Welcome to our Ask a Mechanic column where our expert mechanic Daniel Slusser answers your bike maintenance questions. If you have a question for Daniel, please post it on our Facebook Wall or e-mail Daniel directly at firstname.lastname@example.org. Today’s column features tips for solving chain suck (when your chain gets jammed between your chain rings and frame).
I am having problems with my chain getting stuck to my chainrings and wrapping around the bottom and jamming between my chainstay and chainrings. It is driving me crazy and wrecking my frame. Will new chainrings fix this, or is the chain the problem? From: Kyle
Chain suck (the name of the condition you describe), sucks. It always happens at the worse possible time, which is typically after executing a front downshift. I’ve seen frames get destroyed in extreme examples of chain suck when the rider is pedaling so hard they don’t notice the problem until after they have jammed the chain into the frame up front and ripped the rear derailleur off out back!
Damaged chainrings are the primary cause of chain suck. It is either caused by burrs on the chainring or extreme wear. The extreme wear scenario is characterized by teeth that resemble shark dorsal fins. These shark fin-like hooked teeth tend to grab onto new chains that don’t mesh properly with chainrings in this condition. Replacing the chainring is the only fix in this case. Chain suck caused by burrs on the chainring are an easy fix. Just look for sharp metal shards that extend from the base of the chainring teeth and use a small file to eradicate them.
Daniel Slusser is a professional bicycle mechanic with over ten years of experience. He holds a bachelor’s degree in business administration from HSU and a master’s degree in history from Cal Poly. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.