An often-overlooked item – a torque wrench for a bicycle. After all, for so many years, my father and grandfather disassembled and reassembled bikes with cheap wrenches, screwing everything together "to the color of their faces," so who cares? "It's just a bike." Meanwhile, some things have changed somewhat. And while assembling a typical cross bike is easy enough without a torque wrench, with more expensive components, things start to get risky. You don't want to crush a carbon steerer tube or strip a thread in a fork leg housing that costs several thousand złoty, do you?
Even just browsing through articles about wrenches, I found twice that a bicycle torque wrench should operate in the range of 0-20 Nm. This is complete nonsense!
What exactly do you need a torque wrench for on a bike?
The most common component with a torque rating marked on the bolts is the A-head stem. With aluminum components, you can easily do it by eye (within reason—you can screw that up too), but with carbon steerer tubes and handlebars, it's very easy to crush the tube. The same applies to the seatpost clamp and carbon seat rails. Generally, all bolted carbon fiber components should be treated with caution and, whenever possible, follow the manufacturer's recommendations for tightening torque.
What else? First and foremost, the cranks. Particularly vulnerable are those in Shimano's Hollow Tech II system, where the bolts are easily damaged, leading to annoying drilling. The opposite problem occurs with Miche or SRAM cranks, for example, which are tightened with a single large bolt. Here, the torque values are around 50 Nm. That's really significant. Therefore, most people who do it "by feel" end up undertightening, which translates into play.
Shock absorbers. A complex topic. In my experience, RockShox and SunTour are quite tough in this regard, but with Fox and Manitou, I advise against skimping. A dynamometer allows you to tighten everything precisely without worrying about play, leaks, or stripped threads.
Another application that many people forget about is the rear derailleur clutch, which in many models is adjusted using a torque wrench. Besides this, there are other components that require a torque wrench (for example, some hubs, classic stems, brakes, or clamps). However, this is less common. Cassettes are a particular problem – most of them are marked with a very high torque value (around 40 Nm). However, such a force can easily damage most freehubs, especially aluminum ones. Therefore, almost all mechanics choose the torque based on intuition and experience.
So which torque wrench should you choose for your home workshop?
Workshops usually have at least two. A smaller bicycle torque wrench with 1/4" sockets and a larger 3/8" one. The former is used for stems, calipers, crank arms, and all sorts of smaller bolts. The larger one is used for shocks (the smaller one, too, actually), bottom brackets , and some cranks.
Scope of work
In practice, this means that the smaller one should have a torque range of approximately 3 to 15-20 Nm, and the larger one from 10-20 to 55 Nm. Ranges vary, of course, between models. The key is to avoid a gap between the two wrenches. Of course, this only makes sense if you have components on your bike that require it. Many people will only need the smaller one.
Key type
For amateur use, I recommend a breakaway or trigger key. If money isn't an issue, an electronic key is certainly a great option, although I think it's a bit of a triumph of style over substance. More important than the key's operating mechanism, however, is its proper calibration – a reliable mechanical key will work better than an electronic bargain from Aliexpress. And then there's the accuracy. A measurement error of around 4% is acceptable.
What about a tilting bicycle torque wrench?
I worked with these (Park Tool) for several years, often on high-end bikes. Contrary to popular belief, they're not bad tools (provided they're not from a department store, of course). The truth is, accuracy is lower, and you have to align your line of sight with the needle to avoid confusing the readings. A significant advantage is the speed of use—there's no need to adjust the wrench itself. Unfortunately, the Park Tool TW-2 is no longer manufactured, but I think it would be an excellent choice for home use.
In any case, avoid those costing a few dozen zlotys. A torque wrench for a bicycle used by amateurs doesn't have to be top-of-the-line, but there are limits. Especially since many screws and threads on bicycles are prone to wear or stripping.
So tiny
Finally, something bordering on interesting. You can find very small torque wrenches integrated into T-connectors, multi-terminal holders, or single Allen wrenches. Sometimes they're adjustable, and sometimes they're set to a specific value (usually 6-7 Nm—safe for most bridges and terminals). There are even adapters for Allen wrenches with ratchets. I think this is a rather compromise solution—it's better to buy a simple, reliable torque wrench and not mess around.
Main photo by John Rees
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