Over-torquing non-carbon components?

NASHIE
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Re: Over-torquing non-carbon components?

Postby NASHIE » Sat May 19, 2018 7:02 pm

CKinnard wrote:
10speedsemiracer wrote:+1
I'm, with Tim and Thoglette and others on this.


Oh well that's it then.
I am erasing all that I've witnessed because 4 internet 'aircraft mechanics' haven't had a catastrophic event not using a torque wrench.


Plenty of catastrophic events from using a torque wrench.....ie using anti seize on wheel nuts and torqueing to factory spec is the biggest no no unless you want to be passed by your rear wheel. Torque readings are for dry unless stated otherwise in the manual.

human909
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Re: Over-torquing non-carbon components?

Postby human909 » Sat May 19, 2018 7:03 pm

CKinnard wrote:Oh well that's it then.
I am erasing all that I've witnessed because 4 internet 'aircraft mechanics' haven't had a catastrophic event not using a torque wrench.

Or try to be open minded and engage in a productive and informative discussion.

What you have witnessed and your conclusions sounds awfully alarmist and doesn't seem to consider a full data set. Not too similar to this medical professional's conclusions:
Doctor Urges Cyclists to Wear Mouthguards

CKinnard
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Re: Over-torquing non-carbon components?

Postby CKinnard » Sat May 19, 2018 7:29 pm

human909 wrote:
CKinnard wrote:Can you provide an authoritative reference supporting that torque values are for ungreased threads.

A quick search reveals mixed information. The only authoritative reference is the manufacturer that provides the torque values for a specific bolt for a specific component. Some manufacturers don't provide guidance at all which makes torque figures much less precise.


Where's the information showing Shimano recommends not applying grease or loctite analogues to threads in general or specifically, with 'tightening torque' supplied?

Page 13 provides very unmixed information.
http://si.shimano.com/pdfs/dm/DM-PD0002-07-ENG.pdf

Every bolt, based on thread diameter and pitch, has a recommended tightening torque range.
If a manufacturer doesn't provide torque recommendations, I'd expect a proficient mechanic to know and adhere to these values, as would a prosecuting barrister in the case of mechanical failure after a LBS bicycle service.

human909
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Re: Over-torquing non-carbon components?

Postby human909 » Sat May 19, 2018 8:03 pm

CKinnard wrote:Page 13 provides very unmixed information.
http://si.shimano.com/pdfs/dm/DM-PD0002-07-ENG.pdf

Yet in the same document there is sections that don't mention the greased or non-greased condition of the bolt. Hence MIXED.

CKinnard wrote:Every bolt, based on thread diameter and pitch, has a recommended tightening torque range.
If a manufacturer doesn't provide torque recommendations, I'd expect a proficient mechanic to know and adhere to these values, as would a prosecuting barrister in the case of mechanical failure after a LBS bicycle service.

Yep all those prosecuting barristers for loose bolts on front derailleurs. :roll:

Seriously man. Worry more about lightning striking while riding. :wink:

(Oh and to preempt you. Yep I know there have been bicycle maintenance related lawsuits.... There have also been deaths from lightning strikes. So lets just get that out of the way shall we?)

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MichaelB
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Re: Over-torquing non-carbon components?

Postby MichaelB » Sat May 19, 2018 9:48 pm

CKinnard wrote:
Every bolt, based on thread diameter and pitch, has a recommended tightening torque range.
...


Edited to look at a specific comment.

And actually, I’m an actual aircraft airframe fitter (RAAF - 12 years).

You are right, to a point. As there are so many variables with bolts that can also vary that torque that is required - such as material, temperature range, whether in tension or shear application, whether ther is proof stress as well, cyclic forces etc.

A ‘competent’ mecahnic (actually a fitter is a better term) will know what is a good torque based on skills for a specific job.

Reminds me of an old saying that we had

Tighten it until the tread strips, then back it off half a turn.

