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EXT Arma HBC Rear Shock

Vital Rating: (Spectacular)
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Tested: EXT's Rally-Inspired Arma HBC Shock

An Italian race weapon. Learn about an interesting downhill shock option with our long-term review of the Arma HBC.

Rating: Vital Review

The Italian word “Arma” translates to “Weapon.” If you currently don’t know anything about this company or piece of suspension, that's at least a pretty good starting point. Extreme Racing Shox, better known as EXT, is an Italian brand that has been immersed in the world of racing for 55 years. They have been helping make rally, F1, Le Mans, and pretty much anything that needs to go fast, do so under precise control with their unique valving technologies and future-minded approach to product development. In 2014, EXT decided to take their decades of experience in motorsports and bring it to the world of mountain biking. In 2017, Vital rode an Arma HBC-equipped test bike in Val di Sole, and at the end of the afternoon our interest was piqued – something special was happening, but we needed more time to really get to the bottom of things.


EXT Arma HBC Features

  • Gas monotube design
  • External low-speed rebound (8 clicks), low-speed compression (12 clicks), high-speed compression (14 clicks), and hydraulic bottom-out control adjustments (HBC, 8 clicks)
  • Unique rebound system to separate bump and rebound oil flow
  • 29mm diameter high-flow main piston / 24mm valve piston / 28mm reservoir floating piston
  • CNC machined in 7075 T6 alloy and titanium
  • Special seals and proprietary steel chrome shaft coating to reduce friction
  • Low reservoir pressure (40psi) for improved sensitivity
  • Low hysteresis for high dynamic response
  • Service suggested at 50 hours (race) or 100 hours (general use)
  • Weight: 790g (claimed, 241x76mm shock with 325-lb/in spring)
  • MSRP: €799.00 (~ $930 USD)
  • Two-year warranty

Standard Sizes

  • 220x70mm
  • 241x76mm
  • 267x89mm
  • Custom sizing available

EXT Spring

  • Super Steel Spring (proprietary lightweight design)
  • Extreme Linear Ratio
  • Hard epoxy coating
  • Internal diameter of 38.5mm
  • Lengths: 117, 140, 175mm
  • Shock stroke compatibility range: 50mm to 89mm
  • Lightest steel spring on the market (claimed)
  • Developed through motorsports programs
  • Next generation after the Super Alloy Racing springs
  • 25-pounds spring rate increments
  • Adaptable for all types of coil dampers in the market
  • Life duration of over 500,000 cycles

EXT Spacers

  • Spacers allow the spring to fit any shock on the market from 200x57 to 267x89mm
  • Available for FOX, RockShox, Marzocchi, CaneCreek, BOS, DVO, Ohlins and more


We received our Arma EXT shock in Queenstown, New Zealand during one of the driest summers the Wakatipu Basin had seen in several years. The bike park was in dire need of some TLC… the perfect conditions for a shakedown of a hydraulic damper. Reading the instruction manual (yes, we did that), it was clear that the adjustments were easy to understand. At the factory settings it could be ridden out of the box. We tinkered slightly, giving the shock the following settings on a Zerode G27.5 downhill test bike.The detents are easy to feel with a subtle "click".

Initial settings, maybe huck-approved:

  • HBC: 4clicks from closed
  • High-Speed Compression: 9 clicks from closed
  • Low-Speed Compression: 12 clicks from closed
  • Rebound: Closed

Both a 475 and 500-lb/in coil spring came with the shock. EXT provides two springs with every shock sold, which are based on your riding style and bike (which you specify when purchasing the shock). The Super Steel Spring is the second iteration of the famed Special Alloy Racing Spring, and is made of a special alloy that is comparable in weight to titanium but less expensive.

475-lb/in spring mounted, with the HCB piggyback prominently displayed, and the high-speed compression (12mm hex), low-speed compression (4mm inside the hex), and HBC (right-most 4mm) visible to the right.
The second spring, a 500-lb/in, which we mounted when the riding warranted it.

