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Mastering Torx Screws: Understanding, Proper Usage, and Evolution in Bicycle Mechanics

February 22, 2024

When it comes to Torx screws on bicycles, some people may harbor negative impressions. However, the issue often lies not with the Torx screws themselves but with poor-quality screws paired with equally subpar tools, resulting in the screws being easily stripped. To dispel misconceptions about Torx screws, let's delve into the specifications of these screws in detail.


Overview of Torx Screws


What are Torx screws? Torx screws, formally known as ISO 10664 screws or internal Torx screws, are also referred to as star-shaped screws. They were developed by the American company Camcar Textron in 1967, with the trademarked name Torx, hence the name Torx screws.


These screws feature a six-pointed star-shaped recess, enhancing the durability of screwdriver engagement. Over the past few decades, Torx screws have found widespread use across various industries. Compared to conventional screws, Torx screws increase the contact area between the screw and the screwdriver, meaning they have a greater torque capacity.


In the realm of bicycles, Torx screws became mainstream for disc brake fixation due to their reliable torque control. Since then, nearly all bicycle component brands have adopted Torx specifications for their aluminum or titanium screws, which offer lower torque and lighter weight.


However, Torx screws are not without their flaws. Their shallow recess design only allows the tool to insert with limited depth, and the materials used for Torx screws are often soft. In such cases, slight tolerances can easily lead to screw stripping, causing significant inconvenience.


How to Properly Use Torx Screws?


If you want to dismantle or tighten Torx screws without stripping them, it's essential to use high-quality tools and follow the correct installation method.


Firstly, you need to determine whether the screws you're working with are Torx or Allen (hex) screws. While some Allen tools can manipulate Torx screws and vice versa, it's best to differentiate between the two before proceeding.


Once you've identified the standard Torx screws, the next step is to determine their size. Unlike Allen screws, Torx screw sizes can be somewhat ambiguous, and using the wrong size can lead to problems. For example, a T10 screwdriver can manipulate a T15 Torx screw, and similarly, a T25 screwdriver can handle a rare T27 Torx screw, such as the one used to dismantle the XTR M9000 disc rotor fixation screws. If you're unsure about the correct size, try multiple sizes and choose the one that fits snugly.


When tightening screws like Torx with shallow recesses, ensure there are no foreign objects or debris inside the screw recess. Any foreign material affecting the tool's fit increases the likelihood of problems.


Lastly, applying the correct torque and vertical pressure is crucial. When rotating the tool to tighten the screw, vertical pressure should be applied downward to prevent tool slippage or dislodging.


In summary, the importance of these precautions increases with higher screw torque and shallower recesses. While these may be basic skills for experienced technicians, they require learning and attention for the average cyclist who rarely deals with screws.


Using High-Quality Tools


For common screw specifications, inexpensive old tools are usually sufficient as the likelihood of issues is low. However, when it comes to Torx screws, investing in a set of high-quality tools is essential. Comparisons between mid-range and high-end Torx T25 screwdrivers conducted by external media outlets demonstrate this point. When disassembling the same batch of new T25 Torx screws, the mid-range T25 screwdriver stripped the screws at 8.8 Nm, whereas the PB Swiss T25 screwdriver raised this value to 14.9 Nm.


Furthermore, smaller Torx screwdrivers are not only more prone to wear or breakage but are also typically less precise, with users easily feeling the tool's edges and gaps compared to the screw. During practical tests, it was found that the Bondhus T25 Torx screwdriver, made in the USA, could oscillate 10° within the screw recess, whereas the PB Swiss T25 Torx screwdriver had a maximum oscillation angle of 6°.


A larger oscillation angle implies looser fit and higher risk of tool dislodgement, while a smaller angle indicates better fit. Both tools are not extreme examples, as the USAG T-type Torx screwdriver exhibited an oscillation angle exceeding 15° in tests, while the Wera stainless steel Torx screwdriver had the smallest oscillation angle, less than 4°.


It must be said that Wera, PB Swiss, and Wiha Torx screw tools consistently provide users with a satisfying experience, while some other high-quality tool brands are also excellent. For example, Park Tool's T-type Torx screwdriver offers a good user experience, and Snap-On tools are also great.


Like Allen tools, the smaller the Torx screw size, the higher the tightening requirements. Loose-fitting installation tools are acceptable for T30 Torx screws, but for smaller T25 Torx screws, the margin for error may not be as forgiving. In any case, it is not recommended to use ball-head tools on Torx screws in the bicycle field.


Apart from tools, issues may also arise with Torx screws themselves. For instance, on Zipp bicycle components, the Torx screw specifications are intriguing. An external media author found that the PB Swiss T25 Torx screwdriver had too much play when inserted, while the Wera Torx screwdriver couldn't fully insert. However, such issues are relatively rare.


Most cyclists may not encounter Torx screws every day, but understanding the basic specifications of Torx screws is still necessary. Torx screws used in the bicycle field range from T6 to T40, with the most common sizes being T8, T10, T15, T20, T25, and T30. If you only need a set of Torx screw tools to meet bicycle requirements, purchasing according to the above specifications should suffice.


Emergence of Updated Torx Screw Specifications


As mentioned at the beginning of the article, Torx screws are not limited to the bicycle field, and Torx screws used in other fields are not just simple six-pointed stars used by bicycle companies like SRAM, Shimano, Campagnolo, 3T, Merida, Pinarello, and others.


In addition to enhancing the durability of screwdriver engagement, Torx screws also serve a more critical role in tamper resistance. Some automotive manufacturers use external Torx screws or even five-lobe Torx screws, while TorxPlus Torx screws feature elliptical geometry and larger blade cross-sectional areas, supporting greater torque. Currently, TorxPlus is a widely used standard in various transportation industries. In the image below, the left side shows a standard T40 Torx wrench head, while the right side shows a TorxPlus T40 Torx wrench head.


However, TorxPlus specifications have never been present in the ordinary bicycle field. Nevertheless, Bosch's latest Gen4 electric bicycle motor uses TorxPlus IP40 specification screws, and it's believed to be not the last bicycle motor brand to use TorxPlus specifications.


Some opinions suggest that TorxPlus screwdrivers of the same size can also be compatible with standard Torx screws. However, official claims state that standard Torx screwdrivers can be used for TorxPlus screws. Conversely, if a TorxPlus screwdriver can manipulate standard Torx screws,


 it indicates that the screw has worn out and needs replacement.


Conclusion


The above knowledge about Torx screws is aimed at providing helpful insights. While most cyclists may not deal with Torx screws daily, understanding their basic specifications is essential. Torx screws offer advantages in terms of torque control and tamper resistance, but proper usage with high-quality tools is crucial to avoid stripping and other issues. Whether in bicycles or other industries, Torx screws continue to evolve, with TorxPlus specifications representing the latest advancements in screw technology.


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