The Limitations of Air Springs

The Limitations of Air Springs

Most forks that come on mountain bikes these days are air sprung, likely due to being lighter and more adjustable when compared to a coil sprung fork. Air spring designs have improved over the years, however there are still compromises on their performance which we will cover below.

To understand how air and coil springs perform, let’s take a look at a spring curve. A spring curve maps out how much force is required to compress the spring, at every point in the travel.

This is a spring curve of a Fox 34 (Evol) with 100psi.

Let’s break it down into 3 sections to analyze: Initial stroke, mid stroke and end stroke. 


Initial stroke - Unlike coil, the initial stroke of an air fork is stiffer, partly due to the spring rate, and partly due to seal friction. It requires more force to get the first third moving and this can generally translate to feeling ‘harsh’. 

Mid stroke - Once we get past this initial stroke, you’ll notice that the curve dips. This is often associated with feeling ‘divey’ and is where the second most common complaint of ‘lack of support’ stems from. Unfortunately, that’s just the way stock air springs are. This feeling of ‘lack of support’ is usually noticeable in corners and very technical sections of trail.

End stroke - A positive characteristic to air springs is the end progression. It protects against bottoming out and in air sprung forks, and can even be adjusted with the use of tokens.

Our upgrades aim to address those characteristics common in the initial and mid stroke of air springs. 

The Luftkappe does this by enlarging the negative chamber, allowing you to run higher air pressure for more support in the middle and end of the stroke, with improved sensitivity in the start of the stroke.
The Secus also does this, but to a much larger scale. It also reduces ramp up in the lower leg (if you’re unsure of what that is, check out this article). Combined with our proprietary mid-stroke support valve, the Secus provides a spring curve similar to that of a coil, that is ironically not much of a curve, but more linear.
The Smashpot aims to address these air spring limitations… by replacing it with a coil spring. With a coil, there are no moving seals to cause friction or leak, and the coil has zero spring rate variation, allowing more mid-stroke support and consistency. Where air springs are usually favored is the end-stroke that protects against bottoming out, and the Smashpot addresses this with a Hydraulic Bottom out system.


We don’t believe in making and selling products that are gimmicky and don't provide a real improvement - our goal is always the best performance-per-dollar-spent.

Nobody needs an upgrade, just like nobody needs a new bike every year, but it can improve the ride quality of performance-minded riders who want the best from their bike.


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