Background:
Up until recently, the downhill suspension market has been well and truly dominated by four major players – Rockshox, Marzocchi, Manitou and Fox, with 5th Element sticking their head in for a couple of years before deciding MTB wasn’t worth their while. A few other boutique manufacturers have put up high-quality suspension products as well, such as Cane Creek and Avalanche, but in spite of numerous small improvements, none of these have really stood head and shoulders above the rest in terms of performance or the all-important race results.

However, in spite of the market domination of these four brands, particularly Fox, in the rear suspension market, there is one name that has stood above all others when it came to the real pointy end of dampers. BOS Engineering shocks, with Olivier Bossard at the helm, have been on more senior men’s downhill World Championship-winning bikes than any other brand of suspension. Their custom dampers and forks, initially developed for 10 times world champion Nicolas Vouilloz, were not readily available to the public “back in the day” due to their prohibitive cost and custom-tuned nature.

 
The BOS S** Toy

Of course, times have changed, and now BOS have released a highly anticipated shock that is closer to “mass production” than ever before, in the form of the S** Toy (Sex Toy or Stoy for short). In case you’re wondering about the name, it simply fits in with the current market trend of sexually-oriented names for shocks (eg Manitou Swinger 6-way, Rockshox Vivid, Marzocchi Roco) The background hype with these things is, as you’d expect, enormous, and from the company that raised the bar for bike suspension more or less single-handedly in the 90s, well let’s just say they weren’t planning on putting out something that was cheap crap. They make no secret of the fact that each shock is valved specifically for the bike it is to be used on as well as the rider it is to be used with, having a number of different tunes for different leverage ratios and leverage rates. This review is aimed at providing a hype-free assessment of the shock in order to give you a realistic, accurate picture of how it performs, rather than simply gushing about how awesomely awesome or terribly terrible it is.

The Techy Stuff:
So what sets the Stoy apart in the real world? Nothing about the appearance or the adjustability is out-there or gimmicky, they provide adjustments for Rebound, High Speed Compression (HSC) and Low Speed Compression (LSC), all of which are fairly standard in both the bike and the automotive worlds. So you’d hope the actual performance is right up there, because these things aren’t cheap.

Pulling the thing out of the box however, and it’s pretty clear that BOS’s approach to building shocks is to find every single little thing they can and eliminate any problems with it. It’s not reinvention or even really innovation, it’s just extremely thorough optimisation. There are little details, like the fact that the preload ring has radial holes in it similar to the bottom-out adjuster of a Fox DHX5 in order to let you turn the thing more easily if it’s tight, and it even has a small hole for a grub screw so that you can lock it in place and be sure your preload won’t self-adjust. Sure, not a big deal, but just little details that let you know they're paying attention.

A prototype Stoy on the shock dyno at BOS's HQ in Toulouse, France

One pretty nifty feature that helps eliminate any stiction in the bike’s suspension system is the use of German-made needle bearings in the shock eyelets, in place of a conventional DU bush. These are sealed with o-rings either side, and run on a hardened steel tube as the inner race, which a conventional 8mm shock bolt goes straight through. The finish on the hardware here is stellar, with a fit between the axial spacers and the inner bearing race a hand-press-fit with no play. What this also means is that unlike shocks that use DU bushes in their eyelets, you can rotate the reducer hardware in the eyelet by hand with next to no friction, something that is nearly impossible with most other shocks. This is but one step in BOS’s anti-friction plan.

Needle bearings in the Stoy are super trick and give virtually zero friction - a clear-cut advantage over standard DU bushes used in most shocks.

The next measure taken by BOS to reduce friction is the use of very special carbon linear bushings for the shaft of the shock. According to the BOS distributor, these have extremely low friction compared to the standard DU bushes used in most shocks (again, such as Fox), and when comparing the friction of the damper units with no spring on them using my extremely precise, Australian-made, regularly calibrated Steve’s Two Hands, there is noticeably less stiction in the BOS damper unit than there is in a Fox DHX, even when the Fox has been depressurized well below the recommended running pressures. In fact, the BOS is the only shock I’ve ever managed to get visible movement out of by compressing it by hand WITH the spring on. Sensitivity of the shock was clearly one of BOS’s goals.


