Cool Tool Tuesday #10: Talking Torque wrenches, part one
Cool Tool Tuesday #10: Talking Torque wrenches, part one
I can’t believe it has been five months since the last Cool Tool Tuesday. Well, it’s back! And it’s time to talk torque.
Textbooks exist to explain just the basics of fastener torque, and there are bound to be situations where different material mixes and unique requirements throw those textbooks out the window. I admit that I won’t be able to cover nearly everything on this topic. Instead, with this two-part article, I’ll aim to arm you with fundamental knowledge for safely torquing all fasteners on a modern bicycle. This first part covers the basics of torque wrenches suited to bicycle applications and the things to consider before you buy such an instrument. Part Two will cover the correct usage and most common mistakes when using torque wrenches.
What is a torque wrench, and why do you need one?
A threaded fastener, whether it’s a bolt or screw, is an engineering marvel. The head of the fastener is designed to clamp or hold a load under tension. Meanwhile, the thread stretches just enough to create and hold that tension. And it’s this load that a torque wrench aims to quantify. “A torque wrench is a tool that allows you to control the amount of force you’re applying to a fastener, which ultimately determines the clamping force of that fastener onto the thing that it’s holding down,” explained Alex Boone, a hardware quality engineer for Motiv Space Systems (a contractor to NASA) – and a guest on an upcoming and related Nerd Alert podcast episode.
Bicycles of the past were commonly made up of hardy steels where tightening everything till it was “tight” was just right. If you under-torqued something, it would slip, and there weren’t many consequences for over-tightening something. However, times have changed and just about any performance-oriented bicycle will have safety-critical components where under- or over-tightening the relevant fasteners could spell bad news. This is relevant wherever carbon fibre is involved, but it can apply equally to lightweight aluminium, steel, titanium, and whatever else. As a result, when looking at a modern (and quality) bicycle, just about every fastener will have a recommended torque to tighten it to. As a result, a torque wrench has become an increasingly important tool to own.
OK, so you may be one of the masses who believe a torque wrench doesn’t offer anything over an experienced hand. Perhaps you’ve never broken a bolt or a carbon component. There is merit to going by “feel”, but you may also be surprised by how far off and inconsistent you actually are.
“The ‘Prestacycle PBMA A.T.T.A.C.K. torque survey’ pretty much put all the nails in the coffin on this topic at Interbike (ed. a now-defunct cycling industry tradeshow) a few years ago,” said Silca’s Josh Poertner about the idea of whether going by feel can be accurate. “The competition was to see who could get the closest to 5 Nm in a blind test. Within the test, 78% were self-identified mechanics from the industry that tried it, and the range was 1.41-13.96 Nm with the average being approximately 1.2 Nm too high.” Now 1.2 Nm isn’t much, but it could be enough to compress a carbon steerer or handlebar more than intended and fracture the structure. Meanwhile, under-torquing something could cause the part to slip, a danger to the rider and one that could also cause unwanted damage to a component.
Poertner points out that every hand tool offers subtle differences in the resultant torque. For example, the length (and therefore leverage) of your hex key has a direct impact in the amount of force applied for a given load. Ditto where you hold it. Those variances exist across the multiple different types of hex key, and then even the handle shape, material flex or lengths of a given tool can impact what you feel a fastener is doing.
The cycling analogy that came up from a few respected sources is that using a torque wrench is not unlike how pro riders use power meters. These pros spend enough time looking at actual numbers they get a feel for it. As a result, many pros can be told to hold 200W and they’ll hit that number. But add a headwind, a different bike, or fatigue, and their “feel” for 200W will likely waiver, which is why they look at the number. A professional mechanic who uses a torque wrench every day probably has a decent feel for that 5 Nm figure. Meanwhile, someone who never uses a torque wrench simply can’t know what that number feels like.
For me, I know when my pre-set 5 Nm torque wrench is going to click. I can consistently get within a few % points of 40 Nm when tightening a cassette. And I can feel when the thread of a bolt has stretched. And yet, I still own and use more torque wrenches than anyone should care to count. Part of it is knowing that regardless of whether my day is going good or bad, the bolt I’m tightening is done to the same consistent and recommended spec. Part of it is knowing that if a part does fail, I at least know it was done to what the manufacturer recommended. And part of it is accepting that no matter how consistently accurate I am, I’m only human.
