Riding the New Vorsprung Secus

Since Steve Mathews started Vorsprung, mountain bikers have been treated to several interesting aftermarket suspension options. Steve and his team are driven to rectify what they see as shortcomings with some suspension products. First was the Corset, then the Luftkappe and their Smashpot coil spring conversion. But this time, Vorsprung's outside the box thinking is more literal than ever. Introducing their new Secus.

The Secus expands the air chamber of your favourite fork, giving the air more room. This minimizes the aggressive build of pressure associated with an air spring going deeper into its stroke, especially in the fork lowers. Steve informed me that pressure build-up in the lowers can be quite severe for some forks, but all air-sprung forks have it and the Secus aims to remedy this too.

Features:

• Available for most Fox forks with Float NA2/Evol air springs, with exception to StepCast options or forks with recessed foot bolts.
• Options for 32, 34 and 36 forks are available (38 and 40 fork options coming soon).
• Fits most RockShox Debonair forks from 2019–2021 or earlier models updated to the 2019–2020 Debonair air shafts.
• Now available for Pike, Revelation, Lyrik, Yari (Boxxer fittings will be coming soon).
• MSRP: 425 CAD / ~320 USD at time of publication (Free shipping anywhere in North America.)

What is the Secus?

The Secus provides three stages of control over the air spring.

Initial stroke: An enlarged negative air spring chamber delivers a soft, supple initial stroke for improved small bump compliance.

Mid-stroke: Where traditional air spring rates drop off in the mid-stroke, a proprietary Mid-Stroke Support Valve technology boosts the mid-stroke spring rate to maintain linearity. This improves support, predictability, ride height and compliance.

End-stroke: An enlarged lower leg volume reduces overall progression even at higher pressures. This allows a wider range of end-stroke ramp options to be utilized with standard fork volume spacers.

The Secus looks to combine the best characteristics of an air spring with those of a coil. An enlarged negative air spring provides a softer initial touch and while this probably isn’t something new to most readers, Vorsprung's change of approach has opened up greater potential. The Luftkappe does similar but is limited by the space available within the fork. Vorsprung says that while the Luftkappe works well, whenever the initial stroke is softened, the end stroke progression increases. This results in many riders installing a Luftkappe needing to remove at least a token/spacer from their air spring. In some cases moving to zero tokens is possible. Vorsprung also notes that this effect eventually creates a “practical limit on the negative chamber size.”

Where the Secus begins to differ more is how it affects the mid stroke. Reaching a soft initial touch can result in a lack of mid stroke support and even the new 2021 Fox 36, while very good, still has the characteristics of an air spring here. The Secus utilizes a proprietary Mid-Stroke Support Valve technology that provides additional control of the port during this portion of the stroke. This maintains the linearity that coil springs have where a typical air spring would ramp up. This results in more support, increased ride height and better grip on the trail.

As the fork reaches full travel, the Secus provides a gentle end stroke progression – something a coil spring can't do – thanks to the enlarged lower leg volume. Volume spacers/pucks/tokens can still be used to customize the end stroke feel. This makes it possible to get a comfortable, supportive fork with the first two-thirds of the stroke acting like a coil spring, without the harsher feel in the end stroke often encountered with an air spring.

Below are Vorsprung's positives and negatives of the system.

Secus Advantages:

• Distinctly improved small bump compliance, particularly in the early travel (yes, even compared to the Luftkappe).
• 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 top out without any quibbles (including on Debonair B1 air springs) and fully compresses without an excessive ramp.
• Considerably lighter than coil conversions - adds approximately 130g.
• Allows more lower leg bath oil to be used for superior lubrication.
• 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 foot stud to change at most.

Secus Disadvantages:

• Costs more money than not having it.
• 130g is still more than 0g.
• Can be damaged if you have it, can’t be damaged if you don’t.
• Still has seal friction like any air spring – since we use the factory moving seals, friction is unchanged
• Bottom out control is not externally adjustable - need to use volume spacers which still entails removing the top cap.

Riding the Secus

I first spent a day testing the Secus in Whistler on AM/PM. It’s a short section of trail that’s been raced in the EWS and involves plenty of twists, turns, a few rock rolls, compressions and some chatter from roots. Conditions were hot – in the mid 30s Celsius – and it was hardpack with a thin layer of dust on the surface. I began the day with a couple of runs on my bike with the Öhlins m.2 I’ve been riding all year. After those, a stock 2021 Fox Factory 36 was fitted to the bike. It took two runs on that to get to a happy place before tearing down the fork and fitting the Secus.

