Tightening my Nuts

photonic69
photonic69 Posts: 2,416
in The workshop
So you know when you have two bolts to tighten to a specific torque e.g. stem bolts on the steerer or a two bolt collar on a seat post. You tighten them in turn and use a torque wrench for the final tightening. Tighten bolt A to 5Nm then bolt B to 5Nm, then go back to bolt A and you need to turn it quite a bit more to get 5Nm on the wrench again. Then back again to bolt B and the same thing. Surely this is tightening the clamp a lot more than the first 5Nm and risks deforming the seat post or steerer. I always err on the side of caution but what is the correct way and final torque?

This puzzles me and keeps me awake at night, leaving me feeling miserable and tired in the morning. So much so I shout at the dog and kick the cat, not that we have a dog or a cat.


Sometimes. Maybe. Possibly.

Comments

  • lincolndave
    lincolndave Posts: 9,441
    Just tighten the once, never had anything come loose or drop off
  • masjer
    masjer Posts: 2,558
    For me, re-tightening (in stages) each bolt in turn until they're at the same torque is best practice- both bolts are then set at the required (equal) torque. It doesn't mean the part will be over-torqued.
    When a part (stem etc) has a torque figure on it eg 5NM it usually means the maximum torque (for the part), not the required torque. I usually go a bit lower than this.
  • First.Aspect
    First.Aspect Posts: 14,623
    I don't own a torque wrench. As soon as the Allen key starts to bend or the carbon fibre starts to crack I give things a last little tighten and bobs your uncle.
  • veronese68
    veronese68 Posts: 27,297
    I'm relieved this isn't another thread about the home secretary
    Kinesis Pro6
    Marin Nail Trail
    Cotic Solaris
  • mully79
    mully79 Posts: 904
    Torque on a bolt is exactly that. The torque on the bolt.
    It doesnt necessarily relate to how tight the clamp is that the bolt is trying to tighten.

    Alignment of the clamp (ie on a stem with two bolts) means that the torque isnt relevant until the clamp is aligned square.

    If a thread is poor then the higher friction required to turn the bolt results in less clamp force for a given torque.

    In a sense torque settings are generally only truly relevant on new bolts in new threads.

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