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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 12-08-2008, 10:27 AM   #1
ken@bimmertools
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Arrow Torque Wrench Facts - Read Them. Seriously.

Let me start by saying that this thread is not intended as an advertisement for anything I sell, nor is it intended to spark a debate about the value of torque wrenches. If you don't think you need to use one when working on your car, good for you - I'm probably not going to be able to convince you otherwise. However, please allow other people to make up their own minds based on facts.

Ok, enough of a disclaimer.

Facts:

1. A torque wrench is one of the most basic tools you can own, even though it is often considered to be only for 'advanced' mechanics. They are simple to operate, simple to maintain, and quite honestly, a tool that should be one of the first things in your collection. If you can use a ratchet and read numbers, you're qualified and ready to use a torque wrench.

2. Virtually EVERY fastener on your car has a torque spec. Not only are these specifications designed to ensure something is tight enough, they are intended to PROTECT the fastener from over tightening. A bolt is a simple machine - the threads are like a continual ramp or wedge. The tighter you turn a bolt or nut, the more force you place on that piece of metal. Bolts are designed to stretch JUST ENOUGH to ensure a secure mechanical fastening. Stretching them too much can weaken their basic structure, creating an unsafe situation. A torque wrench is intended to prevent that.

3. Most fasteners require WAY LESS force than you can exert with basic tools. It is generally believed that making something as tight as you can get it is good. It's not. Seriously. Kicking a lug wrench to tighten wheel lugs on can easily DOUBLE OR TRIPLE the required torque to properly stretch the bolts. Use of a breaker bar or larger-leverage tool can do even more damage - let alone the use of air tools like so many shops seem to do today.

4. Most commercially available torque wrenches today are 'click type'. This means you set the tool to the desired level of torque (based on the documented specification for a particular fastener), start turning the fastener, and the tool will 'click' as the spring mechanism reaches the proper torque. The click represents a slight yield at the turning head as it allows a bit of flex without turning the fastener. That's not to say you can't apply any more force, just that the click tells you when to safely stop turning. It's that simple.

5. When you're done using the torque wrench, return the setting to zero. This relieves the tension on the spring, which can prematurely stretch it out, resulting in less reliability and accuracy.

6. Although your torque wrench is 'reversible', meaning you can use it to apply force in counter clockwise or clockwise motion, they are not to be used to loosen a fastener. Let me repeat the point - DO NOT EVER USE A TORQUE WRENCH TO LOOSEN A FASTENER. This can damage the spring mechanism very quickly, destroying accuracy. Why make them reversible then? Because some fasteners are tightened with a left-hand or reversed thread. If your torque wrench has ever been used as a breaker bar to loosen wheel lugs, it's probably just an expensive stick now. Consider replacing it.

7. Don't leave your torque wrench laying in the sun. Excessive heat can cause damage to the spring.

8. Torque wrenches come very cheap to very expensive. Price differences generally reflect accuracy, reliability, and features. I recommend buying a torque wrench that comes from a trustworthy brand, otherwise, plan on replacing it on a regular basis. There are MANY available in the $100-$200 range that are excellent values. There is another level of torque wrenches in the $500-$1000 range that feature interchangeable heads, easy calibration, and accuracy guarantees among other amenities a basic tool will not offer.

9. Torque specs are available from many sources. For more technical/critical items, it's advisable to seek a couple of sources in case there is an error. For non-M, non-Xi E46s, we've created a small reference card with over 60 of the most common specs. We sell this, but also give it away with most larger purchases.

10. To properly tighten BMW wheels with 17mm lugs - first, hand start the threads. Using an extension and socket, or lug wrench, turn the bolt until it stops spinning freely. Don't make it very tight at all. Then, set your torque wrench to 88.5 Lb/Ft. Install a socket and extension, turn the bolt clockwise until the tool 'clicks'. You're done. Notice how LITTLE force 88.5 Ft/Lbs is - you could easily apply more force with the lug wrench, potentially harming the bolts.

