BOS Suspension's New Inverted Fork and Coil Shock - Eurobike 2017

Aug 30, 2017
by Mike Kazimer  
Eurobike 2017



Meet the Obsys, BOS Suspension's new inverted downhill fork. Boasting a whopping 220mm of travel, the fork is air sprung, with a design that was heavily inspired by BOS's work in the motocross world. Why go with an upside down design? According to Olivier Bossard, the company's owner, they found that the fork felt more composed under heavy braking, with a precise and accurate feel that they weren't able to achieve with a more typical design.

BOS Obsys Details

• 220mm travel
• Air sprung
• 42mm stanchions
• Wheel size: 27.5" or 29"
• Externally adjustable rebound, low-speed compression, air preload
• Boost 20 x 110mm spacing
• Weight: 3180 grams (claimed)
• Price: TBD
• www.bos-suspension.com/mtb.html/

Two valves protrude from the top left side of the fork, where the air spring resides. One valve is to adjust the base air pressure, and the other to adjust the air preload, similar to what would you'd find on a coil sprung fork. The preload feature allows riders to dial in their ride height by adjusting the amount of effort it takes for the fork to begin going through its travel.

The Obsys' right stanchion houses a closed cartridge system, with similar architecture to what's found in BOS' Idylle RaRe fork, including the Frequency Control Valve (FCV), an inertia valve that relies on a weight perched atop a spring to control the flow of oil through the damping cartridge. The spring-loaded weight remains in place when a rider pushes down on the handlebars, but when the wheel encounters a bump it moves downwards, which lets the oil flow freely, allowing the fork to soak up bigger hits.

Low-speed compression is adjusted by finding a flathead screwdriver and turning the screw found on the damper side top cap. A hydraulic bump stop makes it virtually impossible to completely bottom out the fork – no matter how big you go, there shouldn't be any need to brace for the a harsh impact upon landing.
BOS Obsys



BOS Obsys
The base air pressure and air preload are adjusted on the left side...
BOS Obsys
...And compression is adjusted on the right side.


BOS Obsys
The axle pinch bolts are tilted slightly outwards to make it easier to use a T-handled wrench without hitting the wheel's spokes.
BOS Obsys
The weight-saving cut outs on the guards makes it clear they aren't designed to protect against mud - instead, they're meant to shield the stanchions from impacts.



Traditionally, upside down (USD) forks haven't been as stiff as 'regular' forks, partially due to the lack of a brace between each side, but BOS has taken steps to ensure that the Obsys is stiff enough for the roughest DH tracks. Those steps include going with 42mm stanchions, increasing the clamping area of the crowns, and ensuring that there's plenty of bushing overlap as the fork goes through its travel. The fork will work with either 27.5” or 29” wheels, with two different steerer options available to adjust the offset. One steerer has the standard offset, while the other allows it to be set at +3 or -3mm.

How much will the Obsys cost? That number is still up in the air, but when it's determined sometime in the next few week, one thing's for sure – it won't be cheap.


BOS Syors

Along with the Obsys, BOS have a new coil sprung shock on the way, one that's aimed at both enduro and DH riders. The Syors has a completely new piston design, one that was derived from BOS' work in motocross and rally racing. There's a hydraulic rebound bump stop that prevents the shock from bucking when it gets deeper into its travel, along with a 'Kick Valve,' which BOS says helps minimize the harshness that comes from high speed, square edged hits.

The Syors will be available in November in a range of sizes, including metric and trunion mounted options. There will also be the option to install a compression lever to firm up the shock for pedaling. Like the Obsys, the price of the Syors is still yet to be determined.

