"An air spring with a truly better spring rate curve than a coil"
Big claim alert! Vorsprung Secus is “air spring with truly better spring rate curve than coil, without it actually being worse in any part of the travel”.
Vorsprung Secus need to know
- Enlarged negative spring for small bump compliance
- Midstroke Support Valve boosts the midstroke spring rate for support, predictability, ride height
- Enlarged lower leg volume reduces overall progression whilst retaining volume spacer tuneability
- Approx 130g
- $425CAD SRP (approx £243)
You may know Vosprung from their air-to-coil Smashpot conversion kit. Or their Luftkappe aftermarket air assembly. Their new Secus is another aftermarket hop-up kit for air sprung RockShox and Fox forks.
Enlarged negative chambers are often something of a double-edged sword. The increased off-the-top suppleness is nice but the increased ramp-up in progression of the end-stroke is not so nice, particularly if you’re a lighter weight rider who will probably not be able to achieve full travel.
Forks with large negative springs can also feel like they’re overly eager to fly through the mistroke and hit the aforementioned ‘brick wall’ of end-stroke ramp-up.
Another issue of increasing negative chambers in the past has been a loss in available travel; the fork can sit significantly into its travel when unweighted ie. not extend fully.
As seen with the EXT ERA fork announced last week, the Vorsprung Secus offers an increased negative chamber but crucially also claims to solve the twin dilemmas of harsh progression and lack of mid-stroke support.
Yes, our old friend midstroke. The neglected part of suspension travel that often plays second (third!) fiddle to supple sag and bottom-out control. The Vorsprung Secus is more than just larger air chambers, there’s some additional valving in there too. Specifically, the Secus contains something dubbed a ‘Midstroke Support Valve’.
In a nutshell, the Vorsprung Secus is supposed to perform like a coil for the first 2/3rds of travel with the final 1/3rd acting more like an air yet ramping up less progressively than air typically does.
And, if you do want to increase the end-stroke ramp-up (say, you’re a heavier and/or more aggressive rider), you can still bung in volume spacers like on a regular air fork. Thus, there’s a wider range of end-stroke options.
Any downsides? Well, besides having something a bit odd bolted to the end of your fork, the Vorsprung Secus still has the same seals as air forks with the attendant friction and service requirements.
What forks does it fit?
Most Fox forks with Float NA2/Evol air springs but not StepCast forks or indeed forks with footbolts recessed in the lowers.
Most Rockshox Debonair 2019-21 forks. But the Vorpsrung Secus is not currently recommended for use with 2021 Debonair C1 shafts.