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torque wrench question

Old 08-06-13, 04:57 PM
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kraftwerk 
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torque wrench question

Given that when choosing a torque wrench you need a tool that will deliver the needed torque, in the middle of its range, not towards the end of its range, so, what is the average torque requirements on a bike? I was thinking a range of 2 - 24 NM should do it

Last edited by kraftwerk; 08-06-13 at 05:56 PM.
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Old 08-06-13, 05:12 PM
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Sounds about right.

https://www.performancebike.com/bikes...90_-1___000000

EDIT: not enough for a crank or cassette though - at least not on my bike - but it hasn't really been an issue.
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Old 08-06-13, 05:24 PM
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You need 3-15Nm for most stuff then 40-50 for cassettes, pedals, some cranks and BB cups. Most of the time I'm using 4Nm for seat post, stem bolts and other small stuff, 8-9 for seat rails, 13 for Shimano left hand crank bolts. If you're only getting one wrench then 2-24Nm woul be the most useful; the big stuff can just be done up pretty damned tight.
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Old 08-06-13, 05:35 PM
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40-50Nm is foooookin tight!
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Old 08-06-13, 05:36 PM
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My entire bike was between 4 and 14 and nm
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Old 08-06-13, 05:37 PM
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OP...if you want to be a relatively serious home mechanic including repairs to your car like changing a water pump etc, rotating your tires etc...you need 2 torque wrenches, 1 with 3/8" drive and bigger one with 1/2" drive. This will cover the range you need for pretty much all the stuff you will work on including bikes and cars and motorcycles. I use a 3/8" Craftsman torque wrench for my carbon seat tube and a 1/2" drive for my cassette.
If getting only one wrench, get the 3/8" drive for your smaller carbon bits and swag the cassette lock ring torque.
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Old 08-06-13, 05:40 PM
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Park Tool Co. Repair Help and Education - Torque Specifications and Concepts

Bicycle Tutor - Torque Specifications

Shimano Torque Tightening Specifications
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Old 08-06-13, 05:42 PM
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Originally Posted by robbyville View Post
My entire bike was between 4 and 14 and nm
Not quite.
Shimano and SRAM specify 40N-m (30 ft-lb or 354 in-lb) and Campy specifies 50 N-m (37 ft-lb or 442 in-lb) for cassette lockrings...a good application for a torque wrench.
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Old 08-06-13, 06:32 PM
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Originally Posted by killa View Post
40-50Nm is foooookin tight!
Isn't it true that it depends upon the diameter of the fastener. E.g. the lock ring of a cassette is much larger in diameter than a 5 mm allen head bolt. Doesn't that level the "tightness" between the two at very different torque readings? Honestly I am not sure about this myself. It just occurred to me to ask.
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Old 08-06-13, 06:42 PM
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Originally Posted by Campag4life View Post
OP...if you want to be a relatively serious home mechanic including repairs to your car like changing a water pump etc, rotating your tires etc...you need 2 torque wrenches, 1 with 3/8" drive and bigger one with 1/2" drive. This will cover the range you need for pretty much all the stuff you will work on including bikes and cars and motorcycles. I use a 3/8" Craftsman torque wrench for my carbon seat tube and a 1/2" drive for my cassette.
If getting only one wrench, get the 3/8" drive for your smaller carbon bits and swag the cassette lock ring torque.
True, two wrenches are needed for the bike. I think I have a 1/4 inch drive and a 1/2, but the 3/8 is fine too as long as it has the right torque range. There are always adapters to go either way. Another idea is to have only the large torque wrench and a torque key like the ones offered by Ritchey and Giant for the saddle clamp, stem, etc.
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Old 08-06-13, 06:43 PM
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Originally Posted by rpenmanparker View Post
Isn't it true that it depends upon the diameter of the fastener. E.g. the lock ring of a cassette is much larger in diameter than a 5 mm allen head bolt. Doesn't that level the "tightness" between the two at very different torque readings? Honestly I am not sure about this myself. It just occurred to me to ask.
It comes down to force per unit area i.e. sustainable stress. So yes, typically larger fasteners have higher torque...for two reasons:
1. clamping force is proportional to surface area contact e.g. screw head and surface

2. Torque based upon pitch calculation (trig) can be correlated to tensile force which should correlate to:
a. cross sectional area of fastener
b. material properties of fastener.
both a and b determine stress strain.

Bolt Torque versus Clamping force:
The equation T = .2DF is a general equation to estimate applied fastener axial loading for industry standard threads – steel material.

The equation is imperfect as is the torque process..

There is more accurate force to torque equations available for critical applications however; even these equations are ultimately imperfect.

For installations that are expected to be assembled and unassembled repeatedly:
F = .75(At)(Sp)

For permanent installations”
F = .9(At)(Sp)

Where
F = Approximate axial preload force applied
At = tensile area of fastener
Sp = proof load of the fastener

Let’s rewrite the top most equation

From
T = .2DF

To
F = cDF

Where:
F = force
D = diameter (Major)
F = Axial force applied
c= roughness approximation
Steel and zinc plated, dry threads = .2
Cadmium plated = .16
Lubricated = .16 to .17

There are equations that attempt to compensate for thread pitch and flank angle however if one needs torque and axial clamp force that accurate for industry standard fasteners thay should consider alternative installation designs.

