Ok, So What Does An Air Spring Do? | How Did We Get Here? | Updates and Rider Benefits
When we started reimaging our 2023 fork lineup, a new air spring wasn’t in the master plan. But as we developed a new chassis, Charger 3 damper, and Buttercups, we threw out our previous air spring design to create air springs for Pike, Lyrik, and ZEB around a shared design philosophy tailored for each ride style: trail, all-mountain, and enduro. Our development team toiled through iterations, hammering out different prototypes in quick succession to see what worked and what didn’t. The fruits of our labor—DebonAir+.
Ok, so what does an air spring do?
Let’s talk air spring theory. An air spring works similar to a coil spring—it absorbs energy from the trail or the rider and then quickly releases it. We pair springs with dampers to help control the rate at which the spring absorbs and releases energy. In our forks, you’ll find a spring (typically an air spring) in one leg of the fork and the damper in the other. We use air springs because they are lighter (they use air molecules instead of metal) and are infinitely tunable to different rider weights and styles— they can be adjusted by adding or removing air, which will change the force needed to push the piston through its stroke. You can also affect the spring curve of an air spring by adding Bottomless Tokens (volume reducers) to increase bottom out resistance by making the air spring more progressive.
Many different components make up an air spring, but from a high level, it's a sealed chamber made up of the air spring piston, shaft, seals, and most importantly—air. Technically, there are two chambers inside the air spring: a positive and negative chamber. As the fork is compressed, it pushes the spring shaft up, propelling the piston into the positive chamber. As the piston moves upwards, it compresses the air molecules inside the positive air chamber, creating pressure (when the molecules turn green in the animation below). That pressure then counters the force from the compression event and forces the piston back down.
Now, the pressure within the positive chamber requires a certain amount of force to move the piston—anything less than that force will transmit that damage to the rider. So, we balance out the air spring by applying negative volume to the underside of the piston, creating equal pressure on each side of the piston and allowing it to exist in a neutral position. With equal pressure on either side of the piston, it almost floats within the chambers and can move easily when a compression event arises.
When an air spring is pressurized, air fills the positive air chamber first. So how do you pressurize the negative air spring? There’s a dimple inside the upper tube of the fork where the air spring lives that allows the air to swap from the positive chamber to the negative chamber where it can equalize the pressure on either side. It does require cycling the fork after pressurization to make sure the air will swap as needed between the positive and negative chambers.
In our 2023 fork lineup, we took a long, hard look at how each of these aspects works together as a complete system (let’s be honest, these things are more complicated than what we can get into here) to come up with our best air spring to date.
How did we get here?
In the midst of COVID, wearing masks in an empty office six feet apart, four members of the development team held what they refer to as a “moonshine event”. Two engineers worked through designing the air springs, the technician machining their designs, and the test engineer gathering data on updates. All four of them focused exclusively on the air spring for three weeks straight, working through four iterations to refine every detail of the air spring—the placement of the dimple, the top out bumper, the negative volume – all of it poured over and discussed in great detail.
Each morning, they'd start with an idea before splitting off to work through their piece of the puzzle. The goal was to test their updates by the afternoon. They'd follow up the test ride with a debrief, rinse and repeat. It was a fun, iterative, and collaborative time, digging into what they knew about air springs and what they did not know. Senior Design Engineer Tim Lynch questioned, "What exactly does this do? We don't know. How do we even measure it? We don't know. And so, in addition to creating that stuff, we were also creating testing."
Because we started with all-new everything, we had a lot of freedom to dig into the details of each aspect of the air spring. We would often find small gains from one piece of the puzzle, and then another day, pick up another criticism. We’d go back and assess what caused it and how we keep the gains we’d made.
–Eric Neeley, Design Engineer
Updates and Rider Benefits
What changes did we make? The first, most visual update we made was moving to an aluminum piston. Because aluminum can be made thinner than plastic while still maintaining integrity, we were able to tweak the volume in the chambers. Next, we moved to a glide ring and backup ring on the air spring piston, allowing the aluminum to play nice with the upper tube and for a better interaction with the dimple.
Another major update we’ve made: tweaking the positive and negative air volumes incrementally based on each fork’s use case. Pike (silver) and Lyrik (red) look relatively similar, but ZEB’s (gold) air spring looks different. To match ZEB’s use case (bigger, harder hits, more travel), we wanted to maximize negative volume without affecting the location of the dimple inside the upper tube, allowing for backward compatibility with the existing ZEB chassis. The development team extended the top of the piston and added a hollowed-out top hat, adding more volume to the negative chamber.
Ultimately, we refined the shape of our spring curve, and it took looking at how all aspects of the fork work together for us to evolve the entire system. We mapped out the upper tube volume, the lower leg volume, and precisely how the damper and air spring impact one another.
As we started to test the air spring, we found we were getting a lot more comfort through breaking bumps and square bumps, while still having good control. It was stable and yet still comfortable, which is a difficult balance to strike.”
What all of this means for you—the rider—is you can initiate travel easier, so it feels more plush off-the-top while still maintaining mid-stroke support. It also means a higher ride height, so you can utilize every millimeter of travel for more confidence on rowdy trails. You’ll find improved small-bump absorption, so your fork is extremely reactive over every inch of trail.
By hyper-focusing on the air spring, and iterating in quick succession, these small tweaks add up to big results.
Why change a good thing? To make it unbeatable.
DebonAir+ is compatible with 2023 Pike, Lyrik, and ZEB forks. Not exactly sure how to set your air spring up for you? Check out Trailhead—our suspension setup app that will give your pressure and adjustment recommendations for your ride style. Questions about travel change or fitment? Check out our 2023 Fork Collection FAQ page.
Renderings by Ray Bach. Photos by Anthony Smith and James Stokoe. Words by Sarah Walter.