# Bicycle Mechanics - Bicycle Torque Specifications?

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View Full Version : Bicycle Torque Specifications?

BicycleTutor
09-27-08, 12:07 AM
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?

Albinus
09-27-08, 05:59 AM
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!)

Retro Grouch
09-27-08, 06:17 AM
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.

Dago
09-27-08, 07:09 AM
Great tutorial subject! I'm especially interested about tightening carbon bits. I like your tutorials, keep on going :)!

Deanster04
09-27-08, 07:29 AM
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.

HillRider
09-27-08, 07:52 AM
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.

biker128pedal
09-27-08, 02:07 PM
It is pound-force feet or pound-force inches. Here are the conversion factors.

NIST (http://physics.nist.gov/Pubs/SP811/appenB9.html#TORQUE)

Convert Tool (http://www.onlineconversion.com/torque.htm)

:troll:

BicycleTutor
09-27-08, 04:29 PM
Thanks for all of your tips... this is going to be very helpful!

BCRider
09-27-08, 04:33 PM
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.

Al1943
09-27-08, 04:40 PM
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?

Al1943
09-27-08, 04:47 PM
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

BicycleTutor
09-27-08, 07:11 PM
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?

biker128pedal
09-27-08, 07:17 PM
Here plug and chug. And you thought you only had to deal with three unit sets.

Torque Conversion (http://www.onlineconversion.com/torque.htm)

biker128pedal
09-27-08, 07:22 PM
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 (http://www.exploratorium.edu/ronh/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.

HillRider
09-27-08, 07:28 PM
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.

miamijim
09-28-08, 06:57 AM
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

Albinus
09-29-08, 02:44 AM
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!

G piny parnas
09-29-08, 01:59 PM
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!?

Al1943
09-29-08, 02:07 PM
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.

DMF
09-29-08, 04:59 PM
Yes.

DMF
09-29-08, 05:05 PM
Here are the conversion factors.

NIST (http://physics.nist.gov/Pubs/SP811/appenB9.html#TORQUE)

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.

Al1943
09-29-08, 05:57 PM
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.

G piny parnas
09-29-08, 06:37 PM
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?

operator
09-29-08, 07:00 PM
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?

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.

?

tellyho
09-29-08, 10:03 PM
My torque number is always "tight enough". Never used a torque wrench, never will.

mx_599
10-06-08, 11:42 PM
this country is more used to inch/foot pounds. use inch for lower torques and foot for larger torques

mx

somegeek
10-07-08, 12:31 AM
Ft lbs... only because that is the side of my torque wrench that I am used to reading... to convert, I'd set it to the equivelent in nm. Viola!

http://s7.sears.com/is/image/Sears/00944594000?qlt=90,0&resMode=sharp&op_usm=0.9,0.5,0,0

bmorey
10-07-08, 01:10 AM
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.

Only at the consumer level. US industry is metric and has been for zonks.

I would have thought British measurements would have disappeared into Boston harbor along with the tea. Odd, really :p

G piny parnas
10-07-08, 11:53 AM
update: we aren't building lasers...... torque wrenches are worthless to me on a bicycle---
by a show of hands out in the audience today (BF= 1000 lookers) who regularly uses a torque
wrench on their bicycles--- Most questions on BF i have encountered are written by folks
who dont even know how to use a ratchet-- not to be snarky, but could we put these beautys
back in our 1000.00 snap roll-offs and encourage youth to use the proper grease instead of WD40.?
sincerely-- venting with no booze in sight..................................

DMF
10-07-08, 11:53 AM
It's what we're used to. I know bananas are 49¢/lb and that I should buy two pounds. No idea what the equivalent is in pence and stones...

biker128pedal
10-07-08, 05:46 PM
Cannot answer the poll. The last set of units are wrong. It is pound-feet and pound-inches.

NIST Guide to SI Units (http://physics.nist.gov/Pubs/SP811/appenB9.html#TORQUElength)

MOMENT OF FORCE or TORQUE
To convert from to Multiply by
dyne centimeter (dyn · cm) newton meter (N · m) 1.0 E-07
kilogram-force meter (kgf · m) newton meter (N · m) 9.806 65 E+00
ounce (avoirdupois)-force inch (ozf · in) newton meter (N · m) 7.061 552 E-03
ounce (avoirdupois)-force inch (ozf · in) millinewton meter (mN · m) 7.061 552 E+00
pound-force foot (lbf · ft) newton meter (N · m) 1.355 818 E+00
pound-force inch (lbf · in) newton meter (N · m) 1.129 848 E-01

Besides you should know how to use them all. Most torque wrenches have both US and SI units in the appropriate range.

