With the mainstreaming of carbon frames and components – and at so many price points – you probably already know that the best way to safely tighten modern carbon parts is by owning and using a torque wrench. Torque wrenches allow you to tighten metal parts properly, too.
But did you know that even some experienced mechanics use torque wrenches wrong? And that incorrect use can damage or break parts the same as not using a torque wrench?
I had no idea until Park Tool Product Manager John Krawczyk was kind enough to clue me in. I was a little embarrassed to admit that my Park Tool torque wrenches were the old beam-and-needle type versus the easier-to-use click-type torque tools Park and other companies sell and recommend today.
Beam versus Click
To explain, a beam type tool flexes as you tighten and, as it flexes, an indicator on the tool points out the torque on a calibrated scale printed on the tool. These tools work fine but you can only tighten a certain number of times before the beam weakens, changing how tight you’re actually getting things. You then need to adjust the tool to zero the indicator again. It’s not hard but is a bit of a pain.
Click-type tools are either factory-set to one or several common bicycle torques, or can be adjusted with a dial to the right torque before use. Then, during use, the tool will make a click sound and at the same time stop tightening. You feel the handle of the tool suddenly stop resisting, move forward a bit and stop. The click and the handle suddenly letting go tells you the part is at the correct tightness.
Torque wrench trouble
With a way to hear and feel that you’ve tightened correctly, these click-type tools seems foolproof. But let me hand it over to John to explain the torque troubles they’re seeing at Park Tool. They want to get the word out so that mechanics everywhere understand. He points out that even the best tool is only as good as the mechanic who’s using it.
John says: “Jim, you have no idea how many calls and emails we get insisting that someone cracked their handlebar or frame because their new Park torque wrench was ‘defective.’ Yet, in all the years people have sent these purportedly defective torque wrenches back, never has one been out of spec or defective. Instead, it was simply used incorrectly.
“Please notice in the photo that there are two torque wrenches with worn away or worn out labels. While we found them still working perfectly and within our spec, they were ones returned as faulty. We put our new torque wrenches in the photo so you can see what the tools used to look like.
“The label damage is from choking up on the tools. It’s amazing how many experienced and professional mechanics (team mechanics, shop mechanics, etc.) do this on their torque wrenches in the mistaken belief that they are then safely under-torquing the bolt. But what they don’t realize is that they are, in fact, doing the exact opposite and actually over-torquing the fastener!
“It’s unfortunate that people will spend hundreds of dollars on carbon bars or stems, or even thousands on carbon bikes – plus even more on a good torque wrench – only to use the wrench incorrectly and do exactly what they want to avoid (i.e. over-tighten and possibly even break their carbon components or frame)!
“The correct way to use a torque wrench – and the only way to get the torque right – is by holding the handle. At Park, we think this is a critical topic and appreciate you sharing it with readers.
“Please watch Park Tool’s Calvin Jones demonstrating the wrong and right ways to use torque wrenches in this short video.”
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s cycling streak ended in February 2022 with a total of 10,269 consecutive daily rides (28 years, 1 month and 11 days of never missing a ride). Click to read Jim’s full bio.
I have no idea why that would be. Surely the torque wrench would ‘let go’ at the preset torque wherever on the handle you applied the force.
I concur.
The release in the wrench is independent of where the hand is placed (or how long the user’s arm may be).
Click-release wrenches have preloaded springs. If the spreng weakens as it ages, metal fatigue, it will release at lower torques, not higher. This protects delicate parts from over tightening, not the opposite. The same is true for beam type wrenches, the only change possible with repetitive use will soften the wrench.
Article fails to mention proper use of click-release wrenches is to always return the dial to zero after use so the spring is stored unloaded, and never to use the torque wrench to loosen a bolt or nut.
So the remarks from the Park Tool fellow are illogical, wrong.
Don, watch the Youtube video of Calvin Jones. He tells (and shows) how and why this is the case, using a real-time gauge to demonstrate the over- and under-torquing when holding the wrench in the wrong places.
Nice article!
