How tight is 50nm?!

Viewing 35 posts - 41 through 75 (of 75 total)
  • How tight is 50nm?!
  • jkomo
    Member

    Simply tighten until your elbow clicks.

    Premier Icon molgrips
    Subscriber

    50nm is firm but not too bad with a normal ratchet.

    The hub bolts on my car are 200nm AND 180 degrees!  FFS.  200nm is really hard on the torque wrench, then I fit a long pipe to my breaker bar and heave as much as I can, I can only manage about 90 degrees.  I even bought a faffy little angle gague to do it accurately, what a waste of time that turned out to be.

    Premier Icon leffeboy
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    Anyone else twitching at ‘nm’? It is quite clear from the context what is meant but it still makes me twitch.  Need help

    Premier Icon molgrips
    Subscriber

    Sorry.  I meant nM of course.

    Premier Icon leffeboy
    Subscriber

    Was that stricktly neccessarie

    oldtalent
    Member

    Not as tight as I though as I sheared the bolt when refitting my x01 cranks with a normal sized ratchet.

    I am quite hamfisted though,

    thedude
    Member

    It’s a stupid design, always used Shimano with no torque wrench and never had a issue. I hoped the next generation would see direct mount chainrings with the pinchbolts but the new Xtr have dropped them and gone to one bolt like on the Sram and RaceFace:(

    Premier Icon richmars
    Subscriber

    <span style=”display: inline !important; float: none; background-color: transparent; color: #222222; font-family: ‘Open Sans’; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; line-height: 22.4px; orphans: 2; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; -webkit-text-stroke-width: 0px; white-space: normal; word-spacing: 0px;”>Anyone else twitching at ‘nm’? It is quite clear from the context what is meant but it still makes me twitch.  Need help</span>

    Yes, managed to wait until now to say that 50nm is a distance.

    spursn17
    Member

    Despite their bad reputation I’ve been using GXP BB’s with SRAM cranks (2 road bikes, and 1 MTB) for ten years with no problems. I put this down to torquing them up to 54nM every time I refit them. I reckon that doing them up too tight helps knacker the bearings.

    Premier Icon Poopscoop
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    I gave in last year and got a small bike specific wrench and a normal car type one for not much money.

    It’s strangely satisfying to feel that click and know that (decent calibration allowing) you are about on spec.

    The purchase of a carbon frame and components are really what prompted me to get the torque wrenches. A good investment I reckon.👍

    greyspoke
    Member

    Wikipedia says the symbol for newton metre is N m or N-m.  Dunno what an Nm is.

    fossy
    Member

    I’ve never used NM calibration, as most bike parts have always been at what’s speced – a little mechanical appreciation is expected – even 20-30 years ago you could wreck the parts if you were ham fisted – it’s the new ‘legal sheite’ that stuffs manufacturers.

    swoosh
    Member

    FFS it’s always N m with a capital N, as in the name Newton. The man was a genius, please give him the credit he is due.

    peaslaker
    Member

    50Nm on a crank bolt can be felt on most cranks as a sudden change in resistance as the crank bottoms out on the splines.

    I’m fond of this approach.  Seen too many stripped threads from click type torque wrenches.  Truth is that after everything is “tight” it is only ever a handful of degrees to stretch the typical fastener.  So feeling for when it goes tight is much more precise than a TW that might never click.  Correct fastener stretch is positional – the thread pitch ensures that.  Trying to back calculate position to a torque, affected by various sources of friction and measured by a mechanism that may be loaded off-axis and may or may not conform to anything approaching a calibration is topsy turvy.

    Spring type torque wrenches are more sensible.  Dial spring type torque wrenches are effective as you can see the point where the torque starts to ramp.

    Failing that (and preferred), using a proportionally sized lever helps you feel the nipped up point.  Small bolt, small lever.  Big bolt, bigger lever.

    jonnyboi
    Member

    apropos of nothing, the correct torque setting for anything made by magura is 0.00005 NM.

    Premier Icon leffeboy
    Subscriber

    Spring type torque wrenches are more sensible.

    Ah, now it’s pointed out it is obvious. I had always wondered what the point was but now I get it

    It’s a bit like weather gauges.  I always wondered why people had to tap them to get them to read properly and didn’t realise they are actuality designed that way

    The world is good.  Well, at least bits of it. Swype keyboards on phones still suck

    Not tight enough if you don’t use locktite 243 on the collar nuts holding your rear sprocket onto the carrier of your rear wheel on your KTM950SM☹️  Cheapskate garage that previous owner used……

    At work we have a special unit of Torque named after my old boss who worked on Harriers.  These used to shake a lot and everything was done up FT and loctited apparently.

    He carried this over onto his new industry where he’d often be heard going “little bit more, little bit more, fu@k it!”.

    So we named that amount in torque where you just begin to feel the threads collapse on any size bolt/screw/nut as “1 Spellman”.

    Just remember that next time you strip something😁

    daern
    Member

    These used to shake a lot and everything was done up FT and loctited apparently.

    FT is an ISO standard measure of torque these days…

    peaslaker
    Member

    apropos of nothing, the correct torque setting for anything made by magura is 0.00005 NM.

    Does big M mean “Mile”?

    Still a low torque value FWIW.

    Premier Icon Greybeard
    Subscriber

    [SI unit pedant]

    Confusing thread title!  50 nanometres is indeed a tight gap – but while 50 Nm is high for compared to most bike parts, it’s not really that tight; my car wheel nuts need 120 Nm.

