[MG537]

This question is directed to all mechanically inclined or certified mechanic readers.
I'm asking this because not once have I seen my LBS take out a torque wrench to adjust any part of my bike and believe me I've made several tript to that store.
I do own a carbon fiber bike and I also read that many of today's aluminium parts are made so thin that over tightening them may one day result in material failure.

The other day I went in for a left crank arm adjustment and saw the the owner basically put his whole weight in tightening it. (FSA SLK crankset).

Should I be worried a lot, a little maybe or is this whole torque wrench thing just marketing stuff?

 

[russotto]

A torque wrench comes in very handy in telling you that you were NOT overtorquing that bolt when it snapped off..

 

[unit]

I have always been uber-anal about torque wrench use. I was always perplexed at how all the LBSs in my area never used them, and could not produce one when I asked where the shop torque wrench was.

I will not bore you with details, but this absence of torque wrench thing, eventually led to me doing all my own wrenching.

Now several years later I my town has been blessed with another LBS that the owner/head wrench has and regularly uses several torque wrenches. He and I share the belief that no human is perfect, nor can a person generate consistent torque on a nut or bolt. For this reason, man invented tools (such as a torque wrench).

Yes there are great mechanics out there that can build a nice bike with no torque wrench, but I have *never* heard a good wrench site a good reason for not using a *properly maintained* torque wrench. I have heard a lot of lame excuses, but never a good reason.

 

[Kuma601]

Find another shop to wrench your bike. Some parts my tolerate over or under torquing the bolts/nuts but it isn't the smartest way in building up an assembly to be trouble free.

is this whole torque wrench thing just marketing stuff?

:shocked: :confused5:

 

[tom_h]

I am fanatical about my cars, and always torque fasteners to Mfr's recommendation (unless it is just cosmetic trim). Certain fasteners, if not torqued properly, will lead to spectacular failure & destruction (eg, head or connecting rod bolts in a hi-po engine).

This has carried over to my bike wrenching. I always have a 1/4" drive, 100 inch-lb wrench nearby. Admittedly, with experience, one can come reasonably close to the correct torque , +/- 20% maybe. But I tend to think many mechanics are just sloppy about not using torque wrenches, and have little clue how much torque they're applying.

I like how my wife's Specialized bike has several discreet decals spec'ing the torque values for seat post, stem, handlebars, etc. The tech documents at Shimano's website also usually include recommended torque values.

 

[PeanutButterBreath]

Most competent mechanics are not going to over-torque bolts. They've worked on enough bikes to know when a fastener is tight enough.

IMO, over-torquing is mainly a problem for people who lack experience or confidence in what they are doing, and end up over-tightening a fastener "just to be sure".

I own both Park beam models but use them only rarely. Most people don't use them at all and most people never have a problem.

 

[runner0382]

Thanks for the posts. I hadn't even heard of this until I got my Ridley last week and the shop brought out to adjust the seatpost height with one and I was like, "what are you doing?"

I don't know many bike mechanics in L.A. who use them at all. Question is - do I need one for my bike? I'm confident I know when enough is enough - a tiny tiny bit above the minimum force needed to secure should do.

Especially for a seatpost!

 

[Dizzy812]

Go get one - same cost as replacing a crushed seat post!

 

[chas0039]

Unfortunately, you will need two to cover the range of fasteners on your bike, unless you skip the smaller ones.

 

[raymonda]

A torque wrench is expecially helpful with Carbon because often it is not a bolt that needs to be replaced but a part or a frame.

That being said I've never used one in over 20 years but then again I don't have a carbon seat post, handlebars or frame.

 

[tom_h]

Unfortunately, you will need two to cover the range of fasteners on your bike, unless you skip the smaller ones.

Curious which fasteners you're thinking of.

I haven't done any work on bottom bracket or headset , but for everything else a 100 inch-lb wrench has been ideal.

 

[bzweig]

A torque wrench is a necessity , especially regarding CF. More to the point: FSA cranksets are JUNK, and chronically fail at the bolts. Check out the blogs and/or your honest LBS on this point. I would not risk my safety by owning one. If FSA had any character it would recall them all.

 

[Mr. Versatile]

Where can you find torque specs? Do they vary with brands? Within models? By Years? I know they vary by materials.