Last edited by Campag4life; 08-06-13 at 06:51 PM.
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Old 08-06-13, 06:44 PM
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I bought a Sears Craftsman in/lb wrench on sale for $50 last winter...it has done a great job for me so far.
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Old 08-06-13, 06:57 PM
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Originally Posted by rpenmanparker View Post
True, two wrenches are needed for the bike. I think I have a 1/4 inch drive and a 1/2, but the 3/8 is fine too as long as it has the right torque range. There are always adapters to go either way. Another idea is to have only the large torque wrench and a torque key like the ones offered by Ritchey and Giant for the saddle clamp, stem, etc.
But the point isn't about using adapters which yes will adapt to different socket sizes including allen sockets.
The key point about torque wrench drive size is it typically correlates to a workable range of torque...smaller drive = lower torque range.
Second point is, there is a correlation of torque arm length relative to torque range. 1/2" torque wrenchs not only have a higher range of torque..say to be used for a 30 ft-lb cassette, but a longer lever length which makes higher torque easier to apply. T = F X lever arm distance
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Old 08-06-13, 06:58 PM
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I use 1/4 drive and 3/8 drive wrenches. Remember torque suggestions are for dry threads. If you are lubricating the threads, reduce torque appropriately (20-33% depending on the fastener)
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Old 08-06-13, 07:02 PM
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Originally Posted by Campag4life View Post
Not quite.
Shimano and SRAM specify 40N-m (30 ft-lb or 354 in-lb) and Campy specifies 50 N-m (37 ft-lb or 442 in-lb) for cassette lockrings...a good application for a torque wrench.
I stand corrected !

i used a torque for all the small bolts, carbon fasteners, etc but basically for bigger items just cranked away until tight, I have very weak biceps!
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Old 08-06-13, 07:05 PM
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Originally Posted by Campag4life View Post
But the point isn't about using adapters which yes will adapt to different socket sizes including allen sockets.
The key point about torque wrench drive size is it typically correlates to a workable range of torque...smaller drive = lower torque range.
Second point is, there is a correlation of torque arm length relative to torque range. 1/2" torque wrenchs not only have a higher range of torque..say to be used for a 30 ft-lb cassette, but a longer lever length which makes higher torque easier to apply. T = F X lever arm distance
Yesirree! That's why I said the socket connector size didn't matter a whole lot as long as the wrenches have the correct range. Arm length is another thing, but is usually consistent with the range of the wrench. Hey we are agreeing here. Savor the moment!
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Old 08-06-13, 07:10 PM
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Originally Posted by pdedes View Post
I use 1/4 drive and 3/8 drive wrenches. Remember torque suggestions are for dry threads. If you are lubricating the threads, reduce torque appropriately (20-33% depending on the fastener)
You are absolutely right about dry vs. greased. That is consistently overlooked.
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Old 08-06-13, 07:27 PM
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Originally Posted by rpenmanparker View Post
You are absolutely right about dry vs. greased. That is consistently overlooked.
And a subject of many internet debates...to anti seize or not to anti seize and what it does to retention torque and even bolt tensile strength.
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Old 08-06-13, 07:30 PM
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I get away with 1-12 in the shop for 90% of stuff but when it comes to cranksets typically 25-35 or higher. Depends how extensive your wrenching is going, if you're not doing press fit cranks like bb30s, I'd imagine you'd be fine picking up a basic torque wrench. I've been using the Shimano PRO one lately and enjoy it.
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Old 08-06-13, 07:43 PM
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I use a S/K (not cheap) 1/4 drive that's 30 in-lbs (3.39nm) to 200 in-lbs (22.6nm).

Since I restore old cars as a hobby I also have 3/8, 1/2 and 3/4 drive torque wrenches.

Good quality tools are an investment. I still have a number of my original S/K 3/8 drive sockets I purchased back in 1969.
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Old 08-06-13, 07:56 PM
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Yes by the way, I do have a huge wrench for my automotive needs, wheel lugs etc. just now finally getting a smaller one for my bike. I did use the big 3/8 drive for the BB cup.
The Old Craftsman "beam' wrench just ain't cutting it. Maybe it is but I am skeptical.

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Old 08-07-13, 05:52 AM
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40nm is about as tight as you think it should be, plus a tiny bit more.

(I use a torque wrench, not always with success it has to be said)
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Old 08-07-13, 06:16 AM
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Originally Posted by jolly_ross View Post
40nm is about as tight as you think it should be, plus a tiny bit more.

(I use a torque wrench, not always with success it has to be said)
You really do not need a torque wrench to tighten the lockring on a cassette. First, if you look at the specs for Shimano cassettes, you'll see it expressed different ways. I've seen >40nm, as well as 29-49nm. Point is that it needs to be tight.

And it's virtually impossible to overtighten it, provided you don't cross thread it, you've greased it, and you're not using a 2 foot long pipe wrench.

If you just tighten it to the point it starts to stutter, you'll be fine.

Somethings need tighened to a specific torque range: cassette lockrings aren't one of those things.
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Old 08-07-13, 07:05 AM
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This has worked fine for me so far.......https://www.nashbar.com/bikes/SubCate..._202334_202376 with an additional 20% off, good deal. 1-24nm
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Old 08-07-13, 07:33 AM
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Originally Posted by merlinextraligh View Post
You really do not need a torque wrench to tighten the lockring on a cassette. First, if you look at the specs for Shimano cassettes, you'll see it expressed different ways. I've seen >40nm, as well as 29-49nm. Point is that it needs to be tight.

And it's virtually impossible to overtighten it, provided you don't cross thread it, you've greased it, and you're not using a 2 foot long pipe wrench.

If you just tighten it to the point it starts to stutter, you'll be fine.

Somethings need tighened to a specific torque range: cassette lockrings aren't one of those things.
I think a point here is people are at different skill levels depending on experience and to the less frequent builder, a torque wrench really does help...not only for overtorque which is common for ham fisted strong guys...but undertorque...pit falls to each. I have had a cassette come loose before. I wasn't life threatening and I figured out what happened. All said, I generally use my torque wrenches sparingly...in other words, not always.
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