Your tyre size will almost always be written on the sidewall of your tyre. For plant and construction tyres it will look similar to one of these formats:

• 460/70R24, 405/70-20 - The first number is the tyre width in mm, the next number is the tyre profile % (tyre sidewall height as % of tyre width), an 'R' represents Radial construction or a '-' represents Crossply construction, and the last number is the rim diameter in inches. 
• 15.5/80-24, 16.0/70-20 - The first number is the tyre width in inches, the next number is the tyre profile % (tyre sidewall height as % of tyre width), an 'R' represents Radial construction or a '-' represents Crossply construction, and the last number is the rim diameter in inches. 
• 12-16.5, 8.25-20, 10R16.5 - The first number is the tyre width in inches, a '-' represents Crossply construction or an 'R' represents Radial construction, and the last number is the rim diameter in inches. 
• 23X8.50-12, 27X8.50-15 - The first number is the tyre height in inches, the next number after the 'X' is the tyre width in inches, a '-' represents Crossply construction or an 'R' represents Radial construction, and the last number is the rim diameter in inches. 

Ply Rating's are usually only given on plant or construction tyres that are of Crossply construction, that is the size should have a '-' before the rim diameter. Newer Radial tyres, that have an 'R' before the rim diameter should have a load index number given instead. A Ply Rating is similar to a tyre Load Index and is an indication/measure of a tyre's strength, telling you the maximum weight that the agricultural & industrial tyre can safely carry. Tyres with a higher ply rating carry more weight but cost more due to their superior construction and the extra materials used.

In general, with plant and construction tyres you shouldn't switch to a lower ply rating than you currently have. You can normally increase the ply rating of the tyre used, but bear in mind the higher a tyres ply rating the stiffer a tyres sidewall usually becomes. This can be advantageous in helping to avoid punctures in the tyre sidewall, but may reduce the suspension/cushioning you experience riding your machine.

The exact carrying capacity of plant & construction tyres can vary by axle, speed, pattern, pressure and manufacturer. Tyre manufacturers often provide detailed information on how much weight a tyre can carry in their technical tyre books, so please check the Technical Link of a product or Contact Us if you need help.

Most modern radial plant & construction tyres have a speed and load index stamped on the tyre sidewall, sometimes also known as a service index. A tyre's Speed Index is the maximum safe speed that the tyre can be run at, and is represented by a letter from the very slow (A1) to the very fast (Y and beyond). Many plant and construction tyres are slow speed rated at A2 (6mph), A6 (19mph), A8 (25mph) or B (31mph).

The Load Index is the maximum weight that a plant & construction tyre can safely support. This is represented by a number, and the higher this number is the more weight the tyre can carry. It is imperative for the safety of the vehicle and its occupants that tyres with high enough Speed and Load Indexes are chosen, and you should always check your current tyres rating before replacing it. The table below shows load index values and their corresponding weight in Kg.

The bigger majority of plant & construction tyres are of the older Crossply construction. Crossply construction gives firm tyre sidewalls with better puncture prevention and provide a firmer more stable ride. It is a cheaper production technique than the newer Radial construction method, so crossply tyres are often cheaper. 

Radial tyres are a newer and more modern tyre construction invented in 1946 and allow the sidewall of the tyre and the tyre tread to work as two independent features. This gives more flexibility to the tyre as well as increasing the tyres strength. Radial tyres can absorb impact shocks and bumps more effectively than crossply tyres can, so they give a more comfortable ride and allow the driver to work longer. The flexibility of a radial tyres sidewall enhances vehicle stability and provides maximum contact between the tyre and the road surface. This improved contact with the ground reduces the wear on the tyre tread meaning radial tyres last longer than crossply tyres. It also helps spread the weight over the ground reducing soil compaction. Radial tyres tend to have higher speed ratings as they can dissipate heat better, so for some faster road going machines Radial tyres are the only usable option. A downside of Radial tyres can be the intial cost, as they do tend to be more expensive than crossply alternative. Radial tyres should be viewed as an investment that will pay off in the long run.

Tubed type (TT) construction tyres have a separate tube fitted inside the tyre which is often purchased separately to the tyre. Tubeless tyres (TL) have their own inner liner which prevents leaks from the rim and minimises the damage done by punctures. They therefore do not require a separate tube to be purchased (if you rims are in good condition). Tubeless construction tyres are more resistant to overheating, but air leakage can occur if the tyre has not been fitted properly or if the rims are old or damaged.

At Big Tyres we want to take all the hassle out of buying and fitting tyres. We offer a nationwide mobile fitting service where one of our professional fitting partners will come to your site and fit your tractor tyres for you. No matter the size or application we can generally have your new tyres up and running fast. You can add fitting when ordering online, or mention that you require fitting with your tyres when you order by phone, and we will add the cost to your order and take payment. Read our Fitting Page for more detailed information on how our fitting service works.