After years of testing and prototyping, here it is: the Challenge Chain Keeper from T-Cycle. Anyone who owns a Challenge knows that one of the biggest difficulties is the stock chain keeper. Challenges are beautiful bikes and a jammed chain or bent chain keeper shouldn't stop you from enjoying it to its fullest. The T-Cycle Challenge Chain Keeper is a specifically designed part that completely prevents jams and derailments by controlling the chain in all directions. Built for unbeatable durability, the Challenge Chain Keeper gives you complete chain control for complete confidence!
Installation is very simple. The kit comes with two mounting plates: small square and large circle.
Remove your existing chainkeeper, and match the new mounting plate to the old chainkeeper. Attach the chain chute to the proper mounting plate and reinstall your idler with the new chainkeeper.
Reattach the chain tube, then adjust the angle of the chaintube holder to match the exit angle of the chain.
- At first, we thought something simpler would be enough—a sturdier chain keeper 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. When when you hit a bump, a wave forms in the chain. The wave would veer toward the idler, and in combination with the fact the chain was already moving toward the idler, the chain would crash very hard against the idler and the chain keeper. 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 chain keeper 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. T he 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 Kit, since it moves the mid return idler down out of the way of the power side chain and provide a floating chaintube to protect the fork.
- All known Challenge bikes using the big 19T plastic idlers with the large 40mm ID bearing.