Large-dimension harvest tyres for extensive soya farms in the state of Mato Gross in Brazil

Why such an evolution in the size of harvest tyres?

Authored by: Tractor tyre expert | 18 July 2023

During the past 15 years, there has been a major evolution in the size of harvest tyres. While the 650mm tyre size was the norm in the years 2000 to 2010, there is now a much higher demand for the 900 tyre size which offers real advantages and reflects a change in mentality and the size of modern farms.
When a trend is so pronounced, this clearly shows what works best for most farms. In this article we look at the reasons for such a rapid evolution in the use of harvest tyres.

1. The 650mm harvest tyre: the most popular tyre 15 years ago

Over the last sixty years, the demand for grain products has continued to rise, leading to a transformation of many small family farms into agricultural enterprises with a concentration of field crops on the arable land available.

During the same period, productivity has shot up together with the size of the machinery used and more specifically the harvesting machines.

Twenty years’ ago, the key factor in improving productivity was to rely on increasing the machine’s power rather than on its working environment.
Fitting 650mm harvest tyres was the norm because this offered a good price/efficiency compromise, bearing in mind the average loads borne by the harvesting machines.


The benefits of 650mm harvest tyres

If you work on an average sized farm or if it is made up of lots of small fields with roads in between them, you will certainly have a compact harvester that is easy to handle.

In this case a 650mm tyre is right for your working environment and the weight of your machine.

This is why it was the standard tyre size for a long period of time.

Harvester equipped with standard 650/65R32 tyres
Harvester equipped with standard 650/65 R32 tyres

The limits of the 650mm tyre for your combine harvester

If the soil conditions are not ideal on your farm, if the terrain is rugged or if you live in a wet region, 650mm tyres will soon reach their limits.

If your soil tends to be soft, it will be necessary to increase the size of the tyre footprint to obtain a larger contact patch with the ground in order to improve traction, which will not be the case with 650mm tyres.

With tyres that are undersized compared to the weight carried by your harvester, you will be obliged to increase inflation pressure in order to cope with this load.
Rolling resistance will increase.
Your tyres will have a tendency to sink into the ground causing more slip and greater soil compaction.

Depending on your tyre technology, it may not be possible to work at a low inflation pressure with major consequences on future productivity in your fields.
This will be even more prejudicial during autumn harvesting, such as sunflower or grain maize.


2. 800mm tyres have become the norm

This is the most common tyre dimension today, because it offers a good compromise between the load capacity and soil preservation.

The harvester is a major investment on a farm or at the least it plays a crucial role even if you only rent it.

This is the heaviest agricultural machine that will work in your fields and it would be a shame to damage your soil because the harvester is not properly equipped with the right tyres.

Firestone 800/65R32 harvest tyres
Firestone 800/65 R32 harvest tyres

800mm tyres are the right balance for average-sized farms

There are many benefits to be gained from increasing tyre dimensions compared to the 650mm tyre:

  • The soil footprint becomes bigger, which has the immediate effect of improving traction capacity and reducing slip.

  • The 800mm tyre has relatively limited overall contact dimensions with the ground, making it easier to drive on the road or in narrow streets when passing through villages.

  • The load capacity increases and for a harvester that has to manage a variable load, this is certainly one of the major benefits.
Firestone’s Maxi Traction Harvest 800/65R32
Firestone’s Maxi Traction Harvest 800/65 R32

3. There has been a sharp rise in demand for 900mm harvest tyres

On large farms spanning one hundred hectares or more, the harvesters are generally bigger in order to boost productivity.

You need to be able to make the most of every harvest day to generate a high productivity level.

High air volume tyres which have a greater load capacity than standard tyres with average dimensions will therefore be much more suitable.

High air volume tyres which have a greater load capacity than standard tyres with average dimensions will therefore be much more suitable.

Harvesters equipped with 900mm tyres in the plains of Saskatchewan in Canada
Harvesters equipped with 900mm tyres in the plains of Saskatchewan in Canada

Large dimension tyres to carry more load

For powerful machines with a higher harvest throughput, the hopper has a higher load capacity and the tyres must be able to cope with this rapidly increasing load.

The variable quantity of grain in the harvester’s hopper has a direct impact on the tyres whose inflation pressure is not modified between each loading and unloading cycle.

With high air capacity tyres you will be able to increase the load without any problem. Production does not have to stop between inbound and outbound trailers as the tyres are designed to manage cyclic loads and can easily bear 5,000 to 6,000 kilos of additional grain.

Firestone’s Maxi Traction Harvest tyre
Firestone’s Maxi Traction Harvest tyre

Une prise de conscience de l’impact des pneumatiques sur la compaction des sols

This trend towards very large dimensions and high air volume tyres is also linked to the desire to preserve the soil in our fields.

The machines are more powerful and as such they are also heavier, which has major repercussions on deep soil compaction.

To compensate for this evolution towards heavier machines, 900mm tyres allow you to spread the load over a larger contact patch with the ground.

Large dimension tyres offset the weight of the harvesters better
Large dimension tyres offset
the weight of the harvesters better


4. The 900mm Maxi Traction Harvest tyre: perfect for large farms

This is a high capacity tyre designed specifically for cyclic operations such as harvesting.

Its construction around a very robust casing makes it more resistant than standard tyres.
As it is perfectly adapted to powerful harvesters, this 900mm tyre is designed to carry 70% more load during cyclic operations.

A much higher cyclic load capacity

The structure of the Maxi Traction Harvest tyre is reinforced with extra layers of fabric and stabilising ply to obtain an extremely robust casing.

The sidewalls are reinforced, which allows an optimal variation in pressure between 0.8 and 3.2 bar with a cyclic load bonus which allows you to increase pressure to up to 4 bar at a reduced speed.

It is also highly efficient in managing load transfer difficulties when working on sloping land or steep inclines.

Greater load capacity for the larger dimension tyres

Tyre dimensions Load capacity at 40 km/h - max. 3.2 bar Cyclic load capacity
at 10 km/h - max. 4 bar
650/75 R32 6,300 kg 10,710 kg +70%
800/65 R32 7,500 kg 12,750 kg +70%
900/60 R32 8,250 kg 14,025 kg +70%

The table above highlights the huge difference in load capacity between the three tyre dimensions, with a 30% capacity gain between a size 650 and a size 900 tyre, for a pressure of 3.2 bar and a speed of 40 km/h.

The difference is even greater with cyclic loads and can reach 14,025 kg with a 900mm tyre, i.e. a possible load of 28,000 kg on the front axle of a harvester.

More powerful traction with larger tyres

The Maxi Traction Harvest tread has a specific design with asymmetric Dual Angle lugs which increase the contact patch with the ground.

Each lug has a better grip on the ground which multiplies the machine’s traction capacity.

The pulling capacity is boosted further with 900mm tyres which have a bigger contact patch with the ground. On large farms, optimal traction leads to less fuel and considerable time saving.



The evolution towards 900mm tyres with a high volume of air has occurred naturally over the last 20 years because of the resulting improvement in your harvesters’ capacities.

You can obtain a significant reduction in operating costs thanks to the time saved as a result of improved traction, the cyclic load bonus (which avoids having to interrupt production) and a very solid casing that is designed to last.


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