Can you please add a paragraph to explain how choking up on the wrench causes it to fail? Is it just that this wears out the label so that people cannot see the correct settings any more? The photograph is a little too tiny to easily assess that possibility. (ps there is also an english usage error “use torque wrenches wrong” -> “wrongly”).
After watching the video, a simple explanation is that the torque measurement depends on the ratio of distances between where you hold the wrench and the black-dot pivot, vs. the black-dot pivot distance to the socket head. Holding it closer to the pivot produces a higher torque, and holding it at the very end of the handle will produce a lower torque.
Sorry for the confusion, Don. The torque wrench itself doesn’t fail, but what happens is you end up getting the tightness of the part wrong and this can cause the part to break. Hope that explains better.
In addition the handles of beam type wrenches have a pivot and force must be applied to the handle so as to keep the handle free to pivot, that is, not at a stop. If it is at a stop you are applying a force and a torque with the handle and the beam is only calibrated for an applied force at the pivot position.
I wondered why there are so many online reviews that say many manufacturer’s torque wrenches do not work. This must explain it. Like most problems operator error is the most likely cause.
You always hold a torque wrench by the middle of the handle because that’s where the wrench is calibrated to be used. Choking up essentially shortens the handle, requiring more force to tighten the nut (basic physics). The clicker mechanism can’t tell where you are holding the wrench. I find it helps to just use a couple of fingers, rather than your whole hand, especially at lower torque values.
The Park video doesn’t mention that you also need to make sure the handle is perfectly perpendicular to the rotation of the screw, nut or whatever. Simply put, that the screwdriver or socket is squarely and solidly on or in whatever you are tightening. If not, the torque reading can also be off.
Finally, a torque wrench should not be used to remove a tightened nut or screw, especially if it’s high torque. Continually doing so could throw off the calibration.
A good article indeed. I got some valuable information about torque wrench. Thanks for posting such a blog. Keep it up.
This is a great article. Torque wrenches are really needed so that you don’t over tighten the bolts and strip them.
I just ran into an interesting conundrum with click-type torque wrenches. Shimano gives a torque recommendation for setting the tightness of the clutch on their clutch rear derailleur.s. Measuring the torque requires a torque wrench that clicks when rotating it as for a left-handed thread. My torque wrench doesn’t click in that direction. Are there some that do?
Park Tool’s click torque wrenches allow for this.
I was also advised by an automotive mechanic to “unwind” the torque setting back down to the minimum torque on the wrench after use.
I have advised quite a few people who have carbon bikes to invest in a quality torque wrench. I’m partial to Park, but know there’s a few other good ones out there. I love my tool storage chest from Harbor Freight, but there’s no way I’m using their $25 torque wrench on my $5,000 bike!
Granted, it’s not a $25 wrench or one you’re likely to be using on your bike, but Harbor Freight’s ICON torque wrench was independently tested against SnapOn and found to be more accurate. The “high end” HF brands are actually pretty good. They still sell the cheap stuff as well if that’s what you prefer.
That’s interesting information, thanks. And I do not prefer cheap tools by any means.
It is also important to remember that the torque wrench measures torque most accurately when the bolt is still moving. Once it stops, it takes more torque to restart the movement, resulting in an error in the measured torque on the bolt.
“I was also advised by an automotive mechanic to “unwind” the torque setting back down to the minimum torque on the wrench after use.”
My Craftsman torque wrench, which I got when Campy started posting torque settings for their BBs and cassette lock rings, had that exact recommendation. I’ve seen it in many other places since. My Craftsman wrench is for high-torque applications (Campy BBs used to be 50 n-m) and I have a low-torque wrench for other settings. I do the same with both wrenches – wind back to zero after use.
Thanks for making that point, Kerry – and others who did. Most torque wrenches I’ve seen do say in their instructions to zero the tool after use.
Thanks!
Jim
This comment relates to the video of Park Tools rock star Calvin Jones.
