Review: Vorsprung Secus Fork Air Spring Upgrade

May 20, 2021
by Seb Stott  

Air springs are lighter, more adjustable and more progressive at the end of their stroke than coil springs, and this has made them the most common option for mountain bikes. But one of their biggest drawbacks is that the spring is usually much stiffer at the start of the travel than in the middle, which can give them a less ground-hugging feel and less mid-stroke support than their coil counterparts.

One of the most important trends in air suspension over the last few years has been towards higher spring volumes which provide a more linear "coil-like" spring curve. Vorsprung suspension has been at the forefront of this trend with their Corset and Luftkappe air spring upgrades, both of which increase the negative spring volume to offer a softer beginning stroke and a more linear spring feel. The Secus is the first air spring mod (as far as I know) which offers a truly linear beginning-stroke, so the spring stiffness doesn't drop off at all as the fork goes through its travel.

Before getting into how this $453 CAD upgrade rides, it's worth going into a bit more detail on the problem the Secus is trying to solve.
Secus Details
• Makes air forks perform more like coil, but with more bottom-out control and adjustability.
• Increases negative volume to give a linear-progressive spring curve.
• Also increases lower leg volume to reduce unwanted, non-adjustable ramp-up.
• Roughly 130g heavier than stock.
• Requires removing the air shaft to fit.
• Compatible with most RockShox and Fox forks plus Marzocchi Z1 (see website for details).
• Can be swapped between forks with compatible foot stud.
• MSRP: $453 CAD (including shaft clamps for at-home fitting)
vorsprungsuspension.com



The spring rate, or the stiffness, is the increase in spring force for every unit of additional travel used. In other words, it's the gradient of the familiar spring curve with force on the vertical axis and travel on the horizontal axis. Conventional air springs have a very high initial spring rate, but a very low spring rate in the middle of the stroke. This gives the spring curve a distinctive S-shape which starts off steep, then levels off a bit before steepening again at the end. The decreasing spring rate/gradient in the beginning stroke is known as the digressive phase of the spring curve, while the increasing spring rate towards the end is the progressive phase.

Some older air springs could be ten times stiffer at the very start of the stroke than in the middle, while in modern air springs that ratio can still be around three-to-one. That's like having a coil spring suited to a 150 kg rider at the start of the travel and one suited to a 50 kg rider in the middle. In practice this can make air springs feel harsh and abrupt when the suspension extends towards the start of the travel (say after a bump or in a hole) then reconnects with the ground. The high spring force near top-out can also makes the spring keen to over-extend past sag, potentially making it feel unsettled and unable to track the ground. Meanwhile the soft mid-stroke spring rate can result in too much wallowing or brake dive. As we'll discuss later, there are upsides to this "old school" spring curve, but the gist is that the digressive phase is bad news for both traction and predictability, at least if it's too pronounced.

How does the Secus work?

The Secus bolts onto the bottom of the hollow air spring shaft in Fox and RoskShox forks and connects the negative chamber to a reservoir inside the Secus. This greatly increases the spring's negative volume. As an air spring moves into its travel, the negative pressure (below the piston) drops while the positive pressure (above the piston) increases. This difference in pressure is what causes the build up in spring force through the travel. Because the volume of the negative chamber is increased with the Secus, the negative pressure drops off more gradually, so the spring force builds up more gradually especially at the start of the travel.

The Secus has another trick up its sleeve. The Midstroke Support Valve closes off some of the negative volume once the fork gets past a certain point int the travel; this causes the spring force to build more rapidly again, which increases the mid-stroke spring rate. This allows the Secus to create a spring curve that very closely approximates a linear spring curve in the first 2/3 of the travel, before it becomes progressive towards the end.

Finally, another chamber connects via the foot-stud to the spring-side lower leg cavity. This reduces the unwanted and non-adjustable progression at the end of the travel caused by trapped air in the lowers being compressed.

Measuring the effect

The first thing I did after fitting the Secus to a RockShox Zeb was to put the fork on a basic spring dyno to measure the spring force throughout the travel. I've already done this on a stock Zeb, so it was easy to compare the two spring curves shown in the graph below.

This graph shows the force required to compress the forks against travel. The Fox 38 is also shown for comparison. The stock Zeb and 38 could only be measured up to 120mm due to the limitations of the equipment used. Due to the effects of friction and measurement errors, it's best to ignore the details, but the basic takeaway is that the stock Zeb is the most digressive and the Zeb with the Secus is the least digressive.

This shows the Secus does what it says on the tin. There's no digressive phase at all, but rather it's roughly linear in the first part of the travel then progressive at the end. If anything, the curve I measured is slightly progressive throughout, but this could be caused by the build up of pressure in the lowers, changes in friction, or just a measurement error.


Installation

Installing the Secus is a little intimidating but isn't too hard if you're used to servicing forks. You'll need everything you'd normally use for an air spring service including replacement bath oil (you may be able to retain the old oil if the fork is fresh, but if you're like me you may end up with an unknown quantity of oil on your shoes, and you don't want to guess how much to put back in) and snap ring pliers to remove the air spring. You'll also want a heat gun to remove the old foot stud and a torque wrench with crow's foot adapter to install the new one, plus shaft clamps, which you can buy with the Secus if you don't have some lying around. Clear instructions can be found on Vorsprung's website though, and if you don't fancy the task it shouldn't cost too much extra to get a suspension tuner to do it for you if you're having a service anyway.

Speaking of which, it's worth pointing out that if you're swapping the oil while fitting any fork modification, the fork is likely to perform better anyway thanks to the lower friction. In this case I used a Zeb which was freshly serviced before I fitted the Secus.

It's important to remember to press the gold Midstroke Support Valve button on the base of the Secus after pressurizing or changing pressure in the fork. If you forget, the spring curve won't be as intended.

The gold button at the base is the Mid Stroke Support Valve, which should be pressed after adjusting pressure and equalizing the fork.

Setup

Vorsprung recommends 20% more pressure in the spring with the Secus fitted. I'd run the stock Zeb at around 64psi, so that would put me at 77psi. However, with the stock 170mm travel I preferred it a little firmer (around 80-84psi) to hold it up, but after I'd fitted a longer air shaft 77psi was about right. I found I could run the rebound a little faster (around 14 clicks from closed) as the softer spring force near top-out made it more settled into its travel even with the rebound fast. I set the high-speed compression fully open to compensate for the stiffer spring in the mid-end stroke and allow more use of the travel. I stuck with zero tokens throughout testing.

I tested on this Privateer 161 with a MegNeg rear shock air can to better match the feel of the fork.


Performance

The effect of the Secus is not subtle. It's immediately noticeable that the fork sags into its early travel more easily than the stock Zeb or even the Fox 38. It even engages its travel when pushing the unloaded bike over rocky ground. When riding over rapid-fire roots rocks, the front wheel feels more stuck to the floor, especially with the rebound on the faster side. Yet when braking hard or landing, the support builds up smoothly but strongly, resulting in very little unwanted movement or dive, something which I found to be an issue with the stock Zeb.

However, on some trails with consistent braking I was finding the fork was sitting a bit too low. Raising the bar height helped, but in certain situations I felt the steeper dynamic head angle caused the bike to feel more "upright" - less willing to tip into turns. Raising the pressure above 80psi made it a little harsh in big hit situations.

At first I was running the Secus in a 170mm Zeb on a Privateer 161, so I considered upping the travel to 180mm, but as the Zeb is available with up to 190mm of travel I decided to go all in. That way I could have a similar (or slightly higher) dynamic ride height as a stock 170mm Zeb while running lower air pressures than I had been using with the Secus. I also switched to a MegNeg air can on the rear shock to give a more similar spring feel at the rear of the bike.

