Torque wrenches or dorque wrenches?

[BroDeal]

Near useless according to this guy's testing..

"The data is clear – my testing with aerospace grade fasteners, calibrated torque wrenches, and calibrated load transducers shows min and max preload can vary from -38.5% to +84.1% from nominal. If you think that torque wrench is getting you the correct value, think again. That’s a huge error, and I’ve heard about too many broken carbon bits to put my trust into some number stamped on a part with no other information."

http://james-p-smith.blogspot.com/2011/05/torque-wrenches-and-bicycles.html

 

[Parera]

Awesome read. Thanks. I stopped using torque wrenches after having a bike shop employee partially crush a carbon seatpost despite using the recommended setting.

 

[RDV4ROUBAIX]

Never use dorque wrenches, always go by feel, and I also put star nuts into carbon steer tubes instead of those dumb plugs.

 

[liftman]

Being a mechanic (not bicycle) this was a very interesting read. A torque wrench can serve one basic purpose. Preventing some inexperienced soul from putting 1000% too much torque on a critical part. At least it gives some frame of reference for those without the experience to know what something should (feel) like.

 

[Boeing]

of course we here are all above the Fray at a level far superior to the common man and perhaps, no should, set the standard for the industry. the posters of this forum are at a level of sophistication unequaled in any industry. It is what we say it is and after all the purpose of this thread

 

[BroDeal]

of course we here are all above the Fray at a level far superior to the common man and perhaps, no should, set the standard for the industry. the posters of this forum are at a level of sophistication unequaled in any industry. It is what we say it is and after all the purpose of this thread

Nice description of yourself. Do you ever do anything other than complain about other posters?

Did not read the article, did you?

...ttug

 

[bc_hills]

Being a mechanic (not bicycle) this was a very interesting read. A torque wrench can serve one basic purpose. Preventing some inexperienced soul from putting 1000% too much torque on a critical part. At least it gives some frame of reference for those without the experience to know what something should (feel) like.

I cracked a water pump in my truck once using a torque wrench. I remember thinking at the time, "man, I can't believe I'm not over-torquing this bolt, but the torque wrench says it's all good".

 

[Bustedknuckle]

Near useless according to this guy's testing..

"The data is clear – my testing with aerospace grade fasteners, calibrated torque wrenches, and calibrated load transducers shows min and max preload can vary from -38.5% to +84.1% from nominal. If you think that torque wrench is getting you the correct value, think again. That’s a huge error, and I’ve heard about too many broken carbon bits to put my trust into some number stamped on a part with no other information."

http://james-p-smith.blogspot.com/2011/05/torque-wrenches-and-bicycles.html

So instead of 'putting your trust into some number stamped on a part', you would rather just wing it with a wrench and hope it's somewhere in the vicinity of correct. Most things aren't broken by over tightening, most are undertightened and then things like crank arms, fall off. Spokes get loose, stems rotate when the bike is ridden, handlebars rotate, seatposts slip.

Even if a torque wrench is somewhat inaccurate, by this guy's claims, it is closer most times than just some persons hands/feel.

"tighten it until it cracks, then back off a quarter turn".

 

[Houdini]

Nothing new here. Torque is an imperfect proxy for bolt tension. Measuring actual tension is difficult and, for cycling fastener tolerances, unnecessary. From a manufacture’s perspective supplying a torque value is enormously better than providing subjective guidance or no guidance at all. This guy is not *****ing about the accuracy of torque wrenches but rather the imperfect correlation between torque and fastener tension. Even if you get the torque PERFECT the tension will vary by as much as -38.5% to +84.1%. Any additional inaccuracy inserted by your “feel torque” will have a multiplicative effect on that -/+ range. The author’s incremental slip test procedure is tedious and presumes you know and will be able to apply the maximum operational load.

As implied by all those manufacturers’ recommended torques, the bicycle industry has endorsed the use of torque wrenches as a best practice. It’s not perfect, but it’s the best real-world solution.

