Torque wrench tips and best practices with some of the industry's biggest manufacturers
We recently published a piece on torque where we looked at how torque in the bike industry compares to others. This second instalment in our deep dive into torque sees a discussion on torque and torque wrenches with some of the biggest tool manufacturers in the bike industry.
We sent some questions to some prominent tool manufacturers to get a take directly from the horse's mouth. The internet is full of tips and advice on all things bike maintenance but not all of it can be relied upon. For the most part, going direct to the manufacturer whether it be for tools or components will usually provide you with the best advice.
We spoke with Jernej Muzga from Unior Tools, the Slovenian tool manufacturer, Alberto De Gioannini founder of Swiss torque wrench specialists Effetto Mariposa, Thomas Chasseport from VAR Tools a longstanding French bicycle tool manufacturer and finally, we got to speak to Topeak, a Taiwanese toolmaker of over 30 years as well as the UK Topeak distributor Extra.
As mentioned in our previous article, most road bike owners are encouraged to own and use one of the best torque wrenches to ensure they are accurately tightening their bolts to the correct torque specifications, helping to properly maintain their bike. Nearly every reputable bike shop or workshop will also be using a torque wrench on bolts and fasteners to ensure no mistakes are made.
Torque wrenches are precision tools and need to be treated with care, and ideally recalibrated at fairly regular intervals which is a topic we will be exploring in more depth. We posed a series of questions to some manufacturers with the idea of trying to learn more about how torque wrenches actually work, re-calibration and support processes for different manufacturers' products. We also asked for their tips on getting the most from your torque wrench and whether brands think we need to be more aware of torque wrench calibration in the cycling industry.
Cyclingnews. Why should shop or home mechanics use a torque wrench on their threaded fasteners?
Jernej Muzga: A torque wrench should be used to torque the components to the manufacturer's torque specifications, which can nowadays be found on almost any bike component. Respecting the manufacturer's torque specification ensures the components don`t get damaged by overtightening. Damaged components represent a huge safety risk for every rider and damage might not even be seen at first glance.
Alberto De Gioannini: The answer in one word is: safety. Across all mechanical industries, the use of torque wrenches has become standard practice, for very good reasons. There are potential issues for mechanics not using torque wrenches when working on customers' bikes if there is ever a problem.
Thomas Chasseport: Bike manufacturers, transmission manufacturers and components manufacturers are creating products that are even more precise. Mix it with even lighter and/or technical materials (steel, carbon fibre, aluminium…), and using torque wrenches becomes mandatory. There is a tiny line where the fasteners are correctly tightened. The range where this line sits is very large, beginning with a “not tightened fastener” and ending with “something is broken”. Applying the correct torque leads to the correct tightening.
Topeak: To avoid over-torque, especially Carbon Fiber products, if over-torque is easy to cause product damage
Cyclingnews: How does a click-style torque wrench actually work? (click style torque wrenches are probably the most common type of torque wrench used in the bike world)
JM: The head (beam) of a click torque wrench is attached to the handle at the pivot point. Inside the handle click style torque wrench feature a spring-loaded mechanical ˝clutch˝. The spring provides a force to the clutch, which prevents the torque wrench from rotating at the pivot point.
When applying the force at the handle at one point the clutch is no longer able to withstand the force and slips, this is where the ˝click˝ happens. Adjusting the dial at the end of the handle will compress the spring and add more force to the clutch, meaning more force will need to be applied to the handle before the clutch slips and we get a ˝click˝.
AG: It's a simple but precise mechanism, based on a calibrated spring that is put under a certain load when setting the "torque" dial. The spring is compressing a bearing placed under the wrench head. When the torque applied to the bolt reaches the torque value set in the tool, the bearing allows the head to move and "click". It's good old mechanical functioning, no need for batteries.
TC: To summarize, a click-style torque wrench works like a spring-preloaded cam. When the applied torque reaches the spring tension, the cam is liberated, allowing the head to “knock”.
TP: The click-style torque wrench operates in such a way that when the locking torque reaches the preset torque value, a CLICK sound will be generated due to the instantaneous jumping of the mechanical structure. For example, if the torque is set to 6Nm when the locking torque reaches 6Nm, the internal structure will instantly Slip and generate a click sound to remind the user that the preset torque has been reached
Cyclingnews: How are your torque wrenches calibrated during manufacturing?