Common types of torque wrenches
Regarding bicycle-friendly torque wrenches, all aim to measure the load on the fastener applied at the fastener head. This is just one method for measuring torque, and other industries have other means such as fastener angle measurement (e.g: torque to 50 Nm and then a 1/4 turn) or even ultrasonic-based, but I digress. Below is a list of torque wrench types that apply to cycling purposes.
Beam style
The simplest of torque tools is a beam torque wrench. This style relies on a fixed torque scale and the natural stiffness of a material (often steel). Loading a socket sees the indicator flex and align with the torque scale, providing a visual cue for the running torque of a fastener, a good example of this wrench style are the recently reborn Park Tool TW-1.2 and TW-2.2.
Another form of this style torque tool uses a spring instead of a beam – these have become popular in recent years as they offer a compact size that’s often placed in a bit-style cylindrical form. Examples of such cylinder-style beam tools can be seen from the likes of Silca, Topeak, and Lezyne. Meanwhile, a similar concept involving a dial can be found in a different form factor from Feedback Sports and PrestaCycle. And PrestaCycle also offers similar form factor tools based on a beam design.
These beam or spring-style tools are good value for money, offer visual identification if they’re out of calibration, are simple to use, don’t require you to reset them to a low torque after use, and overall are just a highly accessible torque wrench. They can also be used for measuring running torque and break-away torque: more advanced purposes I’ll cover in the second part of this article.
The downside is that they can be impacted by temperature (but perhaps not any more than click-style torque wrenches), they don’t offer any mechanical prevention to stop the user from over-tightening a fastener, they typically have a somewhat cumbersome shape that isn’t great for use in tight areas, and they require a direct line of sight to see the torque – something that isn’t super easy when you’re reefing on a crank bolt or working on something that is upside-down. The most obvious negative of these flex-based tools is that it’s entirely up to the user to hit the target torque – and how easy that is depends entirely on your line of sight, the visibility of the torque scale, and the graduations between that marked torque scale (some are tiny).
Click style
That leads me to the most ubiquitous style, the click-type torque wrench. These also work with a coil spring but are designed to ‘break away’ with an audible and tactile ‘click’ when the desired torque is met. Often this style of torque wrench offers a user-adjustable torque range and features a ratcheting head for more efficient use.
In many ways, this style of torque wrench answers many of the negatives attributed to beam-style torque tools, including the ability to use them without a direct line of sight and offering feedback when your intended torque is met. The ability to set them to your exact target torque allows for more efficient usage, especially if multiple fasteners of the same style await. And I may be biased, but there’s something quite satisfying about a good definite click of a torque wrench.
In turn, they introduce other trade-offs. They’re typically more complex to manufacture and, therefore, more expensive. Adjustable versions can be slow to adjust to the required torque, and then you need to reset them after use, not leaving the internal spring under load. Perhaps most worrisome is that the mechanism is more susceptible to wear, coil spring stretch and corrosion – all of that will impact the calibration (which you should periodically test to know it is within tolerance). And then some click torque wrenches, especially cheap ones, lack a definite ‘click’ and so it’s all too possible to accidentally over-tighten a fastener even after the torque wrench has tried to tell you to stop turning it.
Click-type torque wrench comes in many different forms, shapes and sizes. They also come in the form of adjustable and pre-set.
Pre-set click torque wrenches are pre-configured to click at a single torque figure. This style of tool was initially created for mass-production situations where a single tool is used for a specific task. However pre-set torque tools are also extremely common and sensible in cycling applications given that many handlebar, stem, and seatpost-related fasteners call for a 5 Nm torque. This 5 Nm figure and the use of pre-set torque tools has become so common that many brands now design their components to work to this exact torque figure.
