Author Topic: How do you know the fasteners on your bike are not overtorqued?  (Read 5855 times)

Andre Jute

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How do you know the fasteners on your bike are not overtorqued?
« on: November 20, 2013, 06:51:27 pm »
It is better to torque only up to the lowest recommended setting. Unfortunately, with the best components the suggested band is normally quite small, so an instrument of reasonable precision is required. This is the one I use: http://www.wiggle.co.uk/bbb-btl-73-torqueset-torque-spanner-set/
and SJS sells this one from Shimano which is similar http://www.sjscycles.co.uk/shimano-pro-3-15-nm-torque-wrench-set-prod25639/

Why do you need a torque wrench? For a start, on a modern bike most torque settings are pretty low, too low to judge by the suck and it and see method still common in your average bike shop.

The standard LBS method of checking that your bike is "tight", of putting a spanner on the head of the bolt or the nut and twisting, is absolutely guaranteed to over-torque just about every fastener on a modern bike. If you have a torque wrench, the better way is to set a torque, then check all the bolts on the bike of that torque, then set the next torque, etc. All correctly fastened bolts will click immediately you turn the handle.

This assumes that you know the bolts were correctly fastened in the first place, of course, as they were if they came from Rohloff or SON or were torqued up by you with the aid of a torque wrench. I release and retorque everything not from a reliable German or Taiwanese factory every time I get a new bike. Only way to know.

Only place where this doesn't work on my bikes, regardless of which bottom brackets and cranks I have, is at the crank bolts. Those I fasten, regardless of manufacturer's ratings, by parking the bike against a post cemented into the ground, bracing the pedal against the pole, putting a lever on the crank spanner and repeatedly stepping up on the lever one foot away from the bolt with my 200 pounds plus (you can work out the torque...). Otherwise the thing always comes loose and starts squeaking. Another cyclist claims I pedal too powerfully because I don't change gears often enough. Maybe he's right: now that I have electric assist, I haven't had a loose crank bolt such as used to plague me all the years of my cycling.

StuntPilot

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #1 on: November 20, 2013, 07:30:57 pm »
Andre

Some useful figures here ...

http://bicycletutor.com/torque-specifications/

Richard

jags

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #2 on: November 20, 2013, 07:45:04 pm »
would have no idea Andre never used a torque  wrench in my life never over tightened a bold or had one break so i must be doing something right ;)

Andre Jute

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #3 on: November 20, 2013, 07:53:03 pm »
Thanks, Richard.

Wait until you get a carbon bike, Anto. Then you'll be here daily crying in your beer about breakages. Why do you think Thorn doesn't offer a carbon frame?

jags

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #4 on: November 20, 2013, 09:12:25 pm »
had one Andre look kx light stunning bike full carbon rode like a dream sold it for feck all ::)
someone should really kick me up the arse for all these stupit thing i do selling all my best bits for little or nothing. :'(

macspud

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #5 on: November 20, 2013, 09:33:44 pm »
It is better to torque only up to the lowest recommended setting. Unfortunately, with the best components the suggested band is normally quite small, so an instrument of reasonable precision is required. This is the one I use: http://www.wiggle.co.uk/bbb-btl-73-torqueset-torque-spanner-set/


The same torque wrench on Amazon for £40.56 inc delivery at the moment.
http://www.amazon.co.uk/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=BBB%20BTL-73%20TorqueSet%20Torque%20Spanner%20Set

mickeg

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #6 on: November 21, 2013, 03:35:19 pm »
The only bolts on my bikes that I use a torque wrench on are the crank bolts.  And I use the manufacturer recommended torque for those.  When I have removed crank bolts later, they have felt much looser than the original torque settings from installation.  (I only use square taper, thus I may have a different experience than others.)  I have no explanation for this, I have suspected that the crank arms over time worked onto the square taper to a more snug fit, loosening up the pressure from the bolts, but this is only a suspicion on my part.  Since my crank arm pullers always indicated that the cranks were on really tight, having  bolts that were less than initial tightness has not bothered me at all as long as the bolts were tight enough to not fall off of the bike.

I use blue locktite on all rack bolts.  Many brake bolts come new with a similar thread locker on them.  Thus, I feel that having a proper torque setting on such may be less than critical.  Most other bolts like water bottle cages, fenders, etc., do not really need a high torque setting as long as they are tight enough to stay on.  I often grease these, the viscous fluid helps keep them from vibrating off if then get loose.  I also use blue loctite on and kickstand bolts because I put these on with a pretty low torque setting, I try to get them only tight enough so that the kickstand does not shift position and the bolts do not vibrate loose.  I often have to re-tighten kickstand bolts later but I still do not torque then very tight.

I have noticed that bolts on Cane Creek or Tektro brake levers that have a polymer body appear to loosen over time, I find that I am tightening these a few times months after a new installation, same with shoe cleat bolts.  I suspect that the plastic shoe sole material and the plastic in the brake lever body deforms a little, reducing bolt tension.