We started with the 475 spring and left it on for the New Zealand portion of our testing. Being that Skyline Bike Park is steep and rough, having the bike sag a little more is helpful to level the bike and keep rider weight in a more neutral-rearward position. The high-speed and low-speed clicks make notable changes in the shock’s behavior and feel, and tuning is simplified because of this. It only takes two clicks to feel a big change, with one click providing that fine touch. We ran the rebound as slow as possible, as the shock is tuned to be ridden really fast – it’s specifically race equipment, so the rebound tune is a bit faster overall than other shocks on the market… basically you can’t turn it into molasses. The valving on the rebound also separates rider-influenced rebound and bump-related rebound, effectively internally-designed high- and low-speed rebound, with a single exterior adjuster.

The rebound knob is actually removable, leaving just the adjuster allen bolt. If you forget to take the knob out it will self-extract and become part of the trail you are riding (not a big issue, but we still felt dumb).

When using aftermarket suspension it is crucial to understand that there often isn’t really a "base tune," though it is designed to be a custom piece of equipment specific to the intended user and application. The springs we were given were 50 and 75-lbs/in lighter than the spring we’d been using on the previous shock. This is no accident, though, thanks to the EXT’s unique Hydraulic Bottom-out Control damper – the “HBC” in the EXT Arma HBC. This allows a lighter spring to be run in favor of improved small-bump absorption, as HBC kicks in during the last 15% of the stroke and ramps up the shock as if it were a more progressive suspension design or air shock.

EXT's HBC technology explained

HBC was an exceptionally helpful feature for our needs, as the Zerode bike we used for testing doesn't have a ton of progression. By the end of our test time we were running the HBC setting fully closed, achieving a ride characteristic that was almost too encouraging. With a rearward wheel path and what felt like bottomless travel, hucking become even more commonplace.


Testing in New Zealand

The Arma worked so flawlessly it became something we didn't have to think about. After a few laps and some minor tweaks, it did its job and we were able to focus on riding. Using flat pedals (because we win imaginary medals), a shock’s ability to eat high-frequency chatter and g-outs alike is a crucial point of contention. After our first "fast" run down the hill on the first day of riding we were sort of stumped about why something felt weird. Sitting in the gondola queue mulling it over, we realized that our feet had remained perfectly planted on the pedals with no jostling or fidgeting about. The Arma was working so well, it felt weird! After that all bets were off, and we proceeded to hammer everything in sight, including huge holes, loose corners, and lots of heavy hits. The feeling of not having significant feedback from the rear suspension was such a treat, especially during one of the roughest mid-summers in recent years.

The Arma fits right in on the Zerode with its industrial appearance.

This theme continued through the remainder of the New Zealand summer, with pace getting higher and higher and our grin getting wider and wider. Finding new lines and hitting old ones harder, the confidence the Arma shock provided was something special. It was especially interesting when hitting really big compressions/holes/things in the trail as there wasn’t any bucking or weird chassis movement. The rebound circuit is something to behold, it keeps the bike under an almost abnormal amount of control, casing a 45-foot table because we were tired was no longer the scariest part of our day. We hit g-outs and bump-jumped some sizeable objects, and the bike just kept rolling forward with no up/down/sideways kick. There was also no squirming in corners – just pure traction and exit speed – another notable attribute the bike gained with the addition of the shock.

Something we liked (but took a moment to adjust to) was the slight whisper the shock emits as it compresses, akin to a turbo blow-off valve. It fades into background noise, but on the first run of the day or after lunch when you’re warming back into “ride mode,” the soft hiss of the shock eating up the rough is a fun reminder that things are under control and it’s time to get sendy!


Testing Continued, Back Home

When we returned back to New Hampshire, the race season was right about to start. With new changes to categories of the Eastern States Cup (they added a Pro Open category), we saw an opportunity to put the Arma through some new paces at our old stomping grounds, Plattekill Mountain – East Coast hardcore at its finest. Few places in the world compare to how steep Skyline Bike Park in Queenstown is, so we swapped up to the 500-lb/in spring to help the bike sit up a little more on the less-steep home pitch, and we also closed down the low-speed compression two clicks. No matter how much we tell ourselves, “We’re just gonna chill,” when there is a race plate tied onto the front of the bike things are getting turned to 11.

Zach, about to launch the Arma into a boatload of shale.

