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  1. #1
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    Newton and his meters of force (8nM tightening)

    So I got a new pair of carbon bars today, Truvativ Noirs, and after I finished intallin' them on my rig, I took a look at the "manual" (you know the 10 language tiny font piece of onion paper &$#*@!.) Whew, anyway, they say to tighten to no more than 8nM. Now I don't know what 8nM feels like, but it there an equivalent "human" scale? You know, hand tight, one quarter crank past hand tight, put your weight into it and crank that puppy down, etc. Anyone know this mysterious Newton and his meters?

    Many thanks,

    Noir.
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  2. #2
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    I would not stick my neck out installing carbon parts without a torque wrench. Too low torque the bars slip, too much they crack.
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  3. #3
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    I use Ritchey WCS bars and stem, i never needed a torque wrench. Always used a short allen key to give me just enough leverage to tighten beyond the slipping point but no more. Developed a pretty good feel in the process, and when checked with a torque wrench i always crank it down 10-15% under spec.

  4. #4
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    are these bars on a 29er or 26er?
    -It's time to shred some mild to moderate gnar!!

  5. #5
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    both, neither, doesn't make a difference texass. <

    How about my stem choice? I've heard mutterings about stems being "incompatible" with carbon. Any way to tell/check? I suspect it doesn't Really matter too much because otherwise all the stems would be labeled one way or the other.
    Jamis Dakota '06
    Jamis Sputnik '10

    We're all wrong.

    2 meters tall. 13.37 Stone. Yeah, I'm a freak of nature.

  6. #6
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    But, being in the 29er forum, you'd be safe to assume a 29er..
    Jamis Dakota '06
    Jamis Sputnik '10

    We're all wrong.

    2 meters tall. 13.37 Stone. Yeah, I'm a freak of nature.

  7. #7
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    Quote Originally Posted by NameTaken View Post
    So I got a new pair of carbon bars today, Truvativ Noirs, and after I finished intallin' them on my rig, I took a look at the "manual" (you know the 10 language tiny font piece of onion paper &$#*@!.) Whew, anyway, they say to tighten to no more than 8nM. Now I don't know what 8nM feels like, but it there an equivalent "human" scale? You know, hand tight, one quarter crank past hand tight, put your weight into it and crank that puppy down, etc. Anyone know this mysterious Newton and his meters?

    Many thanks,

    Noir.

    Buy a torque wrench .... then you'll know exactly what 8 N-m feels like

  8. #8
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    Quote Originally Posted by elgordo View Post
    Buy a torque wrench .... then you'll know exactly what 8 N-m feels like
    Not really. Torque wrenches dont have the same feel as a small allen wrench.

  9. #9
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    In human terms, it feels like a little less than 6 ft#. If you don't know how to measure this, I'd either stick with metal bars or get someone that knows what they are doing install it. Or both.

  10. #10
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    Quote Originally Posted by syl3 View Post
    I use Ritchey WCS bars and stem, i never needed a torque wrench. Always used a short allen key to give me just enough leverage to tighten beyond the slipping point but no more. Developed a pretty good feel in the process, and when checked with a torque wrench i always crank it down 10-15% under spec.
    This is not the best advice I've ever heard. You can't know if you are just past the slipping point unless you tighten->ride->it slips->tighten->ride->it slips->tighten->ride->doesn't slip. You get my point? Also, if you are 10-15% below spec, then you are well under the factor of safety built into that spec. Beyond that...if you install the fastener by hand and then check with a torque wrench, you're readings will be skewed high because of the difference between static and kinetic friction.

    I'm sorry, but I've known a lot of good mechanics in different fields and nobody has a calibrated hand. If it is a torque critical application they will use a torque wrench.

    I'm sure some bar stem combos are less sensitive to torques, but why risk your purchase...spend a few bucks on a decent torque wrench, and buy yourself some peace of mind.

  11. #11
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    Quote Originally Posted by NameTaken View Post
    How about my stem choice? I've heard mutterings about stems being "incompatible" with carbon..
    incompatible how? uneven pressure on the bar? if you mean slipping, use friction paste when installing a carbon bar.

  12. #12
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    Torque wrenches aren't that expensive versus buying another set of bars. So many parts come with torque specs on them these days that the torque wrench is pretty much THE most vital tool in the box.

    Friction paste is also a must.

  13. #13
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    It would not surprise me to learn that every rider who owns a torque wrench had a bad experience over-torquing a part, which caused them to spend money on the replacement part that would be in the ball park of the cost of a torque wrench. Learn from others, and get a torque wrench. If not now, sooner or later with the ever-increasing number of carbon parts around, you will crack or break a part, and hopefully that failure doesn't occur in the midst of a ride - the laws of physics do not cease to exist just because you tried your best to guess on the torque. Plus, there is the satisfaction of knowing that the parts have been properly torqued when you are hammering and really put stress on the bike.

  14. #14
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    excellent advice... +1

    Torque wrench is way less expensive than the replacement bar...

    Quote Originally Posted by keeb View Post
    This is not the best advice I've ever heard. You can't know if you are just past the slipping point unless you tighten->ride->it slips->tighten->ride->it slips->tighten->ride->doesn't slip. You get my point? Also, if you are 10-15% below spec, then you are well under the factor of safety built into that spec. Beyond that...if you install the fastener by hand and then check with a torque wrench, you're readings will be skewed high because of the difference between static and kinetic friction.

    I'm sorry, but I've known a lot of good mechanics in different fields and nobody has a calibrated hand. If it is a torque critical application they will use a torque wrench.

    I'm sure some bar stem combos are less sensitive to torques, but why risk your purchase...spend a few bucks on a decent torque wrench, and buy yourself some peace of mind.

