FBinNY 

IMO, this isn't about whether torque wrenches have a place, or whether people should use them. In some cases they should, though in most cases a skilled mechanic can use hand feel and experience to judge properly fastener torque.

My problem with torque wrenches is how they're used. For torque wrenches to have any value, the published specs must be meaningful, and the wrench must be used properly. Unfortunately in many cases one or both of these conditions aren't met.

The other problem is that in many aspects of bicycle maintenance, as in many aspects of modern life, there's a tendency to reduce things to a step by step, follow the numbers approach, discounting the value of the experience and judgement that a professional brings to a task. That means that unqualified, mechanics will use torque wrenches o blindly tighten a bolt and blame others when it doesn't work out. All to often we hear, "I tightened with a torque wrench and it broke, it must be defective." and that's why I'm not a fan.

IMO, most applications don't require a torque wrench, but might benefit if one is used. However a torque wrench or any tool is not a substitute for user skill.

Ira B

Gazing down Godlike from my lofty perch on high, I do not agree.

I do agree that on modern bikes you need to be much more careful and there is nothing wrong with using a torque wrench on a particular fitting the first dozen times. Also, some people just don't have a very good feel for such things and it may be best for them to use one and if in doubt you probably should.
I am just saying that they are not a magic wand that will always provide the best results. More so on bicycles than many other applications.

I can't believe I am still posting on this.


[QUOTE=rydabent;14529693]A bolt or nut tightened with a torque wrench will alway be tightend to the same torque EVERY time. The same nut or bolt tightened by an egotistical gods gift to the mechanical world will NOT be.

mechBgon

As I mentioned earlier, several times, with real-world examples, having the proper tools and doing the job "right" (meaning, blindly trusting a manufacturer's instructions) sometimes breaks stuff in the real world. And in other cases it leaves things insufficiently fastened. I co-developed the torque specsheet we use at work, and could point out several instances where we started by trying the "right" torque specs and ended up reverse-engineering our own, based on what actually gets the job done safely. Trust me, if we could all just blindly "paint by numbers" without repercussions, I'd be the first to tell everyone here but it's not so simple IRL. You know that popular saying about theory versus practice...

As I also pointed out earlier, thread/bolthead treatment vastly alters the applied clamping force that you generate with a given torque value. The blind-faith torque-wrench proponents seldom consider this inconvenient truth.

eja_ bottecchia

^^^this^^^

Burton

My own comment was based on 35 years spent in the aerospace industry in engineering support, process control and technical publications. Technical publications as in the typically 20 some volume maintenance manuals based on engineering data and used to specify step-by-step instructions on the scheduled and unscheduled maintenance of commercial aircraft manufactured by the largest aircraft manufacturers in the world. Followed by 10 years in the bicycle industry which has included exposure to some of the bicycle manufacturing facilities in Asia (where there are also commercial aircraft assembly facilities) and some particupation in R&D in both fields. The fact that as a project manager I had a well established reputation for getting results and had s salary that was double any engineer makes me assume I'm not a total moron. So if you really think the people that push leading edge bicycle design aren't highly qualified engineers and that the materials used in aerospace magically change properties when used in the bicycling industry - you're really kidding yourself.


But since you feel so strongly - we have a fork on the floor of a simple $1,500 Giant mtb thats still leaking oil after being returned TWICE to the distributor for servicing. Obviously they're having trouble with should be a trivial job and I think you should contact them and offer to outsource your expertise

larwyn

Many skilled mechanics accumulate elaborate tool collections over the years. Few tool collectors develop any useful level of mechanical skill in their lifetime.

Kimmo

Next time you might care to employ all that high-paid nous to fully comprehend a post before you fire off another offended, spluttering reply replete with posturing irrelevancies...

There's one thing in common; highly engineered aerospace materials. Carbon's anisotropic, hence may not be as strong in some directions as it looks. We all know that...

But hey, if you want to keep insulting folks with your oh-so eminently qualified by-the-book insistence, thats your call.

temon00

I don't use a torque wrench, but I do have a torque rating system. The ratings are: "dialed" (for a bearing cone), "snug" (for bottle cage bosses, derailleur mounting bolts, etc.), "pretty tight" (for derailleur cable bolts, pedals, etc), and "pretty ****in tight"(for crank bolts, bolt-on axles, BB fixed cups, etc). BTW, anyone have a torque wrench I can borrow?

Ira B

True dat.

Hydrated

Then I guess they certainly don't want to see me early on a Saturday morning drinking coffee and building up wheels while wearing nothing but my underwear. It's more comfy that way... but I normally put pants on when I deliver the wheels to my customer.

Airburst

No shirt?

tomacropod

I broke my arm in a freak chicken-racing accident a few years ago and my Ulna was shattered. I took the liberty, at the time, to have it replaced with a stainless steel beam-type torque wrench. My Neurologist replaced the torque reading points with nerve endings so now I can literally "go by feel" to a high degree of accuracy. My right contact lens also has a set of measurement graduations printed on the inside of it, so my visual estimation of size is very accurate. It's frustrating having to constantly explain these things to over-concerned customers who do not observe the use of caliper or torque wrench.