Of course the 190mm fork makes the bike taller and slacker when unloaded, but it doesn't matter how a bike handles when nobody's riding it. Admittedly, the extra travel definitely creates more wheel flop on the steep climbs, where the front wheel is so lightly loaded that any fork is going to be very close to the start of its travel. But the Privateer's 80-degree seat angle meant this was not an issue and the softer beginning stroke is appreciated when tackling bumpy climbs. Once descending, the fork settles further into its travel giving a similar dynamic position to before, but with more negative travel to extend into holes and keep the wheel in touch with the ground. I found I was able to look a bit further down the trail and trust my bike to deal with the small stuff without losing grip.

But there's a downside to everything. Because the Secus makes the fork significantly stiffer after the sag point and towards the end of the travel, you do get more feedback on big, simple impacts like a big root or rock. Just as a thought experiment, if you're riding along with 300 Newtons of force on the fork, then hit a bump that creates a force of 1000 newtons (ignoring damping forces), judging by the force-travel graph above, the stock Zeb would go from about 20 to 120mm of travel (using 100mm of travel), but with the Secus it would go from about 40mm to 110mm (using just 70mm of travel). This is why in this simple situation the stock fork can be more forgiving, though the flip side is obviously more movement when braking or pushing into a turn etc. In theory the added harshness on bumps can be offset by reducing compression damping (especially high-speed), which will have less of an effect on brake dive.

And although I was running a 190mm spring, this was purely for geometry reasons. At 77psi and with zero volume spacers I I was rarely using more than 160mm of travel, and the highest I've seen the O-ring was about 170mm from the bottom. My local trails are not the stuff of Josh Bender, though, and it's nice to know that if I ever accidentally find myself on a Rampage line I've got something in reserve. But for me I would like to be able to run the fork a little less progressive if using more than 170mm of travel.

Overall, I'd say the Secus offers a significant improvement over the stock Zeb, thanks to that more settled, ground-hugging and predictable feel. I did some back to back runs with the 190mm Zeb with a Secus and a 180mm Fox 38. The difference here was subtler than compared to the stock Zeb, but the I'd say the Secus-Zeb was a little better at maintaining contact with the trail when going light over rattly sections. This isn't so surprising given the force curves above. The 38 was a little more supple and comfortable on long runs though, so it's too close to say which was my favorite. I've not been able to test the Secus with the 38 yet, but I feel less need for it than with the Zeb.

The Secus tucks in quite neatly behind the fork leg with a small gap to the caliper. This shot was taken after a crash where I picked up a few scratches and some tree root in the bottom of the Secus.

Longevity

I've had the Secus installed for a couple of months so I can't say anything about long-term durability, but it's worth mentioning that Vorsprung recommends servicing the IFP and seals in the Secus every 200 hours (see their website for instructions), so there is a little more work involved. My concerns about crash damage are minimal, because if you position it with just a few millimeters gap between the Secus and the caliper (as recommended), the unit is pretty well hidden behind the fork leg. Also, I have crashed hard onto the left hand side over a mat of wet roots, which caused some fresh pine shavings to get lodged in the bottom of the Secus, but no damage was sustained. Vorsprung offers a 12-month no-questions-asked crash replacement too, which adds more confidence.



Pros

+ Does what it promises to the spring curve.
+ Noticeably improves traction, support and predictability.
+ 12-month crash replacement guarantee.
Cons

- Inevitably, more mid-stroke support means more feedback in big-hit situations and softer beginning stroke will sit dynamically lower unless you increase travel.
- Not cheap, not exactly simple to install and requires some servicing.




Pinkbike's Take
bigquotesThe Secus does what it says on the tin. It significantly improves tracking, predictability and reduces brake dive, but this inevitably comes with small downsides; chiefly it's less forgiving on large bumps. I also found that going up in travel was the best way of maintaining ride height while enjoying the full benefit of the soft-beginning stroke, which is something to consider. The benefits and trade-offs may vary with other forks, but with the RockShox Zeb I tested it's a good option for aggressive or stronger riders who are happy to take a bit more big-hit feedback in exchange for more predictability, support and ground-hugging grip. Seb Stott



217 Comments

  • 71 2
 @SebScott Great review, much appreciated technical analysis as always. When plotting the spring curves a top tip from the world of Motorsport is to plot stiffness in N/mm (instead of Force) against travel. This makes it much easier to compare spring rate at each point in the travel.
  • 37 0
 Thanks very much. Stiffness plots are very useful but I think most people are already familiar with force plots and I didn't want to over complicate the theory side with a type of graph many readers might not have seen before. The measurements I made are quite noisy too which makes differentiating them accurately a little tricky.
  • 5 0
 @seb-stott: love the chart (and thorough explanation behind it); hate the color choices! Can you go with some lighter tones next time you use a black background? The maroon especially is really hard to see/differentiate on both phone and laptop.
  • 12 4
 "MSRP: $453 CAD (including shaft clamps for at-home fitting)"

Yeah, I don't know about you but this sounds like a very expensive cock ring.
  • 93 0
 @scott-townes: haven't actually checked fitment compatibility for cocks yet, but maybe you're looking to improve a different type of ride quality to what we originally had in mind...
  • 5 1
 Makes forks softer and the cock stiffer?!?!
  • 5 0
 @VorsprungSuspension: the Vorsprung Corset on the other hand
  • 2 0
 @stainerdome: What a time to be alive.
  • 5 0
 @VorsprungSuspension: can u really put a price on c-rings?
  • 2 0
 @VorsprungSuspension: wouldn’t matter, like seat angles, most would cite some kind of theoretical numbers anyways...
  • 1 0
 @scott-townes:they are very expensive for me, buy it when you are a pro
  • 1 0
 @VorsprungSuspension: I was upvote #69. You’re welcome! Lol
  • 1 0
 Totally agree. If the main claim of the product is related to the shape of the stiffness curve, then plot stiffness! It makes it seem like they are trying to hide something.

And what kind of pseudo-science BS is "support"?
  • 66 20
 Again something to improve shit air spring! Just ride coil simple efficient!
  • 19 0
 Would like to see how Zeb with Vorsprung Smashpot compares to the 38
  • 24 5
 All continue to insist in air spring...it's about weight....it's about adjustability.... It's improved shafts, or air Chambers, or adicional gadgets. Coils don't need improvement, and will always have less stiction, and won't vary with temperature. If it's about suspension performance, then weight penalty is more a fact than a setback
  • 37 7
 Coil is great but has one fundamental problem - too few spring rates and related cost. I have a Sprindex and I could not get back to normal coil. Even 25lbs difference is very noticable on trail, let alone 50lbs you get from most companies, this is insane. Not to mention that is fot the best performance you shoud be able to asjust spring rate to the spot you are riding, e.g. bikepafk vs slower tech. So coil can be a is pain in the ass, especially in forks, unless Sprindex comes up with a fork spring.
  • 10 17
flag TDMAN (May 20, 2021 at 1:18) (Below Threshold)
 @lkubica: sprindex should help some adjustability in case of need (start in dry, starting raining and need for a suppler spring, nice product btw).

I understand your point, and believe that some, have the ability to distinguish a 400lbs spring from a 425lbs, but...

"Normal" riders don't check tires pressure on day ride.
"Normal" riders don't adjust air spring... they simply did it a few months/weeks back
"Normal" riders, don't change rebound or compression settings to not "destroy the perfect setup from factory!"

