What Size Impact Wrench to Use

Impact Wrenches

• Impact wrenches remove or install lug nuts using power generated by electricity or pressure from compressed bursts of air. A common use for impact wrenches involves taking the nuts off a car wheel to replace the tire. According to Clifton E. Owen, author of the book “Basic Automotive Service and System,” impact wrenches work best when used to remove lug nuts. When installing them, the wrenches can over- or under-tighten nuts, due to their varying torque output. The head of an impact wrench moves clockwise or counterclockwise, depending upon the setting.

Size

• Impact wrenches come in four common sizes, three-eights of an inch, half an inch, three-quarters of an inch and one inch. Half-inch impact wrenches are the most commonly used, according to the authors of the book “Basic Automotive Service and Maintenance.” Other sizes exist, though only for specialized use such as industrial applications. The size measurement of an impact wrench denotes the size of the drive, or shank. The drive extends from the barrel of the wrench and holds the sockets you use with an impact wrench.

Size and Performance

• The size of an impact wrench affects its strength. According to a publication from online automotive resource Tech Tire Repairs, a one-inch impact wrench can produce as much as 450 to 500 foot-pounds more torque than a three-quarter-inch impact wrench. The strength of a wrench affects the jobs for which you can and can’t use it. For instance, using a one-inch wrench on a job that requires a half-inch wrench can cause serious damage by over-tightening lug nuts. Likewise, too little torque can lead to instability.

The Right Size for Your Job

• Determining the right size impact wrench for your job comes down to a number of considerations. With a specific job in mind, you should do some research about the torque and size requirements for that job. For instance, removing lug nuts on a car wheel requires a three-quarter-inch impact wrench. Also bear in the mind that the way in which lug nuts were tightened affects the size wrench you need to loosen it. Though removing wheel lug nuts requires a three-quarter-inch impact wrench, if someone put those lug nuts on with a one-inch wrench, you need a one-inch wrench to get them off. Requirements ultimately come down to the power you need.