Ask a Mechanic | How to Tell When Your Derailleur Cable is Shot

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 Today’s column is in response to a question from YouTube and reviews how to determine when cables need to be replaced.
Question: Hi! Great video, I ran through the entire process. Hi and Low limits are set, It seems to shift fine (smallest cog to biggest) but won’t come off the big cog until I click the shifter a few times. I’m confused about the cable tension. Do I undo the anchor bolt, pull the cable tight as possible with the barrel adjuster turned all the way in? I think I am almost there but just need some fine tuning. From: YouTube

Answer: The problem is likely with your shifter cable. Check to see if the cable is corroded under the housing. To check this, shift to the smallest cog and pull the shifter housing out of one of the bosses on the frame; this will allow you to slide the housing and see the cable underneath. If it is corroded, or there is a lot of friction, replace the shifter cable. Dripping some chain lube inside the housing can help too, but may not completely fix it. If the corrosion is really bad, replace the housing as well.

On your question regarding how to set cable tension, you have the right idea. Just follow this process when you replace your cable.

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.