Originally Posted by sivat
If you want to do it right, a torque wrench is nice to have. Its the one thing that I disagree with sheldon brown on, as he says you don't need one. Even an experienced mechanic can't guage torque perfectly. If nothing else, use one until you get the hang of what a newton-meter feels like (or lb-in/lb-ft if thats your thing). Learning how to properly torque a fastener will mean less chance of bolts loosening, less chance of stripping a bolt, and in the case of square taper bb's, less chance of damaging the arms and bottoming out the bolts. Since perfect accuracy isn't crucial, one of the beam torque wrenches will work fine. I like craftsman:
here.
24.99 online
+1.
Back in the day bikes and bike parts were generally overbuilt and it was hard to truly over-torque things. As the trend moved to shaving grams off parts and to the use of exotic materials that are more delicate and expensive the benefits of using a torque-wrench increase.
Over-torquing carbon parts (seatpost binders, brifter clamps, stem bolts, etc.) can not only be expensive mistakes, they can lead to catastrophic failures which can result in serious injury.
Do you need a torque-wrench to work on your 35 lb. 1970's era Schwinn Varsity? Probably not.
Do you need a torque-wrench to work on your 16 lb. Cervelo Soloist? You betcha.
Bob