Max 5nm - do you?

[Splatter Paint]

I was watching a bike repair video on YouTube the other day and the mechanic was diligently torquing everything to the ‘correct spec’. However, somebody pointed out to me that ‘Max’ is maximum torque and by inference perhaps not necessarily the optimum. So, the component is marked ‘Max 5nm’ and is a safety critical and carbon. Do you:

Torque to 5nm
Torque to a lesser value
Do it up without a torque wrench
Something else

Personally I’d torque to a lower value and see if it moves / slips / creaks.

You?

 

[mdvineng]

Check the real specifications as they always have a min max setting.

 

[Gtpulse]

I do have a bike specific torque wrench, I never use it.

I can see a place for this if I had any high end modern carbon stuff I’d be a bit more fussy. I’d struggle to get the sense of how tight it was before it cracked!

I guess also if you’re a paid mechanic you’d want to have some due diligence and standard methods of working in case the worst happened to a paying customer.

Seat post probably gets the most attention from me, that is I usually tighten it just enough to stop it moving, then if it moves after a shakedown a little tweak more. That’s if it’s a bolt, otherwise who knows what torque the qr lever is.

Only thing I’ve ever stripped out through over tightening was a Controltech stem which was like it was made of cheese.

Back in the day I made do with a Raleigh multi spanner, a pair of pliers and a set of those allen keys on a key ring. Chain tool was an old drill bit and a hammer.

 

[Splatter Paint]

I’ve just checked the most recent stem I purchased, the on-line docs say a minimum of 4nm, max 5nm.

When you account for a +/- 5% torque wrench accuracy that could be in the range 4.2nm to 4.75nm.

SP

 

[Chopper the ex Copper]

In reality it matters not, seeing as very few folk even have their torque wrenches periodically calibrated, and they do lose calibration very easily.

 

[TreaderSteve]

NTFT. Not too fuggin tight! It comes with age and feel...

 

[michael franks]

A (very good) car mechanic told me many years ago that:
"you tighten the bolt until it's about to strip the thread and then back it off a quarter turn!" I don't adhere to that advice.

 

[Imlach]

With 'delicate' carbon some are very careful when it comes to torqueing bolts, but although you have to be somewhat careful, you've got to be truly ham-fisted to do any damage. I personally do not use a torque wrench anywhere on the bike with exception of cassettes and cranksets, because I've had too many bad experiences with cranks loosening, so I'm always a strict 45 to 50nm in the crank region, which can seem a bit excessive but I've never had them loosen and round since!

I personally believe the mini-torque key thingymabobs are a gimmick. If you overtighten a front derailleur to a point where you damage the tubing you're a lost cause anyway.

 

[jonnyboy666]

yes, i use various torque set tools, especially when carbon is involved, i see so many rounded off bolts, stripped threads and overtightened seatpost clamps that destroy carbon frames etc.

i hate it when people say "my hands are like torque wrenches", no . . . no they a re not. i think it was Park Tool who did a competition at the bike show, proving that most people massively over tightened bolts by thinking they have feel.

 

[mdvineng]

I am lucky enough to have a few ex aircraft torque tools, including a calibrator rig. Over the years, the drift has been so small, it can be ignored. The temperature of the garage at the time has more affect on variance.

Totally agree with the "Park tool competition finding"