Torque is simply a force applied over a distance (force X distance); hence the measurement of foot-pounds or newton-meters. Theoretically a force of 10 lb applied at 1 ft would yield the exact same torque as 5 lb applied at 2 ft or 20 lb at 6 inches. My *opinion* regarding Calvin’s demonstration that different results are obtained when holding the wrench at different points is this: When holding the wrench very near the head, the required force increases. When the wrench “clicks,” it is difficult to stop the inertia of the increased force, so a higher torque value is registered. Similarly, when holding the wrench at the extreme end of the handle, less force is required, so the inertial force is less, resulting in a lower registered torque reading.
I am shocked to read the number of misconceptions stated above, let alone the number of people adhering to them. Thus proving the necessity of the article as included the highly qualified resource from Park.
In terms of “click type” torque wrenches
1
Them must be held correctly, and positioned correctly, or the resultant applied torque will not be what the wrench is set to, despite the wrench doing its “click”.
2
They are not the most accurate. Dial indicator type are, but they are more difficult to use in terms of getting correct results, and nowadays are more costly.
3
Crucial point, click type wrenches are most accurate in the range of 80 -100 % of full scale. Below 20%, they are very inaccurate, and in a non repeatable way. So, do not use large torque wrenches on low torque applications.
4
Crucial point, click type wrenches should only be stored at the manufacturer’s stated storage setting, and it’s never zero. For example, a Park TW5.2 is stored at 2 Nm. Do not store click type torque wrenches at anything but the required storage setting. Setting at zero is actually worse than storing at mid setting. The typical storage setting is the lowest setting on the primary scale, not the fractional scale.
5
If you have a super critical application, and want the wrench at maximum accuracy, be sure the wrench is at a stabilized temperature (e.g. not still warming up from being taken out of cold storage in the garage to do work in the house), set it to its maximum, then do 5 pulls to click. Typically this means putting a bolt in a good vice and torquing it’s head. This is fine for smaller wrenches, and impractical on bigger wrenches where the vice size and quality come into play, as well as what it’s mounted to.
6
NEVER exceed the wrench’s upper limit, and if you do, or someone you loan your torque wrench does, don’t use it again until you get it recalibrated, which is how they are checked and corrected.
7
Back to accuracy. Any click type torque wrench that you want to have, will be governed by an ISO or ANSI/ASME standard. The essence of which is this: the wrench is +/- 4% accurate between 20 & 100% of full scale ( and +/-6% when used counterclockwise) . Below 20% of scale use, the accuracy is only +/- 0.8% of full scale. To put this in perspective, imagine a 100Nm wrench being asked to torque a critical fastener rated @ 6 Nm. The wrench accuracy when set to 6, would be +/- 8 Nm.
I made a mistake on my example of using a 100 Nm torque wrench for a 6 Nm setting.
I put the decimal in the wrong place doing my calculations. Correct is this replacement statement: The error of a 100 Nm click type torque wrench at a 6 Nm setting would be 0.8 Nm. 0.8 is 13.33 % of 6. So, the accuracy can also be stated as being +/- 13.33 % at a 6 Nm wrench setting.
Any recommendations on how/where to have a torque wrench tested and calibrated? Thanks.
A final point I missed adding in.
Often, higher quality torque wrenches will have certified accuracy test results in the box that holds the wrench when you get it new. Don’t be surprised if you see results that are much better than the governing ISO or ANSI/ASME specified requirements, especially in the partial range of use zone.
“I have no idea why that would be. Surely the torque wrench would ‘let go’ at the preset torque wherever on the handle you applied the force.”
That was the first comment under this article when it first appeared- made by me. I have now read all of the subsequent comments and watched the video by the Park Tool product manager, and I still don’t get it. Unless the handle is not rigid it should make no difference where you hold it. So I wonder how the Park Tool wrench works. Wikipedia lists two designs of click style wrenches: one called a ‘slipper’, with a ‘cam’ with multiple valleys and a spring loaded ‘roller’, and the other just called ‘click’, featuring a spring loaded ‘ball detent’ in a ‘socket’. But the only difference in use would appear to be that with the latter if you keep pushing the applied torque will keep increasing.
I don’t have an actual problem with the use of any of my torque wrenches, but I am curious about what’s going on here. I cannot explain Park’s video, Perhaps Park will do that, preferably with a diagram and a formula.