NOVEMBER 2020
     

Regular safety checks are vital

Caravan Council of Australia discusses the nuts and bolts of keeping safe

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CARAVANNERS have been urged to keep a closer eye on their RV's wheel nuts.

The Caravan Council of Australia's general manager, Colin Young, said the CCA continually received reports of broken or loose wheel studs.

"Sometimes the nuts unwind completely off the studs," he said.

"It must be stressed that if a stud breaks, it is certainly no proof that the stud itself was faulty. There are a number of reasons for the problems."

Mr Young advised caravanners to precisely follow all supplied instructions regarding wheels and wheel nuts.

"It is vital to ensure that if owners or dealers fit aftermarket wheels and nuts, they thoroughly check to ensure the replacement wheels and nuts are completely suitable for the vehicle and axles."

Possible reasons for problems include:

* The pitch circle of the studs in the (imperial) hub not exactly the same as that of the holes in some (metric) wheels, such that all studs bend when the nuts are tightened
* The angle of the taper on the nuts not the same as the angle of taper in the wheels
* Low-grade steel studs being used
* The hole in the wheel centre not compatible with the spigot diameter of the hub
* The serrated studs not 'fully driven home' when pressed into the hubs, so they gradually 'give a little' and cause the nuts to become loose
* Rattle-guns used to tighten rather than to undo wheel nuts set at unknown high-torque levels, causing the studs to stretch and become weakened
* Nuts being tightened in a circular pattern in one action, rather than in a criss-cross pattern, using two or three (increasing) torques
* Wheel centres being highly dished, thus acting as a large spring-washer that gradually looses its tension and causes the nuts to loosen

"Clearly, all nuts must be tightened to the correct torque, and in the correct pattern, in strict accordance with the instructions provided by the wheel or chassis manufacturer," Mr Young said.

"It is strongly recommended that pencil lines are made on one face of each nut ‒ with a mating line on the wheel ‒ so that a quick visual inspection can detect any loosening of a nut."

Clip-on plastic 'indicators' ‒ fitted to each nut with their adjacent 'arrow-heads' aligned ‒ provided an even-quicker warning of any nut loosening.

Mr Young said that continual vibrations and occasional heavy impacts from road surfaces inevitably had an adverse effect on the wheel assemblies.

This was severely aggravated if the tyre pressures and spring rating were too high for the actual wheel-loading.

"Stresses on the wheel assemblies are further increased if shock absorbers (dampers) are not fitted.

"Leaf springs do provide some damping of vibrations, but unfortunately it is mainly on the 'bump' (upwards) movement of the wheel rather than on the 'rebound' (downwards) movement of the wheel … where it would be far more beneficial."

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