Hey guys, I've posted a few times here concerning this subject but I just want to say one more thing....Do I really need to use a torque wrench to tighten the stem bolts on my bike? I don't have a torque wrench and debating whether I should dish out money for a wrench that I probably won't use often. Any opinions? Thanks.

i only use a torque wrench for installing cranks, dont want them loose or else the interface strips out

No, you don't have to have a torque wrench. Just use some common sense and and a good sense of feel when torquing bolts. Torque specs on bicycles are not that critical.
That said, I only use my automotive torque wrench for crank bolts.

Thanks guys...I suppose eventually I might buy one for more critical, mechanical jobs but for now it isn't necessary.

What kind of stem?

The more money you spend for a stem, the more highly I'd recommend using a torque wrench.

Depends on what you think "expensive" is. You can get a usable one for <$20. In essence you're buying insurance against making a mistake. Given the potential cost of mis-torquing some parts, a lot of people should think that cheap. In particular, the number of crank arms ruined through mis-torquing is huge if the traffic here is any indication. And then there's carbon fiber...

Look at it this way. Under-torque one crank bolt and you're out the cost of a torque wrench. So how did much you save?

I've never met an experienced bike mechanic who used a torque wrench at all. Years of experience have taught them a feel for proper torque.

Experience, though, comes from making mistakes -- some of them expensive. So maybe a torque wrench is a good idea for a less experienced mechanic. I used one when I started out. I haven't used it in years...

I don't use a torque wrench for anything but cranks, and even then, rarely.

However, for bikes prone to breakage - like Cervelos - I have a Ritchey preset torque driver that clicks at 5Nm.

https://www.outsideoutfitters.com/p-1...orque-key.aspx

Worst advice on the face of the planet.

You may be able to get away with doing this on steel/al stems/bars, try doing this on carbon fibre anything and you're guaranteed catastrophic failure somewhere.

Because they never work on carbon fibre.

It's pretty clear nobody on this thread is

a) a profesional mechanic
b) works on any parts worth more than $5 and aren't carbon

Stem bolts IS a critical mecahnical job. It allows you to STEER YOUR BIKE.

Fascinating. Not only do you know all the "experienced mechanics" to whom I referred, but you are also familiar with their employment histories as well as the kind of bikes they work on.

Bike Forums continues to impress...

Really. I've personally known several.

To me the factor that separates the professionals from the pretenders is going the extra step and taking the proper precaution when it's appropriate.

Is the argument that anyone not using a torque wrench is a "pretender"? Because honestly, anyone who has spent several years using a torque wrench to set correct torque on carbon fiber (or any other) parts and still hasn't learned how it's supposed to feel is not someone I want working on my bike.

My grandfather was a carpenter, and could eyeball a piece of wood to a fraction of an inch. A bit of moulding that was 'about 4 inches' to me was '3 7/16' to him, and he was always right. Still, even after decades of working with wood, he ALWAYS measured (usually several times).

or to put it differently

Beginners use a torque wrench to make sure they get it right
'pro' mechanics don't use a torque wrench because they think they can get it right
real mechanics use a torque wrench so they know they get it right

I broke a very expensive fork steer tube because I used the stem torque specs and a torque wrench on the stem pinch bolts. Without the torque wrench I would not have used so much torque. My intuitions told me that I was applying a lot of torque, but I was in a hurry, and after all I had specs.

Lessons learned: 1) a torque wrench is good to use as long as you use the correct specs. The torque specification on the stem is a limit for the stem. 2) 5 nm is more than enough for a carbon fiber steer tube.

A 1/4 inch drive beam wrench is good to have for working with CF parts.

There must be several torque wrench threads in the archives with lots of pros and cons arguments. Try the search function.

Al

I always use one on cranks and carbon fiber parts. I want to make sure that I put the cranks on tight enough so they don't creak later and any carbon part, since I am my own mechanic, I find damaging parts too expensive and catastraphic.

Except for perhaps a snapped fork which can cause major injury to the rider, there is no such thing as a 'catastrophic failure' on a bicycle. Torque specs on CF bicycle components are over rated. You can error, say 25% either way and still be fine.

My original advice to the OP is still good advice, unless the OP is built like a gorilla and tends to strip every bolt he tightens. Then a torque wrench in that case may be a good idea.