I have no doubt you have seen lots of stuff, but think that in reality, there are much more common sources of health related injuries such as drugs and alcohol ....

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Re: Over-torquing non-carbon components?

Postby CKinnard » Sun May 20, 2018 8:55 pm

MichaelB wrote:
CKinnard wrote:
Every bolt, based on thread diameter and pitch, has a recommended tightening torque range.
...


You are right, to a point. As there are so many variables with bolts that can also vary that torque that is required - such as material, temperature range, whether in tension or shear application, whether ther is proof stress as well, cyclic forces etc.

A ‘competent’ mecahnic (actually a fitter is a better term) will know what is a good torque based on skills for a specific job.

Reminds me of an old saying that we had

Tighten it until the tread strips, then back it off half a turn.

I have no doubt you have seen lots of stuff, but think that in reality, there are much more common sources of health related injuries such as drugs and alcohol ....


yes the materials being threaded influence torque as do the forces the bolt has to resist.
And you are right I have seen a lot of mech failures due to either overtightened components breaking, or undertightened loosening.

- I remember one of the most challenging rides I've done - we had a top female triathlete with us whose front derailleur came loose on rough country bitumen hours from any shops in the Gold Coast hinterland. The bolt was lost presumably km's earlier when we were climbing and she was on the small chainring. We couldn't McGuyver it, so being never say no type, she decided to ride the rest of the way on the small ring of a compact. It was one of the hottest days I've ever ridden, and we had Numinbah Valley, Mt Tomewin, Springbook, and back to Canugra ahead of us. She naturally got wasted.

- Another time a guy's front derailleur seat tube clamp came loose, and it jammed the chain as he was climbing. He didn't fathom what was wrong and kept trying to pedal up hill, only to break the FD and fall off. His wife had to drive over an hour each way to collect him.

- In the Brisbane to Gold Coast charity ride, I've seen at least a dozen mech failures in one event. I can still clearly remember the screams 30 meters ahead of me, of the poor young girl (about 12) when her pedal came off and her foot went crashing to the bitumen and she crumpled into the road....she had broken her ankle and collar bone, and possibly her wrist. A great healthy family day out had just been ruined. Her poor dad was beside himself, and the girl's injuries would compromise her athletic ability permanently.

If you ride often enough far enough away from suburbia or in races, reducing risk of mechanical failure is something not questioned.
Because even when you do everything to spec and do pre-test checks, failure can still happen though it is less likely.
As I've said, every part of a bike is non redundant, so any failure can easily be catastrophic.

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Re: Over-torquing non-carbon components?

Postby human909 » Sun May 20, 2018 9:51 pm

Yep mechanical failures can happen. I have stories too.

But what does that have to do with your original claims "ways to kill yourself by not torqueing bolts to spec". "if you value your life and limb, respect what bolts do, and learn how to torque to spec, and use either grease or loctite as appropriate."

CKinnard wrote:If you ride often enough far enough away from suburbia or in races, reducing risk of mechanical failure is something not questioned.

Nobody has been questioning that.

CKinnard wrote:so any failure can easily be catastrophic.

Image

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Re: Over-torquing non-carbon components?

Postby fat and old » Mon May 21, 2018 8:24 am

human909 wrote:
CKinnard wrote:so any failure can easily be catastrophic.

Image


I do.

Grade 5, riding my too big Hillman SS to school. It was wet. I had school shoes on. Got onto the pedals going uphill, slipped off one and nutted myself on the TT. Catastrophic? My oath!

I've hated steel bikes ever since :lol:

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Re: Over-torquing non-carbon components?

Postby human909 » Mon May 21, 2018 9:40 am

fat and old wrote:slipped off one and nutted myself on the TT. Catastrophic? My oath!


I hope you made sure your nuts were at the appropriate torsion after that. Having inappropriate torsion in you nuts can be a serious medical condition. :lol: :oops:

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Re: Over-torquing non-carbon components?