Yes setting suspension on a coil can be expensive", but from what I check, there aren't too much complaints about bike prices. Coil spring is "peaners"...and you can resell coil springs that you don't use anymore.
  • 5 1
 @TDMAN: I set my fork with 2.5 PSI precision and then never adjust the pressure, it's true. But I can do it only because I can set it up so precisely.
If you can live with 50lb gap or not depends on your trails really. Typically I spend winter season on more bikeparky trails, with jumps and dirt. Every spring I get back to chunky stuff in the mountains I feel like my teeth would fall off on the first ride. Then I turn the spring by 25lbs, open up rebound a bit, get -5PSI on the fork and suddently I ride a different bike.
  • 15 0
 For all-out performance coil is probably still king. But this is lighter, infinitesimally adjustable and reversible (a coil conversion scratches the stanchions so you can't go back to air).
  • 4 70
flag bigpeaches (May 20, 2021 at 2:41) (Below Threshold)
 @lkubica: you will loose 5-10psi inconsistently when you detach your pump , yes you can pump it up to what ever the uncalibrated display says but I bet you can’t consistently detach your pump the same psi loss each time

But if it makes you feel better then half the game is feeling good - air is for the “now” coil is for ever and will always be the forever , I went back to air cos it was better , said no one ever
  • 3 10
flag kirat (May 20, 2021 at 2:46) (Below Threshold)
 @lkubica: You can preload coils very easily, so you get the fine tune for the spring rate you need. And Marzzochi use to have coils that apart from preload, you could pump some air too into the chamber. It also changed the progressivity of the suspension at the same time, so you got a great range of adjustments
  • 9 4
 Interestingly, automotive industry uses air on their high end vehicles as it's more adjustable and can use preset modes for different types of terrain, comfort, performance, loading cargo etc. It's also always praised as being very sensitive and comfortable. However, MTBers seem to want coil. My interpretation is that gram counting has ruined MTB suspension and that every fork should have oil seals and generally better lubrication. Current air spring forks use just a bit of grease and 10cc of oil in the lowers. That's never going to work well.
  • 13 0
 @msusic: very true. Do take into account that brake away force is less of a factor with a 3000 lbs car than with a 30 lbs bike. Seal striction will therefore not be an issue with the forces involved with car suspension.
  • 51 0
 @bigpeaches: It´s been discussed million times before, you don´t loose anything when you disconnect the pump unless the pump itself is leaking air, it s when you reconnect it when you loose the pressure as obviously you have to fill the pump hose, effectively making the volume of air chamber bigger=pressure lower.
  • 5 0
 @msusic: it´s only true for high end limos, in motorsport you see air used very very rarely.
  • 7 0
 @bigpeaches: you are aware that a good shock pump has a shut-off valve that you use before detaching, right? If not, well, what can I say…
  • 4 3
 @seb-stott: infinitesimally adjustable means you'll be infinently tinkering while never get it right. everyone I know spend time with air pumps, tokens and a whole lot of other mods to get it right(me included) and in reality never got what they hoped, just different amount of compromises, get the right coil and you're done, my pike coil conversion weights 2235gr a bit lighter than my diamond but performance is a couple of steps above. (custom open damper as well) some good forks like dvo and recently f38 the air spring is a drop in cartridge, fully reversible.
Point is, constant tinkering with a million combinations isn't going to be better than a bit heavier well thought out fork.
  • 4 0
 I have a smashpot coil and a zeb ultimate and I’m always surprised when I get back onto the coil fork (ok my ht) how amazing it feels. The two forks just don’t compare, they’re both amazing btw just feel totally different
  • 13 2
 @seb-stott: On the ZEB and I think the 38 too, the Smashpot comes with a PVC sleeve so you can convert back to air if you wanted too, but if you try a Smashpot I don't know why anyone would want to go back to air, if you really wanted to you could just buy a new CSU opposed to a whole new fork anyway. Only air fork I would consider would be the EXT, coil is night and day better in terms of traction, off the top suppleness and support/stability than even the best mainstream air forks and shocks. If it's a big burly enduro rig mainly aimed at dh performance the increased sprung mass only helps..if it is a XC or trail bike you might aswell stick with air to save weight as you are not gettting the peak suspension performance or long travel in those cases anyway.
The trouble is nowadays people expect their enduros to perform like dh rigs downhill but be as versatile as a trail bike. Don't get me wrong I use my sb165 for everything but I bought it with the intention of why Enduro bikes initially came about, to be a dh bike you can pedal uphill. Not to be a trail bike that will pedal up like a 22lb Scott Spark and descend like a V10.
The increased sprung mass does big favours downhill to the suspension performance and is negative up hill, so the ideal do it all bike that can do everything great can't really exist as in one instance weight favours you and in another it's a negative... Unless ofc you talk e bikes which both go uphill easily but have a high sprung mass also.
  • 14 0
 @bigpeaches: Just stop with the "loosing air when unscrewing" BS. The Earth is round and the pression stay where you left it.
  • 5 0
 @kirat: I had a boxxer coil for a while. There weren't enough spring rates available. One was too soft, the other was too firm. Adding preload to a coil sets the ride height correctly, but makes it feel like an old air shock. Sticky off the top and not enough support in the mid-stroke. That's the whole point of an air negative spring, it adjusts the preload to 0. Forks don't work well with coil unless you happen to be in the sweet spot. Manufacturers need to offer coil spring rates in smaller increments if they want coil forks to be a thing.
  • 2 0
 @seb-stott: "coil conversion scratches the stanchions so you can't go back to air". not in an Ohlins fork!
  • 10 1
 I think solutions like DVO and Manitou have are better than self-equalizing negative air chambers. I like having the option to adjust the negative spring separately, like the OTT coil on the Onyx. Sure, it makes the fork a little heavier but the control you gain offsets any weight penalty for me.
  • 8 0
 Coil forks require a method of introducing progression at the end of the stroke. Air forks require a method of introducing support in the midstroke. Both can be done effectively. But that doesn't make me sound gnarly so yeah... air springs are shit and coil are great.
  • 2 0
 @bigpeaches: It's ok... we all learned this way.
  • 1 0
 @bigpeaches: nice little rhyme
  • 5 0
 Installed Vorsprung Coil Conversion into my 2016 Fox 36 and it completely transformed the bike’s handling. Also went from a Fox X2 air to DVO coil out back. The bike rips!!!
  • 2 0
 Does anyone know if there are spring curves for DVO's solution (a negative coil, the same as what the fox 40 does)? The Onyx weighs pretty much the same as a 38, but I'm not sure if its as stiff or not. My experience with my Diamond was that it was as supple off the top as any coil fork I've been on. The fork had other issues, so why hasn't someone (looking at you, @VorsprungSuspension ) create an aftermarket air spring for the other brands that utilizes this approach? I bet it would be 100 gram weight penalty.
  • 4 0
 @hamncheez: I'm a relatively light rider so I haven't had any issues with flex on the Onyx. I followed their recommendation and set the sensitivity with the OTT, and mid-bottom out with the air spring, worked like a charm. It took a bit of time to set the the OTT, pre-load, and damping to all work in harmony, but it was well worth it. This fork blows all the Fox's and Rockshox I've ever had away. Weight is the only negative, but I don't really notice it out on the trail once I'm rolling.
  • 1 0
 @SlodownU: 29er fox 38 is 2.32 kg; 29er Onyx is 2.34 kg . 20 gram weight difference isn't much....

EDIT: Zeb 29 comes in at 2.32 kg as well
  • 1 2
 If going air get the EXT. If coil get a ZEB and fit a Smashpot or something from Avalanche. The ZEB is the stiffest single crown chassis by a big margin, it's around twice as stiff torsionally than even the FOX 38.
  • 3 1
 Or buy the Fox 38, or the EXT Era... the review said the 38 was already excellent. I love my 38, best fork I’ve ever had.
  • 7 0
 @seb-stott: worth noting that the Smashpot coil conversion for the Zeb/38 has a stanchion liner, so should be fine to convert back to air for anyone who does go that route.
  • 14 0
 @msusic: the major difference between automotive and MTB suspension is that car suspension works on the (correct) assumption that the wheels won't often leave the ground. This means you can run highly preloaded systems or those with very stiff initial spring rates without the same downsides you see on bikes - bikes are VERY frequently moving through the first say 0-50mm of travel whereas cars actually do that very rarely. Getting the right ride height and spring rate around the sag point in a car does wonders for its ride quality, so the adjustability of air (even if the spring curve would be terrible on a bike) is very good there.