Posted In:
Reviews and Tech First Looks Forks


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114 Comments
  • 164 0
 Pinch bolts angled outwards so you can use a t-handle without hitting the spokes? What a simple, beautiful, ingenious, thoughtful detail.
  • 59 2
 But the "weight saving" cut outs on the guards? I'll take a few grams over mud and rocks mucking up my stanchions on a fork this high end.
  • 53 0
 @FindDigRideRepeat: Duct tape and you'll be good! haha
  • 30 4
 I was happy the moment I saw pinch bolts at all. Happy to see a come back of an actual clamping system instead of axle integrated QR skewer "for quick on trail wheel removal" hey - you flatted the front tyre, 1st are you ok? 2. It's over baby, may as well reach for multitool
  • 26 7
 @WAKIdesigns: a lot of people transport their bikes without of front wheel and it's kind'a sad to see my buddy trying to not strip those tiny 4 bolts, while I'm ready to go in few seconds...
  • 13 1
 @FindDigRideRepeat: Yeah it's already a pound heavier than the Float 40, no point in trying to save 20g with the holes. It looks cool though, that's probably the real reason they did it.
  • 1 3
 @Ploutre: too heavy!!!
  • 15 1
 As much as I simply am disgusted with BOS and for all that they've done to me (repeatedly) in service, I have to admit, that's some sexy stuff. But, NO. It still won't sway me to ever buy ur stuff ever again.
  • 15 1
 @b-wicked: i think your buddy either needs better allan keys or to practice tightening bolts.
  • 2 0
 @FindDigRideRepeat: Vinyl tape
  • 5 1
 @FindDigRideRepeat: Even more so when this pig of a fork weighs 3180 grams (compared to the 2597 grms a Boxxer WC weighs). Why shave 50 grams of plastic (at much) and providing the possibility of mud and rocks clogging the stanchions, on this heavy fork??
  • 3 1
 @b-wicked: How does one strip pinch bolts? Who in the right mind removes them all the way anyway?
  • 3 0
 @diggerandrider: likewise
  • 3 0
 @frdh: not strip, but round the head off no bother
  • 1 0
 @anyexcusetoride: yup sorry English is my third language...
  • 2 0
 @diggerandrider: +1 for TERRIBLE after sales service from BOS...wish I had Lyrics/36s...

So what I really need is a DH fork with the worst warranty in the game!
  • 1 0
 @FindDigRideRepeat: If you want this fork you clearly want to be more moto. It just gives you the opportunity for the old school outdoor motocross mod like this:

www.vitalmx.com/photos/features/Vital-MX-Pit-Bits-Hangtown,37995/Ryan-Dungey,75234/GuyB,64
  • 54 1
 Well, if you were directly above him, how could you see him?

Because I was inverted.
  • 15 0
 Bullshit!
  • 19 0
 You're dangerous, I'll never ride with you.
  • 5 0
 I feel the need for speed!
  • 6 0
 I don't like you because you're dangerous.
  • 1 0
 Danger zone!
  • 26 0
 It doesn't matter if it is the best fork ever, until BOS can make parts available and have a service center that can get parts, their product is worthless.
  • 4 0
 hahaha .... god that sounds so unbelievably basic but is SO VERY true ..... I've been there - like many of us
  • 24 6
 It's great to see companies like BOS drive innovation. This fork appears next level. Hope to see teams running this at World Cups next year.
Too many teams on Fox...a company with deep pockets that does little for true innovation. It took the RS Pike charger damper for Fox to up their fork game. Their X2 shock is inspired by the Cane Creek DB. They came up with ugly orange springs 'cause Ohlins made citrus coloured springs fashionable and companies like Stentec were already offering light weight steel springs. They were late to the game for offering air spring tunning options, including better shock cans, etc. ...and now they came up with a customer tuning program to keep up with companies like Push, Vorsprung, etc. that "push" innovation for them.
  • 2 23
flag drivereight (Aug 30, 2017 at 8:42) (Below Threshold)
 Inverted fork in not new, it's been done...it doesn't work, expensive as hell!
  • 15 0
 @drivereight: say that to the Dorado.
  • 1 9
flag jaycubzz (Aug 30, 2017 at 15:37) (Below Threshold)
 @therealtylerdurden: was at whistler for 5 days during crankworx, i think i saw 5 dorados the whole time, they must be really good.
  • 4 0
 @jaycubzz: They are. It's just that Fox and Rockshox and more popular.
  • 1 6
flag jaycubzz (Aug 30, 2017 at 15:55) (Below Threshold)
 @therealtylerdurden: why?
  • 7 1
 @jaycubzz: because they're good forks. I don't have time to convince you. Read reviews on it if you actually care.
  • 3 1
 @jaycubzz: The Dorado hasn't had to change for like 10 years, that's how far ahead it was compared to any boxxer or 40 for that matter. I had a 2010 Dorado that was still made in the U.S.A. (not anymore) and it was the best fork ever ridden to this day. Selling my 40 for it wasn't a tough choice at all - and I f*cking loved that fork! Have never owned the newer 40s with air springs though, since I turned full enduro.

On a sidenote... 220mm of travel, 3100g and no Manitou hex-axle? How is this thing not gonna flex like a hot spaghetti?
  • 3 0
 @mazze: 42mm stanchions may help..