  15. #15
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    as a professional bicycle mechanic (working as a workshop manager in a busy workshop with a high number of mechanics working for me) one of my regular tasks is to assess the work my mechanics are producing, which involves lots of investigation of both PDIs on new bikes and QC of repair work

    the first tool I reach for is the RS torque measurement wrench, and with some of the less experienced mechanics, the results can be quite shocking, as they often ignore the torque wrench in favour of their Park P-Handle allen wrenches (despite my constant advice)

    its SO easy to get torque wrong when working by hand, and I see this a lot with customers who have done their own wrenching at home and damaged components because they have not used a torque wrench

    my advice? buy a quality (does not mean expensive) torque wrench and use it every time you work on your bike

    not just talking about working on CF finishing kit, but every bolt on your bicycle will benefit from use of a torque wrench - including cassette lock rings, disc brake mounting bolts, headset cap bolts, crank bolts, etc.

    the torque you "think" you are using when you do it by hand, is often very different to where it needs to be when actually checked with a torque wrench

    be aware that torque wrenches do need re-calibration, although for a home mechanic this is less of an issue, as in my workshop I am using this tools dozens of times every single day

    also, be very aware that simple mistakes like getting grease under the head of a bolt on your stem faceplate will allow you to over tighten the bar clamp whether using a torque wrench or allen key to tighten (the grease reduces the rotational friction between the bolt head and stem clamp surface, giving a false torque reading)

    its a little scary how little information is put out about this, only Thomson and Easton seem to include this info with their products?

  16. #16
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    with proper torque, there are no incompatible stems...

  17. #17
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    Quote Originally Posted by keeb View Post
    This is not the best advice I've ever heard. You can't know if you are just past the slipping point unless you tighten->ride->it slips->tighten->ride->it slips->tighten->ride->doesn't slip. You get my point? Also, if you are 10-15% below spec, then you are well under the factor of safety built into that spec. Beyond that...if you install the fastener by hand and then check with a torque wrench, you're readings will be skewed high because of the difference between static and kinetic friction.

    I'm sorry, but I've known a lot of good mechanics in different fields and nobody has a calibrated hand. If it is a torque critical application they will use a torque wrench.

    I'm sure some bar stem combos are less sensitive to torques, but why risk your purchase...spend a few bucks on a decent torque wrench, and buy yourself some peace of mind.
    I have a torque wrench i just don't use it on bars and stems anymore. You can get a calibrated hand if you always use the same length allen.

    i have had a single instance of slip caused by not paying attention while switching bars and eating gels 5 minutes before a race, but i have not cracked any bars so far.

    disclaimer: i assemble ~20 bikes per week, if you want to learn this at home do yourself a favor and at least replace titanium stem bolts, you will **** them up.

  18. #18
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    Quote Originally Posted by osokolo View Post
    with proper torque, there are no incompatible stems...
    that's not true, contact area is very important. stem design makes a huge difference, specifically one piece vs 2 piece fastenings

  19. #19
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    Quote Originally Posted by hampstead bandit View Post




    also, be very aware that simple mistakes like getting grease under the head of a bolt on your stem faceplate will allow you to over tighten the bar clamp whether using a torque wrench or allen key to tighten (the grease reduces the rotational friction between the bolt head and stem clamp surface, giving a false torque reading)

    its a little scary how little information is put out about this, only Thomson and Easton seem to include this info with their products?
    Greasing the heads of the bolts will have no negative effect on the proper torque. If anything the opposite is true; you'll get a false reading due to added friction.


    http://www.bikethomson.com/blog/wp-c...X2-BMXFull.pdf

    Torque wrench - Wikipedia, the free encyclopedia

  20. #20
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    8nm is a fair bit of torque for a carbon bar. I would be surprised if you over torqued it. However it's always ideal to have the right tool for the job. With bicycles getting lighter and lighter and consumers expecting the same durability I think that proper installation is mandatory. Working on bicycles isn't hard but when working with higher end parts it does take a certain amount of care to do things correctly.

  21. #21
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    OP, 8nM is not much. If you are just starting to wrench on more expensive parts I highly recommend buying a torque wrench. They aren't expensive and can save their cost with just one broken part.

    For others, if you are working on your bike feel free to wing it. If you are working on my bike you better be using a torque wrench...
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  22. #22
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    Quote Originally Posted by customfab View Post
    8nm is a fair bit of torque for a carbon bar.
    Never even noticed that part of the post.

    Most of the stems I've owned/own had/have a 5nm recommended torque.

    I love my torque wrench, and it sees way more use than I would've ever imagined.

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  23. #23
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    can you list a few carbon bar INCOMPATIBLE stems please?

    I have stems with both one piece and 2 piece fastenings. The only difference is weight...

    However - I would appreciate some factual explanation with examples... Thanks...

    Quote Originally Posted by syl3 View Post
    that's not true, contact area is very important. stem design makes a huge difference, specifically one piece vs 2 piece fastenings

  24. #24
    sock puppet
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    you could also use a nail clipper.

    Doing the Crank the Shield this year?

  25. #25
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    Quote Originally Posted by NameTaken View Post
    ....they say to tighten to no more than 8nM.
    Just a warning, the 8 Newton meter is a limit for the bar itself. Above that torque you could crush the handlebar. What is important, is that the maximum torque for most light weight stems is less. For example a Thomson Elite X4 stem specifies a clamp bolt torque of 4.0 Nm. And people are surprised that they have cracked face plates.

    If you are going to work on your bike get a torque wrench.
    The trouble with having an open mind is that people will insist on trying to put things in it.

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