Why you need a torque wrench and how to use one

You probably just rely on a regular wrench to tighten parts on your car, but any important fastener should be tightened with a torque wrench so it will be neither too tight nor too loose. Doing otherwise can cause a part to break, leak or come undone.

Torque wrenches come in three basic types that I list below, but they all do the same thing: allow you to apply a specific amount of twisting force to a nut or bolt to achieve the correct amount of clamping force. Cowboy the process and you can end up with a water pump that leaks or a cracked alloy wheel.

In the US, fastener torque is most commonly expressed in "foot-pounds" or the finer "inch-pounds," depending on the part being fastened and the wrench being used. I won't give you a physics lesson on the definition of those metrics; just know that they are the standard for tightening things. 

There are three main kinds of torque wrenches, listed below in my order of preference.

Read more: Best torque wrench for 2022

Digital wrench: Slick, but don't choose a cheap one

Gearwrench 1/2-inch Drive Electronic Torque Wrench

These wrenches have a digital interface for setting the desired torque and displaying the max torque used when loosening a fastener, which tends to be more trivia than useful information. Digital wrenches typically emit a beep and vibration when you reach the desired torque level rather than momentarily decoupling like a click wrench does. Digital wrenches may seem like the modern way to go but, as with anything electronic, the cheap stuff tends to be crap. If you're going to buy a digital wrench, spend $150 or more. 

$159 at Amazon

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A few finer torque wrench points

• Adding an extension between the head of the wrench and the socket it's driving should not meaningfully skew its accuracy. Use a good-quality, thicker-diameter extension to reduce any small inaccuracy. 
• Do not use a longer handle on the end of a torque wrench to give yourself more leverage. That will likely damage the wrench so that it no longer reads correctly. 
• Grip the wrench where you find the obvious built-in hand grip. "Choking up" on the wrench may throw off its accuracy considerably. 
• Fasten parts without any unusual oils or lubrication. In most cases fasteners are designed to be tightened with a clean dry metal-to-metal interface. Some deep internal engine parts may vary from this, but if you're rebuilding an engine you don't need this article.
• Don't drop or toss a torque wrench. Most wrenches are as tough as nails, but torque wrenches are instruments first, wrenches second.
• If you want to buy just one torque wrench and get the most applicability, make it a 3/8-inch drive as opposed to a 1/4-inch or 1/2-inch drive. The drive size refers to the width of the square peg onto which sockets are attached on the wrench.