Wheel and Rim Systems

Multipiece rim system

Because these rims have a flat centre section, it is impossible to lever the tyre bead over the rim flanges. Therefore, these rims consist of at least two parts; a rim base with the flange integrated as well as a separate spring flange.

Variations of this can consist of more than two parts, sometimes with the addition of a tube and flap, or, in the case of tubeless tyres designed for this type of rim, a sealing ring.

The resultant weight increase of the wheel+tyre unit decreases the final payload of the vehicle by an equivalent amount. Bead seats taper by 5°.

One-piece rim

This was developed for use with tubeless tyres and has a well base or drop centre. Low flanges facilitate the fitting and removal of tubeless tyres and rim bead seats have a 15%% taper to make bead area seating secure under all load conditions.

Dual fitment

This refers to the application of a matched pair of tyres in dual formation.

Dual spacing

For safe operation, separation of dual tyres must be adequate and offset on the wheels chosen must be sufficient for the dual spacing requirements listed in the manual. Each tyre size has different needs to accommodate the bulging of tyres under load.

Offset

The offset of a wheel means the distance between the centre line of the rim and the fixing face. Dual spacing = offset x 2

PCD

The imaginary circle through the centre of the stud holes is called the pitch circle. PCD refers to The diameter of this circle.

The centre bore

This is the diameter of the centre hole of the wheel and in spigot fixings it is critical.