 

[usedtobefast]

I cracked a water pump in my truck once using a torque wrench. I remember thinking at the time, "man, I can't believe I'm not over-torquing this bolt, but the torque wrench says it's all good".

that sucks, i never liked them myself, but they do serve a purpose. some folks don't have the touch to feel they are overdoing it. and sometime sh=t happens.

 

[BroDeal]

So instead of 'putting your trust into some number stamped on a part', you would rather just wing it with a wrench and hope it's somewhere in the vicinity of correct. Most things aren't broken by over tightening, most are undertightened and then things like crank arms, fall off. Spokes get loose, stems rotate when the bike is ridden, handlebars rotate, seatposts slip.

Even if a torque wrench is somewhat inaccurate, by this guy's claims, it is closer most times than just some persons hands/feel.

The point of the article is not that a torque wrench is somewhat inaccurate. They are wildly inaccurate. This passage makes the point well:

"Let’s take the seat post collar. With T=55 lb-in and D=5 mm (0.19685 in) and a completely unknown K value, just what the heck kind of load can we expect? The testing above indicates K can be anywhere from K=.137 to K=.472, which leads to a clamp load from 592 lb to 2039 lb assuming the 55 lb-in is the effective torque on the bolt. I have no idea what the crush load of my seat post is, but has Specialized designed it for this range? Or suppose I liberally lube the bolt such that now my nut factor may be as low as K=0.075 as the data I collected suggests. This would cause the clamp load to jump to 3725 lb. This load is disconcerting, as even a NAS fastener with strength of 160 ksi would fail in the threaded section with this load. And I doubt Specialized is providing very high strength fasteners (i.e., greater than 160 ksi) with their builds."

So clamp load could vary from 592 lb to 3725 lb with the same reading of 55 lb-in on the torque wrench, and that assumes a calibrated torque wrench. How many bicycle mechanics send their torque wrenches out for regular calibration? How accurate are torque wrenches used by the typical home bicycle mechanic? Are they routinely off by 10%? 20%?

At the end of the article he gives recomendations for tightening bolts which would seem to work for stems and such items that can be tested to see if the joint slips. As for things like cranks I have no idea.

The wild inaccuracy is interesting.

 

[Boeing]

When I am working on my bike I must admit I have the magic touch and can pin the exact torque blindfolded. I call my magic hands the cork wrench, as in just enough pressure to hold back the finest champagne. I understand however why they make these wrenches . there are so many commoner bike mechanics beneath my talents and I cant touch every bike.

 

[Cooper]

Also, using grease on the bolt you are about the torque skews the results.

Most torque specs are for dry threads.

The two LBS I go to do not use torque wrenches.

 

[Bustedknuckle]

Also, using grease on the bolt you are about the torque skews the results.

Most torque specs are for dry threads.

The two LBS I go to do not use torque wrenches.

Silly, their hands are also wildly inaccurate. No car repair place worth it's salt doesn't use torque wrenches. Nor aircraft mechanics.

 

[Hawkwood]

Silly, their hands are also wildly inaccurate. No car repair place worth it's salt doesn't use torque wrenches. Nor aircraft mechanics.

My brother joined the RAF in the 1990s and was trained as an airframe fitter (he now works on helicoptors for the US Air Force). As part of his training one of the instructors tested a series of torque wrenches to show the students just how inaccurate they all were.

 

[DirtyWorks]

My brother joined the RAF in the 1990s and was trained as an airframe fitter (he now works on helicoptors for the US Air Force). As part of his training one of the instructors tested a series of torque wrenches to show the students just how inaccurate they all were.

The lessons should have been

1. get your torque wrenches calibrated regularly.
2. Treat your torque wrenches with extreme care. ex. dial the value back to about zero after use.

The problem of wrench inaccuracy is multiplied by the simple fact bike fasteners are measured in inch pounds.

No one seems to recall another critical point in the testing. The fasteners themselves have a very wide range of performance, even for fasteners meeting NAS standards! The bike industry is using fasteners below this standard.

The author's observations are used in this thread to declare torque wrenches useless. The author of the article warns against making this leap in judgment! The author is right.

You still have the fundamental problem of an enormous range of performance in the fasteners that will be used more than once on the bicycle component. In most shops, torque values are a guideline. It's the best you can do unless you want to pay a fortune for fasteners and use them once only. No consumer is willing to do that for their bicycle.

