31x15.50-15 BKT TR315 10PLY

Finding the correct tyre for your machine involves knowing the correct tyre size. The size is usually written on the sidewall of the tyre and can be displayed in a number of different ways. We have detailed an explanation of how the different methods of measuring the tyre can be written below:

Imperial Tyre Sizes - e.g. "12.4 - 28"

This measures the size of the tyres in inches. The first number denotes the width of the tyre which in the example above is 12.4". The "-" symbol shows that the tyre is of cross-ply (Bias ply) construction. The last number is the diameter of the rim (wheel) in inches. in this example it would be 28"

Metric Tyre Sizes - e.g. "340 / 85 R 24"

This is the newer, 'metric' measurement where the first number is again the width of the tyre, but is measured in mm. In this case 340mm. The second digit represents the tyre sidewall profile (height) as a percentage of the width. In this example the sidewall height would be 85% of 340mm (approx. 289mm). The letter R explains that the tyre is of radial construction and the last digit is again the diameter of the rim (wheel), still measured in inches.

PLY ratings can be quite confusing as they don't necessarily mean what they used to! A 'PLY' rating used to state how many plies (layers) of rubber were woven into the construction of the tyre. The more plies of rubber the tyre had, usually meant the tyre was capable of carrying more weight.

However, modern tyre manufacture has introduced a higher level of plastics and polymers such as nylon and polyester to increase the strength, durability and weight carrying capacity of the tyre. By using these modern materials tyres can out perform the old PLY rating indicator with many less layers making the old scale of measure a little misleading.

Modern PLY ratings tend to indicate the strength and carrying capacity of the tyre as if it had the same number of plies of rubber used from the older scale. Usually, tyres with a higher PLY rating can carry more load, but do cost more as the rating increases.

PLY ratings should be correct for the machine they are being used on. It is good practise to have an equal or higher PLY rating than the manufacturers recommend, but although the durability and carrying capacity often increases with PLY rating, the comfort of the tyre is often reduced due to the additional stiffness of the tyre.

A load speed index is usually found on the sidewall of a tyre and is what the manufacturers have tested and rated the maximum loads and speeds that the tyre is capable of. It is very important that you choose the correct load / speed index for your vehicle as per the vehicle manufacturers recommendations. It is usually safe to increase the load / speed index, but again, manufacturer guidelines should be followed.

A load speed index gives the weight and speed a tyre is capable of e.g 116D would indicate that the tyre is capable of carrying 1250kg up to a speed of 40mph. Often in agricultural tyres, the load speed index can alter so that a vehicle travelling at a lower speed may be able to carry more weight. It is always worth checking the tyre manufacturers specifications for further details on this.

Tyres tend to be either designed to work with an inner tube or without. Often this will be marked on the tyre sidewall as to which type of fitment the tyre has been designed for. 'Tubeless' means that the tyre has been designed to fit on a rim without the use of an inner tube. A valve is inserted into the rim that creates the seal and allows the tyre to be inflated.

Tube Type means that the tyre has been designed for use with an Inner tube. The internal construction of the tyre is usually a lot smoother so that the tube doesn't experience unnecessary friction or chafing inside the tyre.

Although it is possible to put inner tubes in a tubeless tyre, it isn't always advisable. The extra friction and wear that can be endured in this situation can cause premature failure of the inner tube, which in turn could lead to premature failure of the tyre. Tube type tyres can fit on most rims, but if changing from a tube type tyre to a tubeless, it is not just the tyre type that needs checking as it also necessary that the wheel itself is capable of being used with a tubeless tyre.