What torque should lug nuts be tightened to ?!

Lug nut torque specifications :

The more you tighten, the better! Get over common misconceptions about tightening or lug nut torquing, and follow our three recommendations to ensure your team is providing the right level of torque.

March 15, 2024

Tire changing Impact Wrenches Tools Expert Corner

As supervisors and maintenance managers, you need to ensure that the heavy vehicles or machinery that go through your workshop are appropriately maintained following manufacturers specifications, especially when it comes to tightening applications. One specific area that needs attention is tire changing.

What questions should I ask to ensure my team is providing enough torque?

Are ‘blue books’ available for your team to consult?
How often do you review your internal tightening processes?
Do you carry out surface preparation as standard during your processes?
Are the tools used ensure to reach the right torque?

Tire changing on any type of vehicle is a regular job for mechanics and it can seem quite straight forward. As such, operators can tend to overlook the tightening specifications (or torquing specs) recommended by the vehicle manufacturers. This practice should be avoided however, as it can lead to downtime and serious safety consequences.

Common misconceptions «heard in the field» about lug nut torquing

The more you tighten, the better. False. In most cases, more torque means more tension applied to a bolt, resulting in overtightening which increases the risk of stud break.
The more a truck is carrying, the more you need to tighten. This is a myth; manufacturers’ recommended torque specifications should be followed at all times. Believing this myth can lead to overtightening lug nut and its disastrous consequences.
To get the right torque applied, you just need to count 1, 2, 3 while tightening. Well…, that’s false! Proper torque requires using the correct torque tools, procedures and patterns as our torque sense blog explains.

Recommendations to share with your team to get the right tightening:

Be aware of the manufacturers’ specifications and refer to them

Manufacturers always provide recommendations for each tightening job, and these can be found in the specifications book, or maintenance manual, which is more commonly called ‘blue book’. Before you start tightening you should double check the book to ensure your job is performed to the best standard.

With new innovations in materials and tools, it’s important to keep your knowledge current and follow the latest specifications. For example, nowadays most wheel rims are made from aluminum instead of steel but this does not mean that aluminum rims are harder and more torque is needed. The rim material affects the torque that should be applied. Continuous training is highly recommended and this can be offered by different providers.

Surface preparation is key

A substantial amount of torque is “lost” or wasted by friction during tightening. Therefore, we advise preparing the surface properly by cleaning all the elements to eliminate any rust, dust and dirt. Once you finish cleaning and before you start tightening inspect all components: wheel, studs and long nuts. Find out more about tightening preparation tips in our “torque sense when changing wheels” blog.

Clamping force can be affected by other factors: parts quality and tools maintenance or calibration.

Nil Gauter , Product Marketing Manager Heavy vehicles

Prevent over-tightening

Wheel nuts that are over-tightened can often become damaged or broken, especially when hitting bumps in the road. This can result in a potentially catastrophic failure of the wheel, posing a serious risk to the safety of the heavy vehicle and its drivers. It’s important to use the right combination of tools to prevent this and achieve the right level of torque.

If you spot any signs of deformation or stretch on a stud, there is a high probability that tightening is above manufacturers specifications. Therefore, it’s key to replace the stud as soon as possible, and review your tightening processes.

Justin McWatters , Product Marketing Manager Vehicle Service

3 recommended tools (or combinations) to prevent over-tightening:

To prevent over-thightening there are Manual Torque wrench
To prevent over-thightening for passenger vehicles there are Torque limited impact wrench + torque wrench
To prevent over-thightening for heavy vehicles there are Pneumatic or cordless nutrunner, designed for tire changing. (We recommend to check the torque applied by the nutrunner with a torque wrench).

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