- Joel

Ira B

This has gotten even worse than a chain lube thread.

FBinNY 

Nothing could be worse than a chain lube debate.

wroomwroomoops

That's nothing! I have an XRD and an XRF detector instead of my right eye, while my nose contains a small but powerful source of X rays. The sensors are directly wired to my brain. That way, I can instantly determine both the composition of the bolt and the stress of the crystal grains in it, from a distance of two meters!

Ira B

Reading the previous post, do you want to stand by that statement?

tomacropod

It sounds like we should start a workshop together. Consider the efficiency gains, we'll have all the more time to watch Youtube bike crash videos at the end of the day.

- Joel

JonathanGennick 

What do you think of the torque values printed on, say, stems for the bolts that clamp the stem to the steering tube? I wonder about those values sometimes. What do they really mean? Presumably a given torque translates into a given clamping pressure on the steerer tube. Is the torque chosen with that in mind? Did the stem manufacture talk to the fork manufactures? Or is the torque instead a max torque beyond which the screws will break, or beyond which the stem will break? Or did he the manufacturer just pull a number out of their backside?

OTOH, there is probably value in getting the two (or four) bolts evenly tightened. For that reason alone, I will use a torque wrench on something like a stem faceplate even when there is no torque spec given -- I can at least be sure all four bolts are tightened as evenly as I can get them.

rydabent

If you dont have time to do it right (using a torque wrench), when will you have time to do it over?

FBinNY 

Absolutely. That's just comic relief. In chain lube threads you'll see equally nonsensical stuff said in earnest.

Burton

OK - I give up - so lets go with your years of shop experience and 'feel' for things instead.

Wait a minute! Aren't you the same guy that used those plastic shifter ferrules in your brifters - on the brake cables - where everyone knows they never should have been used - please let us know.

Kimmo

1, I didn't put em in there, and 2, I don't blame the guy who did, since it's hardly a noob mistake to assume you'd want ferrules on the end of shift housing. They aren't hurting anything; they just won't come out.

Your ad hominem needs work. Can you overhaul a brifter, smart guy? Or, you could stick to the actual subject...

Here's some help to avoid the straw-manning, if you'd like to give it a shot.

* I don't disagree that it's wise to use a torque wrench on carbon.

* I agree entirely with the professionally-trained mechanics here with, I dunno, say a century, of combined experience who say it's not as simple as just tweaking by numbers.

* I'm asserting that with enough experience, it's possible for a skilled mechanic to assemble a high-end bike properly without a torque wrench, again in agreement with many of these guys.

* I'm not claiming I'm one of those guys. Although I'm experienced enough to consider any alleged need for a torque wrench on metal bikes quite laughable, I haven't worked on much carbon and would appreciate the frequent use of a torque wrench for a while to calibrate my feel with the numbers.

wroomwroomoops

I'll go against the grain (maybe?) and say that I have my feet in both camps: I don't use a torque wrench when working on bikes, but I wish I had a torque wrench. I still wouldn't use it much, for two reasons:
- Honestly, you don't need a torque wrench in the great majority of cases, especially when you're conservative with frame materials (almost always steel) and components (mostly steel and some aluminum alloy parts), like me.
- In my scientific work, I often perform a specific experiment where we need to tighten 8 small screws with as much precision as possible, and use a small-torque calibrated wrench for the purpose. From what I have learned by reading available literature AND first hand, the linear clamping force (or tensile stress on the bolt, whichever way you look at it) is extremely variable, even if the torque wrench gives a very specific reading. I.E. it's very difficult to infer an exact linear force from the torque on the bolt. You can get close to what the formulas say if you lubricate the threads very carefully. So in summary, the clamping force is rarely proportional to the torque on the bolt. That explains the misadventure with carbon parts some have reported here. Having a "bio-feedback" based on many years of experience will, I think, help with preventing over-tightening a screw on a sensitive part.

That said.... I have found myself wondering a number of times, about the ballpark of the torque I'm applying to stuff like diskbrake bolts. I think I bolted them down strongly enough without stripping the threads, but I did wish I had a torque wrench to check the ballpark. IOW, I'll get a good socket torque wrench when I can afford it.



I hope I managed to piss off both camps with this post.

tomacropod

Not nearly inflammatory enough to piss off either camp I fear.

Just to add some clarification to this whole thing, the stem on my heavy steel touring bike cracked yesterday as I was tightening the steerer tube bolts (hadn't nearly reached the recommended torque, materials failure). Whether the frame/bar/stem/seatpost is carbon or not doesn't change the torque principles or ratings.

- Joel

wroomwroomoops

It does, a bit: most alloys used for bicycle parts are more forgiving to overstress than carbon composites. I'll submit to you that your stem had a built-in stress from when it was forged. This is akin to the very few but nonzero cases where an aluminum alloy crank breaks during normal pedalling.

(DIPYO now?)