After a short hiatus, there's been a resurgence of coil-sprung shocks and forks hitting the market, but this time around they aren't getting installed on downhill bikes. Instead, they're showing up on everything from mid-travel trail bikes to full-blown enduro race machines. Air-sprung suspension has become incredibly evolved, but there are still plenty of riders out there who prefer the extra small-bump sensitivity that a coil-sprung setup can provide.
Push first joined in on the coil revival with the release of the eye-catching, steampunk-esque ElevenSix shock back in 2015, and last year the Colorado-based company followed up with the ACS3 conversion kit.
Push ACS3 Details
• Converts air-sprung fork into coil-sprung
• Kits available for RockShox Pike, Lyrik, Yari, and Fox 36
• Air-sprung bump stop
• Seven spring weight options
• Weight: 367 grams more than stock on a 29" 150mm Lyrik
• Made in Colorado
• MSRP: $389 USD
The ACS3 allows riders to convert their 2015-2018 Fox 36, 2014-2018 RockShox Pike, or a 2016-2018 Lyrik or Yari forks from air to coil. All of the components are hand assembled and manufactured in Push's facility in Loveland, Colorado, which helps explain the kit's $389 USD price. Installation
Installation of the ACS3 kit is a straightforward process, and if you've ever performed a lower leg service on your fork is shouldn't be too much of a hassle. Even if you've never done anything except add some air and twist a few dials on your fork, Push have created instructional videos
that goes through all of the steps in a clear, easy to understand manner.
I'd budget in an hour for the procedure from start to finish, but in reality it'll probably take much closer to 30 minutes. Basically, you're pulling off the lower legs, undoing the C-clip that holds the air spring in place, removing the air spring, and then putting in the lower portion of the ACS3 kit. The lowers are then slid back on, 20cc of oil is put into each leg, and then the foot nuts are tightened down. After that, it's just a matter of dropping in the correct spring, installing the top cap, and airing up the bump stop to the desired pressure (anywhere between 5-50 psi).
One of the downsides to a coil fork is that it's not possible to control the spring rate as precisely as you can with an air fork, where it's easy to add or remove one or two psi. That being said, Push have seven springs available, which, on a 150mm fork, means there are options for riders from 115 to 240 pounds.
It's also worth noting that once you install the ACS3 kit, it's a relatively permanent conversion. You can't swap your fork back to air, due to the fact that the spring may scuff up the inside of the stanchion, which would allow air to go to where it doesn't belong. Performance
Push recommends installing their seal kit at the same time as the ACS3 for the best performance, which is good advice, but I kept the stock seals in place in order to reduce the number of variables I was changing. Based on Push's reference chart, I went with a blue spring, which is the suggested choice for riders between 155 – 175 pounds (I weigh 160 lb).
Without Push's nifty Air Bump Stop that spring rate would likely have been on the softer side of things, due to the inherently linear nature of a coil spring. But, with the air chamber inflated to 25 psi the fork sat exactly where I wanted it to, delivering a super-supple feel at the beginning of the stoke, before ramping up to avoid any harsh bottom outs. I also ended up dialing in a little more low-speed compression than what I was running in the fork's air-sprung configuration. This provided a little more support at the beginning of the travel for pushing into corners or to preload before hitting a jump.
One of the selling points of coil-sprung forks and shocks is the superior small bump compliance and on that front, the ACS3 doesn't disappoint. I was amazed by how responsive the fork felt with the ACS3 kit installed – it takes almost no effort to initiate travel, and I found myself taking lines in the wet that I usually reserve for dry days due to the increased amount of grip. The kit delivered an instantly noticeable increase in traction, a sensation similar to running really low tire pressure. The wheel felt glued to the ground, tracking over every root, rock, and bump in the trail without getting bucked off line. Issues
I didn't run into any performance issues, but at first the ASC3 made more noise than I would have liked. When faced with repeated large impacts the fork made a loud “thwack” noise that sounded similar to a wooden ruler hitting a desk - you can hear it if you turn the volume up in the video. At first, I thought it was the spring knocking against the inside of the fork's stanchion, so I installed more shrink wrap and a healthy dollop of grease to quiet things down. That made a small difference, but the noise was still present - the culprit seemed to be the air bump stop hitting top of the lower shaft. There's a small bit of rubber on the bottom of the bump stop that's supposed to keep things quiet, but it wasn't working as intended.
Push sent me a replacement Air Bump Stop, which had a thicker piece of rubber in place, along with what seemed to be more negative pressure - it was slightly shorter when aired up to the same pressure as the original. The replacement did the trick, and the noise that had been annoying me before was replaced with a blissful silence. According to Push, if a customer had experienced that problem they would have received the same treatment that I did - a replacement would have been sent out to correct the issue at no charge. Pinkbike's Take