The Ride:
But enough crapping on about how nice the shock is when it’s in a cardboard box, the important thing is how it rides. So, in a highly controversial and rarely-used test method, I bolted the shock into my bike and rode it for a while. The first thing you notice is that it’s softer than usual, and there isn’t any stiction. Most shocks these days don’t have much stiction, but the BOS gives you that feeling like it’s actually somehow almost oversensitive, it moves with the slightest input. This can have the noticeable downside that if your frame doesn’t have good pedaling characteristics on its own (ie it relies on the shock for a “platform”) then your bike is going to bob a lot more than it did before. Don’t kid yourself, most downhill bikes don’t pedal very well on their own (remember the old Fox RC days before platform shocks?), and having a huge marketing spiel behind your TLA (Three Letter Acronym) suspension linkage doesn’t necessarily mean it does what it claims to. The upside, of course, is that the shock is able to respond to smaller inputs than its competitors are, relying less on the tyre to take up small bumps. Running over a single piece of gravel placed on concrete produces a tiny but visible movement of the shock, sensitivity which is simply unmatched by other competitors.

The soft feeling comes from the fact that BOS typically specify lower spring rates than most shocks do, in order to let the damper do more of the work. This of course means more sag, and that the shock needs to run more damping than a conventional shock in order to control the use of the travel, as well as preventing excessive bottoming out. It should also be mentioned that this shock doesn’t appear to have any position-sensitive compression valving (unlike DHX’s, 5th Elements and Manitou Swingers/Revoxes), which means that the overall level of compression damping has to be higher than the equivalent position-sensitive shock in the mid-range of the travel, in order that the bike isn’t constantly bottoming out.

Once on the trail, the BOS simply does its job, in fact what it does most noticeably is stay completely out of your way so that you don’t notice it or have to think about it. The small bump sensitivity is improved over say a DHX (used as a standard of comparison since it’s more or less the benchmark), and the shock reacts to smaller inputs than pretty well anything else, in fact it almost feels hypersensitive, like it’s slightly overshooting the amount of travel it really needs to do anything – but this is what LSC adjusters are used to control. Cornering, particularly in berms that can really be hammered hard, the shock squats nicely into its travel, and again how far it does this, and how this relates to the pitch (how far back or forwards your bike tips) when you corner can be easily adjusted with the LSC adjuster. I found it ideal to use about 5 clicks of LSC, which reduced the squirming feeling coming from the rear tyre when pushing hard in corners (particularly bermed corners), and also prevented the shock from bottoming even on one particularly harsh high speed g-out, which it had been doing previously. Landing jumps or drops, even to near flat, had the shock working its beefy mid-speed compression damping to maximum effect, with a controlled deceleration of the bike and rider that did an excellent job of walking the line between blowing through travel, and a harsh feeling.

Hucking a race-tuned shock. It was an accident, honest.
Photo: Bradley Metherell

Bashing through big rocks at high speed, the shock doesn’t easily get unsettled, and likewise with big braking bumps. Whether this makes a significant difference to the speed you can actually ride through these things at, or the level of traction you have when compared to say a well set-up DHX is debatable, but at the least you can be sure that you’re certainly not going to be any worse off than on any other shock. BOS claim big improvements but the realistic difference doesn’t feel huge, though in fairness to BOS, it’s hard to actually work out what constitutes a “big difference” – what feels faster or slower to the rider is not necessarily what the stopwatch tells you either. By staying out of the way of the rider, and simply by virtue of not doing anything wrong, hard to deal with, or unpredictable, you may find yourself going faster without knowing it. To put this in perspective, a gain of 0.1 seconds in any given section would be more or less undetectable by the rider, but 0.1 seconds gained in each of say 30 corners on a track can translate to 3 full seconds over the course of a run. I’m not going to pretend I can quantify this claimed improvement other than to reiterate that you are certainly as well off or better than you would be with most other shocks. It might not be significantly speeding you up, but it sure as hell isn’t slowing you down. If you’re not riding your bike constantly near the limits of grip, the benefit will be small, maybe negligible/zero compared to any other shock. If you are the kind of rider who regularly has the rear end of your bike stepping sideways or squirming under hard cornering loads, you stand to benefit more from the extra sensitivity of the shock than the “average” rider or weekend warrior. I hate to sound elitist, but this basically means any advantage of the shock in terms of traction is bigger for better riders.