For sure the lubrication side of things needs regular attention in air suspension, that will probably always be a downside unless we start using airbags instead of pistons.
  • 1 2
 @Heidesandnorth: I run coil so I wouldn’t know :-)
  • 2 0
 @crazy9: I tried !! :-)
  • 2 0
 @bigpeaches: yes shock pumps aren't calibrated very well (neither are most coil springs for that matter) but if you detach a shock pump the valve is closed before any air escapes. The hissing sound is the release of the air from the pump tube and not the valve. When you screw that same pump back on, the air spring will loose pressure to fill up the volume of the pump tube.
Also, say your spring rate is correctly set up at say 100 psi on your pump, when reinflating to 100psi with the same pump your springrate is still correct for how you had it set up (even if calibrated equipment reads that at 108psi, your pump will inflate to actual 108psi again dispite showing 100psi).
  • 2 0
 @msusic: my understanding is that air springs have more stiction/break away force than coil. If the vehicle is a fixed heavy weight, when a bump is encountered it will break away without upsetting the chassis. Because bikes are so light weight and the heaviest part of the system is the dynamic rider (as opposed to the more fixed weight of a heavier vehicle) that break away force is more noticable on a bike, being felt as harshness to the rider
  • 25 2
 Just buy a Manitou with IRT .....
  • 3 6
 The IRT doesn't achieve the same performace and is more complicated... but there's no doubt that it's better than anything RockShox that's for sure Smile
  • 6 0
 @romphaia: IRT more complicated than Secus? Really? It's a sliding piston and a valve to inflate.
  • 3 2
 @PhillipJ: simpler construction for sure, but more complicated to set up in that you've got two chambers to adjust individually rather than one.
  • 1 0
 @VorsprungSuspension: @VorsprungSuspension: Be interesting to know your viewpoint on the Dorado airspring, given IMO its the only airspring I've ridden with comparable performance to a Lufkappe.
  • 1 2
 @RobByatt seb reviewed the mezzer pro, he didnt fare it too well: youtu.be/7Y_RliBb0YA?t=140

@seb-stott curious on your take of IRT vs the fork in this review
  • 17 0
 Vorsprung shpuld make a fork already
  • 35 0
 That'd be awesome, then we could make upgrades for our own forks! Smile
  • 1 0
 @VorsprungSuspension: Hard to upgrade perfection though, isn't it?

I wouldn't know, my list is longer than my hair.
  • 8 0
 Excellent work from Seb I think.

Now, having read this and considering the principles Seb explains are correct regarding spring gradient, can someone explain the rationale behind RockShox's recent move to a smaller negative spring/equalisation at zero travel? It feels counterintuitive to me.
  • 6 0
 As far as I can tell from the marketing, it seems to just be because people don't like their fork sitting into the travel when there's no load on it. Perhaps there was more to it than that, but that seemed to be where they focussed their message they made the change
  • 7 0
 Thank you. I think for RS the C1 spring always measures up to the intended travel, which means fewer disgruntled customers, and it's more foolproof to setup because you don't need to equalize the spring by pushing on it then re-set the pressure. In back to back tests the difference in performance is fairly subtle to be fair, but I still prefer the older spring.
  • 1 0
 @seb-stott: I hope they will update the spring again for old style, i miss that ground hugging feel of it
  • 2 0
 Does anyone not like the super saggy airsprings? I have put luftkappe in a few bikes and sort of never get along with it. Been on the 2nd gen lyric with the B1, feel like I have to run wayy too much pressure to keep it from just diving through the 1st 1/3rd of travel.

I bought the C1 but havent installed it, I think really I just need to go up 10mm with the B1 and it would be the best but idk if they exist anymore.
  • 1 0
 @skerby: vorsprung still sells b1 shafts as far as i know for luftkappe conversion
  • 1 0
 @Noeserd: A1 shafts are required for Luftkappes, B1 shafts (or B1 sealheads on C1 shafts) are required for the Pike/Lyrik for the Secus. The Zeb only has one air spring variant currently, which is Secus-compatible.
  • 1 0
 @skerby: So what you don't like about "way too much air pressure"? Too much end-stroke progression?
  • 8 0
 @skerby: so this is an interesting scenario that we have with singlecrown forks in particular:
1. Your fork initial length is set by your fork travel (for a given model and wheel size). This initial fork length gives you your fully extended geometry.
2. The fork's ride height is then determined by the initial length minus the sag.
3. The sag is determined by the spring rate curve.
4. The way the fork behaves on the trail, in terms of its ability to suspend the bike from the wheel properly, is also determined by the spring rate curve. The Secus and Luftkappe are both intended to soften the initial travel, which is why you feel like it moves through the initial travel more easily - because that's what gives you the initial compliance.

Now if you want a certain (quasi-static) ride height, and your fork is a certain travel, then your hand is being somewhat forced in terms of the spring rate curve you end up with. You're basically forced to change your suspension behaviour, quite possibly in a way that you don't like, to make a geometric adjustment.

But if you subsequently don't like the on trail behaviour of the suspension (eg initial stroke feels harsh), adjusting the spring rate curve (either scaling it up/down by altering pressure, or changing the curve's shape with a Luftkappe, Secus or Smashpot for example) now also changes your geometry and fork ride height.

If you had an independent length adjustment for axle to crown or axle to handlebars then you could adjust that out easily enough, like for example on a dual crown fork you'd just move the stanchions in the crowns.

With a SC fork, raising/lowering your bars is usually the easiest form of this, but it doesn't affect BB height or head angle, and it does affect the bike's fit somewhat. Or you can do what Seb did, which is to adjust the travel to get the ride height you want (20mm is pretty extreme though) - but now you've got a spring rate that may or may not be matched to the amount of travel you have, and then many riders will feel like they're not able to "get full travel" in spite of everything else because the o-ring doesn't end up at the crown.

My recommendation there (which is in line with what your current approach seems to be) is to get your suspension feeling the way you want it to feel on the trail first, then adjust the axle-to-bar length via whatever means you prefer (travel or just stem/bar adjustment).
  • 2 0
 @VorsprungSuspension: 100 percent agree with this. I don’t like a super firm front end but if I run it plush then my bb height is too low, (these new crop of bikes are WAY too low anyways). So I’m stuck running higher pressure with less volume spacers and less compression. Until I get a new bike.
  • 1 0
 @seb-stott:

I think It may be subtle in well supported in bike park type terrain but won't that extra force required at the start of the travel mean less traction over myddy, off camber, awkward tracks, flatter turns and natural terrain (enduro/trail riding) when compared to the 38 and zeb+secus curve?

I feel it's strange that so many people don't realise what sag is for. It's like the forks were dumbed down at the cost of performance.

One thing that stood for out me from your testing was the fact you went on to add more travel (more sag?) to ajust the geometry and mostly didn't use the (expensive) damping options. Does this mean you liked how the necessary force to start movement was reduced but maybe not so mutch the finishing spring force (too hard)?

cheers!
  • 2 0
 @VorsprungSuspension: Or you could change right height (once you've install Secus) Jesse Melamed style with a -5mm reach adjust headset with a huge (ugly) lower cup youtu.be/O7Q8-UHWsow?t=643 Wink
  • 7 0
 In france, Vrosprung is not the first to enlarge the positive chamber of air springs, to have a curve closer to a coil spring.
Novyparts released in 2007, a piston for this, for the Rockshox lyrik mk1 and the Rockshox totem and the Boxxer.
He continued with the following forks: Sektor, Revelation, Pike, Lyrik, yari, all Boxxer, Zeb.
In addition it is Bos engenering, who with his experiences in motorcycles and in car racing, released the first forks with very large negative volume and with high pressure, long before Rockshox or Fox, with the first Bos Idylle Pro (also the first fork pressurized!)
  • 9 0
 BOS was ahead of the curve (LOL) on this for sure.
  • 3 0
 @seb-stott: it´s weird how their newest 39mm stanchioned forks went under the radar huh?
  • 2 0
 @Mondbiker: influencers didn't get their cut
  • 2 0
 Vorsprung isn't enlarging the positive chamber. It's the exact opposite. The Secus provides a much larger negative air chamber volume over the early part of the stroke, then the mid-stroke support valve kicks in, reducing the effective negative chamber volume, which allows for "normal" air spring ramp-up.
  • 6 0
 I could be wrong on the history here, but from memory the Idylle Pro had the externally mounted base valve (from the Stoy IIRC) and a pressurised damper but the spring was actually coil, the Idylle Rare went to an open bath damper but had an air spring, and the first air spring that I ever tried that didn't feel terrible (this was in about 2013 or so). It was tricky to equalise and prone to getting stuck down because they used an o-ring instead of a quad ring on the air piston though, but it did feel good while it was working.

