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Brands like Canyon are delivering their bikes with torque wrenches that are based on the torsion resistance of the metal that mades up the wrench, like the one pictured below (for the working principle).

torsion based torque wrench

To describe it simply: once the bolt is ready to be tightened, applying torque will twist/deform the metal proportionally to the torque. A needle and gauge allow a measure of the deformation, and hence the torque.

Given they only cost a fraction of more professional wrenches, a tool like this would be relevant in the toolbox of those who do their maintenance themselves. I'm wondering how "good" they are:

  • does the torsion characteristic of the metal evolve over time or with temperature, of if "abused"?
  • do they offer a level of accuracy that is compatible with torque-sensitive applications, such as the tightening of a carbon seatpost?
  • what are the attention points when buying one?

What would be the pros and cons compared to a more traditional torque wrench?

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    If looking for cheap torque wrenches that are accurate, it's hard to beat beam-type torque wrenches. They are normally highly accurate, durable, and can be easily re-calibrated by the user if needed. In the US, they have typically been available in the $20-30 range for at least the last few decades.
    – Armand
    Feb 17, 2022 at 10:07
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    @Criggie I would not consider that tool suitable to be taken on a long ride: too many long items that can bend when packed tightly, and too bulky to be stored in a "bottle cage storage". I would think that their qualities are to be good enough for a cheap price — especially for the purpose of a brand like Canyon, who sells bikes online and can order the wrenches with adequate specifications. For touring, that seems much more appropriate.
    – Rеnаud
    Feb 17, 2022 at 13:00
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    @WeiwenNg this type doesn't seem quite the same as a beam type. Both rely on elastic deformation of metal, but beam types bend a lever arm, and torsion types twist the drive shaft (think leaf spring vs torsion spring). But they're closer to beam type than to cam/clutch type
    – Chris H
    Feb 17, 2022 at 13:30
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    @Criggie I have this one. It really is not suitable for on-road use. The plastic is too fragile and it is too bulky. Feb 17, 2022 at 16:48
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    I've built a lot of Diamondbacks packed for direct to consumer that come with a similar plasticky beam type torque wrench, not this exact design. They are pretty legit for the purpose. Feb 17, 2022 at 19:51

4 Answers 4

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Note, except where I mention a specific model, this is a discussion of the flexure type of torque wrench, and not any specific example.

This type of design should be OK for occasional use in easy conditions. It does have a few downsides:

  • It's bulky
  • You need to watch it constantly. In a busy workshop this isn't good. Consider a set of bolts, like stem bolts: once the first is engaged and you're using the tool, your other hand is already reaching for the next bolt, and so are your eyes. The clicky type won't over-torque doing it up blind
  • You really need to be able to get a good look at it to read it accurately. I suspect the Topeak review quoted in the comments was either hard to read or something had got misaligned. The design means you're quite likely to be looking off-axis which will cause an error.

I don't have any carbon bikes, and haven't calibrated my torque wrenches, but I prefer the "torque screwdriver" style. Mine goes up to 8 Nm but I normally leave it on 5 Nm. This doesn't have enough leverage for crank bolts, cassette lockrings etc. I just do mine up tight these days, having got enough of a feel for it. When I did feel the need for measured torque on those I used my automotive-style torque wrench with a 1/2" square drive. That doesn't go light enough for little things

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  • Another problem is that its accuracy is dependent on exact fit of the torsion and readout shafts into the plastic handle, and of the plastic scale onto the torsion shaft. Even if manufactured to very tight tolerances, the plastic/metal interfaces will wear and only become more sloppy. The Ocarina and traditional beam torque wrenches avoid these problems by having permanent metal connections between the torquing handle and the readout arm.
    – Armand
    Feb 17, 2022 at 10:02
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    Yes, I was referring specifically to the Topeak - thanks for clarifying. An all-metal design would be better, but would still suffer from slop if the parts were not permanently attached to each other. I cringe a bit every time I look at that Topeak photo. :(
    – Armand
    Feb 17, 2022 at 10:32
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    An old-school mechanic taught me to use a measuring tool "in the upper half of its quoted range" where possible and never in the bottom quarter. So a 0-100 torque wrench would be ideal between 50 and 100, and less should be done with a smaller tool. 25-50 is okay if you don't have better, but under 25 would have been too flakey. Like trying to measure 50g of butter for cooking but using your bathroom scales.
    – Criggie
    Feb 17, 2022 at 11:49
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    @Criggie yes, I think the (smallish) automotive torque wrench would be on the first mark for most bike parts - and believing the reading, which would be the hard part. I probably am in the bottom quarter even on crank bolts but square taper alloy onto a steel axle the torque wrench is more to convince the user to go tight enough than a measuring tool - that's about the only bike thing that reaches "gorilla tight" on my descriptive torque scale (take up the slack - finger tight - hand tight - tight - tight tight - really tight - extra tight - gorilla tight - put some weight into it)
    – Chris H
    Feb 17, 2022 at 11:56
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    @Criggie Vernier scales excepted ;)
    – DKNguyen
    Feb 17, 2022 at 17:43
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As I understand it, if a torsion torque wrench is accurate on the day it's manufactured (i.e. the scale is in the right place), it will remain that way unless physically damaged.

