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I have a bike that is no longer in production, but it has a standard drivetrain (FSA). I had some shifting issues the past couple days, and to my surprise when I did a clean/inspect, three of the 5 chainring bolts had dropped out and the other two were finger loose.

I salvaged some bolts from my donor bike. I needed a breaker attachment to my 5mm hex to get them off. There was no residual threadlock on the threads. Now I'm unsure how hard I should tighten them onto the first bike.

Why would they have come loose in the first place? How hard should I tighten them to prevent this from happening again? Would a dab of threadlock be good insurance?

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A Shimano "General Operations" manual states the tightening torque for road chainwheels is 12-14 N-m. For mountain bike chainwheels it's upped to 14-16 N-m for large and middle ring and 16-17 N-m for the smallest ring of a triple. The website: http://si.shimano.com/#/ The manual number I'm referring to: DM-GN0001-20-ENG.pdf Blue loctite or equivalent threadlocker is indicated here as well. I can't accurately surmise the cause of the loose and lost bolts in this specific case. However my experience with situations of loosening bolts or part failure due to "coming apart" in various mechanical settings often comes down to incorrect or incomplete tightening of the fastener (bolt, nut, etc). Part of this process is rechecking and re-torqueing after a break-in period of normal use.

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Park tool has a great reference Here (all inch-pound) Chainring bolt- steel

Shimano 70-95

Campagnolo® 84-120

Race Face&erg; 100

Truvativ® 107-124

Jury is out on thread lock on chain ring bolts. A do not believe a light thread lock will hurt ( until you need to remove them), but also believe correctly tightened bolts should not need it. The problem is the little two prong thing used to hold the nut is unlikely to allow a decent torque.

Better to give the threads a good clean and lightly grease the threads.

  • I use low strength loctite 222 on the bolts and always carry a spare chainring bolt – Vorsprung Nov 28 '18 at 13:01
  • If tightened to the correct torque, I have never had a chainring bolt come loose with the application of light grease. I agree that thread lock could cause more problems than help. – Rider_X Nov 28 '18 at 14:27
  • @Rider_X Do you mean to grease the inner threads so as to prevent crossthreading or grease the outside of the female part so that it plays more freely in the chainring recesses? Also what grease do you use? I will cinche down to bolts to the specified torques without chain lock and look after them for a week to see how they fair. – AdamO Nov 28 '18 at 15:04
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On my race BMX's I put cable ties through the chain ring bolts once they are correctly tightened as this prevents them falling out if they come loose. You need to still check them regularly to ensure that they have not come loose.

Cable ties are a good insurance policy to stop them dropping out.

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