Formula's Neopos air-volume spacers are a foam version of the solid plastic tokens we are used to finding in most air-sprung suspension nowadays. For those out of the loop, adding or removing "tokens" or spacers from a fork's (or shock's) air spring is a method to tune the spring curve and the ride feel by altering the volume of air in the spring chamber. Neopos foam cylinders are made from a 'secret closed-cell foam material' that are said to give your fork a more consistent compression stroke, and get it closer to having that sacred 'coil-like feel.' A pack of three Neopos costs €29 EUR / $36 USD.
Installation & Theory
Previously, Formula didn't offer a plastic token option for their forks. Instead, it was recommended to add between 5cc to 35cc of oil to the main air chamber, which is effectively the same as adding plastic spacers, but with the benefit of infinite adjustment to the spring's volume.
Installation of the Neopos couldn't be easier – just remove the top cap from your Formula fork's air spring side (deflating the air pressure first) and throw them in – they do not need to be screwed or clipped to anything, they can roam free. Neopos are a much easier solution than adding oil to the fork, which was a faff to add, drain, and measure each time you wanted to make an adjustment.
Formula says that only one Neopos is needed to give its claimed benefits of a more linear feel, putting in more than one will not make it any more linear. Adding more than one will continue to increase mid- to end-stroke pressure, the same reason you'd add more plastic spacers.
You can read Formula's press release here for all of their science and graphs, but here is the layman's description: The initial stroke of the fork will feel the same at the same air pressure, mid-stroke support will be increased slightly, but the main difference will be less ramp up towards the end of the stroke. This is because, as the foam compresses, its volume reduces, which gives a more linear curve to the air spring, closer to a single rate coil spring which is perfectly linear.
The Formula 35 fork's air spring was originally tuned by displacing its volume with a measured amount of oil.
Speed-Sensitive Air Spring
The second claim is that, because Neopos' slow-memory foam compresses at a measured rate, the volume it displaces changes with the speed that the fork is compressing the air spring. For example: If you compress a fork to bottom out slowly, the max pressure could be 300psi, because the Neopos has time to compress at the same rate of the surrounding atmosphere. But, if you compress it very fast, the Neopos will not compress completely, the air-spring's volume will be reduced and the bottom-out pressure could be as high as 380psi.
Neopos' speed-sensitive action also controls the high-speed rebound rate. Because the bottom out pressure is higher at faster shaft speeds, the rebound speed is correspondingly faster. If the fork is held near full bottom-out, however (say, in a G-out situation), the Nopos will continue to shrink as it adjusts to the ambient pressure in the air spring, which will reduce the internal pressure to that original 300psi, thus slowing the rebound speed significantly. The result of using Neopos is a more consistent feel in both compression and rebound over a much wider range of impacts and speeds and, in theory, allow the rider to use all of the fork's travel, while retaining mid-stroke support, and without continuously bottoming.
This graph shows how the Neopos affects the spring curve. The two most important lines are the two middle lines at 60psi with a solid volume spacer vs. Neopos. We can see how the beginning and mid-stroke are the same, but there is a difference at the end of the stroke as a solid token will ramp up much more as air volume inside the decreases rapidly. Image: Formula
Riding the Neopos
Does it work as claimed? "Yes," is the short answer, I have tested the Neopos for months in different situations, but this describes one test ride: I found a short section of super rough trail in Finale (not a difficult task) with some corners and rocky straights. Starting with 10cc of oil (the equivalent of one volume spacer), I did a few laps to get a feeling for the Selva fork. Previously, my fork settings had felt over-damped and I wasn't getting full travel under any circumstances.
Out with the oil and in with the Neopos. I started with one. A few more laps revealed that there was a slight increase in mid-stroke support, which was easy to feel. More difficult to tell was if there was a benefit in the repeated and rougher big hits. It was hard to put my finger on, as the sections were rowdy, so I was more focused on the trail features. That said, there appeared to be an increased calmness to the fork in at the times where I was gritting my teeth and holding on the hardest.
Back to the workshop, I added one more Neopos and then headed back up. The fork retained its sensitivity (the Selva fork is one of the smoothest out there), and there was a more noticeable increase in the mid-stroke support. Now, however, the Selva was slightly harsh towards the end of the travel. The culprit, I discovered, was the Formula's 'e-bike' CTS (Compression Tuning System) chip I had previously installed in an attempt to increase the mid-stroke support of the fork. With the increased support from the Neopos, it was unnecessary. I switched it out to the original, 'Special Soft' CTS chip and the fork was spot on.
A few more laps determined my fork was working better overall, with more mid-stroke support and less ramp-up towards the end stroke. The lighter tune from the softer CTS gave me better tracking, bump absorption and less feedback into my arms and hands. Better still, the O-ring on the stanchion tube proved that I was getting full travel.
So I can put the Neopos in any fork, right?
No. The Neopos are not designed to work with non-Formula forks. For this reason, the official position of Formula is the following: "Neopos is designed and engineered to be compatible exclusively with Formula 35 and 33 mm stanchions diameter air forks. Formula is not responsible for any improper use of the Neopos on non-Formula forks." But, for the sake of our loyal commenters who would have instantly posed the question, and because I have heard of riders on the World Cup circuit using them in other brand's forks (even chopping them up to fit inside shocks), I decided to see what would happen.
The first great (and remember, not recommended) benefit of the Neopos is that they can be popped into any fork, and coming from a guy who has a drawer full of colored tokens - but never the right one - this promised to be a great problem solver. The next experiment was to try the Neopos in a 2017 RockShox Lyrik fork, swapping three tokens for two Neopos. I found a similar improvement, with increased mid-stroke support, although the Lyrik is already more linear than the Selva, so it didn't have as harsh an end-stroke feeling as I had to start with my original setup on the Formula fork.
My Neopos appeared to be degrading after a few months use in non-Formula products. Some mechanics who have done the same reported finding chunks of foam blocking the positive/negative transfer ports.
The third fork that the Neopos spent some time in was a Fox 36 on a Mondraker Level eMTB. After numerous days on this bike, the Neopos started to show signs of degradation, with lots of small pieces of foam inside the fork's main air chamber. This has not caused any problems for me so far, but I have heard reports from some World Cup mechanics that the small pieces of foam can work their way into the tiny air transfer ports that allow flow between the positive and negative chambers, which could affect fork performance. The takeaway is, use Neopos in non-recommended forks at your own risk. I wouldn't want to strip and clean my fork just to remove a bunch of foam particles.
To conclude, Neopos do perform as claimed in their Selva fork – a more linear spring curve and more predictable. For the €29 price tag, I would recommend that any Formula owners at least try the Neopos to see if they give the performance change they might be looking for. Another PB editor using Neopos exclusively in a Selva has had zero issues with degradation after well over 100 hours of use (more than Formula's suggested replacement interval).
The degradation I saw when I tried them in forbidden forks was likely caused by irregular-shaped air chambers or incompatible lubricants, so I do not recommend the use of the Neopos in other brand's forks. If I were a pro-racer with a mechanic or an avid suspension stripper, however, I would use them without a doubt.
Warning: Don't think that you can save yourself €30 and put in a chunk of your Mum's kitchen sponge and achieve the same thing.
Neopos is a recommended solution for riders looking to tune the mid-stroke and end-stroke characteristics in their Formula fork. They are easy to install and live up to their improved performance claims.—Paul Aston