I have worked with techs and mechanics all my life. There are no "expert" mechanics that can accuratly torque a bolt to a specified torque. You can meet up with the "old pros" or youl can meet up with the ones that do things right. The real expert mechanic will have all the right tools, and that includes torque wrenches. And he will use them, and his work will be done right. Things wont fall apart, or parts wont be damaged.

Just in the last month alone, I've seen stuff that will fall apart, malfunction, be unsafe, or get damaged if blind adherence to the "right" torque is used without a dose of prudence. Stems losing grip on bars. Stems losing grip on steer tubes. Derailleur clamps that will break or dent the frame. There's stuff I'll use torque wrenches for, most definitely, but I won't rely on them blindly.

To quote myself from another thread, just a few instances of the many shades of grey in this field:

MECHBGON

The expert that uses the right tools and the torque wrench in question will see to it that everything is right. He will not torque a rusty or damaged bolt and call it right. A job done right according to specs by the engineers that designed and tested the product WILL work.

Now there is an interesting statement. It seems to me that torquing a fastener without a torque wrench is the "blind" way to do it. Or are we saying that bicycle company engineers are clueless about specifying proper torque? I guess it's possible that some torque spec's might be wrong but I haven't really encountered it, at least in the automotive world. I torque most fasteners on cars and motorcycles . Less so on bikes since I don't think the torque setting on a cable clamp, seat clamp or the like is all that critical. I have found the torquing by "feel usually makes you overtighten drastically on the low end and undertighten quite a bit on the high end. If you put an Octalink crank on without a torque wrench you will probably end up with a ruined crank because it won't be nearly tight enough. When I tighten small bolts on my cars to spec I am amazed at how little torque is specified. "Feel" would have had me putting them on twice as tight. And they don't don't leak and don't loosen. I would say that if you plan on working on your own mechanical devices you should own a torque wrench. I wouldn't not put the stem on and not ride until I got one but I would get one. Its just a tool you should have and the old beam style wrenches are accurate enough and dirt cheap. Keep in mind that small fasteners are most often overtightened and are even more so given the bicycling community's fetish for lubricating fastener threads.

Wrong. To cite a couple specific examples...

1) I was building some new aluminum Treks and looked up the official torque spec for the clamp-on front derailleurs. 44-60 inch-pounds. Sounds good. I lubed the bolt, set the torque wrench for 55 inch-pounds, and began torquing. Wrench vertical, slow & easy... textbook technique. I tightened, and tightened, and tightened, and tightened. And finally overrode the torque spec, because one of three things was about to happen: the bolt would break, or the clamp would snap, or the frame would begin to crimp. This is Shimano, they're not exactly lightweights in the engineering department.

2) we built a Madone 6-series for a guy. Seatmast cap would not stay up, it kept sliding down. It was torqued correctly to max from the get-go. We had to solve that one using FSA carbon-assembly "grit paste." Nice engineering job, Trek. Oh, and it was all for naught, since the highly-engineered frame started cracking before much longer. Wheee.

3) Another Madone 6-series was built for the guy who eventually bought the shop. Wooohoo, Bontrager XXX-Lite carbon stem on carbon steer tube. Torque it precisely to 5.2 Nm (the "max" value printed on the stem). He takes it out and what do you know, the stem swivels on the steer tube. And this is high-end stuff all made (or at least marketed) by one company. The brilliant engineers at Bontrager included an anti-collapse spacer in the stem's slot, and it's too thick. It prevents the stem from getting secure grip on the steer tube. That one's my bad, I should've done a vigorous twist-the-bars-while-holding-the-front-wheel-between-the-knees check, but it illustrates the point: if bike companies made aircraft, I'd be scared to get onboard.

I'm not sure what your own background is, but I've been an LBS mechanic since '89 and worked on bikes for much longer than that, and the empirical evidence does not support your "the spec is always right" ideals. Sorry. By all means use your torque wrench, but don't let it be a substitute for prudence and common sense.

See my comment above. Torque spec's are usually NOT calibrated for lubricated fasteners. Lubricating them reduces the required torque by over half in most cases.

^ This.

Zipp had the same problem for a while with the plastic inserts in their stems.

And as I mentioned before that, most component manufacturers don't bother to specify one way or the other. But two of my three examples are Trek/Bontrager products where they do specify that the bolts' threads and heads shall be lubed, and even at MAX torque spec, they failed. And both of those are instances where the same company produces both items that are being mated to one another.