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 explains proper torque application for cassette lockrings.
Question: I recently noticed that my cassette seemed to wobble a bit, not while spinning, but to the touch when I held it and moved it laterally with my hand. I took the wheel off and then was able to loosen the lock ring with my hand. So I figured it was too loose. Tightening it noticeably lessened the wobble.
However, I noticed it had what seemed to be a torque measurement. I tightened it down pretty good. It sort of clicks as I did it. I did not use close to all the force I could. On forums I’ve read that even bike shop mechanics don’t torque down a cassette. What do you think? From: Bob
Answer: I’ve never worked with a mechanic that used torque wrenches when installing a cassette, because the max torque spec is incredibly high for a bicycle part. Shimano’s Dura Ace lock ring calls for 40nm of torque! For an aluminum part that is often interfacing with another aluminum part, that is very, very high. Compare that to a stem bolt with a MAX torque of 6nm (go to 8nm and I guarantee they will strip out).
Park chain whips have a hex broach in them to fit Park’s Shimano lock ring tools and those chain whips are a little over a foot long. An experienced mechanic likely applies about 30nm of torque using this huge tool. I’ve seen other mechanics put the cassette tool in the vice and use the wheel as the wrench (effectively a two foot long wrench). I would estimate that the knurling on the 11-tooth cog and lock ring ensures that they won’t wobble loose if torqued past 10nm. I’ve never had one come loose on me and I’ve even used 6″ long wrenches for lock ring installation on some of my personal wheels at home. Bottom line: give it a good solid torque and you should be fine.
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.