JM: The last step in the production of all Unior torque wrenches is calibration on specialized calibration devices. Calibration devices are certified and regularly checked.
AG: The calibrated spring is made in such a way as to have a linear behaviour and the needed constant of elasticity in the range of torque we use it. We just have to finely adjust the beginning of the scale so that it displays the torque value that is actually applied
TC: Torque wrenches are individually calibrated, as each spring is different. We cannot 100% predict how will the spring behave, so a calibration bench is required to ensure the correct setup. The bench sets a torque reference, and the calibration process is about how to correctly preload the spring. Then, it’s a control/adjustments steps of the torque wrench on the bench. You have to check your preload at different graduations to ensure there is no spring deflection throughout the process.
TP: There is Calibration with a digital torque gauge for every piece
Cyclingnews: Is it ok to use a converter socket with a torque wrench? I.e ⅜ to ½”
JM: It's ok to use the torque wrench with the adapters. When using the adapters make sure the adapter is designed to withstand the force you are applying with the torque wrench. This might not be an issue when working on bikes, where torque values are low, but it can be a factor when dealing with higher torque values and downscaling interface with the adapter (I.e. 1/2˝ to 3/8˝).
AG: Sure, as long as it doesn't move the application point of the torque, extending or shortening the "length" of the tool.
TC: To be perfect, the fewer converters you use, the more precise you remain. Torque is a couple of forces around a rotation point, adding converting sockets (of any size) will add imprecision to the torque you apply as there is “play” between your converting sockets. So, if your torque wrench has a 3 / 8 ‘’ square drive, you (ideally) need 3 / 8’’ sockets and bits.
Cyclingnews Pre-set torque wrenches are popular now, but some cannot be calibrated. Is this the reason Unior does not currently offer one?
JM: Preset torque wrenches are in our plans.
AG: Pre-set torque wrenches are useful tools, however, we decided to focus on professional torque wrenches with a very long lifespan, that can be recalibrated.
TC: VAR pre-set torque wrenches cannot be calibrated. Our professional torque wrenches (DV-10400, DV-10500, DV-12100 and DV-12200) can be re-calibrated.
TP: No, because it is a consumable
Cyclingnews: Is it better to undo a bolt and then torque it to spec or is it ok to check the torque spec as is with the bolt already tightened?
JM: Always undo the bolt first and then tighten it to spec. You don't know at what value the bolts have been torqued previously, if it's rusted, cross threaded, etc. When undoing the bolt first, we take the guesswork out of the equation and also prevent damaging the torque wrench. Never use the torque wrench for undoing the bolts.
AG: That's a good question. We recommend doing the first, undo and then torque to spec, as static friction can lead to quite different final tension values in the bolt over dynamic friction, for two bolts tightened at the same nominal torque.
TC: Both answers are correct, and not correct. It’s correct to apply the right torque by undoing the bolt and then reapplying the correct torque. By doing so, you are 100% sure that you applied the specified torque. Also, you can check if the bolt is tightened as you are undoing it. It’s not correct because you may break the pre-applied thread locker and reduce the thread-locking power.
Checking the torque while the bolt is already tightened has limitations: you only can check if the bolt is tightened, but not how. Let’s imagine a bolt that is tightened to 10 Nm, with a specified value at 8 Nm. Set your torque wrench to 8 Nm, you are not able to know that the bolt is over-tightened.
TP: I think it's best practice to undo the bolt with a normal Allen Key or wrench and then re-torque as required. If you were using a pre-set torque wrench then by just checking the bolts you wouldn’t be able to tell that they have been over torqued.
Cyclingnews: What is your warranty and calibration process for customers wanting to calibrate their own torque wrenches?
JM: We have certified service partners all over the world, that can calibrate and service our torque wrenches. We are constantly working on adding new service partners to this list, to offer the best possible customer service. A list of our service partners can be found on our website.
AG: For Giustaforza owners based in the US or Canada, they might want to check this link(opens in new tab). For Giustaforza owners based anywhere else, we can recalibrate their torque wrench here in Switzerland. The cost is 50 CHF, including shipping back. Normal turnaround time is 10 days and the wrench will come back calibrated, cleaned and lubricated, with a certificate of calibration.
