Nerd Talk: The Merits of Torque Wrenches
Comments
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To be fair, the requirements for tightening most things on a bike are pretty simple.
a) It shouldn't fall off
b) Don't break it.
A bit of experience gets you in between those two boundaries pretty quickly.- - - - - - - - - -
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Totally agree0 -
chrisw12 wrote:oh and to add I would trust no one with my bikes (whatever the price) and always check them over on the rare occasions that they have work done on them at the lbs, as I'd imagine most people on here do.
That's the one time I don't bother checking, because my LBS man is a way better mechanic than I am, PLUS, and you know this is coming,,,, he uses a torque wrench on anything carbon.
I wheeled my bike into his shop one day and while I was still 15 feet away he reached for the hex key to adjust the front left brake block angle, which was *very slightly* off. I got a lecture. He then noticed I'd changed the setup, with a 5mm spacer now above the stem, and bars at a fractionally different angle. That sent him diving for the torque wrench to check my handiwork (all carbon steerer tube, stem and bars), even though he'd sold me the same wrench to use at home and given me another lecture on its proper use.
I do most of my own maintenance on all my bikes, have done for years. There is a fortune in tools in my shed, because my Significant Other is an aircraft engineer, and if you want to meet someone, well, fussy about doing nuts and bolts up correctly, chat to one of them sometime!!Open One+ BMC TE29 Seven 622SL On One Scandal Cervelo RS0 -
chrisw12 wrote:1) How do you know that your torque wrench is correctly calibrated?
As per other answers - they're calibrated at the factory. After this you're on your own. Unless you have a torque watch.
Q: How do you know the torque watch is calibrated......
You can't go wrong with a torque wrench, and the torques used on bikes appear to be have a fair tolerance anyhow.0 -
Q: Why was the torque wrench invented?
A: because people stripped fasteners by over tightening them or had them come undone by under tightening them.
Engineers don't normally do things just for the good of their health (except cycling possibly).http://www.strathspey.co.uk - Quality Binoculars at a Sensible Price.
Specialized Roubaix SL3 Expert 2012, Cannondale CAAD5,
Marin Mount Vision (1997), Edinburgh Country tourer, 3 cats!0 -
Apologies, yes I have stolen someone else's work.
I think perhaps it's a question of who you trust, a pro bike mechanic, the lbs guy, yourself, the manufacturer's of ALL the parts or the guy on the forum below who actually sounds like he has done the experiments. Or you just keep on thinking the earth is flat 'cause someone told you so.
Anyway :- http://forum.slowtwitch.com/Slowtwitch_ ... s_P2505690
Just read his first post if you're time starved.0 -
chrisw12
yep and that was written by someone who knows what feels right. through using/fitting lots of stuff.
then take a bike shop where they have been working bikes for years and years and know what they are doing. But then they have a number of issues with the same "part" on lots of bikes. This was cured by the generous application of a torque wrench.
parts with a high torque number on a bike actually have less need of a torque wrench while it is the parts with the small numbers that benefit greatest as they dont get over tightened.
But I have seen so many failed bolts/parts through poor use of torque wrenches.
1 people miss reading the scale. 2 people not checking the tool is working correctly on Dummy part in a vice. 3 people missing the Click as the setting is only just on the scale etc etc.
if a part has a torque number on it and it fails as you did not follow the guide lines what do you do? it is obvious what happened by the failure.
I know one case where a part was tightened to the stated setting and it failed. it was replaced as the number was wrong.
I sometimes wonder why i have 2 torque wrenches and a torque screwdriver.
"Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
Parktools :?:SheldonBrown0 -
every part on a modern bicycle should be torqued correctly
this include ali, Ti, carbon, steel etc
i've seen cracked stems, frames etc due to overtightening (and not only on carbon)
modern lightweight bikes uses lightweight components which use the least amount of material as possible, this light weight approach leaves a much smaller margin of error and overtightening can cause component failures which is usually very expensive and can be very dangerous.
under tightening can also be a problem and can be a safety issue.
experience is great and the vast majority of times this may be fine but its like driving a car on the road with a non working speedo. try driving at a constant 50mph by guess work, i'm sure even the most experienced will find this difficult without a speedo. there is a margin of error with speedos but this will be accurate enough, a torque wrench will have a calibrated accuracy many times more accurate than a car's speedo.
for components without recommended torque settings, there are very comprehensive charts available for all the major parts manufacturers, the blue book has recommended torque settings for parts, zinn maintenance book is excellent for this and covers many manufacturer's recommended torque settings0 -
With notable exceptions, like crank tapers. I keep mentioning this because it is an interesting special case. Because it is a dynamic interface – the elements are in continual fretting motion against one another – the torque range of the attachment bolt is of particular importance. But because few people realise how the interface functions, it is habitually undertightened, leaving the bolt unsupported (and liable to drop out) as the crank climbs naturally up the taper. I think if a torque wrench is used nowhere else on a bike, it should be used here. (admittedly it's largely irrelevant now, as taper spindles are rarely seen..!)nicklouse wrote:chrisw12parts with a high torque number on a bike actually have less need of a torque wrench while it is the parts with the small numbers that benefit greatest as they dont get over tightened.
Much the same applies for a spoke tensiometer, which is a special-case torque wrench. The common factor in these cases is that the mechanics and fitters don't necessarily understand why the specified values are as they are, hence "feel" may be untrustworthy. Both crank bolts and spokes should be much tighter than most would guess.0 -
tri-sexual wrote:experience is great and the vast majority of times this may be fine but its like driving a car on the road with a non working speedo. try driving at a constant 50mph by guess work, i'm sure even the most experienced will find this difficult without a speedo. there is a margin of error with speedos but this will be accurate enough, a torque wrench will have a calibrated accuracy many times more accurate than a car's speedo.
This isn't a totally accurate analogy though is it? A better speedo analogy would be to say, if your speed drops below 30mph the car will explode or if it goes above 80mph you'll be arrested. So you aim for 50mph as it's in the middle but you can afford to drift away from it a bit with no ill effects.
If you were really desperate to hit a tensile load then the mfrs would be using torque+angle targets instead.- - - - - - - - - -
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