NUTS AND STUDS

Rim / wheel bolts, nuts or studs are a critical safety issue on your vehicle.

Missing, incorrect or mixed/different wheel bolts, nuts or studs on the same wheel could cause the wheel to vibrate loose and possibly come off the vehicle.

The same bolts, nuts or studs as specified by the vehicle manufacturer must be fitted on the same wheel / tyre assembly.  On passenger and commercial vehicles there should be at least 3 threads visible above the nut.  All bolts, nuts or studs must be in place.

It is highly recommended that replacement wheel bolts, nuts or studs should be of the type fitted as Original Equipment by the vehicle manufacturer or as recommended in the vehicle manufacturer’s handbook.

Loose / Missing Wheel Nuts

Wheels are subjected to a variety of forces, from road vibration, to vertical forces from the vehicle and its cargo, and   cornering and shock forces when the vehicle turns, rotational forces from the turning of the wheel, particularly during acceleration and braking.

When a wheel nut loosens the clamping forces are redistributed among the remaining nuts and studs, but mostly to the nuts and studs adjacent to the loose nut, causing these nuts to eventually fail.  This loosening process increases with each successive nut that loosens, as the total clamping force decreases, the stress concentration on the remaining nuts and studs increases.  At this point these studs can crack due to fatigue or overstress, accelerating the process further – especially with heavy cargo loads.

When the wheel forces exceed the clamping force of the remaining nuts and studs, the wheel will move relative to the hub which results in side loading and loosening of the remaining nuts, bending, fatigue failure of studs, elongated bolt holes and wheel pilots on the hub, fretting fatigue cracks between the bolt holes, and wheel separation if not detected quickly.

The rate of this deterioration process, and thus the potential for detection prior to wheel separation, depends on the type and magnitude of the wheel forces being experienced.