Using a torque wrench correctly

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Using a torque wrench correctly

Postby InTheWoods » Sat Feb 02, 2013 12:16 am

This might be a dumb question but there are meant to be no dumb questions right...

I have an aero carbon seat post on my new bike :mrgreen: And a torque wrench :|

The seat binder has the usual 2 bolts with one facing each way. Is the correct method to tighten them up:

[Edit: When I say seat binder I mean the seat clamp that stops the seat post sliding down the seat tube so you have the correct saddle height]

a) gradually tighten them up, doing each bolt a bit at a time and alternating between them, until the torque wrench gives way on each bolt just once

or

b) using a) above ...but normally once you tighten one bolt to the correct torque, the other bolt is then loose and needs tightening again. This might need to be repeated a few times until the torque wrench gives way on each bolt without any further progress.

or

c) (starting with both bolts loose) tighten one bolt all the way up till the torque wrench gives way, then do the other one.

Is the process the same for doing the 4 stem handlebar clamp bolts?
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by BNA » Sat Feb 02, 2013 4:10 am

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Re: Using a torque wrench correctly

Postby human909 » Sat Feb 02, 2013 4:10 am

InTheWoods wrote:b) using a) above ...but normally once you tighten one bolt to the correct torque, the other bolt is then loose and needs tightening again. This might need to be repeated a few times until the torque wrench gives way on each bolt without any further progress.


This is the correct process as it will result in all bolts being at the correct torque thus the total clamping force being at the correct force.

InTheWoods wrote:Is the process the same for doing the 4 stem handlebar clamp bolts?

Yes.
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Re: Using a torque wrench correctly

Postby InTheWoods » Sat Feb 02, 2013 7:52 am

Phew!

Thanks human.
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Re: Using a torque wrench correctly

Postby jasonc » Sat Feb 02, 2013 8:26 am

human909 wrote:
InTheWoods wrote:b) using a) above ...but normally once you tighten one bolt to the correct torque, the other bolt is then loose and needs tightening again. This might need to be repeated a few times until the torque wrench gives way on each bolt without any further progress.


This is the correct process as it will result in all bolts being at the correct torque thus the total clamping force being at the correct force.

InTheWoods wrote:Is the process the same for doing the 4 stem handlebar clamp bolts?

Yes.


as above, i always do them up (evenly) a bit at a time, and then "torque" them
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Re: Using a torque wrench correctly

Postby beanspropulsion » Sat Feb 02, 2013 9:14 am

Don't forget to loosen the lock nut on the wrench after use.
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Re: Using a torque wrench correctly

Postby RonK » Sat Feb 02, 2013 9:36 am

Where are multiple fasteners the aim is always to tighten them evenly, so (b) is correct.

It's probably going OT for seat post and stem fasteners, but you could initially set the wrench at a lower torque and tighten the fasteners in stages. This is standard practice in the automotive world.
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Re: Using a torque wrench correctly

Postby toolonglegs » Sat Feb 02, 2013 4:51 pm

Yes start at lower torque and work up... evenly between the number of bolts.
Make sure its a good torque wrench.
Make sure the threads are pristine as this affects the torque a large amount... use a light lube if possible of the threads.
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Re: Using a torque wrench correctly

Postby InTheWoods » Sat Feb 02, 2013 6:08 pm

Will do the starting lower thing next time. brand new frame so threads pretty clean :)
I didn't torque it to the max labelled on there anyway.

It's the torpedo 7 wrench which I've seen in another thread on here.

It's kind of scary that too tight = broken frame and too loose = broken frame as if post goes down while I'm sitting on it, it will hit the part of seat tube that changes shape and gets narrower.
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