AG Tire Talk: Differences Between Sprayer and Tractor Tires
Pay Attention to Traction, Operating Speeds and More
Modern Tire Dealer has partnered with AG Tire Talk to provide answers to insightful questions that farm tire dealers have about farm tire technology. This is the next installment in our ongoing series, which is designed to help farm tire dealers better connect with their customers. A trending question, followed by answers, will appear in our Commercial Tire Dealer section every other month. For complete answers, click on www.agtiretalk.com. (You can access the latest episode of the AG Tire Talk podcast here.)
Question: What is the difference between a row crop sprayer tire and a tractor tire and why is it important to match the correct tire for each application?
DAVE PAULK, manager, field technical services, BKT USA: Although tractor tires and sprayer tires are used interchangeably at times, there are major differences concerning the two applications. Standard tires for tractors and tires for sprayers can be the same sizes, which can lead to some confusion.
An example is 380/90R46, a popular size used on both tractors and sprayers. The 380/90R46 is made in a standard tire for tractors and increased flexion (IF) and very high-flexion (VF) versions for sprayers. A standard BKT tractor tire, the RT945 380/90R46 159A8/B, is rated to carry 9,640 pounds at 58 psi at 30 miles per hour.
A BKT sprayer tire, the VF 380/90R46 Agrimax Spargo, is rated to carry 13,760 pounds at 61 psi at 40 miles per hour. There is quite a bit of difference between the standard and VF in speed and load carrying capacity.
Most modern self-propelled sprayers are heavy and run 40 miles per hour, carrying a lot of liquid weight. They are driven on the highway to get to the fields. The tires used for this application must be able to handle the speeds, loads and the highway with some stability. These tires are generally R-1s. An R-1 has more lugs - or less void ratio- for highway contact and a shallower tread depth for less squirm from the lugs.
Traction is generally not as much of a concern for sprayers as it is for tractors. For this application, tires should be IF- (20% more load than a standard tire) or VF (40% more load than a standard tire)-rated to carry the excess weight. Since air carries the weight, the IF and VF tire are rated for a higher air capacity than standard tires. The VFs are better in this application because of the higher load carrying capacity.
There are smaller self-propelled sprayers on the market that require smaller tires. These smaller sprayers don’t have the heavy weight and run the high speed of the larger sprayers. Again, dealers should be careful to make sure that the tires used can carry the weight of the load and are rated for the speed.
Self-propelled sprayers can be retrofitted with different tire sizes according to the region of the country they are in and when they are being used. Wider tires are sometimes used for flotation and less compaction before planting. Once crops are planted, narrow tires are used to fit between the rows. Regardless of the width and size of tires used, they must be able to handle the speed and the weight to minimize the potential for tire failure.
Standard tractor tires can be R-1s, but many are R-1Ws. The R-1Ws have a few less lugs per tire and have a deeper tread depth. Although there are a few high-speed tractors on the market that run from 40 to 45 miles per hour, most of the common farm tractors run about 30 miles per hour. The high weight carrying capacity and speed are not needed in this application. If standard farm tires are used in a sprayer application, they will generally fail in the sidewall at the ply turn-up, a few inches above the bead.
Some sprayers are made as pull -behind sprayers. Generally, the tanks on these sprayers are smaller and carry less fluid. Tires are not as critical on these as on self-propelled sprayers. There are a variety of different sizes and tread designs used, including R-1, R-1W, and R-3. The sprayer will only travel as fast as the tractor that is pulling it. There is no torque applied to the tires, as they are free-rolling. The tires must be rated heavy enough to carry the load.
IF and VF tires are used for general farming, as well as being used on sprayers. In this application, less air pressure can be used to create a larger footprint and minimize soil compaction. In a sprayer application, the weight carrying capability and higher air pressures are needed.
DANA BERGER, ag business development manager, Continental Commercial Specialty Tires: For those who haven’t driven by a self-propelled sprayer on a back-country road, you are missing out! Admittedly, there is a level of fear that develops when you realize you’re playing chicken with a machine like that. Once that subsides, you cannot help but notice the tires. Self-propelled sprayers most commonly use row crop tires- aptly named for their use between rows of crops. These tires are built considering a specific set of demands, including high speed, highly variable load and stability. There are several topics that address these requirements - void ratio, tread depth/design and load/speed.
A high void ratio means there is more gap in the tread than rubber contacting the driving surface.This is a benefit for self-cleaning efforts and soil compaction, which are common to tractor tires. A lower void ratio provides good traction, a smoother/more comfortable ride and provides better stability - common to sprayer tires.
Sprayer tires are often running R1 treads, which is considered the standard tread depth for farm applications. R1 treads are better on dry surfaces, as the tread block is roughly 20% shorter than the R1W tread designation, which is commonly used on tractors. The tractive qualities of the R1W fit the needs of equipment driving in wet conditions because the additional height from the lug grabs at the soil and propels equipment forward, reducing slippage and fuel consumption.
In the interest of compaction, it sounds harsh to have a tire lug “grab” the soil, but the impact of the lug’s grip is minimal when comparing against the damage that can be avoided from the equipment sliding in the field. This does not mean the R1W is the best option for all equipment, however.
A self-propelled sprayer is quite tall to clear the growing crops and it carries herbicide, pesticide,
and fertilizer solutions at varying speeds. These solutions are loaded in tanks, which will experience the effects of inertia as the sprayer drives faster, slows or stops. The sloshing inside the tanks causes the sprayer to rock and transfers this movement to the tires. A taller tread block will cause instability and can create uneven wear. Therefore, the shorter block of an R1 tire is better-suited.