Regardless, it did not do exactly what the Secus does. Enlarging the negative chamber is only one part of that.
  • 2 0
 @Mondbiker: whoa. hadn't seen those, thanks for the tip. Pretty soon all the stanchion diameters will have been taken!
  • 1 0
 Novyparts was a very nice company. What happened to them. Their www is nonsense. I have their RS Reverb lever on my bike. Awesome part.
  • 1 0
 @goroncy: thanks for your comment. NOVYPARTS feel good thanks. We will be happy to improve what is wrong for you, drop us an email Wink
  • 2 0
 @brianpark: there is always the possibility to go .99 Big Grin
  • 1 0
 @sebazzo: SRAM already has the x8.99's
  • 7 0
 There is no free lunch, when it comes to spring rates.

Either you get a progressive air spring, where the decision is for a soft initial and hard ramp-up end stroke. On the neg side you get a fork that's still quite plush in the mid-stroke, i.e. it sits deeper in the travel than you may wish.

Or you get a linear coil spring, where you dont have that mid-stroke valley. On the coil side of things you just get to decide, whether you want big hit compliance or soft initial stroke. I must say, for DH purposes, a stiff coil is still the bees knees, who cares for a soft initial stroke, when charging hard.

With respect to this product, great innovation by Vorsprung as ever. And it moves the air spring into the direction of a coil-like rate. IMO the above generalisation still applies.

You may be able to eke out a more coil-like fork at a slight weight advantage with this system.

How's this for armchair engineering?
  • 1 0
 Agreed. Hard, fast and linear is the way to go. Don’t have to choose between a wallowy midstroke or the end stroke being super harsh. Then fine tune with tyre pressures.
  • 11 0
 That's a pretty good synopsis, although the initial stroke stiffness can vary hugely between air springs because most stock springs are initially quite stiff, and there's friction and pneumatic damping effects (polytropic hysteresis) from the air too.

You're right that there's no free lunch (at least, at any one small region in the travel). If you want more support, you have a higher spring rate, which delivers more force within that region. If you want more compliance in a given section of the travel, it's also going to push through more easily.

However, you can look at where in the travel most sharp impacts are beginning (usually, though not entirely, early in the travel), and where in the travel people are asking for more support (usually under braking or big impacts, so deeper in the travel) and try to match the respective spring rates to the most common demands on that part off the travel. It won't mean it's perfect everywhere, because if you're say 50% of the way through the travel and have a high shaft speed impact beginning at that point, it'll be quite a bit stiffer than a more typical air spring rate would have been, but that happens pretty infrequently compared to hitting square edges beginning at say 15% travel. Conversely, trying to get support under hard braking on steep terrain isn't usually happening at 15% travel, but you may well be at 50% travel there, where the stiffer (relatively to a standard air spring) spring rate is beneficial.

It's fairly evident to anyone who's ridden a coil that the linearity typically works well for small to medium bump compliance for the majority of the travel, but as you point out, you run into significant compromises with excessive movement or bottoming on bigger hits there, which is usually a deeper stroke issue.

The Secus was designed to mimic the behaviour of a coil spring in terms of overall spring rate for the first 2/3 of the travel (though you still have air spring friction and the pneumatic damping effects) but also allow you an appropriate amount of ending stroke ramp. By appropriate, I mean the majority of riders on the majority of terrain should be able to find a setup that allows them to use full travel on occasion, without the overall ride quality being too soft or too firm.
  • 6 0
 I bought one a month ago and self fitted it (which I managed but was shit scared that I was going to scratch my airshaft - I didn't in the end and once I had the fork stud off it was really easy). I bought it as I disn't want to convert my 38 irreversibly to coil. It's also lighter than a coil conversion and if I didn't get on with it I can remove it easily. It is as stated an immediate difference on the trails and I'm loving it, plusher, small bump sensitivity increase etc., - am also getting some top 10s on strava on the downhills which has never happened before.
  • 4 0
 is there a reason that an air spring can't be stacked with a (short, light) coil spring to give small bump performance as well as overall light weight?if the coil just gave, say, 10mm travel, there shouldn't be much material but it'd overcome pretty much all sticktion and initial stroke force..
  • 3 1
 I think Avalanche are offering this in their hybrid set up. Unfortunately it's pretty hard to find reviews or even buy it if you're in the UK. Frown
  • 3 0
 The DT Swiss F535 and EXT Era have a coil-air hybrid spring just as you describe (sorry, you're too late to patent your idea!) In my humble opinion though, if you just make the volumes large enough it's not necessary.
  • 1 1
 There's a DT Swiss fork that uses that.
  • 3 1
 @seb-stott: DVO also, I believe? Though their negative coil is quite long. Great small bump compliance, though as a light rider I've had some difficulty getting the stock components working for me; at the positive pressure I need, I'm outside the adjustment range of the negative spring preload, and this is one of the main drawbacks of a hybrid/fixed-rate system. It leaves me with too much dive and a low ride height, albeit with the tradeoff of negative travel for good traction (and it's very good indeed). I also re-valved for lighter compression damping, just as you touched on in the article. Next step is to swap the negative spring for a lower rate one. The suspension quality is excellent, but it's certainly taken a lot more fettling to find a sweet spot if you're not average weight - and you lose the wide range of tuning that air springs theoretically provide. The secus looks a better option for those of us not in the middle of the bell curve!

There's also the issue of variable rider weight - riding with a pack, or even bikepacking, and still being able to set up the suspension to work optimally. Not easy with coil at all. Again, an air-air system works better here. Admittedly it's a minority use case.

Didn't Intend's Bandit aim to integrate much of what the Secus does within their asymmetric fork?
  • 1 0
 @seb-stott: Ahh ignore me. You're talking about coil/air both on the positive side. Though points about tunability of hybrid systems still stand!
  • 3 0
 Manitou Minute MARS spring did the same. Doesn't seem more supple than the Dorado Air in my Mattoc though.
  • 1 0
 There was a Fox 40 Hybrid on the Trek Session 9.9 2012. I still own and ride this fork and love how you can fine tune it.
  • 1 0
 @dominic54: same problems with the dvo onyx sc if you’re over the expected rider weight. Either soft enough initially to feel comfortable but then too little ride height or too harsh initially and enough ride height.
  • 3 0
 @unclesomebody: Avy hybrid is pretty sweet. $$$$, especially with optional high speed blowoff valve (which I went for on a hardtail.) Easy to install, and great feeling. Craig can be- how do you say it? Uh, "rude." He is a wizard, but just a rude wizard.

In the world of dual spring forks there are also the dual chamber air springs, just for the sake of arguement. Manitou Mezzer pro IRT, DSD runt drop in cartridge (for many fox, rs forks), and I guess the EXT Era is also in this category as well, as I uses both a dual air chamber, and a small coil spring, but its also a $2k fork.
  • 2 0
 @seb-stott: You need to talk Brian into sending you the Era Razz would love to hear your thoughts vs the 38, the secus, and coil forks.
  • 1 0
 @Planetx888: I have the Avy Hybrid too and I really like it. I also have the EXT ERA on another bike and right now I prefer the Avy. I'm still trying to get the setup right on the ERA though. The Avy comes setup right from the get go, just a little rebound and compression tuning so that's pretty nice.
  • 1 0
 @unclesomebody: I swapped out my Fox 40 Grip2 damper on my V10 and have never looked back. It gets ridden every weekend the DH parks are open and I couldn't be happier with it. It really seems to offer the best of both worlds.
  • 1 0
 @unclesomebody: Well, I can give you a positive review on the Avy hybrid coil plus open bath cart in a Lyrik from the Tweed valley! As the spring sits on top of the damping cartridge there is zero damage potential to the air spring side and it allows you to run very low air pressure (27psi 75kg rider) to fine-tune spring rate and ramp-up. I had an EXT Era and the Avy setup just plain outperforms it on grip, compliance and mid-stroke support and for significantly less outlay when upgrading a Yari or Lyrik Select. I have heard comments on Craig's polarising attitude towards some customers, but in fairness, he has been nothing but helpful and provided excellent aftersales support. Just a shame there is a large ocean and customs to negotiate for any upgrades!
  • 3 0
 "Inevitably, more mid-stroke support means more feedback in big-hit situations and softer beginning stroke will sit dynamically lower unless you increase travel."

