Over-torquing non-carbon components?

[prox]

Hi all,

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

I see the obvious necessity of only tightening carbon components to the recommended torque values - if you over-tighten them, you could easily damage the carbon fibres and render your investment useless. That makes total sense to me.

But for parts made from more pliable materials like 6061 alum, or steel, or even potentially titanium, is there really such a concern with torquing components to values higher than recommended specs?

What's your opinion and/or experience on this topic?

[P!N20]

^ The main risk is stripping threads (ask me how I know.)

[prox]

^ The main risk is stripping threads (ask me how I know.)

How do you know?

[Tim]

A fundamental skill of any mechanic and engineer be they of the bike, motorcycle, car, truck or any other variety is correctly tightening fixtures by feel.
There is a right way, and many wrong ways of doing a job.
Over-tightening parts is just plain wrong and unskilled. You risk stripped threads as mentioned, broken bolts and studs and damaged parts. An example; overtightening a front derailleur band clamp can crush the frame seat tube, especially an aluminium one, ruining it.
Non-carbon parts don't necessarily need precise torquing ie. measured with a torque wrench but they do need to be tightened correctly within a slightly more forgiving range of ham-fisted butchery.
Carbon fittings can be tightened without a torque wrench with a degree of skilled and experienced feel.

[Thoglette]

is there really such a concern with torquing components to values higher than recommended specs?

No.

What's your opinion and/or experience on this topic?

Traditional materials; engineering and tool design meant that a reasonably calibrated wrist would get it close enough 90% of the time.

It was only rare high stress (e.g. head bolts; connecting rods or bus/truck wheels) that needed enough preload to warrant cracking out the torque wrench. Or really fragile structures.

And bikes didn't have any of these.

[10speedsemiracer]

....It was only rare high stress (e.g. head bolts; connecting rods or bus/truck wheels) that needed enough preload to warrant cracking out the torque wrench. Or really fragile structures.

And bikes didn't have any of these.

+1
Have only ever used a torque wrench for head studs, VW cases, conrod bolts, that sort of thing. The one and only time I have used a torque wrench on a bike was installing a new BB on a carbon Bianchi Intenso, because it wasn't mine.

[human909]

I've worked for years in industrial construction. Both structural and machinery. I don't think I've ever seen a torque wrench being used.

Of course plenty of things are supposed to be torqued up correctly. But for the smaller stuff that is where a thoglette's 'reasonably calibrated wrist' comes into play... For average structural steel it normally is just a badly calibrated rattle gun and massively over engineered bolted connections.

That said on the other side of the fence there are plenty of mission critical needs for torque bolts reliably and accurately.

[Thoglette]

Of course plenty of things are supposed to be torqued up correctly.

Oh, the fun I've had over the years having to explain "snug-tight " (as referenced in AS/NZ for tower construction) to QA inspectors who have a torque wrench fixation.

[mikgit]

Got my first carbon bit in 1996, before that was loads of light aluminium bits... and many many parts thereafter... never used a torque wrench, didn't even know they existed till a few years ago.

[P!N20]

How do you know?

Managed to strip a Shimano 600 crank thread using a crank extractor incorrectly.

Still, it's pretty hard to do.

[duncanm]

http://nla.gov.au/nla.obj-160219588

[duncan16v]

I play on steam engines. There are generally 3 torque settings: tight, very tight, and very (insert rudey word here) tight. For everything else, I get the torque wrench out.

[ball bearing]

I like my torque wrenches and I often use them on my bikes. I don't really understand the problem.

[eeksll]

sounds like the OP is wandering what negative/failures occur when over tightening non-carbon components. Stripped threads seems to be one.

e.g I have a alloy seatpost/collar/frame and the seatpost keeps slipping, if I keep tightening that thing up until it does not slip and the screw threads haven't been stripped, am I "A-OK"?

[duncanm]

sounds like the OP is wandering what negative/failures occur when over tightening non-carbon components. Stripped threads seems to be one.

e.g I have a alloy seatpost/collar/frame and the seatpost keeps slipping, if I keep tightening that thing up until it does not slip and the screw threads haven't been stripped, am I "A-OK"?

I had a handlebar that kept slipping. Had it nice and tight (4-5mm allen key, so not spanner-like tight), and one day the bolt went 'ping' on me.

It had a crevice-corrosion type failure that took some time to develop. Half the break was rusty.

[Mulger bill]

http://nla.gov.au/nla.obj-160219588

All good.
The bloke on the ladders job is to say "CLICK" when "she's about right"...

[RonK]

Traditional materials; engineering and tool design meant that a reasonably calibrated wrist would get it close enough 90% of the time.

