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.