Danneaux

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #7 on: November 21, 2013, 08:03:10 pm »
Quote
When I have removed crank bolts later, they have felt much looser than the original torque settings from installation.
Hi mickeg! Joint relaxation (creep), bolt stretch and materials compression are all factors in making bolts loosen at lower torque than they tighten (to).
Quote
Since my crank arm pullers always indicated that the cranks were on really tight, having  bolts that were less than initial tightness has not bothered me at all as long as the bolts were tight enough to not fall off of the bike.
<nods> Torque to the correct value in one continuous motion of possible, then...stop. Don't go back for a second go. A few applications require repeat torquing to torquing an intermediary value (cylinder-head bolts come to mind) or to a torque-angle (crankshaft pulley bolts), or if a torque-to-yield fastener is used, but these are all rare in bicycles. :)

One thing to keep in mind when torquing fasteners coated with threadlock compound (in its liquid state) is the difference between "dry torque" and "wet torque". See: http://www.thorncycles.co.uk/forums/index.php?topic=6805.msg42269#msg42269 In bicycles, assume "dry" unless instructed to use "wet". A handy table of dry torque values for metric fasteners I often use is here: http://www.engineershandbook.com/Tables/torque1.htm For comparison, take a look at dry vs wet values and variations caused by bolt coatings: http://raskcycle.com/techtip/webdoc14.html Though this last link is for SAE fasteners, the difference in values and rues of thumb hold true regardless. In general, there will be more torque variation with a dry fastener than a lubed one.
Quote
Most other bolts like water bottle cages, fenders, etc., do not really need a high torque setting as long as they are tight enough to stay on.  I often grease these, the viscous fluid helps keep them from vibrating off if then get loose.
All true, but there's another factor in play here as well: If one uses dry torque on a lubed fastener, it will be tightened more.
Quote
I have noticed that bolts on Cane Creek or Tektro brake levers that have a polymer body appear to loosen over time, I find that I am tightening these a few times months after a new installation, same with shoe cleat bolts.  I suspect that the plastic shoe sole material and the plastic in the brake lever body deforms a little, reducing bolt tension.
Yep; materials compression.

Pre-applied threadlocker (the dry-crusty stuff already on the threads of new bolts sometimes included with components) adds some complications. It is not just "dry", but sometimes is robust enough to clog the threads and so cause a momentary rise in tightening torque that is artificial.

Loosening torque can sometimes be  greater than tightening torque due to galvanic corrosion between the metals in a joint, or grease/anti-seize drying-out a bit or if threadlocking compound is used or if washers of various sorts are used.

For all these reasons and more, it would not be a good idea to use loosening torque as a measure of tightening torque. Tightening torque is just that.

An interesting article on torque in automotive applications is here: http://www.popularmechanics.com/cars/how-to/repair/torque-wrench-101-how-to-get-the-right-amount-of-force-2

Best,

Dan. (...who is a "nut" about correct torque values and the things that affect it)
« Last Edit: November 23, 2013, 01:39:58 am by Danneaux »

davefife

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #8 on: November 21, 2013, 09:18:06 pm »
Quote
The standard LBS method of checking that your bike is "tight", of putting a spanner on the head of the bolt or the nut and twisting
would wish to read the evidence/experience that allows this assertion to be made!  As a bike mech of growing renown round here (and a builder of carbon framed bikes) I can assure readers that this is not always the case ;)  whether steel, alu, carbon or bamboo frames  (I have no experience of the latter) so could not comment ;D
 

Andre Jute

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #9 on: November 22, 2013, 12:45:23 am »
would wish to read the evidence/experience that allows this assertion to be made!  As a bike mech of growing renown round here (and a builder of carbon framed bikes) I can assure readers that this is not always the case ;)  whether steel, alu, carbon or bamboo frames  (I have no experience of the latter) so could not comment ;D

Eh? You've never seen an old-fashioned bike mechanic test pre-torqued fasteners by twisting them? You must have led a pretty sheltered life, Dave.

I can state unequivocally that I've seen a bike mechanic with decades of experience twist off fasteners on my bikes more than once. It is one of the reasons I started doing the work myself, because the only bike shop in striking distance was operated by rejects from a blacksmith training school.

"Growing renown", eh? Congratulations. You wouldn't want to move to lovely rural Ireland, would you?

davefife

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #10 on: November 22, 2013, 01:04:12 pm »
LOL, cycled thru your part of the world 20 yrs ago, have another 10 years on the bike repairs, then mobile home and retirement, who knows!! Cobn, Millstreet and Blackwater River are etched memories also Rock of Cashel.
keep torquing!
Dave
 

julk

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #11 on: November 22, 2013, 02:05:05 pm »
Andre,
"You wouldn't want to move to lovely rural Ireland, would you?"

Hands Off! Dave’s transfer fee is too expensive...

Dave is reasonably local to me and hopefully staying for a while  ;D
Julian.
« Last Edit: November 22, 2013, 02:07:38 pm by julk »

Andre Jute

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #12 on: November 22, 2013, 08:42:14 pm »
Andre,
"You wouldn't want to move to lovely rural Ireland, would you?"

Hands Off! Dave’s transfer fee is too expensive...

Dave is reasonably local to me and hopefully staying for a while  ;D
Julian.

Heh-heh. A fellow at the Pentagon that I used to drink with once sneered about the immorality of the CIA people, "In Foggy Bottom it is a crime to steal a man's cook. The theft of a wife passes unremarked."

davefife

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #13 on: December 18, 2013, 01:29:48 pm »
Our recent musings on torque leads me to share this photo of my 30yr old campagnolo 5mm allen key helping me build my road bike for next summer, the dimensions seem to be just right for the nipping up cable anchor bolts, brake pads, seat post bolt etc etc, a beautiful tool that will outlast me.
https://pbs.twimg.com/media/BbsqiwTIYAA27FF.jpg

Bike is a columbus frame handmade by Zullo in Northern Italy, its having a racing triple 8 speed drivetrain and chorus hubs onto campagnolo omega 19 rims and in a departure from Europe a Nitto 105 handlebar and nitto quill technomatic stem 1" of course ;)
 

Andre Jute

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Re: How do you know the fasteners on your bike are not overtorqued?
« Reply #14 on: December 18, 2013, 03:27:40 pm »
My, that is a beautiful tool, Dave. Thanks for showing it to us.