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When I see/hear people reference torque when it pertains to nuts and bolts, what does that mean? How would I measure it without special tools?

For example, I saw a clip where the mechanic says "tighten down the axle nut to the torque listed in your owner's manual..."

Thanks,
jF
 

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When I see/hear people reference torque when it pertains to nuts and bolts, what does that mean? How would I measure it without special tools?

For example, I saw a clip where the mechanic says "tighten down the axle nut to the torque listed in your owner's manual..."

Thanks,
jF
You need the proper torque wrench to torque fasteners.

Typically, a 1/4" torque wrench is used for smaller bolts like case bolts and bolts with 8 and 10mm heads.

A larger, 3/8" torque wrench is used for larger fasteners like the axle nut you mentioned.

When you get into torquing things like auto lug nuts, a 1/2" torque wrench is used.

I own all 3, and just bought another one, that looks like a big screwdriver, for tiny bolts that need critical torque values.

Here's a video that will give you some background -

https://www.youtube.com/watch?time_continue=153&v=3v3hLvuO_KU
 

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Yup, jlv45's info was spot on.

Here you can see it used on the axle nut like you mentioned in the question, as an example of real world motorcycle maintenance.

If I had to choose only one size to get first I'd go with 3/8". You can use cheap adapters to 1/4" or 1/2".
 

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When I see/hear people reference torque when it pertains to nuts and bolts, what does that mean? How would I measure it without special tools?

Thanks,
jF
Torque is the force or strength with which you tighten a bolt or a nut. Each bolt and nut on the bike has a specific torque which is indicated in the service manual.

And yes, you need a special tool as mentioned above.
 

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A torque wrench can also get you into trouble.

Plenty of people have snapped or stripped bolts/threads by trying to torque to the "proper" spec.

Small bolts (8mm/10mm heads) usually need to be "snug", and some times trying to hit a certain number will snap them. A dab of blue loctite is often a good idea if the fastener is critical.

The quality of the fastener is also a factor. Some CBR250R owners have found out the hard way that the smaller bolts on the CBR can't reach the "spec" torque before snapping.

My youngest boy was replacing the rear sprocket on his R6 a while ago, and wanted to torque the nuts. He asked me about it, and looked up the spec. When he told me what it was I told him I thought that was too much for a nut that size. He went with the spec, and stripped out numerous nuts before stopping (I wasn't home at the time...stop after the first...).

He used the published spec. Numerous other R6 owners have found out the hard way it's too much.
 

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^^ Good tips!

Also, don't use the torque wrench to loosen bolts or nuts, and when tightening, don't keep tighten after the click.
 

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A torque wrench can also get you into trouble.

Plenty of people have snapped or stripped bolts/threads by trying to torque to the "proper" spec.
I'm not sure I agree with that as a generalized statement. As with all things in life, you gotta use reason (if not, what statement doesn't have some form of caveat?), but snapping a bolt using OEM torque recommendations in normal conditions isn't normal. Rather, I'd imagine it's more often than not a case of Dunning Kruger. Getting units right is a big PITA in the US between N*m, ft*lb and in*lb - mixing them up is far from uncommon. Also, bolts stretch over time. And probably the most common error, torque specs are given dry (unless stated otherwise). Many home mechanics that just bought their torque wrench at Harbor Freight slobber the bolt in Loctite not realizing threadlocker is technically considered a lubricant, and as such torque values should decrease by 30% or so to maintain the same force under the bolt head. Same goes for oiling them.

In other words, I'm not saying using a torque wrench can't get you in trouble, but I am saying that an educated diyer is probably more likely to get in trouble by disregarding torque values than by trying to respect them. ETCG1's recent video on YouTube "Are mistakes the best teachers" is a good example why following instructs is generally smart.
 

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Never thought I'd see such extensive explanations of "torque" on this forum.....nor references to the Dunning-Kruger effect!


:)
 

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I'm not sure I agree with that as a generalized statement. As with all things in life, you gotta use reason (if not, what statement doesn't have some form of caveat?), but snapping a bolt using OEM torque recommendations in normal conditions isn't normal. Rather, I'd imagine it's more often than not a case of Dunning Kruger. Getting units right is a big PITA in the US between N*m, ft*lb and in*lb - mixing them up is far from uncommon. Also, bolts stretch over time. And probably the most common error, torque specs are given dry (unless stated otherwise). Many home mechanics that just bought their torque wrench at Harbor Freight slobber the bolt in Loctite not realizing threadlocker is technically considered a lubricant, and as such torque values should decrease by 30% or so to maintain the same force under the bolt head. Same goes for oiling them.