Postby macca33 » Mon May 21, 2018 10:14 am

I 'spose ckinnard is so passionate about his point of view because he HAS seen the worst of the bad things that happen to people - often. People who were too uneducated, or ignorant, to understand that there is a greater likelihood of things going awry if their equipment or individual circumstances were not properly managed/assembled/used to begin with.

Others may not agree, given their lack of similar experience...
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human909
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Re: Over-torquing non-carbon components?

Postby human909 » Mon May 21, 2018 10:45 am

macca33 wrote:I 'spose ckinnard is so passionate about his point of view because he HAS seen the worst of the bad things that happen to people - often.

All quite true. But that is the thing letting your emotions and the frequency of seeing injury affect you assessment of the broader safety landscape.

The bias has lead the Australian medical profession to be ardent supporters of MHLs. Likewise with the recommendation for mouthguards for cyclists.

Take a guess at how many dutch bikes see a torque wrench on their bolts during assembly and maintenance. How many dutch are riding and how often? Given the lack of common use of torque wrenches you would think that if ckinnard's fears were warranted and not extremely low probability events then we would be seeing epidemics of incidents.

(Now don't get me wrong. I have no reason to argue that appropriately torquing EVERY bolt to the appropriate torque is 'best and ideal practice'. But in the real world a good mechanic is more than adequate. Also a cyclist who is does not ignore the warning signs will keep him/herself much safer.)

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Re: Over-torquing non-carbon components?

Postby ball bearing » Mon May 21, 2018 11:00 am

Pertinent observations....


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P!N20
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Re: Over-torquing non-carbon components?

Postby P!N20 » Mon May 21, 2018 11:39 am

^ Yeah, but we're not talking about about carbon fibre frames or components.

prox wrote:I was wondering if I could get some thoughts from the community about the relevance of correctly torqued non-carbon components...

human909
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Re: Over-torquing non-carbon components?

Postby human909 » Mon May 21, 2018 11:42 am

ball bearing wrote:Pertinent observations....

I have no reason to disagree with the need to avoid over tightening on lightweight carbon components and frames. I would continue but I don't want to side track the conversation into one about fragile frames.

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Re: Over-torquing non-carbon components?

Postby fat and old » Mon May 21, 2018 12:24 pm

macca33 wrote:I 'spose ckinnard is so passionate about his point of view because he HAS seen the worst of the bad things that happen to people - often. People who were too uneducated, or ignorant, to understand that there is a greater likelihood of things going awry if their equipment or individual circumstances were not properly managed/assembled/used to begin with.

Others may not agree, given their lack of similar experience...


I can't/won't cite similar experience; but I will cite advancing age as a reason to be overly/more pedantic about things. At 53, riding down a hill at 70+ kmh has me checking the front skewer repeatedly for example. At 25 or even 30, I'd have considered jumping off into a commando roll for fun :lol:

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Re: Over-torquing non-carbon components?

Postby human909 » Mon May 21, 2018 12:50 pm

fat and old wrote:At 53, riding down a hill at 70+ kmh has me checking the front skewer repeatedly for example.


On that tangent.... When it comes to safety one of my often repeated words of wisdom to the people that I teach is that FEAR is a good thing. Fear keeps us alive, and embracing it and being a little paranoid about things is a good thing (within reason).

My equivalent to checking my front skewer while riding at 70kph is triple checking that the rope tied to me is tied correctly while I'm hanging 100m up in the air. It isn't particularly rational they are things you really should be doing before you get there! :lol: But hey if it gives you the comfort to keep at it safely then there isn't much harm.

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Thoglette
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Re: Over-torquing non-carbon components?

Postby Thoglette » Mon May 21, 2018 1:34 pm

human909 wrote:The bias has lead the Australian medical profession to be ardent supporters of MHLs.


I use emergency room doctors as the example of a perfect set of bias conditions that result in flawed beliefs.
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