That can't be a con. "Mid-stroke support" has been a damn golden goose holy grail buzz word for waaaaay too long. So many reviews can be found saying X is better than Y because X has more mid-stroke support.
  • 6 1
 The fork this device was attached to doesn’t want to be identified as either air or coil...
  • 4 0
 I rode a Vorsprung Fox 36 and an Ohlins m.2 RXF36 coil. I'd choose coil every time, though the Secus is remarkably better than the regular air spring.
  • 2 0
 I got the reverse from the reviewer on the dynamic ride height, or maybe I'm confusing ride height with stability, but on my 160mm zeb, on steep stuff braking is so much more confident, I'm much more confident, I feel locked into a comfortable position with the wheel tracking nicely, rather than my body having to compensate for instability and having to move around a lot. I feel like I don't need to raise the bars and if anything, "feel" higher. I do have my sag roughly the same as without the secus.

But apart from that, I echo the review, does what it says on the tin, more supple for tracking and more support.
  • 1 0
 It sounded like the reviewer didn't bother to adjust the damper compression and rebound to the spring curve. (which is mandatory since the spring is so radically different)
  • 2 0
 @seb-stott - The harshness you're reporting on bigger hits is very interesting to hear. I've been riding my Secus on a '21 160mm Fox 36 since last October and I can't say I've felt the same thing; small bump sensitivity has been off the charts, mid-stroke support keeps me pretty high in my travel, and bottom out resistance has been great, even on huck-to-flats. I feel like the Secus has really delivered on making the fork feel extremely linear up until the last ~25% of the travel.

Something worth noting, however, is that I'm actually having to run about 20% LOWER pressure than I used to without the Secus to achieve proper sag and support. I'm currently at 69psi (nice) with two tokens. Despite these major differences, I'm still experiencing all the benefits @VorsprungSuspension claims on the box. Maybe I got a "bad" apple that's somehow still amazing? Perhaps they can chime in here...
  • 1 0
 For what it's worth, I'm about 175lbs/79.4kg all kitted up on a large '20 27.5 Stumpy.
Fork settings:
~20% sag
HSC - fully open
LSC - 8 clicks from open (right in the middle)
HSR - 2 clicks from fully open
LSR - 3 clicks from fully open
  • 2 0
 I have the exact same fork with Secus. I agree with the sentiments and also have had it since last October. My 36 was underwhelming and just didn't feel good at all until the Secus. I don't find my fork sags in any negatively noticeable way compared to stock, overall it rides higher. Perhaps it has something to do with running one token versus none? I was also running less pressure initially but then eventually worked up to just under suggested Vorsprung psi which has been better for the higher speed DHs.

I wouldn't say you have a bad apple at all. I've seen many riders in the forums who like it with less pressure. Just depends on your ride preferences. I have found that as I gain better cardio and strength the firmer settings have been more appealing as I ride harder. I haven't played with anything for months and seem to have found the sweet spot. Overall, this really transformed the ride experience. Bike mod gold if you have a Fox or RS fork.
  • 3 0
 Great review!
A small side note: you don't need a shaft clamp nor heat gun to remove a foot nut from RS air shaft, there's a 8 (or 10) mm socket slot on the air piston.
  • 2 0
 That is correct on the Pike/Lyrik, but on the Zeb if you do that you may find the piston coming off instead of the footstud however - they're threaded on.
  • 1 0
 @SebScott Great review! Thanx!
As I moved to a MegNeg on my own privateer 161 just recently, I had some issues with balancing front (Lyrik ultimate) and rear (stock shock with MegNeg). I like the feel of the MegNeg, but it's in my opinion, on this bike, not the best companion to the Lyrik. So, I filled the MegNeg negative chamber with 4 bands. That seems to be a decent compromise. Based on your review, getting back to more negative Volume in the rear would lead to bying a 38 or a Secus. Thanx for that ;-)
  • 1 2
 There's also the Luft Fusion for the Lyrik. Same as the secus but without the external can.
  • 7 1
 @romphaia: By "same" it seems like you mean "does not have two separable negative spring chambers that boost the spring rate in the middle of the travel, nor a means of substantially increasing the lower leg volume to improve spring rate scalability in the form of reduced non-adjustable end stroke progression" which is actually "not the same" Smile
  • 1 4
 @VorsprungSuspension: in stock air springs the rate drops 2-3 times from the start to the middle of the travel. A decrease of only 20% or so is practically undistinguishable from a perfectly linear rate.
The Luft Fusion does not increase the lower leg volume but increases the positive chamber.
  • 1 0
 But I already have a 190mm air spring in my Zeb (also mainly for geometry reasons), so it looks like I'll have to wait for Vorsprung to make an aftermarket 210mm one.
One thing I'll say about the Zeb is that I found it VERY good on initial small bumps from new, basically it felt as good as a coil, but with about 70 hours on it now it's clearly due a lowers service and is a bit more pingy.
  • 2 0
 Yes about 20 hrs ago!!

Every time I get to 50 hrs on a fork (about once per month) I think to myself "Is it really working any worse? Do I really need to service the lowers and change the oil?". I prevaricate for a day or two and then luckily get a rainy day where I think I might as well be tinkering in the workshop.

About five minutes into the next ride, post service, on my 'new' feeling Zeb or Lyrik (depends on which bike is due) I am shaking my head and wondering why I left it any hours past the 50 hr mark at all!!

And I go through this almost every time - so I must be a slow learner.

The upside of the RS 50 hr service is it is just a clean out and fresh oil, one doesn't have to replace foam rings and seals, which makes it simple and relatively economical.
  • 1 0
 @andrewbikeguide: I know it's overdue, that's why I gave the riding time - but don't shoot me for letting it go a bit over.
That 50hrs comes round very quick y'know - getting ProBikeGarage has really been an eye-opener.
  • 1 0
 Seb has become my go to for suspension reviews after his thoughts on rockshox "taking a step backwards" with their latest air spring while other reviewers raved about it. I bought a 2021 Lyrik which preserved the ride height/support in smooth G-out situations such a berms but was terrible everywhere else. Between the harsh top out and the massive build of support early in the travel, the fork felt like a pogo stick when you were in situations where you don't want to push your weight into the front wheel. The fork also seemed to spend more time in that near bottom out danger zone on bigger impacts as well. I ended up installing an older air spring and the fork feels perfectly predictable and balanced now. Some people complained about the way the old air spring pulled the fork down into its usable travel about 8-10mm but this is easily fixed by either using a longer air shaft or using the longer foot nut used in the updated air spring.
  • 1 0
 The Fox 38 force / displacement curve looks a little funky, with the wobbles in the beginning of the stroke. To the extent the 38 is a fork with a single negative chamber and a single positive, it should display a more "S" shaped curve. Any idea why the plot shown in the article appears to deviate so markedly from the expected behavior?
  • 1 0
 " The Secus is the first air spring mod (as far as I know) which offers a truly linear beginning-stroke, so the spring stiffness doesn't drop off at all as the fork goes through its travel."

The Secus is awesome engineering.

