I have learned that some bike and component manufactures have specific torque specified and others don't.

One Bontrager stem specifies 5nm and another Bontrager stem specifies 8nm. One stem I had, I think it was a Salsa stem specified 11nm.

There was a time when torques were not specified, as far as I knew. I simply tightened what ever it was to what ever 'seemed' right. With experience, sometimes painfully, I have learned a certain feel for too tight or too loose but often times I still don't tighten to a specific torque. Experience has been a good teacher and I don't usually have any problems with too tight or too loose.

How much does torque matter if no issues are encountered by the rider? Is there that much difference between 5nm and 8nm? Do you torque every bolt and screw?

If no torque is specified, how much torque do you use? Is there a general guide line or chart somewhere with generalized 'best practice' torques for different components?

I use this whenever I'm in doubt. It doesn't wound my pride to admit that I don't know what the right torque "feels like" for everything, yet.

Park Tool Co. » ParkTool Blog » Torque Specifications and Concepts

I broke a very expensive fork because I used the torque limit shown on the stem (8nm). I could not find a limit for the carbon fiber steer tube. For tightening against cf I recommend staying below 5nm, 40 inch pounds is plenty.

Make sure you have a torque wrench that is accurate at the low torque levels required - the torque should be between 20% and 80% of the rating of the torque wrench used. Higher your are risking the torque wrench, lower you are risking components. It is your choice to risk.

+1 Often the torque limit shown on stems is intended for a metal steerer, not carbon.

Consider this: A greased fastener will be tighter when torqued to the same number as a dry or, even worse, an oxidized one. In my experience, torque instructions seldom say whether to grease or not to grease, but it can make a big difference - even the difference between properly tight and snapped off or stripped! I usually rely on feel as much as on a torque wrench, and I think I can approximate torque values by feel with reasonable accuracy. If threads seem dry or galled, I always stop and lube them. I got tired of doing damage.

If you DO grease a fastener (as you should), be cautious and don't over-torque.

habilis:

My recollection is that the SAE (Society of Automotive Engineers) standard torques are based upon the threads being lightly lubricated with 10W engine oil. I suspect that other folks use the same specs..

Joe

No doubt this is true, but I don't recall seeing this recommendation in various Haynes, Chilton, Motor, or other repair manuals specific to given models of cars or motorcycles. When formally schooled, mechanics may learn the SAE recommendation, but the self-taught home mechanic is (I don't think) reminded in the manuals I've seen, though they are intended for home mechanics rather than shop pros. Then again, I could be wrong. The last time I read a Chilton manual from cover to cover (1979 Honda CB750F motorcycle), was about 20 years ago.

For bicycles, I prefer to go by feel.

Just skimmed through the 1973 edition of Glenn's Complete Bicycle Manual. He frequently mentions lubing threads before assembling, but I couldn't find any references to torque values. He just says to tighten things "securely."

I go by "feel", although I do have the appropriate torque wrenches to reference as a "benchmark".
Sheering bolts is not good!
I know, now, when to stop. Ha ha.

You can try the "Fred Flintstone" method: "tighten 'till it cracks, then back off half a turn" but don't tell them I sent you…

After you have been doing it a while you will be able to do most fasteners by feel and not do any damage. Newbies should learn what certain torques feel like. Multiple bolts on things like manifolds or heads should always have their torque measured but we dont have that sort of thing on bicycles. Lubrication is important. A dry fastener as it nears final torque can partially seize and become overtorqued. Stainless, or steel into aluminum should have some anti seize applied so they dont seize or oxidize over time.

-SP