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Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,088
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
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Actually M8 is the threading dimension spec, not the wrench size, and also M8 is not the diameter of thread pitch of many chain ring bolts. The common two piece CR bolt is a 8x.75. As in 8 mm diameter and .75mm per thread. A M8 has a 1.25mm per thread pitch. The two piece bolt and nut has a 10mm OD to the nut, the part that needs to fit within the ring and crank arm fitting.
Don't forget to grease the bolt and nut, then recheck the tightness after a few rides. Andy.