Perhaps, but that degree of feel takes years of experience to acquire. Few amateur bike mechanics would have it, or be likely to develop it.
Typical fasteners used on bicycles tend to be of small diameter and low tensile strength, thus are easily damaged.
For amateurs the smart thing to do is to use a torque wrench.

[Thoglette]

Perhaps, but that degree of feel takes years of experience to acquire. Few amateur bike mechanics would have it, or be likely to develop it.

A very interesting line of thought.

I've been "wrenching" (if you'll excuse the Americanism) since primary school. Paying someone to look after one's bike (or later one's car) was an unaffordable luxury, so you did it all yourself. Or walked (the shame!)

When stuck, you sought advice (and special tools) from an older relative or a neighbour. I particularly recall being coached in determining whether a bearing surface was knackered - this is something that would be very hard to pickup online.

It's a bit like picking where to go fishing; or surfing; or sailing; or knots; or firearm safety (yes, I'm that old): these things were just "common sense". Common sense which was handed down, not just by the family but the whole community.

I still have a habit of using things until they are utterly beyond repair. And as a resultsometimes get stuck by the road for the sake of $50 ($150rrp) of prevention.

[RonK]

Perhaps, but that degree of feel takes years of experience to acquire. Few amateur bike mechanics would have it, or be likely to develop it.

A very interesting line of thought.

Not a thought bubble - real world experience observed during a 5 year apprenticeship and subsequent 15 year career in the automotive industry.

Oh, and a torque wrench is the only wrench in my toolbox - all the rest are spanners.

[skyblot]

What RonK said.
After 40 years driving spanners in the aviation game, I know I have a habit of under-torquing fasteners, and I've also learnt that using a torque wrench is the only way to know the fastener is correctly tightened.

By all means do it by feel, but be aware that the chances of being right are not that good. Fortunately most of our bike bits are pretty tolerant and we get away with a lot.

[Thoglette]

Fortunately most of our bike bits are pretty tolerant and we get away with a lot.

Agree with all that you and RonK said. But this is the relevant punchline.

However, don't let me discourage anyone from using RonK & Skyblot comments to justify buying (and perhaps even using) a couple of torque wrenches

[Duck!]

Traditional materials; engineering and tool design meant that a reasonably calibrated wrist would get it close enough 90% of the time.

Perhaps, but that degree of feel takes years of experience to acquire. Few amateur bike mechanics would have it, or be likely to develop it.

Probably a lot of pros won't get it either... I'd say I have a reasonably calculated feel, but accurate, no. My calculated feel tends to be slightly under, but that's probably better than overdoing it. And for small bolts typical of bikes, it's not a calibrated wrist, but calibrated fingers, or usually just one.

[CKinnard]

ways to kill yourself by not torqueing bolts to spec:

- headsets can get loose quickly and contribute to aptly named death wobble.
- loose stems = no steering.
I even saw a guy do a wheel stand and the steerer tube/fork/front wheel fell off the bike and he came down hard.
- loose handlebars = use your imagination

- pedals can come off cranks and cause serious injury, as I've seen in crit sprints.
- loose cleats and sprinting out of the saddle

- brake cables can slip out of securing bolts
- chain can jam and throw you off the bike when the front derailleur cable slips through its securing bolt.

- saddle to seat post or seat post to seat tube can fail. happened to a guy 200 meters from the start of a charity ride, and I just managed to get around him without going down myself.

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.

yes bikes are not as complex as cars, but everything on them is so critical that any failure = catastrophic failure.
I have done a lot of touring and audax length rides over the decades, and seen non torqued to spec bolts work their way loose.
I have a habit of checking most bolts before big rides and/or every ~2000km.
At least half the loose bolts I've experienced during rides were after a LBS were the last to adjust them, so I don't trust anyone to adjust bolts correctly. Learn to do it yourself.
And components can come loose with under, correct, or over-torquing (thread stripping or otherwise weakening surrounding metal). grease or loctite can help prevent loosening with correct torque.

re carbon component specs, it's not unusual for the components to be damaged torquing them to spec. Many torque them much less.

[human909]

ways to kill yourself by not torqueing bolts to spec:

Or just tighten the bolts appropriately without measuring torque....

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.

Let's not be overdramatic here.

Lets for a second speculate on how many bikes have been built and are still being built without a way of measuring torque. Both for past and present I would say it is the majority.

It is a wonder our roads aren't littered with fatalities from imprecise torquing.

[P!N20]

- chain can jam and throw you off the bike when the front derailleur cable slips through its securing bolt.

Or it just leaves the chain on the inner ring and you keep happily riding along. Catastrophic.