This guide will help you to understand what information you need to give us when asking for a replacement wheel and tyre. It will also help you to determine if your wheels and tyres are standard sizes that we stock, or if they are different sizes that we can order in for you.

'Rim' and 'Wheel'
These two terms are often misused when referring to trailer wheels. The rim is the seat that the tyre sits, whereas the wheel is the complete assembly, consisting of a rim and a wheel disc. The wheel disc is the disc that is welded onto the inside of the rim and bolts to the hub of your trailer.

Wheel sizes
The wheel size refers to the the width and diameter of the rim. Both of these measurements are taken where the tyre sits within the rim. An example of a wheel size is shown below:

4.5J refers to the internal width of the rim in inches. 13 refers to the diameter of the rim where the tyre sits. Essentially this measurement is the diameter of the first 'step' in the rim.

Offsets
The offset on a wheel is the distance between the surface that sits on the hub and the vertical centre line of the wheel. Positive offsets are where the seating surface of the wheel is in front of the vertical centre line. Negative offsets, or inset is the opposite. Some wheels have no offset at all and are sometimes called centre disc wheels.

Tyre Sizes
Tyre sizes are found on the sidewall of the tyre. An example of which is as follows:

'165' denotes the nominal section width of the tyre, i.e. the width of the tread on the tyre. '70' gives the aspect ratio of the tyre. In this instance, the height of the sidewall of the tyre is 70% of the nominal section width. The 'R' stands for a radial construction. This will more than likely be written out in full elsewhere on the sidewall. '79' gives the Load Index of the tyre. This is used with the Speed Symbol, in this instance 'T', to show the maximum load that the tyre can take at the speed indicated by the Speed Symbol. '79T' means that this tyre can take a load of 437kg at a speed of 118mph (190kph).

Ply ratings


Pressures


Torque settings on wheel nuts



More to come soon....