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Secus Fork Air Spring Upgrade Kit (Vorsprung)

Availability: In stock


For the first time, Vorsprung has created an air spring with a truly better spring rate, everywhere in the travel, than a coil.  The Secus upgrade delivers the first and only single crown air spring system to really come indistinguishably close to the linear spring rate of a coil fork for the entire first 2/3rds of its travel, with the advantage of a gentle end stroke progression to prevent bottoming without the “wall of force” harshness that excessively progressive springs create.

10 mm shaft clamp tool for Secus installation is available here.
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Secus Advantages

•   An enlarged negative air spring chamber delivers a soft, supple initial stroke for ultimate small bump compliance (yes, even compared to the Luftkappe)
•   Proprietary Midstroke Support Valve improves predictability and support beyond the sag point
•   Reduced lower leg pneumatic ramp means better scalability of the air spring, particularly for light riders who previously struggled to use full travel
•   Plush and predictable like a coil, bottomless like an air spring
•   Allows full use of travel in both directions - fully extends to topout without any quibbles (including on Debonair B1 air springs) and fully compresses without excessive ramp
•   Allows more lower leg bath oil to be used for superior lubrication
•   Considerably lighter than coil conversions - adds approximately 130g
•   Simple setup - inflate fork, bounce on it a few times, press MSV charge button, go ride
•   Compatible with OEM volume spacers for end-stroke progression adjustment
•   Compatible with other aftermarket top-cap systems such as DSD Runt and MRP Ramp Control
•   Lower compression ratios mean a more consistent spring rate
•   Transferrable between any Secus-compatible forks with only a footstud to change at most

Three Stages of Control


Is the Secus suited to lightweight riders?
Yes, absolutely.  By significantly reducing the ramp-up effect that comes from compressing air within the lower legs of the fork (which generates the same force for all riders regardless of size, i.e. proportionally far more for lighter riders), we can make the fork work much more effectively for light riders.

Is the Secus suited to heavy riders?
Yes - the scalability of the whole air spring is improved.  Heavy and light riders alike will now find the spring system performs much the same for either of them.  However, manufacturer maximum pressure ratings need to be accounted for - typically with the Secus you’ll run about 20% higher pressure than with a stock air spring, so check your fork’s maximum rated pressure and ensure that you’re ~20% lower than that with your current air pressure before purchasing.  While the Secus itself is fine at any realistic operating pressure you’re likely to encounter, we cannot guarantee that the rest of the air spring will hold up if manufacturer pressure ratings are exceeded.

It sticks out the bottom of my fork - what if I hit it on something?

It’s true, you do now have an additional part outside your fork that you could potentially hit and damage. Vorsprung has designed it to be as low profile as possible, able to flex out of the way for vertical impacts until it’s supported by the lowers, and able to rotate out of the way for lateral impacts until it contacts the brake caliper. It protrudes about 15 mm (sideways) beyond the lower legs of a Fox 36. 

However occasionally somebody’s going to get unlucky and damage it in a crash, just like any other bike part. To that end, Vorsprung offers a 12 month crash replacement guarantee - if you damage it in a crash in the first 12 months of owning it, we’ll send you the replacement parts you need - just email us a photo of what’s damaged and your proof of purchase and we’ll do the rest. (Wouldn’t it be nice if someone offered that for brake rotors or derailleurs?)

However, it goes without saying that you do need to use some common sense and be a bit more careful when taking the front wheel off and sitting the fork on the ground, flying with the bike in a bag/box, or throwing it over a tailgate pad, because even better than a crash replacement guarantee is not having to use it.

How hard is it to install? Do I need any special tools?
You’ll need a torque wrench with a crowsfoot adaptor, and 10 mm shaft clamps. Beyond those, nothing special is required - if you’ve serviced your fork’s air spring before, you can install this easily enough.

Does it make it harder to service my fork once it’s installed?
Not really. You need to depressurise slowly whilst holding the MSV charge button, but other than having to slide the Secus off/on the footstud and realign it when torquing the footnut, the process is much the same. Air spring services can be carried out as per normal using OEM factory parts. Lower leg services can be carried out as per normal using OEM factory parts. The o-rings on the footstud need to be inspected every service - if they’re dirty or damaged they’ll need replacement. Each Secus kit includes spare footstud o-rings to make sure you’re covered for this when the time comes.

Does it add any friction to the fork’s movement?
No - while there is an additional floating piston, it’s not directly connected to any of the moving parts of the fork. It only moves once pneumatic pressure in the lowers is enough to overcome the seal friction. All the other moving seals are the factory seals from Fox or Rockshox.

How hard is it to service the Secus itself?
No special tools are required to service the Midstroke Support Valve or the IFP. Service procedures can be viewed on our website.

How often does the Secus itself need service?
Vorsprung recommend servicing the Secus (cleaning and regreasing the MSV and IFP) every 200hrs, or approximately every 4 lower leg services if you’re keeping on top of your service intervals.

Where do I get seals for the Secus if I need them?
Seal kits are to be available from our webstore. Spare footstud o-rings are included with the Secus because these are the ones you’re likely to need first.

Is the Secus transferable from one fork to another?
Yes - you may need another footstud however, there are several variants.

Is the Secus installation process reversible - can I go back to stock if I want to?
Yes - no issues here.

Does the Secus alter the damping?
No - the spring and damper are physically and functionally separate components. This has no direct effect on the damper, so whatever damping characteristics you had before, you’ll still have after the Secus is installed.

Do I need to alter my damping settings or valving if I install the Secus?
Not necessarily - the average spring rate will actually be roughly the same as before, but the proportions change between early/mid/late travel. As a result, you’ll still need comparable amounts of rebound damping, and compression damping is largely based on personal preference regardless of spring curve. You may find you prefer slightly different damper settings with the Secus, but it doesn’t require drastically different damping settings (unless your existing settings weren’t well suited for you anyway).

Should I also upgrade my damper to XYZ cartridge if I install the Secus?
You may prefer the performance of a better damper cartridge as well - however whether you upgrade your damper cartridge or not is actually a fairly separate concern to whether you install the Secus.

The Secus seems to fit a lot of different forks - does it have the same effect on all forks?
Yes, it has a similar effect on all forks - the extent to which it changes the spring characteristic decreases slightly as the fork’s internal volumes increase. Without overcomplicating things, this means it has a slightly larger effect on singlecrown forks (eg 32/34/36/Lyrik/Pike) than it does on dual crown forks such as the Boxxer or 40, however the improvement is marked even on dual crown forks.

Why don’t Vorsprung publish graphs for all the forks the Secus can be fitted to?
Because there are simply too many variations to provide them for - even for one model of fork there are different travels, lower leg volumes by wheel size/year, volume spacer configurations, stanchion lengths, air spring shaft specifications, and then air spring pressure all affect the resulting spring curve slightly. However, the modern Fox and Rockshox forks are generally so similar in their spring characteristics that differentiating between them is basically splitting hairs.

Can I install a Luftkappe with this?
On Rockshox forks no. On Luftkappe-compatible Fox forks it's physically possible but Vorsprung don't recommend it.

Will this work with a Smashpot?

Do the lower leg bleed buttons continue to work?

Yes, continue to use the bleed buttons as per normal.

Do I want/need the Secus?
It’s an upgrade kit for performance-minded riders who want the best from their bike - you don’t need it to go ride your bike and have fun, but it will improve your ride quality.

Will I even be able to tell the difference if I’m not very sensitive to suspension setup/behaviour?
You can feel a big difference just pushing on the fork in the parking lot. It’s not a subtle difference.