Mountain bike drivetrains have evolved from sounding like a bucket of bolts rattling down the trail to something much less distracting thanks to the introduction of the clutch derailleur. In combination with narrow-wide chainrings, it's rare to drop a chain these days. In some cases, that silence and security may come at the cost of suspension suppleness due to the tension in the derailleur, especially on bikes with high anti-squat values that tend to have more perceived pedal kickback.
O-chain’s Active MTB Spider is essentially a chain damping system that claims to “release rear suspension” from the transmission. It does so by adding a floating element between the chainring and crankarm for either traditional bikes or eMTBs. Adding another component or level of complexity might seem like over-engineering, but the Active Spider stands to overcome what the clutch derailleur has undone, all in the name of suspension performance while still producing a stealthy ride.
O-Chain Active Spider Details
• Intended use: All full-suspension bikes
• 4, 6, 9, 12 degrees of articulation
• Aluminum 7076 T6 alloy body, elastomer bumpers
• Mounting patterns: SRAM, Shimano, Race Face, Hope, FSA, E13, Cane Creek, Brose (eMTB), Bosch, Shimano EP8
• Drivetrain specs: 52mm chainline, 30-36T chainring, 104 BCD
• Titanium chainring bolts included
• Weight: 128 grams
• Max rider weight: 100kg
• MSRP: €299
• More info: ochain.bike
In a literal sense, the spider rotates counter-clockwise a few degrees, independently of the crank. Small elastomers captured in the housing of the spider allow it to rock back and forth to help isolate the chain forces from the suspension movement, something the frame designers have tried to skirt their way around by often using more pivots or idler wheels. This does mean that it will require the rider to move the crankarm further through the pedal stroke to compress that elastomer before the rear hub engages, although the feeling is softer and less jolting than the pick-up in a hub with a low-degree of engagement.
The Yeti SB160 without the O-Chain system.
Once installed, you can see how the Active Spider lets the chainring rotate.
O-Chain machines their Active Spiders in Italy and offers anodized black or nickel-chrome treatments for all popular direct mount crank/chainring interfaces from SRAM, Shimano, Race Face, Hope, FSA, E13, and Cane Creek for bikes with 52mm chainlines. Each spider is machined from an aluminum 7076 T6 alloy and is compatible with chainrings between 30 and 36 teeth. This SRAM spider weighed 128g, as claimed, without the chainring bolts. E-bikes haven’t been left out either since O-Chain has kits to work with Brose, Bosch, and Shimano EP8 motor mounts too.
The component arrives in the 6-degree setting and includes the necessary parts to change that float to 4 or 9 degrees as well. Those three settings are aimed at enduro-style riding, however, there is a larger 12-degree float option as well. O-Chain recommends this setting for downhill bikes since they have more rear wheel travel, are often subjected to higher forces and don’t require as many half-pedal, ratcheting movements that are common while climbing.
A gold-coloured metal chip is stamped with the number of degrees (in this case “6”) that the spider can rotate freely - the smaller the chip, the more the spider rotates. Elastomers matching the size of the chip are then situated to soften the rotating half of the spider as the crank engages the chainring.
This only affects the forward rotation of the crank, although there is another set of round elastomers that soften the return of the spider as it reaches the neutral position and dissipates some forces of the ring if it is rotated in the clockwise direction.
Setting up the Active Spider is as straightforward as bolting on a 4-bolt chainring and spider. I began by using the 6-degree, stock configuration and didn’t need to play with the chainline spacing at all. If you do wish to mess with the spacing, O-Chain does sell bolt kits to move the chainline either 3 or 4.5mm to either side of the spider.
Installing Active Spider on the Yeti SB160 wasn’t a hassle, but I did have to move the upper portion of the chainguide well out of the way to clear the spider as it rotated around a 32-tooth Wolf Tooth brand chainring. That’s because the spider is bulkier than a direct mount chainring. This means that the upper portion of the guide doesn’t actually sit close enough to keep the chain from lifting off of the ring. Although I never experienced any derailments, a simple post-style upper guide without captive sides might be best here.
From the outside, this clever device seems simple, but there are a number of intricate pieces placed inside. At €299 the Active MTB Spider isn’t cheap, however this is a one-of-a-kind component for an attentive rider looking to optimize their suspension characteristics.
Two other important considerations are the fact that each Active Spider is brand-specific to the crank interface and you will need to use a 104 bolt-circle chainring (BCD). There is no price difference between mounting-type for the standard spiders but the eMTB is slightly more expensive at €328. O-Chain includes the titanium chainring bolts with the kit but only guarantees fitment with their own chainrings that cost €62. The 30-tooth costs 10€ more because those integrate the female end of the bolt connection.