As the name infers, adjustable torque wrenches allow the user to adjust the torque load at which the tool will click, or more specifically, the load at which a simple internal clutch overcomes the load of the internal coil springs and breaks free. Due to the ductility of the internal coil spring, typically these adjustable wrenches are most accurate within 20% and 80% of the top and bottom marked scale, so for example, a torque wrench that offers a 3-15 Nm adjustable range is likely to be most accurate between 3.6 to 12 Nm.
Break-Over torque wrench
A close cousin to a clicker-style torque wrench, Break-Over style torque wrenches are a rare sight in cycling applications. As the name suggests, these wrenches break over, folding 90° when the desired torque is reached. They’re typically reserved for mass manufacturing, where the risk of over-tightening is removed from the operator. They’re also commonly used in extremely low torque applications in precision industries.
Cost is one reason why they’re not commonly found in the hands of bicycle mechanics. The other reason is that more traditional clicker-style wrenches typically offer more adjustability and better use in confined spaces.
Deflecting beam
Another significantly rarer click-style torque wrench is known as a deflecting beam. In some ways, it’s a hybrid of a beam style and click-style torque wrench. This replaces an internal coil spring with a flexible beam, and when the desired torque figure is met, the beam flexes onto a spring-loaded button that releases a pin to make an audible click.
This tool style often features an externally-adjustable torque scale that’s incredibly quick to adjust through its range. The simple beam mechanism is also less likely to be impacted by wear, corrosion, or poor care and is, therefore, better at holding calibration.
The biggest downside to this style of torque wrench is typically related to its extremely limited availability (it’s an Australian invention, and few manufacturers make this style), and prices can be slightly higher. The shape and profile of these tools are also typically far more cumbersome, with more pointed edges.
Digital
The future is now. A digital torque wrench uses a strain gauge to measure force – it’s not unlike a cycling power meter. These torque wrenches typically offer an LED screen to show you the torque value, and will then beep and/or flash when the desired torque figure is met. Digital torque wrenches have become increasingly popular over the past decade or so, and they’re a common sight in the toolboxes of many automotive techs who work on higher-end cars.
Where more mechanical-based torque wrenches can be impacted by temperature or condition, digital wrenches tend to be more reliable and sensitive to finer torque adjustments. Digital allows you to read live or running torque figures as you tighten up a fastener. And it can be fast, or at least low effort, to set your target torque into the tool – premium options even offer user presets so you can jump to your most used torque figures. And unlike a click-style torque wrench, you don’t need to zero a digital torque wrench for storage.
However, there are certainly downsides. Price is the most obvious disadvantage, and digital torque wrenches remain a premium option. You’ll also be dealing with batteries – probably the replaceable kind as only occasionally are such tools rechargeable. And then there’s typically no tactile feedback (unless the tool is really fancy with a vibrate function) when a torque is reached, which could be problematic if you’re using it in a noisy or overly bright environment.
Inline digital torque adapter
An inline torque adapter is commonly found in a digital variant and is designed to sit between a ratchet and socket to provide a live torque reading. Many of these offer dependable accuracy and work in dual directions. They’re also a popular tool for at-home torque tool calibrations (although you’d be making assumptions based on its calibration).
However, the inline design can make the tool cumbersome to fit into tight areas. Similarly, that increased height means it’ll be harder to keep the tool perpendicular to the fastener while applying torque, resulting in a tool that is more likely to cam off (AKA strip) whatever you’re trying to tighten carefully.
Bicycle-friendly drive size and shape
A torque wrench suitable for bicycle wrenching needs to work with a variety of hex and Torx sockets and/or bits. Some torque wrenches feature a ratcheting head for more efficient usage in tight confines, while others will have a simpler fixed head. The topic of drive size and drive type is one I’ve covered in a previous article about ratchets.
Generally speaking, the drive size of a torque wrench will often correlate with its torque range – the lower the intended torque, the smaller the drive size. A common 3-15 Nm range torque wrench will usually feature either a 1/4” square drive or a 1/4” in-hex drive (for use with common 1/4 inch bits, like those found in most bit-based multi-tools).
