The Mighty Torque Wrench

By BoatUS Trailering Editors

Introducing trailer's essential tool, and a smart addition to your tool kit.

A BoatUS member was watching a BoatUS TRAILER ASSIST service provider change a flat tire on his boat trailer along I-44 near Halltown, Missouri, when he asked the fellow about a wrench that didn't look like the four-way lug wrench he always used on a tire. "It's a torque wrench," the tower told our member. "They're designed for this." Suddenly, the conversation turned from why the tire went flat to why a tire needs a special wrench. Here's the answer: Each trailer has a recommended "foot-pound" calibration for the lug nuts on that particular trailer/tire combo. If they're too tight, the lug bolt is stressed. If too loose, the lug nut can come off or the wheel can become misaligned. Generally speaking, the torque varies with tire size, but each boat-trailer manufacturer has a recommended foot-pound value. Bottom line? Check your trailer specs for the correct foot-pound value.

<h2">What Kind Of Torque Wrench Is Right For You?

The most common torque wrench is called "the clicker" because it will start making a clicking sound when the proper value is reached. Another model has an indicator needle that is set to the desired foot-pound. These are most common in auto-parts stores. A third type is electronic and uses four AAA batteries. Prices range from $60 to $300, and more if extra fittings are sought.

How Much Torque?

Every manufacturer has a different torque range so check your owner's manual. For example, Load-Rite boat trailers have a range of 85-95 foot-pounds for lug nuts while Magic Tilt Trailers use these recommended values:

12" & 13" tire/rim (5-lug)50 ft-lbs. min.75 ft-lbs. max.
14" & 15" tire/rim (5-lug)90 ft-lbs. min.120 ft-lbs. max.
15" tire/rim (6-lug)90 ft-lbs. min.120 ft-lbs. max.
16" tire/rim (8-lug)90 ft-lbs. min.120 ft-lbs. max.

Lug nuts for cars and trucks also have a recommended foot pound tolerance. Unfortunately, some auto shops still use air guns to tighten lug nuts on truck and car tires. Reputable shops will use torque sticks, which are color-coded for specific foot-pound measurements. It's important to ask the shop how the lug nuts are tightened. If the answer is, "It doesn't matter" find another shop. 

This article was published in the Summer 2012 issue of Trailering Magazine.

Torque Wrench Tips:

  • Always use a torque wrench to tighten, not loosen, a lug nut.
  • After use, set the torque measurement to zero.
  • Torque wrenches may require recalibration after a few years of use to ensure accuracy.
  • Begin by hand-tightening one lug nut. Next, tighten incrementally and sequentially by going to the lug nut on the opposite side, continuing in a crisscross pattern so that the wheel is secured evenly on the hub. Then, use the torque wrench following the same pattern but only tightening a few turns at a time — some suggest 75 percent, then 85 percent, before torquing to 100 percent in the final pass.
  • Check the torque on lug nuts before every trip. Some trailer manufacturers recommend checking after the first 75 miles on a long trip.



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