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 ourFacebook Wall or e-mail Daniel directly at email@example.com.
Question: I am having problems getting my Sram Red rear derailleur to shift down to the 11 tooth cog on my cassette. I have the limit screw backed out all the way and it still hesitates to shift. The hanger looks straight so I am baffled at what the solution is. Any ideas? From: Andy
Answer: Experiencing redshift issues? I am no physicist but I think I can help.
First I would check the cable to make sure it is not binding in the housing. At the small end of the cassette there is very little tension on the cable because the derailleur’s return spring is not stretched very far. Check this by shifting into the large cog and then releasing all the cable tension at the shifter by up shifting. Just don’t pedal the bike so the chain will stay on the big cog. Pull on the exposed cable while performing the shifts to make sure the cable is fully released. Once you have done this you will be able to remove the cable housing from the frame’s cable stops without having to undo the cable anchor on the derailleur. This will allow you to slide the housing up and down the cable to check for drag. If there is a lot of drag, try lubing the cable with a light oil like TriFlow or T9. If this doesn’t cure the drag then replace the cable.
If a binding cable is not the problem then it is time to employ a DS Secret Trick™ to alleviate your shifting woes. You need to place a washer behind the derailleur hanger bolt in order to place the derailleur further outboard thereby increasing the spring tension within the derailleur throughout the entire gear range. The type of washers I use are steel 3/8” axle washers commonly used on cruisers and bmx bikes. You can find them at the hardware store. Once the washer is installed simply readjust your limits and cable tension to compensate for the new position of the derailleur and you will be ready to charge into that 11 tooth cog for your sprint down the final straight in your next race!
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 University. When he is not riding, wrenching, or writing he enjoys spending time with his wife and two children.