I can recommend this device: http://www.torqwrench.com/tools/genPage.php?type=M&drive=1 Yes, USD $200+. They have the courage to warranty the accuracy of the device. (about 3%) Get it calibrated regularly. In a shop moving carbon widgets, it's like an insurance policy.

 

[Notso Swift]

Most automotive spec's have gone to a (fairly low) NM or "fingertight" PLUS "X" deg
They also specifiy if this is dry or wet/lubed

 

[Boeing]

I remember my first carbon steerer tube

 

[usedtobefast]

I remember my first carbon steerer tube

what do you remember about it?

 

[Polish]

Big bolts on bikes with higher torques require a torque wrench for sure.
Cranks for example.

Little bolts on bikes with lower torques are a bit trickier.
"Mechanic's Touch" comes into play a bit more I think.
I have success using this little gizmo from Ritchey on the 4mm bolts common on stems and seatposts:

About $20 bucks MSRP.....

 

[Martin318is]

Mechanic at my LBS has come across from being a senior mechanic on a V8 Supercar team. He always uses a digital torque wrench. When queried a while back about it, he pointed out that mechanics who claim to be able to consistently get it right by hand almost always overtighten bolts - often by quite a lot.

Personally, when I am doing over 80kph on a roughish downhill I would rather have had my stem attached using a torque wrench than judged by hand.

YMMV

 

[Polish]

Personally, when I am doing over 80kph on a roughish downhill I would rather have had my stem attached using a torque wrench than judged by hand.

YMMV

Sometimes I will hold the torque wrench with my feet.
Or grasp the Ritchey Gizmo between my teeth.
But thats just when I'm showing off lol.

 

[RDV4ROUBAIX]

Mechanic at my LBS has come across from being a senior mechanic on a V8 Supercar team. He always uses a digital torque wrench. When queried a while back about it, he pointed out that mechanics who claim to be able to consistently get it right by hand almost always overtighten bolts - often by quite a lot.

Personally, when I am doing over 80kph on a roughish downhill I would rather have had my stem attached using a torque wrench than judged by hand.

YMMV

Cool background of your boy, always love me some braaaap! I know a 17 year old kid that could run circles around most seasoned mechanics I know that brag and boast how long they've been wrenching, and he doesn't use a dorque wrench either on carbon anything. Some have got the touch, some don't I guess. Lucky enough to have been schooled in wheel building from none other than the personal builder for a certain Mark Cavendish, he doesn't use a tension meter in his builds, secrets out. Most wheel buliders would consider that highly unorthodox, I use one though.

 

[Martin318is]

I'm not saying that they guy at my shop is any better than anyone else, I was just anecdotally observing that someone who has had a lot of experience in the highest level of car racing in the country (and would theoretically be someone whose feel is quite accurate) chooses to use a tool rather than assume his feel is always right.

All I am saying is, good luck to any mechanic that feels that they can do it by 'feel', just as much as any brickie that lays a wall without a stringline, 'by eye'. Some can, but most are full of ****.

I tighten the parts on my bikes myself - no way I am trusting anyone else to tension the bolts in my carbon components, whether they use a tool or not.

 

[richwagmn]

I'm not saying that they guy at my shop is any better than anyone else, I was just anecdotally observing that someone who has had a lot of experience in the highest level of car racing in the country (and would theoretically be someone whose feel is quite accurate) chooses to use a tool rather than assume his feel is always right.

All I am saying is, good luck to any mechanic that feels that they can do it by 'feel', just as much as any brickie that lays a wall without a stringline, 'by eye'. Some can, but most are full of ****.

I tighten the parts on my bikes myself - no way I am trusting anyone else to tension the bolts in my carbon components, whether they use a tool or not.

Well, you be sure that Honda isn't letting it's mechanics "hand" torque Indy car engines (or any other racing engine). But that's a bit different from wrenching on a bike.

If do use a torque wrench on carbon parts.

Interesting article from Park Tool on torque wrenches: http://www.parktool.com/blog/repair-help/torque-specifications-and-concepts