I've only ridden one Dorito. It was on Melissa Buels race bike before she retired. That thing was fucing fantastic! Need to stop reminiscing get one already!
  • 1 7
flag jaycubzz (Aug 30, 2017 at 19:41) (Below Threshold)
 @therealtylerdurden: I'm already convinced they're not as good as you think they are due to the fact they are incredibly rare in any arena of DH riding.

I'm asking you why you think they're not as popular as the competitors.
  • 2 0
 @therealtylerdurden Mmmmmmmm...Doritos.
  • 9 0
 @jaycubzz: because it's not Fox or Rockshox. Avalanche suspension is some of the best shit you can put on a bike but you never see it. Why? Because people want what's popular, trendy. They think if it's more popular, it must be good. They don't give a f*ck about facts and reviews, they want wants 'in'. You're one of them.
  • 1 0
 @OriginalDonk: lol
  • 3 0
 @jaycubzz: RS' and Fox's marketing departments are way bigger and way more active than Manitou's! Smile
That's why you see lots of Boxxers and 40s all around, and just a tiny number of Dorados.
  • 1 0
 @hitarpotar: yup. Same with Marzocchi. Marzzochi's open bath damping outperforms bother Fox and Rockshox yet they're not as common as either.. Either.
  • 1 0
 @therealtylerdurden: The open bath of Marzocchi is almost trouble-free, needs maintenance rarely, but due to the excessive amount of oil it's heavy and some folks (like me) don't like the feel of the fork (too squishy, too plush). And now Marzocchi's marketing is actually Fox's marketing! Big Grin
  • 2 0
 @jaycubzz: A lot of the reason you see more Fox and Rockshox has to do with what is specced as OEM equipment on new bikes. A lot, a hell of a lot, of people don't upgrade from what came on their bike. And of the people that do upgrade a lot of them don't stray from brands they already had and know.
  • 1 0
 @therealtylerdurden: avalanche may be some of the best freeride suspension but their inverted forks literally weigh a TON, their great on the old heavy freeride bikes but on a newer dh bike their just an anchor. avalanche rear shocks are great though, my biggest problem with avalanche is craig is stubborn as all hell and just does what he thinks is best regardless of what you try to tell him, other than that great products.
  • 2 0
 @whitebullit: literally? 1000kg? You sure about that? Wink
  • 1 0
 @whitebullit: i know they weigh a ton.. I should've said I was speaking of their cartridges. My bad.
  • 2 0
 @alexhyland: yup. One literal ton. You gotta run like... 120 psi to keep from flatting. lol
  • 20 0
 There goes the other kidney....
  • 13 1
 "Traditionally, upside down (USD) forks haven't been as stiff as 'regular' forks, partially due to the lack of a brace between each side...."

Seriously? Might you guys want to qualify that misleading statement?

USD forks ARE stiffer in a particular plane simply because they are bolted up by the slider (as opposed to the stanchion) and there is more overlap between the two.

That said, without an arch (or keyed axle), they are more prone to lengthwise twisting, but some of us believe that's not entirely a bad thing as in the chunder it can become a sort of compliance that allows the front wheel to "find it's own way".

Please take care with comments like these.
  • 4 2
 Remember when Fox was testing that inverted fork, and pros like Gee & Gwin said it wasn't torsionally stiff enough?

Well guess what none of us are pros and can feel a 2 psi difference in our tires. Having some torsional compliance, like you said, would help most of us PB riders.
  • 1 0
 @hamncheez: Not sure I'm following you completely in that second paragraph.

Anyway, please don't look at me as a PB rider. I don't have a shirt. They don't pay me. There are no Pinkbike hookers with bib boobs being sent here.

I'm just yet another dude that likes to ride and understand what he's paying money for.
  • 9 1
 Go ahead bitch about the weight. On a DH bike. Maybe they want the fork to last a whole season. Cool to see more Ud forks for somthing different to drool over.
  • 13 4
 *Looks at state of my current non-inverted fork lowers*
*Looks at that flimsy protection for the stanchions*

