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When Aaron Gwin catapulted out of the starting gate at the downhill in Leogang in 2015, the American's chain snapped. Gwin looked down briefly and then made the best of the situation: completely unimpressed, he raced to the finish without a chain and to victory. 3:34 minutes riding time, without a single pedal stroke. Speculation ran rampant after this spectacular victory. Was the lack of a chain perhaps even an advantage because it allowed the chassis to move more freely? Or was Aaron Gwin so fast in Leogang in 2015 because he knew that he simply had no choice but to carry as much momentum as possible over every tricky section?
What is the Ochain Spider?
The fact that chain forces have repercussions on the Mountain bike suspension is nothing new. Designers deliberately use the chain hoist as part of the anti-squat strategy to prevent the bike from bending at the rear when accelerating. Pedal kickback is the downside of this design approach. When the suspension compresses, the rear triangle elongates and the crank turns backwards, which can be felt as a blow to the leg and hardens the chassis. Exception: On bikes with a high pivot point and idler pulley, the chain pull is neutralised.
The Ochain is a spider with freedom of rotation that can decouple anti-squat and pedal kickback downhill. In the gravity scene, some racers are already using the Italian system, which is installed between the crank and chainring (see interview with Christian Textor). When pedalling, the Ochain behaves like a normal crank - apart from the slightly longer idle travel until the chain engages. However, if you stand on the pedals without pedalling, the chainring is given the opportunity to rotate four to twelve degrees backwards in relation to the crank, depending on the setup. This is intended to prevent pedal kickback on downhills and decouple the chassis and rider. "Free your chain" is how Ochain advertises its concept.
When does pedal kickback actually occur on an MTB?
Critics of the system say that, in principle, pedal kickback can only occur downhill at low speeds. This is because the chain only tightens faster than the hub rotates due to the riding speed in the event of a very fast stroke - which is a prerequisite for pedal kickback to occur when rolling. Even at a high deflection speed of 5 m/s, which occurs rather rarely, the mathematical limit for our Canyon Spectral The first test bike that pedal kickback is even possible downhill in medium gears, at around 18 km/h. In addition, the hub also plays a role. Is the freehub fine or coarse toothed? With coarse gearing with 36 engagement points, as with the DT hub on our test mountain bike, the rotor has up to 10° of rotational freedom before the gearing engages - which makes pedal kickback downhill less likely. However, the position of the rotor relative to the pawls when the wheel compresses is a matter of chance.
The BIKE testers are convinced by the Ochain system
The practical test on Lake Garda contradicted all theory: Ochain convinced the testers for the most part on rough terrain. With the 6° spider, the Spectral felt better and freer than without, even though the bike only has a moderate pedal kickback of 6° in a medium gear and a DT hub with, as mentioned above, rather large rotational freedom was in use.
Theory or not: If you mainly ride downhill, you should try the chainless feeling. Before you hand over 300 euros to Ochain, it's a good idea to tackle a familiar descent without a chain. If you get the Gwin effect, Ochain could be the solution to experiencing it with a chain.
How the Ochain system drives
A total of four testers travelled with Ochain on two mountain bikes, one Santa Cruz Hightower and two identical Canyon Spectral, for direct A-B comparison with and without Ochain.
In our practical test on bumpy Lake Garda trails, the majority of testers were convinced by the system within a few metres of descending. The Ochain Spider decoupled the rider more from pedal kickback. As a result, fewer impacts were felt in the legs, which had a calmer and less tiring effect. It also gave the impression that the rear suspension was able to work more freely, without interaction from the chain. The suspension therefore felt noticeably fuller. When pedalling fast, however, you first have to get used to the large free travel of the cranks. In situations where frequent pedalling is crucial and/or precise timing on technical climbs, the Ochain takes some getting used to.
On artificial obstacles such as stairs, steps and landings, the picture was similar to that on the trail. At a medium speed of 20 km/h, the effect was also noticeable on individual bumps. The Ochain cut the peaks of the impacts, which resulted in a smoother ride. On the stairs, the drive also became acoustically quieter with the Ochain, the effect was more subtle compared to the rougher trail experience.
Advantages of Ochain:
- Decoupled chain and rear triangle
- Drive is quieter
- Adjustable rotational freedom
Disadvantages of Ochain:
- Additional wear part
- more weight
- Soft start
- Fiddly interior
Conclusion from Robert Kühnen, BIKE test editor
Ochain works. The clever active spider can be an asset depending on the bike and riding style. However, the system only really makes sense for enduro bikers with a high proportion of downhill or shuttle riding. Downhill-orientated riders whose bikes have a noticeable pedal kickback are the main target group. It's easy to test whether your own bike could benefit: simply go down a familiar descent without a chain.
Technical data Ochain Spider
Active spider for mountain bike fullys. Is mounted between the crank and chainring and gives the chainring a rotational freedom of four, six, nine or twelve degrees.
- Price: 299 euros without chainring
- Weight: 128 grammes
- Max. permissible rider weight: 100 kilos
- Compatible with Sram, Shimano, Race Face, FSA, Cane Creek, etc.
- 52 mm chainline, 104 BCD, 30-36 teeth
How the Ochain Spider works
The Ochain spider consists of three components: Cover, back and the centre section, the profile of which fits onto the crank. Four steel springs pivot the centre section between the covers and the end stops.
Three interchangeable elastomer buffers give the blade between four and twelve degrees of rotational freedom in relation to the crank. Downhill, when the rider is not pedalling, the chainring can rotate backwards in relation to the crank if pedal kickback occurs. When pedalling, the free travel forwards increases accordingly until the chain engages - a disadvantage in technical uphill riding.
Interview with Christian Textor, 3x German Enduro Champion
BIKE: How long have you been riding with Ochain?
Christian Textor: I started with it in 2021, this season I rode it completely.
What excites you about the Ochain?
I find the idea exciting, and I'm thrilled by the passion with which the developers are going about it. They're not trying to sell you anything, they're doing it because they believe in it.
In which driving situations do you feel a real difference?
Small bumps, one-footed, in open terrain or a hanging bend where you're always in a chain drag. I notice how the bike holds the grip better and also picks it up again when it breaks away. The sensitivity is better than without.
At what speed is the effect of the Ochain greatest?
It is more noticeable at high speeds, but also brings more composure to the suspension in slower riding situations, I am calmer on the bike and ride more uninfluenced.
Which elastomers do you use?
I've tried everything from six to twelve degrees and now ride at nine degrees in the Enduro World Series.
In which gear do you feel the effect most clearly?
I notice the benefit more clearly in the middle gears than in a heavy gear, where the pedal kickback is greater.
How much maintenance does the Ochain system require?
The new system from 2022 requires significantly less maintenance than the 2021 version. We disassemble the bike prophylactically before every race, even if this is not absolutely necessary. As a result, we have also serviced the Ochain. For private use, it certainly wouldn't need that much servicing; I would re-grease it once a season.
You no longer want to drive without Ochain?
No, I have grown very fond of it. A sterile system would be best - a combination of a very fine-toothed hub and an ochain with more angle - then the system would always work the same.
