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The Rotafix Method

By Brad Quartuccio

The rotafix method is a technique to install or remove a fixed cog without a chainwhip, turning the frame and wheel into a no-slip tool with loads of leverage. Attributed to the Italian track racer and master mechanic Giovanni Pettenella, this method allows you to quickly and easily install a new cog properly (tight!) or remove a stuck cog without cursing.

Facing the drivetrain as in inset A and with the chain removed from the chainring and slack on the bottom bracket shell, you will turn the wheel counterclockwise to thread a cog onto the hub. Start by taking up the slack in the chain by slowly rotating the wheel and stacking the chain up on itself as in inset B. This will make the chain fully wrap around the cog and become tight against the bottom bracket shell, effectively turning the entire wheel into a chainwhip that can’t slip. Continue turning the wheel and the cog will be installed as tight as possible, ensuring a long hub life once that lockring is installed to keep everything snug. Reverse directions and turn the wheel clockwise to remove even the most stuck cog. If it doesn’t come off with the rotafix method, it’s not coming off.

With this great power of leverage comes great responsibility. It is feasible to overtighten a cog with this method, pulling the threads clear off the hub. It is also possible to cross-thread a cog completely on, once again ruining the hub threads. As for removing a cog, be sure to remove the lockring first to avoid carnage. Delicate bottom bracket shells should be protected with a rag, this method is likely to leave marks in fancy paint and aluminum frames.