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Torque wrench settings – maximum or exact?

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  • December 5, 2015 at 5:33 pm #25129
    Dan S

    I’m looking at getting a torque wrench for Xmas (we do fancy gifts in my family…) and am considering a small preset one from Park.  I’m wondering which to go for, if any.

    Everything on my bike seems to want to be tightened to 6Nm apart from the stem.  Brilliantly, that wants 6Nm where it grips the bars but only 5.5Nm where it grips the steerer.  Leaving aside why anybody would design a stem like that, would I be OK with a torque wrench set to 5Nm or is that going to leave the bars not tight enough?  I take it 6Nm is no good for a bit that says 5.5…

    Or do I need to go adjustable?

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Viewing 6 replies - 1 through 6 (of 6 total)
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  • December 7, 2015 at 10:47 am #863671
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    hampstead_bandit

    @Dan S

    @Dan S

     

    yeah, the fitting I was talking about is the internal seat clamp in the frame, that secures the seat post in place. 

     

    https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTOC_hGEgEMfhKZMcNUfRgA6EzvSBdKc_E-bSsuqAKocqabO1Qx

    your link to that review is the wrench I recommended. it also has a switch for left hand thread/ right hand thread operation (this is not for loosening bolts, torque wrenches should never be used for loosening bolts)

    I believe Giant are redesigning their torque wrench with a smaller head, as the current one fouls the seat post when trying to use it on the Propel seat clamp! 

    December 7, 2015 at 9:19 am #863669
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    scrumpydave

    If it helps I bought a preset

    If it helps I bought a preset 5Nm torque ket for my carbon frame (alloy bars/stem, carbon seatpost) and even though all the torques required are between 5nm and 6nm I use the same key with carbon assembly paste where appropriate with no slippage issues. 

    December 6, 2015 at 4:24 pm #863667
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    Dan S

    Thanks for that.  I confess I

    Thanks for that.  I confess I hadn’t even checked whether the seat post needed a torque wrench (it’s a new bike and I’ve only ever ridden steel before!).

    Just to confirm, you mean the clamp that stops the seat post dropping inside the seat tube, rather than the clamp that holds the saddle rails?

    The one you recommend: is it this one: http://www.bikeradar.com/gear/category/tools/torque-wrench/product/review-pro-torque-wrench-27926/ ?

    December 6, 2015 at 9:44 am #863665
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    hampstead_bandit

    hybrid forks on giant road

    hybrid forks on giant road bikes are carbon fork blade/ crown and aluminium alloy steerer tube

    its only on Advanced Pro and SL frameset you get full carbon fork

     

    for your Propel I’d strongly recommend the “Pro” brand torque wrench set (its sold under several brand names), it has an extension bar which allows the bit to reach the seat clamp bolt

    some torque wrenches including Giant’s own model and often the preset ‘ritchey style’ tools will foul the rear of the seat post and prevent the bit sitting square in this bolt.

    on the propel its very important to set torque correctly on this bolt as using a hand tool will give the false impression the clamp is tight, if you then set bolt to torque you will be surprised at the number of inputs you need before clamp is actually tightened properly

    I have seen Propels with the back of the seat tube cracked by customers just using a hand tool on this bolt, then sitting down and the seat post slipping 🙁

    be sure to give the inside of the seat tube and the clamp faces a good smear of fibre grip / carbon paste before installing the seat post. another tip to allow you to remove the seat post is to loosen the seat clamp and then grab the saddle and give the saddle/post a sharp rotation tug which will jump the seat clamp wedges apart to loosen the clamp (it can get stuck)

    December 5, 2015 at 11:17 pm #863663
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    Dan S

    Thanks.  It’s a Propel

    Thanks.  It’s a Propel Advanced, so bars and stem are alloy while the steerer is “hybrid”, whatever that means.  The aero bars are carbon (yes, I’m a triathlete: sorry!).

     

     

    December 5, 2015 at 10:40 pm #863661
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    CanAmSteve

    Realistically, either 5Nm or

    Realistically, either 5Nm or 6Nm will probably be fine. You don’t say if the bits are steel, alloy or carbon – with carbon being fussiest.

    To begin with, torque wrenches are often not that accurate (better at repeatability, but that also varies with quality). It’s a bit like the man with two watches (The man with one watch always knows what time it is – the man with two watches is never quite sure.)

    Add in that torque values can be wet or dry (but rarely is this mentioned) and that (for example) you would always lubricate stainless steel into stainless steel to prevent galling, or possibly use threadlock (which is a lubricant while still liquid) or grease (since galvanic action can “freeze fasteners) and you have a very wide range of actual torque values.

    There is special “friction compound” for carbon/carbon interfaces that is essentially sand in the Vaseline, to both preclude freezing parts bit also provide friction and prevent slippage under the low torque specified.

    Bottom line, go easy and you should be fine

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