Beneath the swift current of increasingly capable single-crown air-sprung forks is a whispering demand for coil-sprung options. Push Industries, maker of the Elevensix shock, is whispering back with the new Push ACS-3 kit, which replaces the air spring in a Fox 36 or RockShox Pike with an adjustable coil spring mated to a pneumatic bump stop.
On the Rebound: Coil-Sprung Suspension
Though heavier, there's good reason to choose coil over air. The amount of air pressure required for air-sprung forks to work properly means that a greater breakaway force is needed to surpass the friction of the seals when compared to a coil. This is especially noticeable over small bumps, where air-sprung forks are typically harsher than a coil would be.
So why are all of today's popular single-crown forks air sprung? There's the issue of weight, of course, but air-sprung forks are also more easily adjustable, making them ideal for OEM sales and the mass market. A coil fork will require heavier or lighter springs to accommodate riders of various weights, whereas air-sprung systems can be easily adjusted by increasing or decreasing the air chamber's pressure, or on a more advanced level, by adding or removing volume spacers.
Coils also tend to bottom out more harshly than air springs. That's where the ACS-3's pneumatic bump-stop comes in. It's an air spring that controls only the final third of the fork's travel. It can be adjusted between 5 and 50 psi in the same way as you would change the pressure in an air-sprung fork.
How Heavy Is the Push ACS-3?
Note that the weight of the ACS-3 is dependent on which spring is used. Differences between the ACS-3 and stock Fox 36 air springs are as follows, according to Push:
– Fox 36 Talas 160mm fork: ACS kit adds 65 – 150 grams
– Fox 36 Float 160mm fork: ACS kit adds 210 – 285 grams
A Promising Pairing
Having merged the pneumatic bump-stop with the suppleness of a coil, is Push setting a new bar for single-crown fork performance? We've got an ACS-3 in for testing right now, and will report back with installation and ride details as soon as possible.
Push ACS-3 Kit Details
– MSRP $389, supplemental spring MSRP $80 (seven different spring rates available)
– Fox 36 140, 150 and 170mm travel models and 2018 140-170 kits arrive in late July
– 2015 – 2017 Fox 36 Float or Talas 160mm kits are available now
– RockShox Pike kits coming soon
– RockShox Lyrik/Yari will NOT be offered due to the small inside diameter of the stanchion tube
– Manufactured entirely in the USA
While We're On the Subject…
Also new from the Loveland, Colorado, brand is the Complete Lower Leg Service Kit, which includes new fork seals, a seal driver (also made in Colorado), and enough fork oil and grease for five services. Push says that its seals double the service interval of any fork. MSRP for the kit is $105, with seal-only kits at $36.