A Quick Look Back
In the early 1930’s, most tractors had steel wheels and lugs. They were expensive, heavy and slow. You could get to where you needed to go but would invariably crush anything you rolled over. Enter Iowa based entrepreneur Leonard Holt and his associate, Harvey Firestone. They pushed rubber tyres as an option, arranging for a demonstration to convince some sceptical farmers. Two tractors, one on steel and one on rubber. Which would go further on the same fuel? Yup, you guessed right.
The challenges haven’t changed too much from those early days. We still need tyres that grip so you can reach every part of the farm, doing so without causing damage to the soil underneath. The tyres need to wear well and last long enough to pay back the investment you make in them. We do a bit of road work too, so the tyres need to handle the highway without overheating or jarring the driver around too much.
Tractor Tyre Construction
As with tyres for other vehicles, you get two basic methods of construction, bias or radial.
Bias Tractor Tyres
Let’s jump straight to it - this is old technology. Bias tyres are a single unit design with the rubber plies traveling diagonally from bead to bead. Sturdy and strong but inefficient, quick to wear and thirsty on the fuel. They’re normally only found on old tractors nowadays.
Radial Tractor Tyres
A two-part construction methodology allows the sidewalls to flex, giving radial tyres a much larger footprint. They also last longer, produce a smoother ride and do less damage to the soil underneath. What’s more, they can take heavier loads and operate at lower pressures for better grip. So, no competition really.
Generally speaking, mixing bias and radial tyres is not a good thing. They work differently and have a different footprint, meaning mixing them might throw out your lead ratio. Too much of a lead ratio (4% +) and the back axle will slow the front down, you’ll have trouble steering and the front tyres will wear down too quickly. A negative lead ratio and the rear axle is pushing the front, reducing efficiency and possibly damaging the transmission.
Looking at the Lugs
Here’s where things start to get complicated. It’s long been all about lugs at an angle of 23°, the premise being this puts a good number of lugs in contact with the ground to provide optimum traction. Then came along the 45° lug angle, with its ability to provide better hillside stability and traction in the wet. What do we think? Well… we like the Vredestein Traxion with its curved lugs that run from angles of 15° to 60°. This variation of angle at different parts of the tyre provides the best of both worlds.
Tractor Tyre Innovation
The latest tyres have something known as IF or VF technology and it’s worth knowing about. Both give you some impressive productivity and efficiency gains. Reducing soil compaction, lower fuel consumption and an overall lower cost of ownership will help too.
IF stands for Increased Flexion. Basically, they are called this because of structural and compound changes which allow their sidewalls to operate whilst flexing more significantly. The result is an improvement of tyre performance by 20%. The loads carried can be up to 20% heavier, or you can reduce the tyre pressure by 20% and still carry the same loads as regular tyres.
VF stands for Very Increased Flexion (or Very High Flexion). With VF tyres, you get double the gains. That’s better tyre performance by 40%, the ability to carry loads up to 40% heavier or the same loads at 40% less tyre pressure.
Pressure vs Load Ratings
Tyre pressure is of critical importance. You need to make sure you use the right operating pressure in the field and on the road.
In the field, pressure down for a larger footprint and you’ll get greater traction, less wheel sleep, less soil compaction and a longer tyre life. Pressure down too much and the tyre might not handle the load and you could damage it.
On the road, a tyre without sufficient pressure will lead to higher rolling resistance, greater fuel consumption and reduced life expectancy. Overinflate and the ride will become very uncomfortable and the lack of flex in the tyres will increase wear and tear on them and the vehicle.
All of which means you need to study the less than captivating but critically important tables of information that are provided by your tyre manufacturer. These tables detail precisely what pressure is needed to carry what load, at what speed. You’ll be rewarded for your diligence in $ through tyres that perform better and last longer.
Taming the Terminology
Tractor tyres can be complicated beasts so it pays to understand some of the lingo you might encounter.
This is the synchronization between the front and rear axle. Change the tractor tyre types or size and you’ll need to recalculate the lead ration. Here’s how:
Static Loaded Radius
The height between the axle centre and the road surface of the tyre under load.
The distance of the tyre at one rotation.
Special vehicles for special purposes need special tyres. Yes, really.
These tyres need to be able to stand up to long hours under heavy loads. There’s normally a weight imbalance to deal with a massive load at one end when the harvester is full, not to mention sharp stubble sticking up and pitting the tyres. So you need tough tyres that can handle the load and stand up to the stubble… that also dance lightly enough on the surface so as not to harm the soil.
Row Crop Tyres
These are precisely what they sound like - narrow enough to run between rows of plants in a field, so the plants aren’t flattened under the tractor. Commonly found in horticulture and most often set up as a dual wheels arrangement to ensure the weight of the tractor is still spread across a wider area so as to minimise soil compaction.