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View Poll Results: In relation to bicycles, do you use the terms Nm, Inch Pounds, or Foot Pounds?
Nm (Newton Metres) 34 55.74%
Inch Pounds 31 50.82%
Foot Pounds 14 22.95%
Multiple Choice Poll. Voters: 61. You may not vote on this poll

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Old 09-26-08, 11:07 PM   #1
BicycleTutor
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Bicycle Torque Specifications?

In the next week I'll be putting together 2 video tutorials: the first will give an overview of how torque measurements work, and the second video will give an general overview of torque specifications in relation to bicycles.

I'm was hoping some of you might have suggestions or links to share that would help make these videos more helping in covering the basics. I've always tightened bike parts by feel, so I'd like to do a useful tutorial for those who want to easily understand these concepts. Thank you kindly for your help

1. If you were going to make these videos, how would you do it?

2. Which term do you prefer? Nm, inch-pounds, or foot-pounds?

3. What are your general thoughts about bicycles and torque?
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Old 09-27-08, 04:59 AM   #2
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Newton metres here, remember there's only one country in the world that still routinely uses imperial measurements for torque, the rest are using metric (including the home of the imperial measurement, the UK!)
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Old 09-27-08, 05:17 AM   #3
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1&3. Bicycles are an interesting project for discussing torque specifications. I generally only use a torque wrench in two areas.

The first is cranks and bottom brackets. Left to my own "feel" I would consistantly undertorque them. I think that lots of other people must undertorque too because left cranks falling off is such a common problem.

The second is high end stems. I was surprised at how little torque is recommended. I'd overcook them if left to my own feel. It's important to get the bolts tightened evenly too.

2. I live in the country that still uses imperial measurements. I prefer lb/ft for cranks and in/lbs for the much smaller stem tork measurements.
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Old 09-27-08, 06:09 AM   #4
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Great tutorial subject! I'm especially interested about tightening carbon bits. I like your tutorials, keep on going !
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Old 09-27-08, 06:29 AM   #5
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You should have allowed 2 other choices "All the above", or "ft-lbs / nm." My torque wrenches all have both units. I usually use ft-lbs for the larger torques and nm for the finer adjustments. Your tutorial will be a great addition to bike mechanics. Unless you have worked on cars or are a machinist torque is a little understood item in the amateur bike fixer's arsenal. It is the area where people can really damage parts especially carbon parts. Good luck with your project.
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Old 09-27-08, 06:52 AM   #6
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Quote:
Originally Posted by Albinus View Post
Newton metres here, remember there's only one country in the world that still routinely uses imperial measurements for torque, the rest are using metric (including the home of the imperial measurement, the UK!)
The UK (and Canada) are still schizophrenic about the unit system they really use. The Metric system is the "official" one but Imperial/SAE units persist in a lot of places.

As to the "only one country", yes, that's true but there are a lot of us and we are the world's largest market for many items so the inch-pound and foot-pound are going to remain current for a long time.
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Old 09-27-08, 01:07 PM   #7
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It is pound-force feet or pound-force inches. Here are the conversion factors.

NIST

Convert Tool



Last edited by biker128pedal; 10-08-08 at 03:20 PM.
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Old 09-27-08, 03:29 PM   #8
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Thanks for all of your tips... this is going to be very helpful!
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Old 09-27-08, 03:33 PM   #9
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Provide a chart or links to a place that can covert torque measurements.

A lot of us are still old fogeys with imperial units old tried and true torque wrenches and inch and foot lbs are our torque of choice. Inch-lbs for the smaller stuff and ft=lbs for the bigger stuff. Typically if you hit 3 digits for in-lbs then it's more appropriate to give it in ft-lbs.

Don't forget that while there are charts for bolt size vs torque values for the various grades of bolts it is also limited by the material or application the bolt is used for. For example a seat post retainer bolt is easily capable of deforming or splitting the frame on bikes where there's no slip on collar so some prudence has to be taken. I don't see how you can do a video of this sort without it also turning into a catalog of different frame, wheel and other components and becoming over long but good luck on that.
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Old 09-27-08, 03:40 PM   #10
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Quote:
Originally Posted by Albinus View Post
Newton metres here, remember there's only one country in the world that still routinely uses imperial measurements for torque, the rest are using metric (including the home of the imperial measurement, the UK!)
And the lug on the end of the torque wrench to which you attach sockets, what size is it?
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Old 09-27-08, 03:47 PM   #11
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When it comes to torque wrenches the best advice I can offer bicycle owners and mechanics is to use common sense. The torque specs for a stem is not necessarily appropriate for the steer tube or the handlebar to which you attach the stem. I cracked the steer tube on a very expensive fork because I used the torque spec shown on the stem. If I had used my intuition I would not have cracked the tube.

