Hi Quoc,

the Rotor factory can be a bit overzealous at tightening the lock ring at times... My suggestion would be to head to the closest car workshop and just ask them to use their vise. Once you have opened it using a large monkey wrench or similar is usually enough.

Best
Nicolas

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power2max
http://www.power2max.com/northamerica
official power meter of Movistar Team