In this lower torque range, it’s common for bicycles to present rather unique (arguably stupid) situations that many tools designed for automotive purposes simply weren’t designed for. Perhaps the most common example is seen with certain seatpost designs where the fastener is in a place that offers little clearance for access. For this, you want a torque wrench with a compact head that doesn’t obstruct your ability to use it. The best examples of a compact-headed torque wrench typically feature a 1/4” in-hex drive and include the Effetto Mariposa Giustaforza (similar also available from Tecnogi), the PrestaCycle TorqRatchet Pro Deluxe (similar available from Feedback Sports), and the Topeak D-Torq (ratcheting head).
The torque wrench drive head size isn’t the only limiting factor for what poorly-placed fastener it’ll fit, and here you should consider the shape of the entire torque wrench, too. Most readily-available adjustable torque wrenches will feature a familiar profile that places the socket or bit at a 90° angle to the tool, this is the most versatile shape that can be made to fit various needs by changing out the length of the socket/bit used. By comparison, most preset drivers sold within the cycling industry offer a T-handle shape that is designed to provide straight-path access and easy spinning on common stem bolts. However, this shape can often be cumbersome and simply won’t fit a few seatpost binder wedge designs such as those used on many Canyon and Specialized road bikes.
Tight confines are far less common in higher-torque applications such as those found with crank bolts, cassette lockrings, and bottom brackets, where the drive size and compactness of the drive head isn’t likely a make-or-break feature when we’re talking about tightening torques on a bicycle above 20 Nm. For these torque needs, it’s common to find both 3/8” and 1/2” square drive sizes, and my recommendation is to ideally find a match to the relevant sockets you already own. Or alternatively, you can always use a square drive adapter to make your sockets fit.
The first torque wrench to own
A modern bicycle will likely have many fastener sizes and torque requirements. Keep in mind that most torque wrenches offer the best accuracy within 20-80% of their available scale, and it’s quite likely that you’ll need more than one tool to cover the full spectrum of torque figures found on a bicycle.
My advice is to consider when you’re most likely to need a torque wrench across the spectrum of bicycle servicing tasks you’re likely to complete. For just about everyone, those needs will most frequently demand a tool to work on smaller fasteners between M4-M6 in size that will likely call for tightening torques between the range of 4-12 Nm (35-106 in/lb). These fastener sizes are commonly seen in stems, seatposts, brakes, and derailleurs. They are also the fasteners that are most commonly twirled and where delicate materials are most prevalent. Therefore a torque wrench that covers this torque range is always where I recommend starting first. And having tested countless such torque wrenches over the years, I can attest that there is a long list of suitable options in this range.
If your budget is tight, I’d suggest looking at a more basic beam-style torque tool, which should cost between US$40-US$65. These can be more limited in their available torque range (typically 2 – 8 Nm) and slower to use, but will get you a fairly accurate tool without breaking the bank. The Park Tool TW-1.2 is a time-proven option. Meanwhile, newer and more compact versions from PrestaCycle, Feedback Sports, and Silca offer good features and typically great fitment into hard-to-reach areas. Some of these compact torque wrench options are equally good for travel or even taking on a ride, and it’s a category I’m currently clicking and twisting my way through.
By comparison, low-cost clicker-style torque tools such as those found on eBay, Amazon and AliExpress can suffer from worrying variances in calibration. I’ve seen a few that were so far off their make-believe calibration certificates that you’d be better off saying ‘click’ while tightening everything by hand. As with any precision instrument, I strongly recommend buying one from a reputable brand.
On the assumption you’ll use this torque wrench in a home or professional workshop, there is merit in spending more for a trustworthy clicker-style ratcheting wrench that will provide even easier use, improved speed, and access to confined fasteners when line of sight is tricky. My favourite well-priced torque wrench is a somewhat generic one that offers a 1/4in square drive size and a 3-15 Nm torque range – some examples of this include the LifeLine Pro, Bluechain Pro, XLC, and Pro Bike Gear. More refined and subtly nicer-to-use versions of these tools include the Park Tool TW-5.2 (3/8” square drive head) and Pedro’s Demi Torque 2.0 (1/4” square drive head) – both offer more transparency over factory calibration, better aftermarket support, more comfortable handles, and quicker torque setting adjustment.
