Ask a Mechanic | Fixing Gummed Up Cables

Shimano Dura Ace CableWelcome 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 

Question: I just had my local bike shop replace the derailleur cables on my Cervelo R3 Ultegra and after two rides they aren’t shifting right anymore and the shifting feels terrible. So frustrating! Can you help me figure out how to get it shifting right again? From: Cole

Park 4th Hand Tool

This Park BT-2 tool is the one you need to get your new cables pre-stretched.

Answer: It is not uncommon for mechanics to forget to pre-compress derailleur cable housing (or stretch the cable, depending which side of that argument you are on), and this can lead to derailleurs going out of tune soon after getting cables installed. The videos below will show how to get your derailleurs properly tuned, but you may have an entirely different problem.

My bet is that you have some sports drink that has spilled from your water bottle and ran down your downtube to the bottom bracket. The sugar in the mix crystalizes on the cable guide and gums up cable as it goes through your Cervelo’s cable guide. That is the likely reason why your shifting feels terrible. The good news is that a little soap and water is all you need to clean up the mess. Just get a sponge and saturate it with soapy water to scrub on the exposed section of cable that runs under the bottom bracket. Once all the black gooey stuff is off of the cable, your work is done. Applying chain lube to the cable and cable guide will help to keep the cables moving freely even when they are covered in sugar. Just remember that the sugar will always win out in the end. It might also be time for new water bottles that drip a little less.

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.