In other words, I'm not saying using a torque wrench can't get you in trouble, but I am saying that an educated diyer is probably more likely to get in trouble by disregarding torque values than by trying to respect them. ETCG1's recent video on YouTube "Are mistakes the best teachers" is a good example why following instructs is generally smart.
I've seen it happen more than a few times, but in the case of our rear sprocket nuts, I didn't feel the factory Yamaha torque spec was correct.

Really, for most smaller non-critical nuts and bolts, "snug" is adequate. Using blue threadlocker and tightening M5/M6/M8 bolts "snug" with a 1/4" drive ratchet is generally safe.

Cycles are being made in many countries these days, and the quality of fasteners isn't consistent. That's an area that goes to the lowest bidder most likely.

I torque all critical fasteners, but for the most part learning how tight is tight enough works better for me.
 

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Cycles are being made in many countries these days, and the quality of fasteners isn't consistent. That's an area that goes to the lowest bidder most likely.
(bolding mine)


Not so sure that is factually correct.
Specifications for bolts are pretty well and narrowly defined (and pretty easily checked through QC).
We buy Chinese made metric bolts at my Chinese place of work, and they are INDISTINGUISHABLE in quality to their foreign counterparts.
 

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(bolding mine)
Not so sure that is factually correct.
Specifications for bolts are pretty well and narrowly defined (and pretty easily checked through QC).
We buy Chinese made metric bolts at my Chinese place of work, and they are INDISTINGUISHABLE in quality to their foreign counterparts.
Maybe.

Maybe you have a good supplier.

When a M5 or M6 bolt breaks off before hitting it's recommended, and accurate, torque spec, something is going on...

I'm referring to Hondas built in India.
 

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Not so sure that is factually correct.
Specifications for bolts are pretty well and narrowly defined (and pretty easily checked through QC).
My thoughts exactly.

Specs may not be consistent when one buys generic bolts on Ebay, but you can be sure that OEM manufacturers buy properly rated bolts and nuts. It's not like its expensive to do, and it actually makes purchasing a lot easier since selecting by grade makes it much simpler to sort through vendors. The specifications are objective, well defined and industry standard. With Metric you've got Grade 4.6 @ 400 10^6 Pa minimum tensile strength, all the way up to Grade 12.9 @ 1220 10^6 Pa minimum tensile strength. With SAE you have grades 1 thru 8.2, all with precise dimension standard and strength expectations.

In other words you're unlikely to see manufacturer bolts varying between high quality and pot-metal. Specifications are well defined with high accountability. I'd much sooner suspect user error or an uncalibrated chinesium torque wrench to be at fault than an OEM bolt at OEM torque under grossly normal conditions. Again, not to say exceptions or typos in the shop manual can't happen, but as far as generalities go, I would presume OEM competence before incompetence.
 

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Not saying this is definitely the case here, but:
Also bear in mind that if a fastener is listed as "replace with new when removed" it may be torqued to yield for an increased fatigue life. Basically, the bolt is tightened until it has permanently stretched because the load on the bolt during cyclical stresses remains effectively constant. If you loosen and re-torque these bolt, you are extremely likely to pop the head off before you reach the torque value due to accumulated internal stresses, and even if you can get the bolt "tight" it's still much less strong than before.
Most fasteners are not torqued to yield by OEM spec, however if a manual stated to replace the fastener if removed, I would believe it.
 

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Not saying this is definitely the case here, but:
Also bear in mind that if a fastener is listed as "replace with new when removed" it may be torqued to yield for an increased fatigue life. Basically, the bolt is tightened until it has permanently stretched because the load on the bolt during cyclical stresses remains effectively constant. If you loosen and re-torque these bolt, you are extremely likely to pop the head off before you reach the torque value due to accumulated internal stresses, and even if you can get the bolt "tight" it's still much less strong than before.
Most fasteners are not torqued to yield by OEM spec, however if a manual stated to replace the fastener if removed, I would believe it.

EXCELLENT point!

Also, the bolt torque requirement changes depending on what lube you use when assembling it; i.e. it makes a difference whether you use oil or MoS2.
If the bolt is zinc-coated or not also makes a difference.
 

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Torque to yield is also commonly used when there's a gasket involved as the load is more consistent and evenly spread out. I would assume any cover with a gasket has the fasteners TTY unless otherwise noted. TTY often (though not always) is given as a torque-plus-angle measurement (ie, torque to X and then an extra 1/4 turn).
 