 

[Touch0Gray]

Where can you find torque specs? Do they vary with brands? Within models? By Years? I know they vary by materials.

all Campy's manuals have torque specs.....and I use them.....until I torqued my lockring properly, my rear just didn't shift right. Until I torqued the driveside crank properly, the chainline was not quite right....sometimes it really does matter

 

[bzweig]

Park Tool has a document on its website which has many specs. Many manufacturers list the torque specs in the instructions to their products.

 

[russotto]

A torque wrench is a necessity , especially regarding CF. More to the point: FSA cranksets are JUNK, and chronically fail at the bolts.

You mean the crank-ring bolts? That's actually the chief one I was thinking of when I mentioned snapping one off below the specified torque.

 

[unit]

Under = Over = Bad

Most competent mechanics are not going to over-torque bolts. They've worked on enough bikes to know when a fastener is tight enough.

Heard that one!

One of my LBSs said that to me almost verbatim. This guy has been wrenching for about 15 years, so I believed him...until my non-drive crank arm worked loose and destroyed the splines on the MTB ride the day after the crank was installed...it did feel "tight enough" when the ride started.

"Tight enough" is a lot like "good enough", it is subjective and open to question. I do not want to have any question about my fasteners when I am riding.

I intend no offense. This is just my philosophy. I have learned the hard way.

 

[PeanutButterBreath]

I intend no offense. This is just my philosophy. I have learned the hard way.

None taken.

Clearly, your crank wasn't tight enough. Then again, a lot of the recent "innovations" in crank designs have proven to be problematic.

It is true though that chronically under-torquing things is bad. Handlebars that slip can be extermely dangerous. Seatposts can be damaged when they slip.

Tight enough is exactly what torque specs are about though. Not too high, not too low. An experience mechanic will develop a feel for the correct range based on feedback from the tool they are using. Torque wrenches eliminate that feedback. They can go out of calibraion (especially the click type). Specs are often confusing and I have heard of multiple occasions of people misreading them and damaging a part.

Another issue is that while manufacturers post spec for their components, you are almost always dealing with two components from two manufacturers (i.e. a stem & fork, stem & handlebar, FD and ST). AFAIK there are no concrete standards or guidelines about which to follow. Do you go with the higher and risk crushing something? Or the lower and risk slippage? Manufacturers typically cop-out by saying to go with whatever the other guys recommend, thus shifting the blame if something goes wrong.

 

[tom_h]

... Tight enough is exactly what torque specs are about though. Not too high, not too low. An experience mechanic will develop a feel for the correct range based on feedback from the tool they are using. ...

I know we're talking bikes -- but there is more to it in case of car parts.

With car fasteners (and especially engine), one is often trying to "pre-stress" or "pre-stretch" the fastener to a greater amount than seen from the actual load. Else, the fastener will see repetitive tension loads that lead to fastener failure. Other times, loads on an inadequately pre-stretched fastener can cause fasteners to gradually unscrew, eg wheel lugnuts, balancers. Compressing gaskets to the design spec is another reason for spec'ing fastener torque. Other examples abound.

 

[unit]

Torque wrenches eliminate that feedback. They can go out of calibraion (especially the click type). Specs are often confusing and I have heard of multiple occasions of people misreading them and damaging a part.

Another issue is that while manufacturers post spec for their components, you are almost always dealing with two components from two manufacturers (i.e. a stem & fork, stem & handlebar, FD and ST). AFAIK there are no concrete standards or guidelines about which to follow. Do you go with the higher and risk crushing something? Or the lower and risk slippage? Manufacturers typically cop-out by saying to go with whatever the other guys recommend, thus shifting the blame if something goes wrong.

Great points! I agree that a torque wrench is only as good as the guy using it, and the validity of the readings it gives. I would also agree that many experienced mechanics possess an ability to know when to doubt a torque wrench by the "feel"....as one of those guys, I also know that my doubt has been wrong more than once (human error).

A guy that cares about these things (and concerns him/her self with the interaction of components from different Mfgs) is the sort of guy I want to deal with. I just get a little rage when I recall dealings where a person has used this rationale for not using a torque wrench (wanted to make it clear that that rage is a personal issue and not directed at anyone here). I mean, why not use the same rationale for discarding all tools and just use rocks and sticks like we do in the woods?

I am jacking the thread...sorry.