If the wrench has some specific problem, we should be notified before getting the tool (if it fell hard on the adjusting knob and it's broken, there's no point in sending it in for calibration) but I'd say 99% of Giustaforzas can go on for many years and be recalibrated multiple times.
TC: Each torque wrench comes with its own calibration certificate. We recommend our customers reach calibration/metrology specialists in order to recalibrate their torque wrenches. A calibration each year is the first step to keeping a torque wrench accurate.
TP: For the adjustable Digital and Mechanical Torq Wrench, it is recommended to send it back to the original factory for calibration
Cyclingnews: Most people know to zero their torque wrench and treat it carefully as it’s a precision tool, are there any other tips you have for caring for and getting the best results from a torque wrench?
JM: Besides the golden rule of setting the torque wrench to zero, there are a few other important tips for taking care of a torque wrench. Treat it like a measurement instrument, never use it for untightening, don't drop it, and store it in its original packaging.
AG: We actually recommend taking the torque wrench to the bottom of the scale (minimum value), not zero. Keeping the wrench pre-loaded at 2 Nm won't affect its precision and will ensure all the internal parts stay in place. Taking the dial below 2 Nm isn't a problem per se and most Giustaforzas can go below that... but there is the remote risk that some small parts go out of alignment if - for example, the wrench falls down while totally unloaded. Nothing dramatic, and we can fix it easily, but this is the reason why we recommend going to 2 Nm and not below.
TC: Zeroing a torque wrench is a mechanic rule when you need to stock your torque wrench. By doing so, you release all the spring tension, avoiding any deflection. Also, torque wrenches are provided with a storage box, which protects the torque wrench from shocks, water (or chemicals) projection, and UVs. A torque wrench is a precision / measuring tool, do not let it fall on the ground, and do not use it as a hammer or ratchet. Moreover, a torque wrench is a tightening tool, do not use it to undo a bolt, the spring will be damaged (and then the precision will be affected).
TP: Ensure you’re not using the torque wrench for undoing bolts, keep the tool clean and away from contaminants and try to ensure it's not dropped.
Cyclingnews: Do you think there is slightly less need in the bike industry to use a torque wrench due to the generally low torque values needed on bike components compared to heavier or automotive industries?
JM: It's the other way round, the lower the torque values, the higher the risk of overtightening. The usage of torque wrenches on components with low torque values is crucial.
AG: It's actually the contrary. A torque wrench is very much needed at low torques, as they can be easily exceeded using standard hand tools.
TC: As soon as a torque value is mentioned (on the component and/or on the assembly manual), respecting the specified torque is an investment the mechanic does in order to ensure the best working environment. For instance, some bearing compression bolts are tightened above the specified torque. This ends in a higher bearing drag and premature bearing wear.
TP: The cycling industry is full of materials that must be worked with correctly, Carbon, Titanium and lightweight alloys all have very small tolerances and can have severe consequences if they are over-tightened, as this technology continues to develop in search of saving weight I can only envision the need for torque wrenches becoming even more prevalent.
In addition to this we are seeing components such as cranks, headsets, BBs and bearings all coming through with Torque settings, failure to torque correctly affects the longevity and performance of the products and can even void product warranties.
Cyclingnews: Do you think many shops and mechanics re-calibrate their torque tools yearly? Or do we need a greater awareness of this in our industry?
JM: We need a great awareness of calibration in the industry. We sell many torque wrenches but only get a small part of them back for annual calibration.
AG: We see an increasing awareness of the importance of using torque tools, in a proper way and keeping them in perfect efficiency. The number of Giustaforzas being recalibrated is increasing year by year. A very good sign.
TC: Investing in a professional torque wrench is a real choice that bike shops make. Generally, bike shops are asking us how to maintain, and recalibrate their torque wrenches. As the “torque culture” is growing in our industry, the overall awareness will also grow up.
TP: I think there is a lack of awareness of this within the industry from some shops but not all, however in the case of the pre-set torque wrenches I think more often than not the shop replaces the tool for a new one somewhat regularly and therefore its less than an issue.
A big thanks to Jernej, Alberto, Thomas and the folks at Topeak for their time and for sharing their knowledge.