But which air springs have a drop off in spring rate/stiffness through the travel? Isn't that _the thing_: that an air spring naturally ramps _up_, non-linearly?
  • 3 0
 All other air springs that I am aware of have spring rates that decrease at the very beginning of the travel (which is dominated by the decrease in pressure of the negative chamber), flatten out through the middle of the travel, then increase towards the end. The Secus irons out that discrepancy between the initial stroke and the middle of the stroke. Is it "truly linear"? Depends how pedantic you want to be, because if you throw a coil sprung fork on a spring dyno you'll see nonlinearity as well, but it's significantly closer to it than any other air spring has gotten, because of the Midstroke Support Valve closing off part of the negative chamber in order to bump up the mid stroke spring rate relative to the initial stroke.
  • 4 0
 @VorsprungSuspension: Thanks for the clarification! I think I see it now, at the very beginning as the negative is "pushing back" and it takes a sec for the positive to "take over" and the whole thing to start ramping.

Did not realize there was a valve in there, explains a lot more! It's kind of a position-sensitive spring system?

Again, awesome engineering!
  • 2 1
 "the steeper dynamic head angle caused the bike to feel more "upright" - less willing to tip into turns."

But y'all been telling us forever that steeper head angles make it easier to turn... even too easy; enough that it's been in the "Cons" column on many a review: both as steep making it twitchy or providing "telepathic turns", and slack making it take more effort and be slow to turn in.

Now all of a sudden steep means harder to turn in? Difficult to trust reviews when it goes back and forth like this.
  • 2 1
 He means the bike is upright steering into corners with the wheel instead of leaning over into turns.
  • 1 0
 I previously had a ‘16 fox 36 that I upgraded with a smashpot coil conversion and that was an amazing improvement over the original air spring. Transcendent even! But my new bike has the ‘21 lyrik ultimate and to be honest, it feels pretty damn good. Bit of tweaking to get it right, but super happy with it as is. If I was going to spend $$$, I’d still concert with a smashpot over this I think.
  • 1 0
 @seb-stott Loving the detail on this. On the Cane Creek HELM you have the independent negative chamber valve. I have found that running this about 5psi more than the positive spring does improve the fork (over pressure the positive, charge the negative, let 5 out of the positive down to dsired pressure). This effectively goes a little way towards what the SECUS does, yes? Doesn't increase the volume, but the added pressure with reduce the pressure reduction in the negative spring during the stroke, yes?
  • 1 0
 Seb, excellent rewiev as usually. I got similar experience by using Secus. I’m running a Secus on a Rockshox Zeb (190mm). I have to say that the sensitivity at the beginning of the stroke is noticeably greater - amazing, but it seems to me that it is at the expense of the stroke in the middle/end section. At slower speeds and small bumps, the function is perfect, but when traversing rougher rock gardens at higher speeds, I find that the bumps to my hands are greater than with the original fork. Also, you have to take into account that the sag is over 20-30% (depending on the inflation - still experimenting) and I would always recommend getting a fork higher than recommended for your bike. I'd recommend the Secus for hobby enduro/trail riders who don't plan on riding some heavy sections at high speed and will appreciate its superior ability to smooth out minor bumps. It is also suitable for flow trails where it holds up nicely in the stroke. I don't reckon the enduro fork manufacturers (Lyrik, ZEB, FOX38 - all of which I currently ride) will ever come with this sensitivity as standard. There's always a quid pro quo, and an ultra-fine fork will always have reserves in the rougher use these forks are primarily made for. However, I think there will always be many riders who can't fully utilize these hardcore standard fork capabilities and the Secus will be the perfect choice for them.
  • 1 0
 From what you’re describing I’d say you should consider running more air pressure. Though it’s counterintuitive, you’ll get better medium-to-large size bump compliance by keeping yourself up higher in the travel and away from the end stroke progression until it’s really needed. Higher air pressures in that scenario can actually reduce peak spring forces in rough terrain, and with the Secus it won’t destroy the initial sensitivity.
  • 5 0
 Sickus
  • 12 12
 so for an additional $453(CAD) you can dramatically improve the $1200 ZEB, which makes it ever so slightly, in a few small specific ways, but maybe not....better than the $1400 38???

Sram, I will tell you....you are good at the game you play!
  • 17 2
 You can get the ZEB for $999, buddySmile And in europe the price difference is even bigger between ZEB and 38. Not to mention the service costs.
  • 5 6
 @embi: not in Poutine dollars, buddy.
  • 2 0
 just buy and Ohlins m2 and you can run coil or air.
  • 1 0
 @fartymarty: lol. I currently am on an m2 Smile
  • 6 0
 I think if you already have a Zeb and you're a hard charger it could be worth the money though.
  • 6 0
 @embi: yeah but the zeb is still too expenisve as a base platform. Yari was the best platform for tuning.
  • 1 0
 @seb-stott:
This is the perfect summation Wink
  • 1 0
 @seb-stott: there are cheaper options though like AWK
  • 1 0
 @conoat: me too, lovin the buttery coil goodness.
  • 3 0
 @KalkhoffKiller: AWK doesn´t do a whole lot in case you start with fork with less than stellar initial sensitivity to improve that part of the travel. It does significantly improve midstroke of course, just like other 3 chamber systems do.
  • 1 0
 @Mondbiker: combining Luftkappe and AWK is the cleanest setup
  • 5 2
 So glad they stopped relying on kazimer for suspension stuff. Awesome work Seb!
  • 3 1
 I would have just kept the Zeb at 170mm, add more air like you did and open up your HSC on the fork to soak up the bigger hits.
  • 1 0
 From what I have read on forums, folks are having mixed success with the secus on the zeb . Albeit, it’s all limited anecdotes. Do you plan on trying this with the 38? @seb-stott ?
  • 3 1
 I have a Secus fitted to my Lyrik Ultimate and bloody love it. Simples ...
Running a Super Deluxe coil too (cos i blew up my Fox X2)
  • 3 0
 Everyone has @VorsprungSuspension in Peru! great job guys! Takumi is crushing it!!
  • 2 0
 Thanks for the kind words, Takumi is great!
  • 1 0
 @VorsprungSuspension how well does Secus work with lower-end forks, like Zeb Select or Select+, considering one should change damping settings and only Ultimate has low and high-speed compression adjustment?
  • 3 0
 Awesome article as always, thanks Seb
  • 2 2
 I was riding Fox 38 for couple of last months. This thing doesn't need anything. On my 36 I have extra positive air chamber which is a great addition. 38 doesn't need that. It is an amazing fork.
  • 6 0
 Stoked you're happy with it, but maybe your 38 could be even better Smile
"The best you've ridden is the best you know" - Paul Thede, Race Tech
  • 2 0
 Seems like a flexible connecting hose would be a better solution. Have the can attach to the fork with a breakaway mount
  • 6 0
 We looked at options for that (and we tried for a long time to just fit it all inside the fork!), but because there are actually two connections there, the stack height of the hose connections got too long and ended up protruding further than the Secus does, basically creating a longer and more fragile footbolt that isn't supported in any way. The Secus body can rotate to contact the brake caliper in the event of an impact, or safely flex upwards to contact the fork lower leg for support, so it's harder to damage than it might initially appear.
  • 2 0
 @VorsprungSuspension: Challenge accepted Wink
  • 3 0
 Seb's reviews are the best!
  • 2 0
 If the ride height was too low at the comfortable pressure, then just increase LSC?
  • 4 0
 LSC won't affect static ride height. Basically the difficulty Seb is describing there is that he wants a certain fork length at sag, and a certain spring rate (which doesn't give that fork length), so he changed the fork travel in order to get the length-at-sag that he likes. On a dual crown fork this would have just meant sliding your stanchions down a bit in the crowns rather than changing the travel.
  • 4 2
 Make RockShox feel like DVO except abit shitter. lol
  • 1 2
 We have to go to 50mm stanchions. They will be stiffer, and chambers will be much bigger. Due to better stiffness we can use lighter an thinner materials so weight will be about the same. Only Pros.
  • 6 0
 We need to make a video about this - there's a number of reasons why fork stanchions aren't bigger than they are!
  • 5 3
 Great review. An easy decision for me not to waste my money on a Secus.
  • 2 0
 Love my PUSH ACS3 Conversion. Money very well spent.
  • 2 1
 Doesn't Vorsprung say on their website something about not needing it for the longer travel forks (180+)
  • 1 0
 I think they've warned that things like a Luftkape on long travel fork can make it nearly impossible to bottom. Probably same affect here.
  • 2 0
 @btjenki: correct on the Luftkappe, but not the case for the Secus. The Luftkappe takes volume from the positive chamber to add to the negative - that makes it more progressive, and the longest travel variants of some forks (namely Pikes and pre-2021 36s, but not Lyriks, 34s, 38s or 2021+ 36s) get excessively progressive there. The Secus doesn't do that, it leaves the positive air spring chamber unchanged but significantly increases the lower leg volume so you get LESS ramp up from the lowers. This in turn allows more air pressure without excessive ramp up, and is totally suitable for the longest travel forks.
  • 1 0
 @btjenki: not the same implementation. The luftkappe steals some of it's space from the positive chamber. If you started with zero tokens it will have approximately the effect (on the positive chamber ) of adding two spacers.
  • 1 0
 @VorsprungSuspension: Ah, I must have been thinking about the Luftkappe then. Thanks for the reply!
  • 2 0
 So your saying my decision to get a 38 was the right one!
  • 1 0
 Not if you live in the UK where you can buy Zeb’s and a new pike for yourhardtail for pretty much the same price as a 38.
  • 1 0
 That graph says the Secus makes a Zeb good, but a 38 is already awesome, re: linear-ness.
  • 3 5
 Adding weight to the front of the long bike on a fork that this very website said was a benchmark - nah thanks