The click type wrenches need to be recalibrated. Many people do it annually, but in high precision uses, I've heard of them being recalibrated daily.

NOTE: This is what I've read on the internet, and as Abe Lincoln once said, "If it's on the internet, it must be right". However, I've seen it in enough places that I believe are credible that I do believe it to be accurate. I'm sure with some research, actual, tested results could be found.

The torsion beam wrenches do take more work to ensure that you are setting the right torque because there's no indication of when the desired torque is reached. For the inch-pound settings that are common on bikes, this isn't really an issue for those doing their own maintenance (other comments about "production" work, as in a shop are valid).

For working on a car, where you may be pulling for all you're worth to hit 180 ft/lb, that positive audio & physical feedback can be critical because you can't see the scale and turn the wrench at the same time.

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    It doesn't make sense to recalibrate torque tools daily. Bolt torquing via the nut is wildly inaccurate anyway, due to varying levels of friction on threads and mating flanges. For accurate work, other tensioning methods is typically used in industrial settings. If you aim for more than ±30% use tensioning.
    – vidarlo
    Feb 17, 2022 at 21:31
  • @vidarlo Agreed -- I've heard of tire shops recalibrating weekly because their torque wrenches hit 5000 cycles weekly, but 5000/day seems a little ludicrous
    – MaplePanda
    Feb 18, 2022 at 17:54
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Those "beam type" wrenches are the best. Unless you spent few hundred dollars, you cannot buy a better torque wrench, "the clicky ones", I mean. Cheaper ones are rubbish, and if you have a such tool, you also need a decent calibration device. You shouldn't drop them. You shouldn't use them for unscrewing things, or use them as a crowbar, cheater bar, etc. You shouldn't exceed maximum torque values. They are quite fragile.

Beam types are cheap and effective. Problem with all types of torque wrenches is, the holding hand: I've seen guys on Youtube, shooting videos and entitling themselves experts, using torque wrenches like ratchets.Yes; heat effects them, but heat effects anything and everything. Yes; they get "softer" in time, but at that point, you would have probably tightened a few million screws already, and the handle would wear out first :)

Proper carbon fiber is not that fragile, to be destroyed by %5-10 more torque. If it cracks under such torque, let it be, it's too dangerous to ride anyway...

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This is one variation of the type of torque wrench that you should be using. The other variation is a beam-type wrench.

Click-type wrenches go out of calibration. How they are calibrated is with a torsion type wrench or a beam-type wrench (well actually not a wrench but a calibration apparatus but its principle of operation is the same).

Also, click-type wrenches can only tighten in one direction usually. A problem on bikes where left-hand threads are sometimes used (pedals, bottom bracket).

My advice, however, would be a beam type wrench and not a torsion type wrench. Beam type wrenches generally are easier to use in spaces where a torsion type wrench can't possibly fit.

The wrenches have sometimes a small parallax error, but making sure you look at the scale perpendicularly is enough to eliminate this error in practice.

The problem with a click-type wrench is that you should calibrate it often, actually so often that it would be a major expense, and the calibration probably costs more than buying a new wrench. Beam-type wrenches are also much cheaper than click-type wrenches.

Remember that the only reason professionals can use click-type wrenches is that those wrenches are calibrated often.

My wrenches are 0-200 Nm automotive beam-type wrench + 0-7 Nm very old Park Tool TW-1 beam-type wrench. However, today you can buy Park Tool TW-1.2 which goes up to 0-14 Nm, and is better than the old 0-7 Nm wrench since it covers more use cases. You still need an automotive beam-type wrench for the jobs that require a lot of torque.

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