Additional equipment, service kits and replacement parts are also available through distributors or O-Chain’s website. The 12-degree elastomer kit cost €19 and the service kits are €28.
Maintenance and Warranty
Opening up the O-Chain to change the float is a bit tedious, so patience and steady hands are crucial. The color-coded elastomers are slightly curved, so it’s important to pay close attention to their orientation to avoid damaging the device. A chart depicting each auxiliary elastomer is provided and the switch doesn’t necessarily require removing the spider from the crank itself, but it does make it clumsy to handle the half with the pedal attached.
Throughout the course of the test, the O-Chain was subjected to both apocalyptic dust and buckets of rain but never produced any creaks or unwanted noise. The chainring bolts and housing hardware never wiggled loose either. Throughout the test, the system remained solid feeling underfoot and not once slipped or felt questionable.
The only component that I would question would be the thick, waxy paper seal between the housing halves. I do wonder how well that would hold up to an entire winter of grit and bike washing.
In terms of the warranty, O-Chain offers a two year guarantee for the original owner, with proof of purchase. When you do need to replace any parts from normal use, grease seal and bolts are available, plus, there’s a full rebuild kit for about 50€.
O-Chain’s Active Spider theory to reduce chain forces sounds like the bee's knees on paper, but how does it operate in the real world? On my first ride, it was immediately apparent that there was magic happening under my feet, but that didn’t come without some acclimatization.
The first reaction you will have with the O-Chain is the newfound “give” that the pedal stroke has compared to a fixed spider. Surprisingly though, that lag is not as severe or abrupt as the feeling of a low-engagement hub. The soft-touch engagement that the elastomers produce is similar to a sprag clutch found on the Onyx brand of rear hubs.
On most mellow climbs a rider continues to spin the cranks in a nearly continuous motion, so the elastomer will stay compressed without any noticeable lag in the chain tension. It’s only when you stop or ease your input on the cranks do you feel that float again. The 6-degree setting never bothered me, even when I had to ratchet my way through some pinch points or hop up a step on the trail. For this reason, I never installed the 4-degree option and hoped to gain more on the descents from the larger of the two choices. Moving to the 9-degree elastomer chip is where my crank inputs took slightly more effort and attention.
I primarily spent time riding the 6-degree setting because that didn’t deter my climbing ability and the reward while descending was clear as day when the bike encountered the first set of bumps. Initially, I thought I lost pressure in the rear shock because the sensitivity of the suspension was incredible. After double-checking the shock pressure and heading out for another ride, it was apparent that the Active Spider had added a serious amount of performance to the bike.
Not only did it allow the rear suspension to move into the travel effortlessly, it also reduced movement in the chain as it oscillated down the trail. Now the Yeti SB160 was already an impressively quiet bike, but on large hits, you could still notice when the chain thumped against the rubber protector on the chainstay. That feature did its job well, but the O-Chain improved that element of damping even further.
Another bike I had the chance to briefly try the Active Spider on was Cotic’s RocketMax. Both bikes came equipped with SRAM AXS derailleurs that have been noted to produce more chainslap. That seemed like the perfect opportunity to test the capabilities of how the O-Chain system could reduce chain feedback. It shouldn't have been any surprise that the Active Spider made the ride plusher and quieter.
In terms of pedal kickback, that can be a tricky topic to dissect. What I can confidently speak to is the fact that the Active Spider brought a sense of riding downhill without a chain. This was most noticeable on repeated square edge hits, like braking bumps.
This sensation may just offer flat pedal riders more security when it comes to keeping their feet in place on the pedals. Proving that is difficult. I didn’t exactly set out to try and blow my foot off of the pedals, but without the O-Chain there is more perceived feedback through the chain and ultimately your feet.
You might ask, why do I need to spend 299€ when a hub with low engagement is less prone to pedal kick back. While the jury is still out there on the physics behind pedal kickback and the instances of when it actually occurs, those hubs don’t remove the amount the chain gets pulled by the suspension. (?) and they definitely don’t reduce the amount the chain oscillates.
Even in the 6-degree setting, which is still higher than some low-end hubs’ engagement, the benefits are very clear on the descents with minimal drawbacks while climbing. If I had the choice between riding a bike with a fixed chainring and hub with 36 teeth (that would engage every 10 degrees), or the O-Chain Active Spider in the 9-degree setting and a hub like the Industry Nine Hydra that picks up the crank input every 0.5 degrees, I’d opt for the later for its ability to isolate the chain from the suspension and provide a quieter ride.
Improves the compliance of the rear suspension+
Reduces pedal kickback considerably+
Calms down chain oscillations which leads to a quieter ride+
Soft pedal feel is more pleasant than a low engagement hub
Lag in chain torque makes ratcheting through technical sections feel strange at first -
Upper chain guides positioned for 30 and 32-tooth rings can contact spider