This post goes to 11 -

11. If you are "checking" torque, applying force with a torque wrench to an already-tightened fastener will not give you an accurate result. Let's say you want to make sure your wheels are properly torqued, but the shop that did the work used an impact gun, leaving them torqued to some ridiculous level like 180 ft/lbs - more than twice the specification. You put your torque wrench on, set it to 88.5, turn it, and it will click. That just tells you it's at least 88.5 ft/lbs. Properly applying or checking torque requires that the fastener be turning from loose to tight as it reaches the desired torque.

I'm sure I missed some points. You can see a selection of torque wrenches on our site - the category is in the 'hand tools' section.

ken@bimmertools.com if you have any tool questions.

Thanks for reading this!

Ken
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Old 12-08-2008, 10:39 AM   #2
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Old 12-08-2008, 10:39 AM   #3
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12. Due to increasing inaccuracy, you should buy a torque wrench that only meets your needs. For example: if you only do wheels, and other small jobs, get a 10-100ft/lb wrench, not a 10-250ft/lb wrench
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Old 12-08-2008, 10:48 AM   #4
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Originally Posted by madchef View Post
12. Due to increasing inaccuracy, you should buy a torque wrench that only meets your needs. For example: if you only do wheels, and other small jobs, get a 10-100ft/lb wrench, not a 10-250ft/lb wrench
Actually, I disagree with this just a tad. For wheel lugs, I recommend a 1/2" drive 25-250 Ft/Lb tool. This is primarily because a torque wrench is generally less accurate near its limits, so using a 100 Ft/Lb tool at 88.5 Ft/Lbs puts it at that upper range. I'm not saying it wont work, but this is why most people who regularly do work on cars will have tools that overlap. A 3/8" 10-100 Ft/Lb and a 1/2" drive 25-250 Ft/Lb is a standard collection that covers a huge range of projects.
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Old 12-08-2008, 11:23 AM   #5
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I only work with torque wrenches that are calibrated every time they are used. mostly snap on wrenches and they only aren't allowed to be used below 20% of max torque. The ones I use are accurate right up to the max torque. I have a personal collection of torque wrenches from different brands so I'll bring them in and calibrate them to see which ones are most consistent.
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Old 12-08-2008, 11:26 AM   #6
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Old 12-08-2008, 11:38 AM   #7
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I feel that those who don't see torque wrenches as a necessary tool might as well use a sledge hammer to tighten bolts.
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Old 12-08-2008, 11:48 AM   #8
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Quote:
Originally Posted by ken@bimmertools View Post
Actually, I disagree with this just a tad. For wheel lugs, I recommend a 1/2" drive 25-250 Ft/Lb tool. This is primarily because a torque wrench is generally less accurate near its limits, so using a 100 Ft/Lb tool at 88.5 Ft/Lbs puts it at that upper range. I'm not saying it wont work, but this is why most people who regularly do work on cars will have tools that overlap. A 3/8" 10-100 Ft/Lb and a 1/2" drive 25-250 Ft/Lb is a standard collection that covers a huge range of projects.
Agreed. Some good info here. Some things I didn't even know/no-no's I do with my own torque wrench.
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Old 12-08-2008, 12:21 PM   #9
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Quote:
Originally Posted by ken@bimmertools View Post
Actually, I disagree with this just a tad. For wheel lugs, I recommend a 1/2" drive 25-250 Ft/Lb tool. This is primarily because a torque wrench is generally less accurate near its limits, so using a 100 Ft/Lb tool at 88.5 Ft/Lbs puts it at that upper range. I'm not saying it wont work, but this is why most people who regularly do work on cars will have tools that overlap. A 3/8" 10-100 Ft/Lb and a 1/2" drive 25-250 Ft/Lb is a standard collection that covers a huge range of projects.
Personally, I have found the 25-250 to be less accurate for lug nuts, but I have only a small glimpse as I've owned only a few torque wrenches, so perhaps overall getting 25-250 is better. I'm not sure.
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Old 12-08-2008, 12:26 PM   #10
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Good stuff. I didn't know you were supposed to rezero them, I've had my 1/2" torque wrench set to 90 lbs for about 3 years now.
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Old 12-08-2008, 12:31 PM   #11
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Let me add my regular disclaimer - my knowledge and understanding of mechanics and technical specs is primarily based on experience, reading up on topics, and advice from wiser people than I. I have no formal training from any particular manufacturer or tool industry. My understanding of the accuracy being in the middle third of the range comes from that background. If that's incorrect, I'm happy to hear it - I've just been told otherwise. I'm always open to un-learning something I thought I knew as truth!