Stepping up in price gets you into the world of pro-level clicker torque wrenches. Some of the better click-style torque wrenches provide superior tactile feedback, higher quality ratcheting heads, and are less susceptible to calibration drift after prolonged use. Examples include options from Effetto Mariposa, Tecnogi, Norbar, CDI, Gedore, and the list goes on.
One of my pet peeves with adjustable clicker-style torque wrenches is that not all are quick or easy to adjust through their available torque range. Some require a full 360° turn of the adjustment dial in order to produce a 1 Nm change on the scale, and that’s a lot of fiddling when adjusting a tool from 2 through to 16 Nm. The popular Wera A5 suffers from just this, which lets down an otherwise good tool.
Similarly, not all tools make such an adjustment easy. Some feature spring-loaded safety collars that you have to pull down as you adjust the torque – this is one thing I don’t like about the new Topeak Torq Stick. The better versions keep the torque adjustment unlocked and open to adjustment until you choose to lock it. And given few of us are likely to be using these tools for mass manufacturing, the ability to lock in a specific torque is hardly a needed feature.
You should also consider the readability of the torque gauge and how easy it is to see the intended figures. The previously mentioned Effetto Mariposa Giustaforza has so much good going for it, but its torque scale is etched in tiny numbers that can be hard to read in poor light. Meanwhile, some of the beam-based torque wrenches can have the torque scale so cramped that you’ll struggle to know whether you’re hitting 3, 4 or 5 Nm.
Digital torque wrenches aim to solve many of these adjustment and legibility issues. Entry-level digital options can be found from brands such as PRO Bike Gear, Topeak, and Unior – all of which come from the same manufacturer but offer subtle physical differences – while premium digital options can be found from a myriad of automotive tool producers such as KTC Japan, Stahlwille, and Norbar. Snap-On is commonly considered the benchmark for digital torque tools and it is priced as such.
I personally prefer the tactile feedback of a clicker-style wrench for most applications. And while I have my hands on a number of premium options, the Pedro’s Demi Torque 2.0 is the torque wrench I find myself using the most. This is mostly because I’ve found it to be the quickest and easiest to adjust through its torque scale. Its ratcheting head is compact enough for all but the dumbest of seatpost designs, and it’s comfortable in the hand. I wish it offered a more positive “click” at torque, but that’s a trade-off I’m willing to take.
The second torque wrench to own
Once you have that first adjustable torque wrench you’ll probably find yourself using it most at a 4, 5 or 6 Nm torque setting. And given the frequency that these figure are found on bicycles, my suggestion is to get a Preset 5 Nm torque wrench as your second torque tool. Like me, you’ll probably use this preset tool more than that first torque wrench.
Part of this suggestion is based on convenience. You’re more likely to use a torque wrench if it’s handy and already set to the required torque. And it doesn’t get handier than a preset torque tool with the correct size bit already fitted. The secondary reason is to reduce wear and tear on your adjustable torque wrench, and a low-cost preset torque tool can help to offset a lot of use.
You don’t need to spend a fortune to get a good preset torque tool. Spending US$20 will get you a PrestaCycle Pro TorqKey (available in 4 through to 12 Nm options) which uses a well-proven internal mechanism that’s shared with other options from Ritchey, Bontrager, Giant, and more. This sealed mechanism somewhat uniquely allows you to undo bolts with the tool and torque them clockwise. Another affordable and even smaller option are the bit-based torque adapters, such as those sold by Topeak and PRO Bike Gear (pictured above on the right).
Spend more, and you’ll likely be looking at Park Tool and Pedro’s. These two are closely comparable, and each provides fancy handles with spare bit-storage within. They also offer a “cam-over” design, where the tool will continuously click once the preset torque figure is reached, meaning you can’t accidentally tighten the bolt more than you should, even if you’re distracted and miss the click. Another option is the original CDI preset – a good option but one that feels a little plasticky compared to the newer Park and Pedros options.