Looking at the Secus mounted to the fork, it’s clear that some riders will be concerned about its durability. It’s a large metal can, added to the backside of your fork’s lower on the air spring side. Measuring the overhang, we found the Secus protrudes 15mm from the fork leg. That’s less than most derailleurs protrude from the rear stays of our bikes. The system has been designed to sit within a few millimetres of the front brake calliper on RockShox and Fox forks and has flex engineered into it. This flex allows it to move rather than break and the setup sees it stopped by the caliper or fork leg if it takes a knock. But to show confidence in the design, Vorsprung is offering a twelve-month crash replacement guarantee. Let’s see that from our favourite derailleur brands, hey?

With the Secus fitted, while seated on the bike I couldn’t see it. Peering down over the handlebars, I had to cock my head or tilt the bike in unnatural ways to get a glimpse. Its effects on the fork were clear though, and despite the initial setup sitting taller than my preference, the fork still rode comfortably. The 2021 36 provides more mid stroke protection than previous models and that required lower pressure to adjust it to my liking. With the Secus installed there was even more support, raising dynamic ride height again.

Although the Secus setup was on the tall side during the first lap, I was pleasantly surprised. The bike remained manageable and I enjoyed the more direct response from the front wheel as I whipped through turns and across chatter. Grip was high in the loose dust and I didn’t experience any discomfort. However, I prefer my bars lower than they were dynamically sitting thanks to the supportive mid-stroke, so I lowered pressure from the initial 95psi to 92psi the following lap.

Vorsprung recommends ~20% more pressure than without the Secus. For the first lap on the stock 36, the fork was set to 80psi as per Fox recommendations. It rode tall and my hands felt more of the trail, causing fatigue toward the bottom of the run. I ended up at 78psi and one token with the stock air spring.

Dropping the Secus setup down to 92psi put me just under the recommended 20% and it felt great. It maintained an excellent dynamic ride height thanks to the supportive mid stroke and progression was gentle throughout the latter part of the stroke. On my final lap, I dropped it down to 90psi. This made the initial part of the stroke lighter again and the wheel was glued to the ground. At this pressure the fork laboured in the mid stroke, delaying response through short, snappy corners. Despite this, reaching the bottom of the stroke didn't produce a harsh feeling as air pressure built up.

During those first runs, the damper settings weren’t changed from my final lap on the stock 36. Vorsprung kindly loaned me the fork with Secus installed for more testing and to tweak the damper to see what can be achieved. After more time riding the Secus 36, I’ve found 92psi to provide the perfect mix of support, grip and comfort. At static sag, I’m sitting deeper into the fork than usual; a touch more than 23% sag. This is possible because of the high level of support offered by the Secus through the mid-stroke yet despite sitting deeper, there’s no sign of the pronounced wall at the bottom of the stroke. Combine this with the light initial portion of travel and high grip, and it makes for a great ride.

With more time on the Secus, I’ve adjusted the damper to suit my preferences. More control was achieved by closing the compression a touch and I opened the rebound up compared to the initial runs. I’ve found with the current settings the fork can take anything I throw at it. The wheel tracks the ground wonderfully and the support promotes aggressive riding. I've especially enjoyed the dry, loose conditions on the Secus and it's been allowing me to comfortably smash into chopped out and rooty sections of trail. It's remained comfortable when banking through choppy arcs and rarely gets unsettled. Retaining bike shape in such situations allows for more focus down the trail rather than battling with body position to maintain control. This has promoted continued momentum down the trail despite the currently tough conditions.

I’ve used full travel once but it was controlled and the bike pulled out of the compression with no more than a slight hesitation – a touch more involvement from my upper body was required but I almost didn't realize it happened. I had to check the fork to confirm it was full travel being achieved that caused the delay. Poor line choice and missed brake points usually mean the bike needs to make up for it, or we crash – thankfully the bike kept me going.

The gradual progression through the bottom third of the stroke feels great too, with the Secus changing the end stroke to be calmer than the stock token system employed in Fox and RockShox forks. It’s tunable, with the tokens still usable to fine-tune how the last portion of travel is engaged, though I didn't need them for my setup.

Verdict

As with other aftermarket suspension offerings from Vorsprung, the Secus has a notable effect on performance. Even with the latest Fox 36 providing more mid stroke support than previous models, the Secus improved it even more and the lighter initial stroke and gentler final portion of travel overall made the fork more comfortable and capable on the trail. The large external air can won't be for everyone but if increased performance with an air spring sounds like your jam, the Secus is worth a serious look.

For full compatibility and more information, head to the Vorsprung website.