Just a heads up that will hopefully save someone some headaches in the future.
Shimano lists the torque values for the inner chainring bolts at 12-14NM. Based on my experience tonight, and the part reviews all over the various sites, this torque value is far too high and resulted in at least one completely sheared bolt head.
During a normal ride on the 4th of July, I developed a mysterious click at each pedal rotation when my right crank arm was at approx. 10 o'clock. Attempted to diagnose on the road but coasting, backpedaling, single leg pedaling I couldn't nail it down.
Tonight during a short Zwift ride, the problem was still present and while being able to look straight down at my crankset, it looked like one of the inner chainring bolts was VERY close to my chaincatcher compared to the others. Crawling under the bike confirmed one of the chainring bolts had backed out to less than fingertight. I looked up the torque values from Shimano and grabbed my PRO torque wrench and T30 socket only to find that not only was that one loose, but all of them were a full turn loose from 12NM. These cranks have approx 3500mi on them and were factory assembled and have never had the chainrings disassembled.
Upon tightening to the minimum published value, one of the heads promptly sheared its alloy head off before reaching spec. This bike gets cleaned after every ride, stored indoors, etc.
When the replacement bolts arrive (changing all 4 just to be safe since these are likely all stretched now), I will experiment with 8NM and blue loctite and hope to avoid any drivetrain noise while also preventing the bolts from backing out again.
Shimano lists the torque values for the inner chainring bolts at 12-14NM. Based on my experience tonight, and the part reviews all over the various sites, this torque value is far too high and resulted in at least one completely sheared bolt head.
During a normal ride on the 4th of July, I developed a mysterious click at each pedal rotation when my right crank arm was at approx. 10 o'clock. Attempted to diagnose on the road but coasting, backpedaling, single leg pedaling I couldn't nail it down.
Tonight during a short Zwift ride, the problem was still present and while being able to look straight down at my crankset, it looked like one of the inner chainring bolts was VERY close to my chaincatcher compared to the others. Crawling under the bike confirmed one of the chainring bolts had backed out to less than fingertight. I looked up the torque values from Shimano and grabbed my PRO torque wrench and T30 socket only to find that not only was that one loose, but all of them were a full turn loose from 12NM. These cranks have approx 3500mi on them and were factory assembled and have never had the chainrings disassembled.
Upon tightening to the minimum published value, one of the heads promptly sheared its alloy head off before reaching spec. This bike gets cleaned after every ride, stored indoors, etc.
When the replacement bolts arrive (changing all 4 just to be safe since these are likely all stretched now), I will experiment with 8NM and blue loctite and hope to avoid any drivetrain noise while also preventing the bolts from backing out again.