A Saturday of excited riding and mock race runs reminded us why we put the big spring on, and also how interesting the Arma was to ride on familiar tracks and terrain. Maybe we are just better riders (having not raced since 2015), but we like to think it was also thanks to the shock. Holding tight lines in the roots and shale, white knuckling rock gardens, and over-shooting short gaps into blown-out braking zones always felt manageable and under control from a suspension standpoint… the pilot, maybe not always. Sections that would have given us a moment of pause were passé and executing consistent runs with accurate line choice almost felt easy. The bike stayed predictable even under changing track conditions, and that was really impressive. Due to a weather-related power outage on Sunday, the riding was consolidated into a single blind race run down a now muddy and wet track (practice was canceled). The race organizer understood it wasn’t ideal for a lot of people and offered a refund to those who chose to not race. We opted for the latter option and decided to hang out and talk bike tech over coffee in the pits rather than take silly risks so early in the season.

Cheeky gap over the main line.
Cornering capability being scrutinized.

At home, after the race, we still wanted to try and find a more refined setting for the summer ahead (more racing!?), as the terrain in Queenstown and the Northeast US are nothing alike. A half-dozen laps on our local test track, a lot of GoPro footage, some settings consulting, and a lot of bug spray later, we have a shock that is truly inspiring. The Arma has us pushing the upper limits of control on a trail that now looks less-than-fresh after shredding it to bits and laughing the whole way down. 

There's a landing, but Zach is opting for the 'test' landing - the flat part past the sweet spot.

At the end of the test, the level with which we are impressed with the Arma is still 100%. From the first day we climbed aboard the exquisite-looking damper to eight months and some wild riding later, it only ever made us smile and try to ride harder.

Final settings, huck-approved:

  • HBC: Closed
  • High-speed compression: 9 clicks from closed
  • Low-speed compression: 5 clicks from closed
  • Rebound: Closed

GoPro footage of the shock at work with a view of what is being ridden. Not the wildest of times, but a good track to test on!

The Zerode G27.5 uses a high-leverage single-pivot suspension design with 6-7% progression overall. Because of this, we closed the HBC to aid in giving it a more progressive feel. The low-speed compression was also cranked down a fair amount to aid the suspension in sitting up in its travel. High-speed compression was to taste, and we were able to run it a little more open thanks to the HBC. Rebound was also to taste, and perhaps a little slower than some might like, but due to the wheel path of the bike it feels more stable with a slightly slower return – we also plow straight down the trail a bit off the back, so a “playful” bike isn’t what we were trying to achieve. The heavier 500-lb/in spring is also the weight we’ve found to be the most suited for our size and style of riding.

The shock was paired with a FOX 40 RC2 fork:

  • High-speed compression: 15 clicks from closed
  • Low-speed compression: 10 clicks from closed
  • Rebound: 12 clicks from closed
  • Air spring: 77psi with one spacer at the bottom (older metal spacers on the air seal/shaft system)


What's The Bottom Line?

If you are really picky about how your bike feels, can sense each click, and like the semi-factory aspect of aftermarket suspension, this is your new favorite shock – especially if you ride flat pedals. The beautifully CNC’d pieces, refined industrial looks, and an insanely cool pedigree make the EXT Arma HBC shock standout. The shock works like a dream, doing everything you'd expect and then some. It also adds some great “bling” factor to any bike.

For those who race, want a bike-tailored shock, and make frequent adjustments to try and eke out every last tenth of a second, this will be a worthy investment. It’s also a great option for anyone who likes the performance of a coil shock but have a downhill bike with a less progressive suspension curve. The price is no doubt on the higher side, but it is race-focused performance equipment.

Visit for more details.

About The Reviewer

Zach Faulkner - Age: 27 // Years Riding: 17 // Height: 5'10" (1.78m) // Weight: 205-pounds (93.0kg)

Also known as #MTBJesus, Zach looks like a circus bear on a bicycle. His riding style has been compared to a landslide, replete with sounds of destruction and debris chasing his rear wheel down the hill. He rides flat pedals because they win medals, and he’s fond of quad-piston brakes on all of his bikes. His zeal for riding is life-long, having been astride a bike since before he was forming memories. Bikes kept him in the woods and out of trouble through his teenage years, and after more than a decade of racing DH, can now be found lying in the dirt next to race courses around the World behind a camera, writing at his computer late into the night, or out on the trail thundering through the woods.

