Torque values

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  • Torque values
  • thomthumb
    Member

    Just picked up a torque wrench, but the range is higher than i thought at 5- 25 Nm

    Do i need lower than this for bike stuff?

    Should I exchange it for something with a lower range.

    Premier Icon LeeW
    Subscriber

    It depends what’s written on the side of your stem/handlebar etc.

    Mine say 5.5Nm so I guess it’d be fine for me.

    dovebiker
    Member

    5Nm is pretty low, not even hand tight so as long as you’re not ham fisted you should be OK. The only type of things with torques that low are tiny screws and bearing adjusters where you’d be using small size Allen keys only.

    slowster
    Member

    5Nm is pretty low, not even hand tight so as long as you’re not ham fisted you should be OK. The only type of things with torques that low are tiny screws and bearing adjusters where you’d be using small size Allen keys only.

    5Nm is fairly common for the bolts used on stems. If your bike has a carbon steerer tube, then I would be far more concerned about tightening stem bolts with the correct amount of torque than any other component on the bike, given the potential for overtightening to damage – and possibly result in catastrophic failure of – such a safety critical component.

    I would either get one or more of the small bike specific torque tools which have a pre-set torque, or an adjustable torque wrench which has 5Nm nearer the middle of the scale, e.g. 0Nm-15Nm or 0Nm-20Nm. The Norbar brand is often recommended when this subject comes up on the forum.

    Premier Icon deadkenny
    Subscriber

    For general coverage of bike stuff you want low torque and high torque wrenches. Stuff like cassette lock rings, BBs, certain crank bolts (e.g. GXP) are way up in the 40-50Nm.

    Most the rest is down around 5 to 10Nm. And pretty much that’s hand tight.

    Depends what you want to check. Will it hold tight and not fall off? Thread lock and hand tight to what feels right. Or want to avoid overtightening and snapping a bolt, then torque wrench… BUT… needs to be routinely calibrated and be very careful with the spec where thread lock is used as it can screw up the torque. I’ve snapped pivot bolts doing them up to spec. Partly could have been thread lock, partly could have been shoddy torque spec on Santa Cruz instructions.

    I generally hand tighten small bolt stuff now. I use the big torque wrench though for the big stuff as doing it with a regular wrench getting it near enough tight but the torque wrench tells me there’s more to go.

    p.s. BBs & pedals – the reverse thread on one side is no go for the click type torque wrenches, even if it can be set to reverse.

    I personally wouldn’t worry much about accuracy of 5Nm torque on a bit of carbon. Steerers, stems, bars and seat tubes/posts can handle a lot. Plus, use carbon paste and you don’t need to do it up so much.

    Premier Icon vincienup
    Subscriber

    Depends how you look at it.

    #1 basic: any (affordable) measuring tool is more accurate around the middle of its range. This is why most tyre pressure gauges are crap for fatbikes and iffy even for Plus. They aren’t sufficiently sensitive at the bottom end of the measuring range to be useful.

    The actual range of 5-25Nm is probably going to cover pretty well the whole bike except maybe a crank bolt (not just GXP, RF have pretty high numbers that you really want a car wrench for if torquing them rather than just going for Yorkshire Tight.)

    The smaller stuff is all going to be in the 5-10Nm range usually, so depending if you plan to just do stem bolts or if you plan to torque a range of things, I’d go with Slowster’s suggestion of either a single setting dedicated unit or a pricier wrench rated 0-15Nm if you’re dedicated to correct torques.

    The other (sloppier, non Engineer) approach is to not see torque figures as set in stone numbers that must be hit accurately. You’re never going to send the wrench off for calibration and testing on schedule anyway. I have a cheapish 5-25Nm unit that I’m aware of the limitations of. I see it as getting the bolts in the ballpark more accurately than I could guess, and I’m fine with that. I guess if a person did a job where they were used to doing things up to small, measured torques on a frequent basis they’d get a reasonable feel for it without a torque wrench. I know I can guesstimate car-size torques reasonably accurately if I need to, but I need a little help with smaller numbers – 5 odd Nm is always less than I thought it would be… 😆

    As alluded to by deadkenny, the torque is only related to the tension (which is what you really want to know) if you know what the bolt should be.

    Bolts that aren’t intended to ever be undone (e.g. towbars) are often dry, and done up insanely tight (140Nm +1/8). If you put threadlock or grease on those you’d strip the threads or crack the bolt.

    That said pretty much everything on a bike should be cleaned and freshly threadlocked. Which is one of the reasons most stuff is very low torque, threadlock is very slippery until it sets so you get high tensions.

    Rule of thumb 5Nm is nipped up with the small end of an Allen key, 15Nm is the long end.

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