009 and then binned in favour of an all-new model for 2010. Generally the Stumpjumper FSR has been positioned firmly in the mainstream, having had 120mm of travel both ends for the last few years. For 2010, though, it’s had a travel bump to 140 while still being described as an “XC Trail” bike. There are, of course, plenty of other 140mm bikes around, but Specialized’s move is an interesting one. For most UK riders, 120mm seems to be about right, and shifting the Stumpy away from that mark moves it away from all its traditional competition. Maybe that’s the point…

We rode what was described as a Stumpjumper FSR Pro at Interbike, although you won’t find that model in the UK Specialized catalogue. The closest thing to it is the £2,299 Stumpjumper FSR Expert, with the same M5 aluminium frame, Fox Talas 110-140mm fork and rear Brain shock. The most obvious change from 2009 is that the shock has been repositioned from vertical to something approaching horizontal. A neat touch is that the shock only has a mounting eye at the front end. At the rear end it’s got an integrated yoke that bolts straight to the upper linkage pivots. It’s usually the rear shock mount bushings that pack up first, so getting rid of them is a good idea.

There are a couple of faintly odd spec choices, given the implied usage of the travel – the Fox Talas fork has a regular quick release, rather than the QR15 you might expect (and, if you’ve got used to through-axle forks, quite possibly demand). And there’s an 8in front brake rotor but a 2in rear tyre. It’s all ever-so-slightly schizophrenic. It’s not a bad weight, though – we hung this one off the scales and it came in at 12.7kg (28lb).

The demo bike was also equipped with Specialized’s Command seatpost, the company’s take on the Joplin/Gravity Dropper adjustable post. There’s a lever on the bars and three settings for the post – fully up for most efficient pedalling, 35mm down and 100mm down. Air pressure holds it up, so it’s adjustable for rider weight.

Out on the trail, it took a few stops to sort the suspension out – the Specialized mechanic said he’d set the FSR up “a bit firm”, and he wasn’t joking. Having let a whopping 50psi out of the rear shock and a bunch out of the fork, we had a bike that, er, still didn’t really work. The more expensive models of Stumpjumper FSR are equipped with Specialized’s Brain, an inertia valve system that sits down near the rear axle and keeps the rear suspension effectively locked out until it hits a bump, at which point the valve opens and the suspension becomes active.

The theoretical benefits of this are that you’ve got a hardtail on the smooth bits and an FS bike on the bumpy bits, with the Brain managing the transition between the two as it sees fit. And there’s the rub – it’s not always right. Initially it was staying locked out on slow, bumpy climbs and thus delivering none of the traction benefits of rear suspension. And all sorts of situations would catch it out on descents, too. Show it a smooth trail that develops into braking bumps and chop on the way into left/right bermed corners and it would ignore the first few small bumps, wake up for the bigger ones but spend a good distance catching up with the trail before finally settling pleasingly into the first berm. And then locking out again before the second one, sitting higher in the travel and changing the balance. It was pretty snappy out of the corner, though.

Fortunately the Brain has an adjustable threshold, allowing you to decide how much of a hit it takes to activate. We set out with it somewhere in the middle and kept backing it off until we liked the feel of it. That point turned out to be the fully-open setting, with the Brain not really doing anything except sitting there adding weight.

We can see the sense behind the Brain system on short-travel race-oriented bikes like the Specialized Epic on which it first appeared back in 2003. If you’re racing then hardtail-like sprinting responses are useful to have. On a trail bike, though, we’re not so sure. If you’re riding challenging trails, then the attribute you really need is predictability, and the Brain diminishes that a lot – you’re never quite sure whether you’re going to have rear suspension or not. It’s nice to have the rear locked out on long Tarmac or fireroad drags, but if the climb’s long enough for a lockout to be worth having, you might as well just flick a lever.

Brain aside, the Stumpjumper FSR is as good as you’d expect. Specialized rarely turns out a duffer, and the Stumpy is light, handles confidently and has decent kit (aforementioned anomalies notwithstanding). The good news is that you can leave the Brain off – the Stumpjumper FSR Elite isn’t so far off the spec of the Expert but does without the Brain and is £100 cheaper. That’d probably be our choice out of the range.

More details at www.specialized.com.