    [/SI unit pedant]

    Premier Icon kelvin
    Subscriber

    Otherwise known as ‘farm boy tight’

    I’m pretty sure this is what it says in the GXP specs (or it should do).

    I carry an extra big tool when riding the bike with carbon SRAM cranks. No weight saved.

    escrs
    Member

    No worries – you have to bear in mind that my responses come from a man who owns a torque wrench but still relies on “hnnnnnnng” as I can either never find it or can’t be bothered to use it………..

    Same as me, bought a torque wrench for when i had to do a head gasket on my old Escort RS Turbo back in 2004

    Has been sat on the shelf ever since……

    Never use a torque wrench on a bike, all done by feel, even with 10k carbon road bikes

    Know of pro road bike mechanics who wont/don’t use them too

    Bit like Italian wheel builders who refuse to use a tension meter, they would rather “pluck” the spokes and listen to the frequency of each spoke to get the same tension

    Premier Icon molgrips
    Subscriber

    Wikipedia says the symbol for newton metre is N m or N-m.  Dunno what an Nm is.

    Sounds like rubbish to me. In science units are always placed next to each other like kWh or with a -1 superscript to denote ‘per’ like ms-1.

    Never use a torque wrench on a bike, all done by feel

    How do you know what it’s meant to feel like? I don’t think you do, you just think you do. I often don’t use one now but that’s because I own one and have used it in the past, so I do know what it’s meant to feel like.

    Stem bolts and disc bolts need far less torque than you think.

    shakers97
    Member

    1nm tighter than 49nm 👍🏼

    walleater
    Member

    When the force results in ‘just beyond a fart’ but also ‘just under a poo’.

    TiRed
    Member

    I’d like to see someone apply 1 nm. Hint 1 nM is of course nano mole  or 6.023 x10^14 molecules. Newton’s are always in capitals. Units matter.

    escrs
    Member

    How do you know what it’s meant to feel like? I don’t think you do, you just think you do. I often don’t use one now but that’s because I own one and have used it in the past, so I do know what it’s meant to feel like.

    Stem bolts and disc bolts need far less torque than you think.

    Well after 30 years of building cars and bikes including bikes for pro athletes Ive learnt to know when something is about to give or when something has enough pressure and needs no more

    Ive only had one or 2 bikes come back with an issue out of the 1000’s Ive built

    trail_rat
    Member

    “I’d like to see someone apply 1 nm. Hint 1 nM is of course nano mole  or 6.023 x10^14 molecules. Newton’s are always in capitals. Units matter”

    Context is importanter.

    trail_rat
    Member

    “Never use a torque wrench on a bike, all done by feel, even with 10k carbon road bikes

    Know of pro road bike mechanics who wont/don’t use them too

    Bit like Italian wheel builders who refuse to use a tension meter, they would rather “pluck” the spokes and listen to the frequency of each spoke to get the same tension”

    Those two things are nothing alike.

    One is guessing the other is a measure.

    Premier Icon gofasterstripes
    Subscriber

    Most all bike fasteners will be tightened into the elastic clamping zone, to some degree. This should be detectable as a sharp uptick in the perceived resistance as the joint moves beyond frictional and alignment/seating torque. An experienced mechanic will likely be able to judge the feeling of this transition and perhaps will then apply the correct degree of rotation beyond that point, corresponding to an appropriate degree clamping load on the joint…or not.

    http://www.pcb.com/Contentstore/mktgcontent/WhitePapers/WPL_23_Understand_Torque-Angle.pdf

    Worth a look to understand the feel of doing up a bolt.

    Point of interest, approx 70-90% of bolt rotation resistance is frictional, so don’t grease threads and apply a torque measurement for non greased joints, dropping friction by, say 50% could cause you to hugely overtension the bolt.

    Premier Icon ratherbeintobago
    Subscriber

    But that is the SRAM way

    I thought the SRAM way also involved coming out with interesting ideas then not developing them any further (See: Hammerschmidt and Automatix hub)

    Premier Icon molgrips
    Subscriber

    Well after 30 years of building cars and bikes including bikes for pro athletes Ive learnt to know when something is about to give or when something has enough pressure and needs no more

    But you don’t do bolts up until they are ‘about to give’ – that’s usually too tight.

    The torque for a bolt depends on all sorts of things, including what it’s clamping.  I used to do the same as you, then I got a torque wrench and I realised that sometimes I was okay, and others I was too tight.  For example, as I had endless trouble with my Marzocchi forks I ended up taking them apart a lot.  I did the legs up to what seemed reasonable and not too tight, but after twenty or so goes the bolt/valve stem snapped.  Under-specced, perhaps, but the official torque specs really aren’t very tight and I’d been overdoing it.

    Of course at this point you’ll assume I’m a ham-fisted idiot who has no clue mechanically (I’m not)…  so I don’t even know why I’m posting this 🙂  Fortunately for you and everyone else who doesn’t use a torque wrench, the margin of error is usually pretty big.  Before I got a wrench I never had issues either except maybe a couple of disc brake bolts when I first got disc brakes.  The torque on those is really low btw.

    greyspoke
    Member

    I’d like to see someone apply 1 nm. Hint 1 nM is of course nano mole or 6.023 x10^14 molecules. Newton’s are always in capitals. Units matter.

    A bit of a non-sequitur there, how does explaining what an nM is help judge what an nm is?

    greyspoke
    Member

    Also the abbreviation for a mole is mol, presumably because the metre had already bagged m.

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