Why Do Wheels Come Loose?

November 2015, - WebXclusive

by Jim Park, Equipment Editor - Also by this author

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Impact wrenches are fine for running wheel nuts up onto the studs, but a torque wrenches must be used to set the nuts. Retorqueing is highly recommended, but few, apparently, get around to it.
Impact wrenches are fine for running wheel nuts up onto the studs, but a torque wrenches must be used to set the nuts. Retorqueing is highly recommended, but few, apparently, get around to it.

Investigations into hundreds of wheel separation incidents reveals that whether it was loosened wheel fasteners or failed bearings due to improper installation or loss of lubricant, better maintenance could have prevented all but a few of the incidents.

In 643 incidents reported between 2000 and 2003, loose wheel fasteners were to blame 65% of the time while wheel bearings were the cause in 26% of the cases. The remainder were a mix of axle and/or suspension structural failures and other causes.

One Canadian report revealed that 83% of the incident reports noted that repairs or maintenance had been performed on the suspect wheels just a short time prior to the separation.

Wheel-end failures result from over- or under-tightened bearings or lack of lubrication. Under-tightening (excessive endplay) can cause the wheel to wobble on the spindle, damaging the seal, which can lead to a loss of lubricant and eventual failure of the bearings. Over-tightening (excessive preload) can damage the bearing causing overheating, seal failure and lubricant loss.

Where fasteners are to blame, several factors can cause nuts to work loose. Excess paint, rust, scale or dirt between mating areas of wheel end components will lead to low clamping force. Failure to follow the manufacturer’s instructions for specified torque, the correct tightening sequence, and routine in-service torque checks have all be cited as causes for loss of clamping force on wheel nuts.

Improper use of impact wrenches and non-calibrated tools have resulted in wheel studs being stretched beyond their yield point. Fractured or worn out nuts with deformed threads have also been linked to loss of sufficient clamping force at the nut flange.

You might think that trailers would fare worse than tractors, since they are typically in the shop less frequently. But the percentage split between tractor and trailer incidents is about even, with trailers representing about 6% more than trucks.

Read more about how to prevent wheel-offs in the December issue of HDT.


  1. 1. Michael GaloratH [ November 25, 2015 @ 04:46AM ]

    Wow this is one of a fleet/managers biggest worries. Whether this caused from any one of the above listed items, The one thing that never happens is the re-torque of fasteners. Any time you get a tire services at a tire shop or on the road service call the one thing always listed on the invoice is you need to have the wheels re-torqued after 50 to 100 miles. Lets face it 99.9% never get re-checked.

  2. 2. Justin [ November 28, 2015 @ 01:57PM ]

    I have yet to see or experience any truck tire service use a torque wrench to properly tighten wheel nuts.They all use impact wrenches.I carry a torque wrench in my truck so that I can torque lug nuts myself.
    I get some dirty looks while doing so.I have never had a loose/missing wheel.

  3. 3. Robert [ November 30, 2015 @ 11:20AM ]

    What about better training for techs?

    I recently retired from a 580 power unit LTL fleet and had two instances when the apprentice started to remount the outside wheel on an older trailer without tighting the inside Budd nut. Darn near came to blows with one till the other mechanic came over and pulled us apart then explained the facts to the apprentice.

    Had a similar experience with a well respected road service company at 0200. But I was more political correct. And as soon as I told him he forgot to tighten the inside Budd the trainer explained to him in detail what needed to be done.

    Never have seen a truck tire man use a torque wrench either but the auto side of the above road service company does. Guess who gets my personal vehicle tire work.

  4. 4. Marilyn [ July 26, 2017 @ 05:44AM ]

    I appreciate the info.I have an older vehicle and it's costing more than it's worth, but, is very reliable to me at this time.

    Thank You


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