No thanks.
  • 3 0
 I can tell you that in my experience, most of the damage you receive on fork lowers is actually not while riding. During storage, transport ect.... I ran several inverted DH forks without stanchion protectors for years, and never had any damage.
  • 5 0
 Open internet question directed @ BOS: What have you done to improve your post sales service? Before we discuss new product launches und commence with incessant internet forum discussions of the pros and cons of your new portfolio please address your international service history. And since I am asking I go first. I choose to acquire a BOS Stoy and Idylle RaRE. (please check my bikes photos; Nukeproof Scalp for a date) I was supplied an Idylle with std stations and the steerer which was internally so poorly machined there was no way to insert a starnut and pull the assembly together without warping the starnut. It took you 6 months of discussions to replace this and the first season was virtually done. And that was just the beginning. Now if you would....please address this question: What have you done to address your service in post sales?
  • 6 0
 Will fork and damper still come as a package with the carbon TUES at no price premium?
  • 5 0
 Not a chance, YT won't touch BOS suspension again after all they went through.
  • 3 0
 @NickB01: can you elaborate?
  • 2 1
 @mazze: I think it has something to do with the bad customer service Bos had until recently. A service that translated not only to the regular aftermarket customer, but to customer companies as well (like YT or Orbea). But that's just rumors i heard. Probably it's real cause Bos has been trying to fix this, i hear. Smile
  • 2 0
 @hitarpotar: yeah I've heard about those service problems too... Just didn't think it made that much of an impact on YT. Because truth be told YT bikes were particularly bought for their components in the beginning with a lot of frames landing in the buy/sell. I suppose BOS parts played a certain role in that, because it was really special to have BOS suspension back in the day. Now that YT has made it, they are bought for being YTs haha... times change.
  • 4 0
 @mazze: The warranty issues became so severe at one stage YT were having to give affected customers Fox and Rock Shox forks in place of the faulty BOS forks at their cost. BOS also couldn't deliver on their orders, leaving frames without suspension, hence the late season 2015 LE bikes with Rock Shox suspension.
  • 3 0
 Someone needs to tell their "webmaster" that people do enjoy reading the streamed HTML in their favorite HTML renderer as opposed to downloading PDF files.

1. Navigate to BOS web site
2. Click on a product to see the details
3. Close prompt for downloading PDF
4. Never return
  • 5 0
 So I can't get my old stuff serviced but new stuff with service kits you can't find will be hitting the market soon?
  • 2 0
 My thoughts exactly...:/
  • 3 1
 Like the adjustable offset feature - Its a nice idea taken from motorcycle racing - Works comp made some for a Fox 40 but cant see them for sale so obviously didnt go past a proto.

Not something you would want guys messing with on $1500 bikes (too much adjustment and potential to screw things up at entry level) but in the world of DH racing I think fork offset could be something to look at for adjustability - Transition and others obvioulsy think things are not quite right yet with fork offset too.
  • 2 1
 I'm still running a pair of Risse Racing crowns, not sure if theyre offset though.
  • 1 0
 @schofell84: Nah different kind of thing, take a look at the crown picture and you will see a silver oval shaped part around the steerer tube - You can remove and re-insert this to give +-3mm of offset, your Risse are just standard replacements.
  • 3 0
 @Racer951: you can change offset with an eccentric part or triple clamps. Motocrossers change clamps all the time to change offset!
  • 1 0
 @MX298: yea well aware of that, I was just pointing out that this was the first application in the MTB industry
  • 7 1
 So many full circles in the bike industry it blows my mind.
  • 3 3
 How many more times do we need to hear, "Why go inverted? Let us tell you..." Zzzz

Not even XC riders use Rock Shox inverted carbon abomination anymore. Flexy flier, but at least 2 years of marketing how much engineering went into overcoming all of the negatives.
  • 1 0
 @PinkyScar: the only path forward that I can see for inverted forks is to do something like the Lefty in one of the legs (and like the Revel) where its keyed, has bearings, or even a linkage to keep it more torsionally stiff
  • 2 0
 Isn't that inertia valve some Specialized Brain patent? I'm not up to date about what the Brain does nowadays, but I recall the first version of the Epic XC bicycle used to work with an inertia valve like that. Or was it something from Fox (tail) suspension?
  • 4 2
 Offset adjust, hydraulic bottom out, big clamp interface... sounds good, but why ruin it with those stanction guards? And it's that FCV system necessary?
BOS likes to go complex in his designs to keep that high tech aura around his products

Nice fork but not as good as the DVO Emerald.
Stronger chassis, trusty twin tube open bath damper, negative spring adjust, user friendly.
  • 5 0
 It's still not on sale to the public and you already know the DVO is better and stronger. :-)
  • 2 1
 @migkab: well.. AFAIK, bigger diameter legs and CTA means stronger chassis. You don't need a review to know that.