I have a set of three Pedro’s Fixed Torque Drivers that I reach for almost daily. These offer solid build quality, easy-to-access spare bits, and a comfortable handle. I prefer the bright colour coding and spare bit storage of these versus the Park Tool equivalents, but otherwise, there isn’t much separating them in functionality.
And this being Cool Tool Tuesday means there are always ways to spend more than is sensible. German tool brands Gedore and Wera both offer some desirable preset torque tools. The Gedore (#763) offers a full metal construction and could be used as a weapon if thrown, whereas the Wera (#0050XX) features a fixed and non-interchangeable tool blade that greatly limits its usability and appeal. The basic PrestaCycle or the mid-tier Park and Pedro’s options are all you’ll ever need for this second torque wrench, but I also won’t judge if you pick something vastly over the top.
The third torque wrench to own, maybe
Now that you have the smaller fasteners and lower torque ranges covered, it’s time to look at the big bolts. Larger fasteners and threaded fitments such as cassette lockings, crank bolts, suspension pivot hardware, and bottom brackets typically call for tightening in a 20-55 Nm torque range. To add complication, it’s common for some of these components to be reverse-threaded and require tightening in the opposite direction to normal.
Compared to the smaller fasteners clamping onto delicate components, these higher-torque applications are typically more resilient to torque variance. I’m still reaching for that calibrated wrench where high-end cranks, cassettes, and hubs are involved. Otherwise, you’ll find me going on feel for threaded bottom brackets and lower-end cranks, and that’s why I typically consider a bigger torque wrench less critical to own.
The top choice for these higher-torque demands is a torque wrench that spans an approximate torque range of 10 – 60 Nm (7.48 – 44.25 ft/lb) and can tighten clockwise and anti-clockwise directions. And there are a few different ways to go about achieving these requirements.
Once again, the most affordable option is a basic beam-style wrench, such as the Park Tool TW-2.2. You’re unlikely to hit any clearance or fitment obstacles when dealing with these higher torque needs, so the non-ratcheting head of a beam wrench is just fine. Another benefit is that you won’t waste any time dialling in the torque wrench to 40 or 50 Nm before you can use it – the beam wrench is always ready to go. However, there is one reason my beam wrench collects dust and that’s due to needing a direct line of sight with it, which can be tough to do while loading a bolt up to 50 Nm all while keeping the socket squarely engaged.
A medium-priced option is a digital torque adapter designed to sit between your existing ratchet/breaker bar and the socket. Many of these offer dependable accuracy and work in dual directions. Unfortunately, they also add a considerable stack to your point of torque and make it more likely that you’ll slip (AKA cam-off effect) the socket or bit off whatever you’re trying to torque.
Torque wrenches in this 10-60 Nm torque range are highly applicable to automotive demands, so it’s easy to find a well-priced clicker-style torque wrench. Add in that fasteners of this torque are more tolerant to a little variance in accuracy, and you’ll be fine with using a lower-cost option from a reputable brand or retailer – the catch is finding one that works in both clockwise and anti-clockwise directions, a demand that rules out many of the best value choices.
My go-to adjustable clicker torque wrench in this range is a CDI 10-60 Nm 3/8 Micrometre adjust (Part #602NMRMHSS). However, there are others to consider, including many that cost far less. Park Tool, Pedro’s, and Effetto Mariposa have nice options in the bicycle world. And then we get to digital options that are genuinely lovely to use and won’t waste time setting the desired torque figure. Topeak and Unior offer closely compared digital torque wrenches with all the features you could ask for. Once again, the likes of Snap-On are widely considered the kings of this space if your budget can extend to a torque wrench that costs more than a Dura-Ace Di2 rear derailleur.
What’s next?
Okay, that was longer than expected! And this was just part one of talking torque. Part Two, coming next week, is for anyone looking to wield a torque wrench and will cover the all-important correct usage of torque wrenches, including some interesting insights from a few experts.
Note: A number of the tools mentioned in Cool Tool Tuesday are not sold through traditional cycling channels and can be hard to find, which is also kind of the point of the series. Access to the tools covered will be easy for those in Europe and the United States. Use a search engine to find the products mentioned.
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