This new chainkeeper system is designed to completely prevent chain derailments and jamming on Challenge bikes with a 19T/40mm bearing power side idler (Fujin, Furai, Mistral, newer Hurricanes, etc.). It takes a whole new, very serious approach to chain control. The chain is guided onto and controlled past the idler with a carefully designed plastic chute. This way, the chain is controlled in all directions as it approaches and goes over the idler. There is nowhere for the chain to go except for where it is supposed to go.

If you are having problems with chain derailment, jamming, and bent chainkeepers on your Challenge bike, this is the solution. This system is the result of years of testing and prototyping. At first, we thought something simpler would be enough- a sturdier chainkeeper arm. That helped, but it was still possible for the chain to get hung up in certain situations. So we tried adding side walls, which helped, but it was still possible for the chain to get stuck. We analyzed the chain flow under extreme conditions, and found that since the idler didn't have side plates, much more side to side control of the chain was needed.

We discovered what was happening was that when you hit a bump, a wave would form in the chain. The wave would propagate towards the idler, and in combination with the fact the chain was moving towards the idler, the chain would crash very hard against the idler and the chainkeeper. Depending on the angle of the wave, the chain could twist and start to come off the idler. Because of the high tension on the chain, the chain would bend the chainkeeper out of the way, and subsequent links would then compound the damage. We determined that the wave energy in the chain needed to be controlled well before it reached the apex of the idler, and that it needed to be controlled both sideways and up and down.

The chute is machined out of very tough, very slippery black plastic material. It is carefully designed so that the chain is guided onto the idler teeth in such a way that there is no other place it can go. The approach angles and clearances are carefully controlled. The chain doesn't touch the chainkeeper in normal operation, but the chain is not allowed to stray very far. If you hit a bump and the chain bounces or sways, all you will hear is a momentary light plastic rubbing sound as the chainkeeper does it's work ensuring the chain is kept in place.

The kit comes with two stainless steel mounting arms, one for each of the two Challenge mounting types. The first has a 40mm ID round hole, for bikes like the Mistral and the newer suspended Hurricanes, etc. where the idler mount is part of the suspension pivot. The second arm has an 8mm square hole in it to match the square section on the back of the 5 pointed star idler mounts on things like the Fujin and the Furai. An adjustable chaintube mounting arm is also provided in case you want to run full length chaintube on the power side chain. This can be removed if you use something like our Fujin/Furai Return Idler kits, since they move the mid return idler down out of the way of the power side chain and provide a floating chaintube to protect the fork.

We've received very good reviews from our testers about this new system, and are confident that the days of jammed chains and bent chainkeepers are over.