Barjarg has no shortage of rocks to plow through, and the whole track works suspension hard.
Photo: Laura Cvetkovski

One issue with shocks like the DHX is that increasing either the compression or the rebound damping deadens the ride significantly, and makes it very hard to pop the bike off lips and so forth. Whilst this is fine when you’re bashing through rock gardens and all you want is minimum feedback and maximum stability, there is a compromise to be struck with stock DHXs, where you can choose from either increased chassis stability or increased liveliness of the shock – but it’s not really possible to get both.  There are two features of the BOS that really do shine, in my eyes. The first of these is the apparent solution of the liveliness vs stability tradeoff – the BOS feels like it has less compression damping than a DHX at super low speeds, yet more in the mid-range in order to control stability, and even with the low speed compression cranked up, it still provides plenty of pop when you want it.

The second thing that subtly kicks sand in the face of other shocks is the limited adjustment range. This sounds counterintuitive, because a bigger adjustment range would naturally sound like a better thing, but let’s look at a couple of examples that show otherwise. First of all is the Motion Control low-speed compression adjuster on Rockshox forks such as the Boxxer. This thing only has 6 or 7 clicks, which translate to “nothing, nothing, nothing, a little bit, tons, way too much, locked out”, which is great if what you’re after happens to fit in with one of those, but having zero compression damping isn’t ideal despite the number of people who set their stuff up that way, and having a downhill fork locked out (or simply with way too much compression damping) is pretty useless, so in reality you have two plausible choices – “a little bit” or “tons”. A Fox DHX rebound adjuster has a similarly wide range, going from ejector-seat fast to watching-grass-grow slow, though at least there is a good linear range of adjustment in between those two. Most other adjusters on most suspension products also have equally overshooting ranges, where the options at either end of the scale (maximum or minimum damping in either rebound or compression) are useless or at the very least far from ideal.

What BOS does that is different here, is limit the range of adjustment you can actually make, which is particularly noticeable with the LSC adjuster. There are about 10 clicks on this adjuster, which range from “A bit but not all that much” up to “quite a lot but not really excessive” – the entire range is usable, and no matter how much you may try, you simply can’t mess the settings up badly. You can’t back the LSC off to near-zero, nor can you increase it to the point where the bike feels way overdamped. The high speed compression appears similar – you can’t back the adjustment off so there’s way too little, or increase it so there’s way too much, which means that when combined with the damper valving that is specifically tuned for your bike, it’s all but impossible to actually find yourself a bad setup. What you change by twiddling the knobs is far more like fine-tuning an already decent baseline setting, than simply getting the thing to work at all. This alone will mean that to many people, the shock can and will feel awesome out of the box compared to a shock with a wider range of adjustments that can actually produce some far from ideal setups.

If you do know what you’re doing with a DHX or similar, you can get it fairly close to the feel of the BOS for the most part, but the adjusters are more sensitive (a couple of clicks either way, or even 10psi in the Boost valve, and you can overshoot your intended mark pretty easily) and it’s easy to find yourself with more or less compression than you want or need – again, the reality is that most people don’t spend all their spare time learning how to tune suspension, so for the general public this is a genuine advantage for the BOS. If you want more cornering pitch stability or g-out protection, simply increase the LSC, if you want the rear end controlled deadened a bit more when you’re hitting stuff hard – like big rocks or sharp lips at speed – then winding on the HSC simply eliminates the problems on your next run without you really even noticing. The only fault I could find with the compression adjustments on the BOS are that you need tools to do it, which simply draws out setup time longer than it would otherwise be.

