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ABOUT THE RIMPACT CHAIN DAMPER
The Rimpact Chain Damper is designed to do what its name suggests: damp chain vibrations. It does so by separating the inner and outer chainring and controlling the movement with a set of springs and elastomers. When there is no force applied to the crank, the outer chainring sits bottomed out against the leading elastomers in the inner chainring, and can rotate up to 8.6 degrees backwards to damp the effects of a flailing or tensioned chain. When a pedaling force is applied at the crank, the springs compress until the trailing elastomers contact at 8.6 degrees and the outer chainring provides drive to the chain.
The Chain Damper system features a labyrinth design, which is sealed by two large x-rings and an o-ring, offering what Rimpact claims to be industry-leading weather sealing. The two inner halves sandwich the outer chainring, fixed together by four bolts. With just a 3mm allen key, the Rimpact Chain Damper can be dismantled for service when removed from the crank.
Rimpact currently offers the Chain Damper with outer chainrings from 30 to 36 teeth. These are all compatible with 11 and 12-speed chains, including SRAM T-Type. Crank fitments are offered for direct mount systems only, with SRAM 3-bolt or 8-bolt; Shimano; Hope and Race Face options. The chainline is compatible with 52mm Boost.
There’s only one color on offer – black center with gold hard-anodized outer. This outer anodizing is ultra-thick at 40 microns, which should provide stellar wear life. The retail price is $375 / £279.99 / €323. The system weighs roughly 240g depending on the option selected, which is roughly a 120g weight increase over a standard Shimano XT chainring.
THE DIRT
Rimpact’s Chain Damper was to be my first experience with a chain device like this. In the past I’ve seldom complained about feedback through the feet, but have certainly complained about chain slap and appreciate bikes that run with minimal vibration and noise. Could the Chain Damper really reduce these enough to make a notable difference and justify the price tag?
It was simple to get the Rimpact Chain Damper fitted to the second set of cranks I attempted. I have the V1 model, which has since been succeeded by a V2 which improved crank compatibility and increased anodizing thickness. The V1 model didn’t fit the Actofive Signature X cranks, so Rimpact sent me the set of SRAM SX cranks you’ll see in the images. With these cranks, fitment was no more difficult than a normal chainring.
Hitting the trail, I was concerned initially. When pedaling softly on flat terrain, the chain damper feels very strange, effectively doubling up on the inconsistency of your power application as the springs compress and rebound out of phase. As soon as you’re pedaling hard enough to fully compress the springs – which took just a slight climbing grade or medium effort pedal on flat for my 115kg/250lbs system weight – there’s little change in pedal feeling compared to a regular chainring. Softer springs are available if you find this effect to be too hard to live with.
The only thing that remains is an “overrun” effect of sorts, where the chain still receives some spring-induced drive momentarily after you stop applying pedal force. In a couple of instances I found this to aid technical climbing moves slightly, giving a little afterboost and smoothing out the power application to the rear wheel. But the effects on climbing were fairly negligible.
The descents were where Rimpact was targeting performance improvements with their Chain Damper, and they have succeeded. That said, the magnitude of the improvements are going to depend on the bike it’s fitted to. I initially tested the Chain Damper on my Starling Mega Murmur long-term test bike last year. This bike ran fairly quietly as it was, thanks to a combination of the steel frame tubing and VHS Tape keeping chain-induced vibration fairly well controlled. On harder hits you would occasionally feel some tug at your feet, which Rimpact’s device helped to reduce. As a result, I found myself winding on a click more high speed compression damping to the Ohlins shock fitted. This helped to reinstate the suspension support in these instances, but the effects were not incredibly profound.
The second bike it found its way onto was the Knolly Chilcotin 155. While the suspension kinematic of this bike produced less pedal kickback than many, I found the chain would flail around and cause notable noise and vibration on medium to large hits. This was extremely detrimental to the ride experience on a bike that promised such descending excellence. The Rimpact Chain Damper saved the day, and immediately quietened the bike down notably. This led to reduced noise overall, as well as reduced vibration through my feet.
Would replacing the chain slap protection on the Knolly with something more substantial, or using a device such as the STFU, achieve the same effects? I’d likely say yes on all but the bikes with the highest pedal kickback. Though of course these devices work in a different, more passive manner.
Through the months of testing, I’ve not yet felt the need to pull the Rimpact Chain Damper apart for a full service. Although the majority of riding has been in drier and therefore less demanding conditions than Scotland’s typical assault of mud. The device began to squeak on two instances. A small application of silicon spray quickly fixed it the first time, and the second time resolved itself in the following hour or so of riding.
The Wolf’s Last Word
The Rimpact Chain Damper does what it says on the tin, and it does it well. It’s expensive, but can make a notable improvement to the calmness of a mountain bike on the descents, and has limited drawbacks aside from its small adjustment period and extra cost and weight. In typical Rimpact style, it’s been well engineered and feels like it’s built to stand the test of time. 
Price: $375 / £279.99 / €323
Website: Rimpactmtb.com
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ABOUT THE WOLF
Robert’s habitat is the Tweed Valley, Scotland, which is renowned for its root-littered enduro mountain bike trails. Robert has been developing his bike handling skills for the last 16 years. Since he was a pup, he’s been riding everything from BMX through to enduro and downhill bikes. Combining a playful style with occasional speed-focused aggression, he favors supportive bikes, and does his best to push them hard.
Rank: European Tech Editor
Size: 6’2” / 189cm | 220lbs / 100kg
Social: @robert_johnston
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