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My thoughts exactly.

Specs may not be consistent when one buys generic bolts on Ebay, but you can be sure that OEM manufacturers buy properly rated bolts and nuts. It's not like its expensive to do, and it actually makes purchasing a lot easier since selecting by grade makes it much simpler to sort through vendors. The specifications are objective, well defined and industry standard. With Metric you've got Grade 4.6 @ 400 10^6 Pa minimum tensile strength, all the way up to Grade 12.9 @ 1220 10^6 Pa minimum tensile strength. With SAE you have grades 1 thru 8.2, all with precise dimension standard and strength expectations.

In other words you're unlikely to see manufacturer bolts varying between high quality and pot-metal. Specifications are well defined with high accountability. I'd much sooner suspect user error or an uncalibrated chinesium torque wrench to be at fault than an OEM bolt at OEM torque under grossly normal conditions. Again, not to say exceptions or typos in the shop manual can't happen, but as far as generalities go, I would presume OEM competence before incompetence.
Another instance where we don't agree...surprising...

So I contacted a friend that works as an Engineer for a major motorcycle manufacturer and asked if he has experienced fasteners that are not in spec.

He said yes - it happens.
 

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So I contacted a friend that works as an Engineer for a major motorcycle manufacturer and asked if he has experienced fasteners that are not in spec.

He said yes - it happens.
You should have bolded the whole sentence, namely "bolts varying between high quality and pot metal". I try to choose my words carefully. Of course there are bolts that should have gotten rejected that occasionally pass through when you're dealing with tens of millions of bolts, but do you really think that the ratio is high enough and quality poor enough to, as a general rule, disregard torque values all together? Ask your engineer friend if he thinks that the small fraction of bolts that may be severely out of spec (some of which will never be installed due to being detected or not threading to begin with) is sufficient reason to advise consumers and mechanics against trying to respect the torque values in the service manual? I sincerely doubt that defective bolts, to the point they would break under normal torque values (more so considering the in-built safety factor), represent more than single digit values in percentage of any given bike. Furthermore, I'd bet that the vast majority of them are in bolts which aren't "important" enough to justify being assigned an official torque value in the shop manual to begin with (like fairing bolts as opposed to the axle bolt).

I dunno, maybe we're talking about different questions? Can a bolt occasionally break when torquing to normal values? Sure, and that's what common sense (I hate using that word) and screw extractors are for. And in my experience you're way more likely to round the bolt head first anyway. But the real question, at least for me, is whether users and mechanics alike should try to respect manufacturer torque values when they are given? I say absolutely, but again without disregarding the intuition born from previous experience.

Or we could just do like everybody's favorite Uncle Bumblefuk AvE and let the 200lb gorilla have at her with the breaker bar until we here the crack and then back off half a turn :p . Anyway, it would seem odd to me if out of torquing 1000 bolts, one had more issues from bolts breaking than from under or over torquing. It's all worth considering I suppose.
 

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So I contacted a friend that works as an Engineer for a major motorcycle manufacturer and asked if he has experienced fasteners that are not in spec.

He said yes - it happens.

It happens, yes. The follow-up question to your friend ought to be: "Were these not-in-spec fasteners used in final production, or rejected and sent back to the manufacturer or discarded?"


I come across out-of-spec stuff every now and then also (made in various countries, not just China), but catch it at receipt-of-goods or sometimes [but rarely] during installation.
 

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As an Engineer for a major aerospace company, I can tell you receipt of non-conforming fasteners can certainly happen, even in my extremely regulated industry. We have many checks in place to ensure proper conforming parts are always used, however there was at least one time in recent memory where I had to lead a portion of an investigation into non-conforming fasteners. These were not strictly counterfeit parts (although that is also a surprisingly big issue in industry) but several batches of fasteners were reprocessed to strip a plating/coating by an unapproved third party. The only reason it was caught was one of our guys in receiving noted a small discrepancy in the conformance paperwork and started looking into it more. By the time we had noted the issue (by one guy doing an exemplary job) we found we had installed these fasteners in several critical joints of several aircraft, and that our internal processes did not guarantee full traceability for fasteners (which is not really a major problem until something like this happens). As a result, several risk assessments had to be carried out, independent testing of sample fasteners was performed, and our internal processes were revised.

All that is to say that even in a crazy regulated industry, things like this can slip through cracks, so I can imagine in the automotive industry the likelihood of non-conforming fasteners making it onto vehicles is much higher. HOWEVER I imagine this is still a very very small percentage, and actual intentional counterfeit parts even less likely.
 
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