For many years, the majority of vehicles have originated from Europe; as a result, South African trailer manufacturers have followed the DIN Spherical Stud mounting which has allowed a high level of wheel fastening compatibility between trucks and trailers. This also allows for an interchange of wheels within the fleet and the possibility of carrying only one or two spare wheels suitable for both the truck and trailer in a combination.

However, most of the “new generation” trucks coming into the country are now fitted with spigot centre wheels, while the majority of trailers are still fitted with stud centred wheels. This obviously creates a great problem with spare wheels and combinations of vehicles in which the truck is fitted with spigot mounted wheels while the trailer runs on stud mounted wheels. And because of this, there is the increased potential of wheel mounting failures. It is therefore important to know, that while the stud centred wheel and spigot centred wheel seem to be similar and the stud PCD is the same, the two methods of wheel fastening are not compatible.

Stud Mounted Wheels

In the case of stud mounted wheels, the stud holes in the wheels are countersunk and the face of the nut, or a locating washer, is bevelled to suit the countersink. It is therefore essential to understand that in the case of stud mounted wheels, the concentricity and the securement of the wheel, in relation to the hub, relies entirely on the bevelled interface between the studs, nuts and wheel face.

As per ISO 4107, spherical and conical centring wheels can only be used on stud centring hubs (the wheel is centred and carries the load on the stud of the axle). The main dimensional characteristics of the wheel are the countersunk holes off either a radius of 18 mm or a 40 degree angle. The bore also has an open tolerance.

Spigot Mounted Wheels (as per ISO 4107)

Spigot mounted wheels are only used on hub centring axles (the wheel is centred and carries the load on the bore of the wheel/hub of the axle). The main dimensional characteristics of the wheel is the 26mm stud hole with no countersink and the tight tolerance bore of 281 mm ( -0mm+0.2mm). The diameter to support the spigot mounted wheel would be 280.8 mm (-0mm+0.2mm).

Friction at the clamping face is of outmost importance to a spigot mounted wheel. Any loss of clamping force between the rim and drum/hub is very serious on a spigot mounted rim because it relies on it for fixing.

For more details on correct wheel fastening, contact your closest JMR branch.

Did you read the article Hub Failures: What to look for?