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Old 12-08-2008, 12:32 PM   #12
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Let me add my regular disclaimer - my knowledge and understanding of mechanics and technical specs is primarily based on experience, reading up on topics, and advice from wiser people than I. I have no formal training from any particular manufacturer or tool industry. My understanding of the accuracy being in the middle third of the range comes from that background. If that's incorrect, I'm happy to hear it - I've just been told otherwise. I'm always open to un-learning something I thought I knew as truth!


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Ken you're so humble.
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Old 12-08-2008, 12:38 PM   #13
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10a. It is good practice to put all lug nuts on and get them all snug before doing the final tightening. That is, DO NOT put the first one on and tighten it to proper spec without first putting all of the lug nuts on snugly to distribute the load. Also, tighten lug nuts in a particular sequence. When doing the final tightening, start with one lug nut, then going in a clockwise (or counter-clockwise, it does not matter) direction, skip one lug nut, and advance to the lug nut two positions away from the first one, and continue around. For example, using the example below, going clockwise (starting with lug nut #1 at 12:00) tighten the 5 lug nuts in the following order:

-----------------
--------#1-------
-----------------
---#3-------#4--
-----------------
-----#5---#2----
-----------------

This will help to ensure the wheel is put on evenly.

Jeff
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Old 12-08-2008, 12:44 PM   #14
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10a. It is good practice to put all lug nuts on and get them all snug before doing the final tightening. That is, DO NOT put the first one on and tighten it to proper spec without putting all of the lug nuts on to distribute the load. Also, tighten lug nuts in a particular sequence. When doing the final tightening, start with one lug nut, then going in a clockwise (or counter-clockwise, it does not matter) direction, skip one lug nut, and advance to the lug nut two positions away from the first one, and continue around. For example, using in the example below and going clockwise (starting lug nut at 12:00) tighten the 5 lug nuts in the following order:
-
- 1
-
- 3 4
-
- 5 2
-

This will help to ensure the wheel is put on evenly.

Jeff

For some reason that did not display correctly on my screen. Another way to say it is to tighten a 5-lug wheel in a "star" pattern, or every other bolt if going in a circle. Amazing how often the hacks at tire stores do this wrong. You'd think they would be trained on this simple fundamental.

EDIT: I see you've fixed it.
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Old 12-08-2008, 12:48 PM   #15
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dkrab, yeah, I saw that too. I first used spaces, but they did not show up, so I used dashes in the "illustration".

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Old 12-08-2008, 12:52 PM   #16
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5. When you're done using the torque wrench, return the setting to zero. This relieves the tension on the spring, which can prematurely stretch it out, resulting in less reliability and accuracy.
I think this depends on your torque wrench. The directions that came with mine direct it to be reset to 10 ft. lbs. when storing.
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Old 12-08-2008, 12:54 PM   #17
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Ken,
Nice job!
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Old 12-08-2008, 01:32 PM   #18
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Great info lads
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Old 12-08-2008, 03:28 PM   #19
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Ken you're so humble.
I am many things to many people - humble is rarely used adjective! Thanks.

And thanks for the further contributions - I like the star pattern diagram - I definitely left that out.

Keep 'em coming!

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Old 12-08-2008, 04:37 PM   #20
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I feel that those who don't see torque wrenches as a necessary tool might as well use a sledge hammer to tighten bolts.
An air impact wrench set at the highest torque setting would work better. Then just let 'er rip until the lug bolt won't ever come out.
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