Originally Posted by
WhyFi
Are you launching your bike in to space or are you tightening some fasteners enough so that parts stay put without breaking said parts? You really don't need the utmost in accuracy and you really shouldn't be tightening to a max spec - you should be tightening until things stay put.
Not quite sure what you meant by your post WhyFi. But will both support it and also provide a counterpoint.
OP, I believe what WhyFi meant and somewhat analogous btw to powermeters...lol...sometimes good accuracy but not perfect accuracy is good enough. Of course this can go over people's heads and I believe what WhyFi somewhat meant. Proof of this are thousands of guys like me who have been wrenching on carbon fiber bikes since they were invented both with and without a torque wrench. A skilled mechanic can build a carbon fiber bicycle day in without a torque wrench and therefore having one that say has 5-10% error in calibration is 'ok'. Most talented bike mechanics are probably no more accurate or a bit less by hand without a wrench. This begs the whole stress/strain engineering analysis of how torques are even derived. This is based upon a predicate of boundary conditions. Assumption about geometry and material properties. There is room for debate even with this protocol.
But...and perhaps WhyFi was looking through his own particular lens which is common with opinions. People aren't the same. There is a range of 'ham fistedness' in the world of people that attempt to work on a bicycle. Some people should never torque carbon fiber bike parts without a torque wrench.
There is also a pitfall worth mentioning. Under torqueing isn't good with carbon fiber. There is greater stress on parts by undertorquing and potential slippage. Undertorquing aka incremental part creep under load can be as hazardous to carbon fiber as excessive compressive load due to over torqueing. So FWIW for those who tend to error more on the low side. Too low isn't good for your bike either, even without discernible slippage.
So, nominal torqueing....or good ballpark torqueing to spec I believe is the sweetspot. For example most torque spec's for the seat binder bolt which is a 4mm hex on most bikes...is 5 N-m or 5.5. In that range. I could get into the whole derivation of torque ranges which btw is a complex analysis but unnecessary here. Set your torque wrench for 5 N-m and you are good.