A lug wrench is a type of socket wrench designed specifically to remove lug nuts. A lug nut is a nut with a rounded base, commonly used to attach wheels on automobiles. Lug wrenches may also be called wheel wrenches, wheel nut wrenches, or wheel braces. The term “tire iron” is also used, but a true tire iron is a lever for separating tube tires from the wheel rim. There are three major types of lug wrenches.
Socket wrench: This is simply a socket attached to a long, angled handle. Most cars come with this type of wrench, packed with either the spare tire or the jack. Sometimes this type of wrench will have a tapered prybar-like end for removing hubcaps. Wrench designs vary from model to model depending on the nut size, nut torque, and storage space available. This has made older OEM wrenches very collectable among those restoring antique cars to original condition.
Four Way: These lug wrenches use two metal rods welded together to make an “X” shape. Some four ways will have a socket at each end, or three sockets and one end with a prybar for removing hubcaps. Aftermarket wrenches are almost always sold in this form.
Center Lock Wheel Nut Wrench: Instead of using several small nuts, some custom high-performance wheels have a single large locking center nut. Wheels intended for drag racing come with a socket for use with an impact wrench while wheels intended for street use will have a wrench with a leveraging wrench to allow drivers to apply the massive amounts of torque needed to tighten the nut securely. For example, the wheel nuts on latest Porsche GT3 requires over 360lb-ft of torque yet light finger pressure is enough to tighten the nut using the included wrench.
There are six common sizes of lug nuts on passenger cars and light trucks: 17mm, 19mm, 21mm, 13/16 inch, 7/8 inch, and 1 inch. Four-ways are roughly divided into car sizes (17mm-21mm) and truck sizes (21mm-1 inch.)
Some cars have “Locking” lug nuts. These have a specially designed head that cannot be removed with common tools. Cars typically come with an adapter nut that fits in the lug wrench, letting it turn the lock nut. Some cars use a similar system to lock the hubcap over the lug nuts. These will have a separate wrench, typically packed with the spare tire.
Lug nuts should be screwed on using a star pattern, moving to the nut furthest from the last one that was tightened. Alloy wheels can be slightly misaligned when tightened by hand which can cause vibrations at high speeds. This vibration can be remedied by tightening the nuts to spec using a torque wrench.
Some older vehicles come with tin-capped nuts. These caps can work loose with age, decreasing the nut’s exterior size. For example, a 21mm lug nut without this cap is about 20mm. Using a lug wrench on these can round off the bolt. The best solution is to use a socket with the correct fit or use a loose cap as an adapter on the wrench.