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24 comments newest first

Any drama purchasing this shock worth mentioning? Their online store is not the easiest to purchase from (they only offered SWIFT payments at the time of my query).

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You claimed that you know which had better small bump mate when you haven’t ridden them on the same bike. Most people in the industry and riders themselves like to make claims when they haven’t really made a proper comparison. Even then there’s so many other factors. Everyone is entitled to their opinion though no matter how invalid it is.

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I have one, amazing duty doesn't have the hydraulic numb stop. And I never use the lock, doesn't need it. Pretty sure they make the arma in smaller sizes too.

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If you have a progressive leverage ratio bike and require a climb switch it’s the shock for you.

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I have the storia lol on my warden. It's amazing, replaced a high end air shock and it's just better everywhere, the low pressure damper works better.
Rb:1 from open. The comp settings 1/3 or so from open.

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Just for a bit of balance, if people really want better suspension performance from their bike, you're far far better off to send your current shock and fork to a reputable shock tuner. Have a long conversation with them about what you want, what you ride and how you ride. This will improve your bike way more than buying off the shelf suspension components and probably save you a ton of cash.
Any of the features that this reviewer liked about this shock are simple to achieve from the shock your bike already has - it just needs the internals fiddling with by someone who knows what they're doing.

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It's a little more complicated than that.

Avalanche has done my last 2 bikes (front and rear) and it's incredibly beneficial. However many of these mass produced components have severe limitations built in to their architecture that simply can not be overcome. Furthermore some of the air cans are not properly sized to get the right ramp up with specific LR's.
On my newest bike (Mondraker Foxy 29) I called Craig at Avalanche and followed his recommendations for which suspension components I should be purchasing for him to mod, he was pretty specific about what gave him the best base from which to work.
~ take care

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I was torn on ordering the bike for a couple of reasons. One was that the color frame set that I wanted was only offered with a coil shock. Which didn't really jive with the regressive leverage ratio. even when I called Fox the rep I spoke to agreed it was not the correct shock for the frame and application. (application: mostly trail but also plenty of drops and a few jumps). The online reviews (i.e. Pinkbike) noted that the bike with the coil bottomed often and hard. I get why the manufacturer did it as it makes the bike eat up chatter and rocks and of course many riders will never do real drops.
So I contacted Avalanche and asked him his recommendations for this LR and my application. He recommended the RS Superdeluxe RC3 but acknowledged that he didn't even know if they made the size I needed. They did and I manged to get one and sent it over for his magic. The fact that this shock has limited adjustability doesn't matter much since it will be valved correctly. Knobs all over a shock and none of them right, is something I have experienced on dirt bike suspension for years and isn't something I needed.
As far as forks he was fine with either of the major players but I wanted to match suspension brands front to rear so settled on the Rockshox fork as well. I was going to order the Lyric and have Avy go through it but Craig was kind enough to point out that the'19 Yari has the identical chassis and air spring, and that he was going to throw out the OEM valving stack anyways. So I found a take off Yari in the dimensions I needed for very little money and sent it off the Avy for his treatment.
Hope that helps.
Take care.

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I don't recall any other shock having a hydraulic bottom out control, so no you can't get any shock to behave the same way that this shock does. Can you improve an existing shock by getting it tuned properly for your bike? Yes (but also the vast majority of stock shocks are actually tuned for the specific bike you bought) improves can definitely be made. Can you get any shock to feel as good as any other? No.

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Unfortunately many popular frame manufactures do not match the correct shock/tune with the specific frame correctly. They believe they do, but many stock tunes can not reach the appropriate rebound speeds. This issue should be fixed soon though with the help of affordable telemetry.

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Just wanted to mention that the lack of pedal kickback/feedback is more due to the Zerode than the shock since the pedals are not connected to the rear suspension at all. Not trying to take away from the shock performance, but the credit for this should go to the right place smile

Would love to give this shock a go as it sounds brilliant.

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Zach had a different shock on the Zerode prior to this, so I am sure he is comparing how the pedal chatter felt before swapping over to the Arma. If he had pedal chatter with the previous shock but less pedal chatter with the Arma, then it would be due to the shock.