The rebound damping in the BOS is a funny thing compared to most shocks. When you first adjust the rebound, you’d swear it’s doing next to nothing. It almost feels like the rebound adjuster isn’t connected to anything, because when you bounce on the bike, the difference is quite small compared to the aforementioned ejector-seat/grass-growing rebound range of a DHX. It appears that the rebound adjuster actually adjusts the high-speed rebound more than the low-speed rebound. High speed rebound (HSR) is what tends to control how much the bike kicks when it’s rebounding from deep in the stroke at high speed, such as hitting a lip fairly hard, whereas low speed rebound (LSR) actually has the biggest effect on traction. Notably even when winding the rebound on tons, the LSR stays quite fast, indicating that BOS simply aren’t going to let you reduce the shock’s traction-keeping abilities simply because you think you know better, unlike every single other shock I’ve tried. This is interesting and really shows that BOS know what’s up when it comes to performance and realistic ranges of adjustment. Winding the rebound from fully in to fully out, like the compression adjustments, will not net you an unusable setup even at the extremes of the adjustment range. What it does allow you to do is set the bike up so you’re not getting kicked off lips or after sharp hits and g-outs, without worrying about compromising traction or liveliness. I don’t actually know how it is that BOS have managed to get this adjuster to work in this manner, but one way or the other, it’s impressive.

The BOS shock nicely matches the colour scheme of red bikes - great news for us gear-wankers!
Photo: Tony Pincan

Unfortunately  since this was a short-term test over the space of a few weeks, the reliability of the shock cannot be commented on, however it would be surprising if these had any significant problems, given the level of detail that has gone into their development and manufacture.

Enough rambling, what are you really trying to say?
So what this shock really is, in a nutshell, is a refined unit that doesn’t try to reinvent the wheel, it simply eliminates all the idiosyncratic issues present in many shocks. Custom valving sets the shock up to a great baseline level, and the adjustments provide realistically usable ranges for fine-tuning without letting riders unknowingly mess things up. It’s hard to fault this shock, in fact its best asset is that it literally does “just work”, letting you get on with riding without having to bother with it. No, it’s not like you don’t even feel the bumps in the trail, but there are physical limitations on how much force can be absorbed by a shock anyway, and if only as a comparative measure, I’d say the BOS is the closest to those physical limits, because it transmits the least harshness of any shock I’ve ridden.

What this shock isn’t, is literally “dozens of times better” than the competition. Make no mistake, the differences between what you CAN get out of a mass-market shock and the Stoy are not as huge as the marketing team would have you believe – there isn’t a night and day difference like there may have been 7 or 8 years ago - but as with any performance equipment, the devil is in the details. To purchase a Stoy over its mainstream competitors, you are looking at close to double the price for something that might provide you with a 5%-10% (completely arbitrary judgment here) improvement in feel over said competitors, and probably more like a 1-2% improvement in actual race times (that’s about 0.5 to 1.0 seconds out of every minute) at most. Bolting this shock (or any other) to your bike isn’t going to catapult you from mid-pack Sport to podium-level Elite. What it might do, if you’re pushing your equipment hard enough, is make that couple of seconds’ difference over a track length that could bump you up a couple of positions in the standings. The better a rider you are, the more you stand to be able to take advantage of what the Stoy can offer.

Arguably the biggest failing of the shock is its inability to make crap cornering style any more photogenic.
Photo: Tony Pincan

That might sound a bit less positive and gushing than you may expect, so let’s put this in perspective – many people are happy to pay $5000+ for boutique frames such as an Intense M6 or a Yeti 303, when there are Giant Glories available complete for $3500 or so, essentially paying double for what amounts to a relatively small improvement in performance that the rider can feel, and percentage-wise an even smaller improvement to the times the rider can set down the hill. Likewise, the BOS shock is not punter-level equipment, but the serious racers (and gear nuts) who appreciate that you don’t go literally twice as fast by paying twice as much, will definitely understand what it is that you’re paying for, this thing is all about subtlety and optimization, not reinvention of physics as we know it. The shock may only justify its asking price to a relatively select market of gear nuts and serious racers, but if you want the best, cost-no-object, this is it.


Weights:
9.5 x 3.0” shock body: 456g
Spring collar: 16g
350 x 3.0 spring: 530g

Shock Tune: ST01
Bike: Banshee Legend Mk1
Average leverage ratio: 2.83:1
Leverage rate curve: progressive to linear
Rider weight: 93kg
Spring rate: 350lbs/in as recommended by BOS

Adjustments:
Rebound
Low Speed Compression
High Speed Compression


BOS mountain bike suspension is distributed in Australia by Rouler Imports. For more information, contact your local bike shop, or speak to Nicho direct on 0402 138 508.
Recommended retail price is $1290au as of 23/11/08.