www.pinkbike.com/news/fox-38-vs-rockshox-zeb-2021-review.html
  • 1 0
 More interested in that bike
  • 1 0
 Does soneone know what saddle is on the Privateer btw?
  • 2 1
 I worry that I would smack that thing on a rock
  • 4 0
 We worried about that a lot too, obviously it would have been better if it was inside the fork! There's a few things that might give you a bit more peace of mind there though, because we spent a fair while working on that:
1. The Secus body can rotate to contact the brake caliper for support in the event of an impact
2. The Secus can also safely flex upwards to contact the fork lower leg for support, so it's harder to damage than it might initially appear.
3. It's a lot less exposed than your derailleur!
4. We offer a 12 month crash replacement guarantee - if you damage it in the first 12 months, we'll get you whatever replacement parts you need free of charge.
  • 1 0
 I haven't hit a thing riding since last October. I also put shrink tube around it and it's scratch proof.
  • 1 4
 Novyparts in France does this since 2013.
He modifies the air spring piston: he does a specific air piston tailored for your weight.
The ratio between negative and positive is different and also he modifies the location of equalization between the two so you don't have the problem that you had with the secus where it sits lower in travel !

And all this only costs 89€...
  • 6 0
 What Novyparts are doing is more comparable to the Luftkappe. It does not do the same thing as the Secus.
  • 1 7
flag Simzesun (May 20, 2021 at 13:33) (Below Threshold)
 @VorsprungSuspension: yeah ..right. but the result is better IMO, cheaper and you don't have something ugly on the bottom of your fork.
  • 6 0
 @Simzesun: the result is better in what way? Fair enough if you don't want something external to the fork - then you can check out the Luftkappe (which is very much comparable to what Novyparts offer - and it's the hydraulic side they modify for your weight, not the air piston BTW) or the Smashpot. The Luftkappe is $125CAD (85€) shipped anywhere in North America.
  • 1 2
 @VorsprungSuspension: Better because it is shaped for your weight and the equalization between the two Chambers is also modified.
Of course the air spring is tailored to your weight because to mimic a coil spring you have to have different negative to positive ratio for different weights !
  • 3 2
 @VorsprungSuspension: hi guy, it seems Luftkappe is more comparable to Novyparts air-kit. Since 2007.
But, yes i never want to work worldwide, i always prefer to do taylor-made, be small, be free and not part of bike showbiz. It's why my products are open-source and not registered.
And i'm really happy for your buziness. I think Suspension and particularly Mtb suspension need something like you to explain the other side of big brands...with 5 engineers and 50 guys for marketing Wink
  • 1 0
 @seb-stott better than the luftkappe?
  • 2 0
 It better bloody be!
  • 1 0
 @chakaping: hope so too for 4 times the price but is it 4 times better that's what I wonder.
  • 1 1
 @ybsurf: it makes a much bigger difference than the Luftkappe. Is it worth 4 times as much? That's for you to decide.
  • 2 1
 @VorsprungSuspension: thanks for the reply love my luftkappe so this upgrade might be the next step.
  • 1 0
 Night and day difference. I've had both.
  • 1 0
 Hey seb shouldnt you want to call it the sebcus?
  • 1 0
 full circle with the air spring adjustments i had on my 03' Z1SL
  • 1 0
 How’s it compare to the luftkappe?
  • 1 0
 More and better.
  • 1 3
 For anyone who rides motocross, this basically turns your air folk into a SHOWA TAC SFF. I have one, and I can tell you, its NOT a good thing. Coil all the way. I'll take the weight Smile
  • 4 0
 If you're a coil stalwart, we also have the Smashpot Smile

The TAC SFF (Triple Air Chamber, Separate Function Fork, meaning damping in one leg and spring in the other) operates a bit differently to the Secus, although I can see the aesthetic similarities! TAC does the equivalent of pressurising the outer tubes (the Secus doesn't, it just expands the effective volume of the lowers, which in this case are the outer tubes) and is otherwise a two-chamber (positive and negative) non-self-equalising air spring, ie you have to manually set three chambers instead of one. The "inner" and "outer" positive adjustments on the TAC function in parallel, not in series like say IRT or other twin-positive-chamber MTB air springs, or like the twin negative chambers in the Secus.

If you were to compare the Secus directly using the same kind of nomenclature, it'd be a four chamber, self-equalising air spring with one of the chambers initially at atmospheric pressure.
  • 3 0
 @VorsprungSuspension: Ah yes, #talknerdytome
  • 2 2
 Lmao, why is everyone with an Instagram posting a pic of a Vorsprung installed on their fork?
  • 2 1
 Tyre pressure is key. Then this!
  • 1 0
 If this means I can actually inflate my tires and not deal with those heavy inserts, I'm sold.
  • 1 0
 I love my Smashpot (。♡‿♡。)
  • 1 4
 It’s cool to see innovation, don’t think it’ll be much of a commercial success but it sounds promising and I’m sure the suspension manufacturers will be testing it and applying things to their future forks!
  • 5 5
 Looks silly, just get The Runt from Diaz Suspension
  • 2 0
 Different systems. Runt doesn't add air volume like Secus for one thing, it splits up the existing. As Vorspring said, it's more of a four chamber system. I tried both, kept the Secus. Once it's on, you don't really ever think about it visually nor does it get hit or in the way.
  • 1 0
 Is there a coil version?
  • 5 0
 The Smashpot would be the coil equivalent.
  • 2 4
 The same performance can be achieved without an external air can attached to the fork leg, and lighter. Look up the Luft Fusion air spring.
  • 5 1
 It's not the same performance, that one is still a single negative chamber without the boost provided by the Midstroke Support Valve. Even according to your own graphs, the mid stroke spring rate is significantly softer than the initial, and it does not address the ramp up that comes from the lower leg of the fork, which is a significant contribution to the overall spring force, particularly for lighter riders.
  • 1 0
 Looks like a coil.
  • 1 1
 But what about beans on toast ?
  • 1 1
 No torque caps!
  • 4 7
 I can feel a big BRAIN Specialized lawsuit coming on.
  • 1 0
 I'm pretty sure the BRAIN does not extend the negative chamber as this does, but I'm with you on the "looks like a BRAIN" train Wink
  • 3 0
 Meh. Not so sure. It's pretty different structurally and functionally from the brain. It's not locking out the suspension.
  • 6 0
 The Brain is a damper, this is a spring. They are totally different things.
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