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Having owned this bike with plenty of different shocks over the years I can say that pedal chatter is something I wouldn’t even think about no matter what shock was on the bike. Even the dhx air I ran was great on this bike. Not saying the ext isn’t great, I know it is but the suspension is so dam good on the Zerode I feel like the test would’ve been more conclusive had it been performed on a different bike.

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Hands down best shock I’ve ever ridden. Been running one on my TR11 most the summer, floated between a 450 and 475 spring. The clicks are easily discernible and the HBC is a super nice feature when switching springs. The small bump sensitivity of this shock is second to none while still providing great support when you need it. The consistent feel and control this shock provides definitely influences you to ride faster and push harder. For comparison sake, I also have an ohlins for the same bike and a push for my trail bike. Both are fantastic shocks but the Arma some how finds another realm of small bump sensitivity while not losing the support needed to push hard.

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also have a TR11, whats your weight? just to get some spring rate reference. cheers

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160 with gear. 450lb spring for loose blown out conditions and steep/rough where I want a touch softer. 475 for general use, and 500 for jumping/freeride type stuff. All SAR (EXT) springs

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Have you run the push vs arma on the same bike? Doesn’t seem like an apples to apples comparison if one is on a trail bike and one is on a dh bike or even on two different bikes in the same category.

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Point missed. You made a comparison based on a non level playing field so to draw a definite conclusion like you have is a little dubious. I’d also argue that most small bump absorption is determined by your tyre carcus, air pressure and volume. I’ve run a myriad of different shocks on the same short travel bike with 2.6” minion tyres and the small bump was brilliant regardless of the level of shock or it’s tune.

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Point ignored not missed. I said for comparison sake, because it is worth mentioning. No not head to head or apples to apples. Tires help yes and for the record that was supergravity casing vs wtb tough casing. But running back and forth between the ohlins to the ext, the ext handles small trail chatter better, no change to tires or pressure. The push handles small bump very well also, not like the ext can though, and that was riding the bikes back to back on numerous occasions. Both tuned to myself and the bike I was on. Again the ext performed better. If I had the chance to, I would ride the ext back to back with the push on the same bike. But, I wasn’t going to buy a push for my dh bike even if they made one, just because. I already had an ohlins and ext for it. And I wasn’t about to buy an ext for the trail bike that had a push when I was about to sell said bike.
I still have my push, it’s currently back in Colorado getting resized to my new patrol. If ext releases a trunnion, I plan on picking it up, then I’ll give you your head to head.

Until then, my point still stands. Every shock review you read is subjective. They’re from different riders on different bikes on different trails. I had a valid comparison of how well each shock handled the situation they were dealt, and both were designed to be in the situations where they were placed. The ext gets the edge, it handled its situation better.
The push is a fantastic shock. I’m comparing 3 of the highest end dampers available here. I’m far from displeased with any of them. The ext is also the most balanced I’ve had against my 40, which I’ve torn into and retuned to my liking.
And yes I’ve owned X2s float and coil, as well as many others.

True, only the clock could differentiate, but the whole point of a review is for an opinion. Take it or leave it are the options.

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Product EXT Arma HBC Rear Shock
Riding Type Downhill, Freeride / Bike Park
Spring Type Coil
External Adjustments Hydraulic bottom-out control (HBC), rebound, high speed compression, and low speed compression
Available Sizes 220x70mm, 241x76mm, 267x89mm, or custom sizing on demand
Weight 1 lb 8.3 oz (690 g)
  • All CNC manufactured in alloy 7075 T6 and titanium
  • Rebound Adjustment System to separate bump and rebound oil flow
  • Ultra-low friction coating
  • High dynamic response
  • Very low reservoir pressure for maximum sensitivity
  • HBC (hydraulic bottom-out control) technology
  • No cavitation
  • Very low hysteresis for high dynamic response
  • High Turbulent flow for very low temperature depending
  • Low friction Energize Seal
  • 100% customizable
  • Dedicate setting for each bike brand
  • Shock include two different Super Alloy Springs
  • Weight: 690g with coil for 241/76mm with a 325-lbs springs
  • Price: 799,00 € + VAT
  • Price N/A
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