BRM wrote: NealH wrote:
AJS914 wrote:Things like stems and seatpost usually say "max" 5 or 6nm of torque. If you use a torque wrench where do you stop? At the max?
I've been wrenching on bikes for 40 years and never used a torque wrench until recently. With carbon bars, seatposts, etc. I was getting worried that I was getting it wrong. So, I bought a 5nm Ritchey Torque Key. What I found was that I was typically under 5nm for things like stems. It seems like too much torque to me.
The margin or overall tolerance is not all that small really. The manufactures typically disregard the friction component of torquing so, even if you lightly lube the threads you will still not over torque it. Just torque to the max figure and you'll be fine.
Very wrong information.
First Lubrication factor really matters. It can dramatically lower the friction with dramaticaly different results.Here is just a sample>Other sample of A Dutch guy that did a test>>
2 bolts where same 5 Nm is used. First picture is dry, second is lubricated
If you want the non lubricated as far squeezed as in second pic you need 14 NM
Here we see that the Lubrication factor is of high importance.
(and now you also will understand that a torquewrench is in fact only useful when you know also the lube factor and properties of the bolt, like threads and material)
When instructions speak of particular torque setting you use that torque.
However when there is just a max torque mentioned then its not that you should use max setting. Max is the max what the bolt can have not what you should use as setting. It's not a torque setting specification, its a bolt specification.
Above is true and adds a huge level of complexity when it comes to bolt torque. If you guys want your mind boggled, pretty much any car forum on the web debates road wheel lug nut torque with and without antiseize on the threads and there is never any consensus.
Suffice to say that clamping torque goes way up when lubrication is applied to the thread at the same torque as shown in the pic..and of course clamping force is a concern and carbon is sensitive to it. In summary, retention in the presence of vibration which is the case on a road bike riding over less than pristine roads...can be reduced with thread lubrication and clamping force goes way up for the same torque applied when threads are lubricated. So adding lubrication to threads in the context of torque and clamping force is a slippery slope when it comes to clamping force and torque retention...forgive the pun relative to thread pitch.
..finer pitch threads retain torque better proportional to the sine of the thread pitch.
As to the OP's question, like many of you guys here...I don't see that one size fits all when it comes to torque wrenches either. My wrenches of choice are click type...3/8" drive small one for the little fasteners on the bike...I primarily use a torque wrench for seat post clamp which is pretty critical...don't want a cracked frame but can live with a cracked stem
...and I use one for bottom brackets as a rule....and cassette lockring. For high torque applications on bikes mentioned which are few, I want a long lever torque wrench and not a little one to more easily achieve desired torque target.
Anyway OP...my thoughts. Again, I don't use a torque wrench on everything but I do find them worthwhile for certain applications when I want to hit a torque spec precisely...again actual clamping is affected by thread lubrication and I tend to use grease on the threads of most fasteners on a bike...so clamping force on my bikes is high relative to industry standard torque targets for bike components...like 55 in-lbs is what I use on a seat tube clamp...with a bit a grease on the locking collar bolt thread.