Tom's Chain Drop Fix
Like many folder owners with a multi-gear rear cog and a single gear front crank, I experienced sporadic and annoying chain drop. My chain would derail from my front crank during quick shifting. Bikes with multi-gear cranks have front derailleurs which help prevent this. Single gears cranks, obviously don't.After reading up on the issue [See Post by Gaerlan] I came up with a solution using a stock BMX/Downhill part, the KORE Chain Reactor.
The part itself is quite well made and installs without requiring you to take off your chain. You will need a small hex key (found on most bike multi-tools). Oddly the Chain Reactor came without printed instructions. I figured it out but if you have trouble, you can find instructions on their website.
Of course, the Chain Reactor wasn't made for this specific folding bike problem so I had to install it in an unconventional way. For starters, The Chain Reactor is designed to hang below the chainstay, pulling the chain upwards. Instead, I installed the clamp upside down so the tension arm pulls the chain down, instead.
My initial install had the roller resting upon the crank (circled). While this worked, it caused unacceptable amounts of vibration, felt through the pedals. Further mods were required.
I took the tension arm apart and re-installed the silver base plate upside down [lower arrow]. The tension spring, which is normally attached into small holes in the tension arm [upper arrow], now rests on top of the arm to help keep it down.
Now the arm rests lightly on the chain, dampening the wavelike motion cuasing during rapid shirts and helping to keep the chain from popping off the crank. Since the install, no chain drops. Problem solved.
Final Notes:
Because the arm is essentially free floating, it creates a bit more gear noise while pedalling. I may find a way to dampen this by adding weight or foam to the arm. Another possible solution may be to find a way to reduce the spring tension and re-installing the arm mounting plate right-side-up.
Given the different frame types found on folders, your set-up may need to be different. I encourage you to submit your results and reviews.
posted by tom @ 9:46 PM
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