My LBS installed my new handlebar slightly off-center (by about 2 or 3mm). It looks simple enough for me to loosen the 4 stem bolts just enough to scoot the bar into its proper place, and then re-tighten the bolts. But before I put my completely non-mechanical hand to it, is there anything I know about applying the right amount of torque, the amount of grip the stem exerts on the bar, etc?

The way I see it, if I just reverse the precise number of turns I made to loosen each bolt, I can't really go wrong.... Or maybe a 2-3mm offset doesn't even merit bothering with?

I haven't seen four stem bolts yet, unless you have a stem extender. In that case, you'd have two pairs of pinch bolts with allen heads. My approach would be to loosen the uppermost pair of bolts just enough to allow the stem to turn with slight force. Make the correction and tighten the bolts sufficiently that you can't easily turn the handlebar while gripping the front wheel with your knees. I wouldn't bother with torque wrenches or counting turns.

Is your handle bar carbon or aluminum? How about the stem? For an aluminum handlebar in an aluminum stem, the recommended torque is about 5 Nm (45 in-lbs) based on my Easton stem's face plate engraving. For a carbon bar I'd think a bit less, say 3 to 4 Nm, would be appropriate.

It's a steel bar in an aluminum stem.

I think you misunderstood the OP. His problem isn't an off-center stem relative to the front tire. His handlebar is off center in the handlebar clamp and 4-bolt handlebar clamps are very common.

A steel bar? In that case you are more likely to break the clamp bolts than damage the bar. Still, 5 Nm should be sufficient.

Yeah, sorry, I didn't express it well. The handlebar just wasn't clamped into place dead-center, according to the guide markings on the bar. But like I said, maybe a couple of millimeters is much ado about nothing....

Do you mean the 4 bolts on the face plate, holding the handle bars in place?

If so, just loosen the bolts until you can center the bars, as you said. Then tighten them back up in a crisscross manner. You want to make sure the gap between the face plate and the actual stem is even on the top and bottom. 5-6nm is generally all you need if you have torque wrenches. If not, just hand tighten them evenly, check the bars to make sure they're not moving. Once they don't move, do an additional quarter turn on each bolt and you should be fine.

As long as you don't have carbon bars, stem, or faceplate, you honestly don't really have to worry about over tightening handle bars.

You expressed yourself fine. Just loosen the bolts a bit until the bar is just loose enough to be able to work into place.Then criss-cross retighten by about as much as you loosened them....to snug enough to keep the bag from rotating under load. Bar slightly off center would bug the hell out of me, also.

Yes, Retighten them just enough that the bar wont slip , no more, no less.

greased threads are a good thing..

1. If 2-3mm offset bothers you it's definitely worth correcting. Life is way too short to put up with petty irritations that are so easily corrected.

2. If it was my bike I'd loosen each of the 4 bolts exactly 1 turn and see it that was enough to slide your bar over (my bet, by the way). The trick on a 4 bolt clamp is to get all 4 bolts evenly torqued. I'd tighten each one just enough until I could start to feel some resistance. Then I'd go back around and snug up each one an equal amount. That procedure is probably overkill with a steel bar but not precise enough for a lightweight carbon handlebar.

If you're wondering what 5nm feels like, take your hand wrench and tighten it snugly. If it slips, tighten it a bit more. You'll get the hang of it. 4nm, 5nm, 8nm they're all the same for this purpose.