Al
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Old 09-27-08, 06:11 PM   #12
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I'm a little confused. If I understand correctly, in the imperial system a foot-pound means there is one pound of pressure applied if the wrench lever is one foot long, and an inch-pound means there is one pound of pressure applied if the wrench lever were only one inch long. Am I right?

If this is right, then how do Newton Metres work?
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Old 09-27-08, 06:17 PM   #13
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Here plug and chug. And you thought you only had to deal with three unit sets.

Torque Conversion
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Old 09-27-08, 06:22 PM   #14
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Quote:
Originally Posted by BicycleTutor View Post
I'm a little confused. If I understand correctly, in the imperial system a foot-pound means there is one pound of pressure applied if the wrench lever is one foot long, and an inch-pound means there is one pound of pressure applied if the wrench lever were only one inch long. Am I right?

If this is right, then how do Newton Meters (US spelling) work?
The pound is the pound-force not the pound mass. Newton is a unit of force. Kilogram is a unit of mass.

Mass and Weight

The bottom line is your manual should list the torque in both English and Metric. The Trek CD does. And the torgue wrench should have both. Mine do.
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Old 09-27-08, 06:28 PM   #15
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Quote:
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The pound is the pound-force not the pound mass. Newton is a unit of force. Kilogram is a unit of mass.
The distinction between force and mass has confused untold millions of Physics students. Some never do get it straight.
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Old 09-28-08, 05:57 AM   #16
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Quote:
Originally Posted by Albinus View Post
Newton metres here, remember there's only one country in the world that still routinely uses imperial measurements for torque, the rest are using metric (including the home of the imperial measurement, the UK!)
considering he's asking on bikeforum.net and not everywhereelseintheworldbikeforums.net I vote for ft. lbs. J/K

Newton meters and ft.lbs
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Old 09-29-08, 01:44 AM   #17
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Quote:
Originally Posted by Al1943 View Post
And the lug on the end of the torque wrench to which you attach sockets, what size is it?
Yup - you got it - either 1/4", 3/8" or 1/2". Fortunately most people are able to convert readily between imperial and metric here, except many younger builders. They only seem to want to know millimetres!
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Old 09-29-08, 12:59 PM   #18
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ok, I do not use a torque wrench on any bicycle ----- I find the material used for bicycles are
generally trash-- from crank bolts to small hex bolts-- all trash -- basically pot metal against
cream cheese aluminum-- I dont find the fascination with this at all.........................
what machinists and techs need to learn are thread pitch, diameter, and lengths...... most
techs have no Idea what kind of bolt they are cranking down to spec.--- and with low end
tools!?
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Old 09-29-08, 01:07 PM   #19
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Yup - you got it - either 1/4", 3/8" or 1/2". Fortunately most people are able to convert readily between imperial and metric here, except many younger builders. They only seem to want to know millimetres!
I'll believe we're all going metric when I see bike chain pitch and steer tube diameters and socket drives in mm.
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Old 09-29-08, 03:59 PM   #20
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Yes.
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Old 09-29-08, 04:05 PM   #21
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Quote:
Originally Posted by biker128pedal View Post
Here are the conversion factors.

NIST
Make it easy on yourself:

ft-lbs = Nm * 3/4
in-lb = ft-lb * 12
in-lb = Nm * 9

Thus 4 Nm = 3 ft-lb = 36 in-lb.
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Old 09-29-08, 04:57 PM   #22
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ok, I do not use a torque wrench on any bicycle ----- I find the material used for bicycles are
generally trash-- from crank bolts to small hex bolts-- all trash -- basically pot metal against
cream cheese aluminum-- I dont find the fascination with this at all.........................
Maybe you've been working on the wrong bikes.
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Old 09-29-08, 05:37 PM   #23
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if what I see from the home front is:
gee I replaced my own road bars--"do you think its tight enough?"
and--- the inside of the hex bolt is round and the front plate is off center---
do you think I would talk this person into a torque wrench?
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Old 09-29-08, 06:00 PM   #24
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Quote:
Originally Posted by BicycleTutor View Post
In the next week I'll be putting together 2 video tutorials: the first will give an overview of how torque measurements work, and the second video will give an general overview of torque specifications in relation to bicycles.

I'm was hoping some of you might have suggestions or links to share that would help make these videos more helping in covering the basics. I've always tightened bike parts by feel, so I'd like to do a useful tutorial for those who want to easily understand these concepts. Thank you kindly for your help

1. If you were going to make these videos, how would you do it?

2. Which term do you prefer? Nm, inch-pounds, or foot-pounds?

3. What are your general thoughts about bicycles and torque?
If you want to put together a real instructional video you'll tell the viewere that all 3 are used commonly and without standardization within the industry. What is there to make a video about anyways? Use a torqure wrench, torque things up to spec.

?
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Old 09-29-08, 09:03 PM   #25
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My torque number is always "tight enough". Never used a torque wrench, never will.
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