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Torque em down....

Discussion in 'Bling and Appearance' at netrider.net.au started by parko, Jul 24, 2006.

  1. Well after I was able to finally download the vtr250 work shop many so kindly provided by Jbot, the w/e just past was spent re-torquing the real wheel nut as per the specs. (after the previous weeks wheel off). Anyway's... I decided to "check" the front spocket bolt and found it to be Waaaayyyy to tight (was torqued at nearly 70Nm) where the workshop manual says to only tighten to 51.6Nm! So I loosened it up and re torqued it as well...

    Anyway, I've had an afterthought, the bolt's been over tightened... would it have stretched so much as to now require me to torque it more? I'm hoping it's not now to loose and will come out when ridding along the Caulder at 100+ kph...

    Any thought appreciated!

  2. Parko - torque aint necessarily torque.

    It's convoluted and involved, but bolts need to stretch inorder to provide a clamping force. It's possible to overstretch bolts, but not likely on bike bolts as I suspect the threads are likely to strip before that happens.

    The torque figure is an ideal figure for an ideally lubricated bolt with ideal lubrication of the nut onto the nut bearing surface. Anything less than ideal robs some of the torque being provided to overcome friction forces. There have been experiments where 30-40% of the torque has gone in friction losses... bolting dynamics is a whole field of engineering...

    By all means, dial up the specified torque on the bolt and if you think you have a less than ideal situation, then add a "calibrated" extra amount... but not too much otherwise you risk stripping or galling threads.

    Getting the torque right really really comes into its own on alloy components [e.g. heads] and for seating gaskets.


  3. Ummmm, 30 - 40% of the torquing force being lost to friction! Whoh!... Thanks for the input robsalvv! I think I'll mabe add another 5%, hope the bolt doen't "go"...
  4. You can NOT find out what a bolt or nut was torqued to by re checking it the following day or month or whenever.

    some will seem under torqued (loose) due to thred/bolt stretch, or temperature diferances etc and SHOULD be re torqued acordingly.

    some will seem over torqued due to binding, corosion, temp diferences etc and should just be left alone if they dont move at say torque setting +10%
  5. :WStupid: What Woodsy said.