Quoth Ken Harper:
Quoted message said:I agree very much re: the utility of a torque wrench. I know Sheldon thinks them unnecessary, and
I suppose that exposes some ambiguity in the term "unnecessary." I rode for years, did lots of
bike work for myself and friends, with no concerns about torque values.
But, each fastener has a "best" value, and I likewise have learned that my "feel" sometimes is
probably good enough but not consistently at or near the values one sees recommended in
manuals, etc.
This is assuming that the "best" value and the manufacturer's recommendation are one and the same.
This is not necessarily the case. There is individual variance in tolerances of manufactured parts,
and parts manufacturers' priorities may be different from yours. Likewise, the manufacturer has no
control over the type of lubrication you apply to the threads and bolt heads, and must assume that
lots of boneheads will install fasteners without proper lubrication.
To take the example of the stem binder, nobody will hold the stem maker at fault if you impale
yourself on the handlebar in a crash, but they might if the stem were to slip and cause you to fall
down. Thus, when the manufacturer weighs the pros and cons in developing a range of torque
recommendations, the risk of imapalement (or just of bending a handlebar) has no weight, because
this is "not their problem."
Another example is crank fixing bolts (hold the crank to the BB.) Manufacturers' torque specs don't
differentiate between the left and right sides, but it really makes sense to tighten the left side
harder than the right.
(When they loosen up, it's always the left side. Overtightening the right side may cause
chainline issues.)
Quoted message said:So, if a torque wrench is unnecessary, fine; I certainly would never discourage anyone from using
one, and I have found mine a lot of fun (and somewhat reassuring).
But, I'm particularly interested in comments on stem binder tightness.
I am aware of a general desire that this bolt be somewhat on the "under tight" side of things
because, I've been led to believe, of the chance of a wreck, in which case you would *want* the
bars to rotate.
OTOH, though, that sure is a crappy bolt to get loose without warning. I check things before I
ride, sorta, but that bolt gets a lot of vibration, won't make itself visibly apparent as loose,
and could leave you in the deep *hit if it totally loosened.
Has anybody ever had a reasonably tightened stem spontaneously loosen up from vibration?
Quoted message said:Off the top of my head, I think the values for that bolt are often around 100 in/lbs. Why not just
stick with that? How much less would still be OK? (Obviously, too much more and you could hurt the
steerer.)
This should be judged by gripping the front wheel betwixt your knees, and trying to turn the
handlebars. It should take considerable, but not brutal force to make the bars rotate.
I used to deliberately keep the stem on my MTB loose so that I could fairly easily rotate the
handlebars 90 degrees for more compact storage. (This setting was _much_ looser than I'd do it on a
customer's bike.)
Actually, I did have it twist a bit while riding a couple of times from hitting rocks and the like,
but this was only a minor inconvenience, and never cause me to lose control.
Sheldon "Rote Numbers Are An Oversimplification" Brown
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