Later we should discuss pressure. PSI vs Bar.

I use a torque wrench. Running or static.:D

10-08-08, 12:08 AM
can anyone recommend where i can buy a quality torque wrench, or set of torque wrenches? i recently purchased a cervelo r3 and am afraid to wrench on it without having exactly the right equipment

biker128pedal
10-08-08, 04:28 PM
can anyone recommend where i can buy a quality torque wrench, or set of torque wrenches? i recently purchased a cervelo r3 and am afraid to wrench on it without having exactly the right equipment

You should spend about 10% of the bike cost for your tools.

Yes their units are backwards. :crash:

5718A43
Dial Torque Wrench W/Pointer, 1/4" SQ Drive, 0-75 in-lbs, 0-9 NM Torque
In stock at \$131.44 Each

5718A71
Dial Torque Wrench W/Pointer, 3/8" SQ Drive, 0-50 ft-lbs, 0-70 NM Torque
In stock at \$156.48 Each

SJX426
10-08-08, 09:24 PM
You should address how torque specs need to be adjusted for lubrication. Most torque specs are for dry, unlubricated threads. In some cases, like wheel bolts (lug nuts), the setting should be 50% of spec. So for a 100 lb-ft torque spec, set your torque wrench to 50 lb-ft.

HardyWeinberg
02-07-09, 03:24 PM
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.

Not easy to find a torque-wrench that goes as low as a Thomson stem recommends, I'm finding.

Retro Grouch
02-07-09, 03:35 PM
I picked lb/ft, because that's the one I use most often.

I use torque wrenches on bicycle bottom brackets, crankarms and stems. I use a 3/8 drive wrench on cranks and bottom brackets and and prefer lb/ft for that. I use a 1/4 drive torque wrench on stems and prefer in/lb for the smaller increments.

Incidentally, I've got a good number of years working on bikes. If left to my own judgement I would consistantly undertorque cranks and overtorque stems. If the number of posts about creaking bottom brackets, left crank arms coming loose and hosed bottom bracket spindles is any gauge, it appears lots of other folks, even some professionals, also have poor judgement in regards to torqueing bicycle parts.

Hawaiiwrench
02-07-09, 04:22 PM
Does everyone have a separate torque wrench for each direction as well??

MrPhil
02-07-09, 04:47 PM
Every torque wrench I've come across in the past 10 years has metric and English units. I use which ever scale is called for. Some equipment has metric specs, some has English specs.

By the way, the million dollar lasers (Cymer DUV eximer type) I've worked on recently use all English spec'd fasteners AND dimensions. They are the preferred semiconductor photolithograpy DUV light source around the world. Almost everything else is metric.

Working on multimillion dollar machines is fairly picky work. Torque wrenches are used on very few assemblies. Everything else just needs to be snug. Of course, nobody is driving or flying this equipment either.

I have not and do not use torque wrenches on bicycles. I did break a lot of fasteners during my first summer assembling bikes. That was in 1970. My boss was very tolerant. I do think using a torque wrench would flatten out the learning curve.

I think training in the actual use and care of torque wrenches is more important than knowing torque specs for each part of a machine. You can always look that up. I've seen way too many electronics techs/engineers completely trash optical/mechanical/pneumatic/hydraulic systems.

Oh, I voted inch/pounds. Just sounds better than pound/inches.

tatfiend
02-07-09, 06:57 PM
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!

The trouble with that is that many of the ISO bike standards are English threads which if expressed in metric sound wierd. The only bike component and thread standards that were straight metric I am aware of were the old French ones, now obsolete.

We are therefore stuck with a mishmash where BB widths are mm but the BB TPI are English. Lots have been converted such a handlebars. A 1" bar clamp is called a 25.4mm and a 1.25" is 31.8mm. Lots of other examples too.

My torque wrench is old enough to be English only but I intend to get a lower reading 1/4" drive one for CF and small parts that is both Nm and inch pounds.