I'm not hating. Fork looks amazing and love inverted.
I just try to say that my bet it's on the Emerald for the best exotic fork
  • 4 0
 Iv had The DVO, Dorado (all generations) and Bos forks over the years and from a test point of view, the Dorado wins hands down with the Bos coming in second and the Dvo a close third, for a general rider the Bos where the easiest to set up followed by the Dorado then the DVO.
All great forks just personel preference as long as they are not Boxxers or Fox 40 lol
  • 2 0
 @derryair: And then there come the Emerald's fan who claim their DVO is hands down better than a Dorado...
A mate of mine's got an Emerald, feels pretty good, but i can't get over the 3.5kg of weight on this AIR fork. It's some 200-250g heavier than my coil-converted Dorado Pro... O_o
  • 1 1
 Motocross sizing... So if a MX bike fork is stiff enough
Even at 36mm and 20 mm axle (a little less thn MX again) for a MTB it should be stiff enough...

At this rate I'll soon be able to take my MX part and put them on my MTB... until they show to be too small...

Mtb business makes little sense,
Well it plays like an ado with an ego surge

(My view only)
  • 4 0
 Like a boss version of a SHIVER
  • 2 0
 Are the holes actually for weight savings? I feel like BOS is too smart for that and the holes must be for air flow over the stanchions to keep things cool and consistent.
  • 1 0
 why do they think we want a shock developed with motocross and rally racing?
why? bikes, weight so little compared to a motorcycle or a rally car....
its really doesnt help to build it around motocross and rally racing.
  • 1 0
 So again you need a tool if you want to change your setup on track? Seems to be the 14 wrench and the head screwdriver again...
  • 5 2
 It's a shame they "can't afford" something else than a Facebook page...
  • 3 1
 www.bos-suspension.com/mtb.html
  • 3 0
 @Ferisko: Working since this months, has been off for a half year. Great they discovered this "internet" again...
  • 4 0
 @Ferisko: with about zero details on current products. So imagine what it is for a fork that's just ben shown!
  • 1 0
 @EnduroManiac: Seems like pdf is the new web Big Grin
  • 2 0
 @EnduroManiac: No comment about the site content. Just wanted to point out they actually do have a working page now for a while. The old domain bosmtb.com has been down for ages without any redirection and www.bos-suspension.com is not the first result in google search (at least in my region) so people tend to assume what @evildos did.
  • 1 1
 Did they forget many DH bikes use 26" wheels?

Good addition to Dorado, that I use. I have not had any issues with them being not stiff enough for downhill bike parks and I weigh 110kg geared up.
  • 1 0
 I don't understand, how the two chambers in the fork work (one for air pressure and the other air preload). What is it for?
  • 1 1
 One of them is probably a negative air chamber, working against the other to provide a neutral sag point and provide the illusion of reduced stiction. So, you can pump up your spring rate loads, and then pump up the negative spring also to give you the sag or 'preload' you require and get the fork riding at the right height. Some MX forks even have 3 air chambers. They're a bitch to set up.
  • 1 0
 Is that a new Spank stem? I'm intrigued. I just can't figure out how it attaches to the bike?
  • 2 0
 Spike stem faceplate removed, mounted to a board and clamped to the steerer simple answer to display conundrum, If ever there was one.
  • 2 4
 claimed 3,180g... so that's going to be about 3,250g in real life. Man, that is not light. Sure it's not as piggy as an Emerald, but I don't think I want to hang an extra 300g off the front of my bike. Where are you at Öhlins??
  • 2 0
 40's are in the 2700g range too. Fox 40's are hard to beat!
  • 2 0
 Wheres the MRP press report???
  • 2 0
 Take a 48mm white power from my ktm950...
  • 1 0
 Curious to know what bike this is going to go on, or at least the axle to crown height.
  • 1 0
 Looks amazing Oliver and BOS! Can't wait to try it! I know it will ride fantastically
  • 1 0
 The Specialized lawyers are gonna have a field day with that inertia valve bit...
  • 5 4
 It's turned my world upside down! Sorry.
  • 1 0
 Another Hamilton fan!
  • 1 0
 That is one beefy looking fork o.O
  • 2 0
 Some deflection is good
  • 1 0
 Looks like an old shiver!
  • 1 0
 220mm travel with 29 inch wheel, wow. That'll plough through anything.
  • 1 0
 Spank Spike Stem For Hanger. Damn.
  • 4 3
 that fork looks bos
  • 1 0
 42mm legs? Sign me up!
  • 4 1
 such burly much friction wow
  • 4 0
 You like that? Avalanche makes some USD forks with 43mm stanchions - I kid you not. The mTN-8 and -10.
  • 1 0
 Yuh ...@strasznyzbigniew:
  • 1 0
 New school Monster T
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