Some tire manufacturers are addressing tire stability with wider tread blocks that overlap the center line, like Continental’s d.Fine lug technology. This delivers a better contact surface for the machine and decreases the void ratio, providing a more comfortable ride.
In the future, the sprayer tire market may be further impacted by hybrid tread patterns that lower the void ratio and amplify stability with on-/off-road tread patterns.
Other components of a tire that are important to tractors and self-propelled sprayers are speed/load rating and suggested inflation pressures. Both types of equipment will often be traveling on the road between fields, which demands a tire with a high speed/load rating. Most standard row crop tires have a 40 miles per hour suggested speed rating paired with a max recommended load - at that speed - of 11,400 pounds and sometimes, that still isn’t enough.
Especially as the weights of machines increase, the market is slowly moving toward IF/VF technology. These technologies allow a tire to increase its carrying capacity at lower inflation pressures, affecting the contact patch and compaction levels. IF/VF tires are also able to travel at higher speeds with lower inflation requirements. That does not mean a dealer should “set it and forget it,” but it certainly provides some forgiveness for a machine with extreme load/speed variables.
Additionally, despite the narrow sizes a sprayer would use, the flexion of IF/VF tires creates a fuller tread profile, promoting traction and reduced soil compaction benefits.
Matching a tire with the right application can be challenging, with so many variables. Suggestions will vary based on driving surfaces, distance, climate and other environmental considerations. The right tire is one that provides the best of everything for that application – carrying capacity, traction, stability and adequate speed.
GREG GILLAND, vice president, global agriculture, Maxam Tire North America: Like all industries, the agricultural market is constantly being driven by the forces of necessity and the need to improve an existing product to meet evolving demands.
Specifically, when we look at the evolution of agricultural tires to the 45-degree lug design, this technology improvement has been one of the tire industry’s most significant design pillars adopted by all manufacturers. The 45-degree angle tread approach was started in the European market as a solution addressing the lug-to-void spacing of older tread designs, resulting in tire vibration, loss of traction, increased slip and more fuel consumption when roading or moving tractors from field to field.
Comparing tires used in both mechanical four-wheel drive and four-wheel drive tractors and self-propelled or towed sprayers, the common element inherent to both is the requirement of roading the equipment from operation to operation.
From Maxam’s perspective, the 45-degree lug design inherent in all our AGRIXTRA family of products allows many features and benefits.
If you then compare tractor or harvester-designed tires to sprayer tires, there are specific items to consider that are uniquely inherent to each farming application.
Self-propelled sprayers will operate both at a slow five to 10 miles per hour average in the field and at an average of 40 miles per hour when roading from field to field. Due to heavy tank loads in cyclic spraying operations, tires must be rated for heavy axle loads in terms of load index or load per tire.
As sprayers operate when crops are in full bloom and therefore require high crop clearance, the resulting tire sidewall or tire air chamber is smaller, which demands stronger structural casing materials and rubber compound designed for high air pressures equal to the load at hand.
In addition, due to the constant roading of sprayer from field to field, tires designed for this application will have more lugs per tire to reduce the lug-to-void ratio, increasing the amount of rubber contacting the surface ensuring improved stability under load and speed.
As machines are getting larger - especially with tractors and harvesters - we are seeing an evolution to D- rated tires. At 40 miles per hour sustained road speeds, the shallower R1 tread depth ensures a more uniform distribution of load per lug and reduces irregular tread wear or cupping caused by tire slip when using deep-treaded tires at high road torque or speed, especially on high clearance self-propelled sprayers.
The advent of VF technology or tires that can carry 40% more load at standard air pressures has given high-clearance, self-propelled sprayer tires the ability to carry the load at reasonable air pressures that can deliver the performance required without compromising soil compaction.
In sum, as a general rule, the following sets a sprayer tire apart from a tractor tire - lower void ratio, higher weight carrying capacity, shallower tread and higher speed rating.
DAVID GRADEN, operational market manager, agriculture, Michelin North America Inc.: When considering tires for a customer’s high-clearance, self-propelled sprayer, it is vitally important that you understand your needs and the limitations of the tires you choose. Your top two considerations should be safety and efficiency.
Compared to a tractor tire, the stability of a sprayer tire is of utmost importance. Sprayer tires are specifically designed to handle the constant pitch and sway of a machine loaded with liquid, in addition to the dynamic loads, with a very high center of gravity. As these machines continue to get larger and carry heavier loads, the tires also must meet or exceed these demands.
Unfortunately, the width of these tires is not able to grow unless our row spacing widens. This, in turn, has forced the industry to move towards IF/VF tires. These tires can carry an additional 20% to 40% more load, while maintaining the necessary widths to fit down a row without damaging crops on either side.
Additionally, whereas tractors in North America are commonly B-speed rated (30 mph), high-clearance sprayers often travel 40 miles per hour, requiring a D speed rating - with some sprayers traveling even faster. Always check to make sure speed rating of tire matches top speed of equipment.
Now, that being said, higher speeds will cause more movement in the lugs of a tire or tread squirm. More movement creates friction and heat, which is bad for rubber and increases rolling resistance. As a result, the lug design of a sprayer tire will look very different versus a tractor tire.
Typically, the lugs of a sprayer tire will be wider, shorter and with less void between the lugs. Wider and shorter lugs will offer more stability, while less void between lugs - or more lugs per tire - and will give a smoother ride.
Couple that with IF/VF technology and you will get more lugs on the ground for improved traction - and in low-torque applications, too.
Remember, wider lugs designed for sprayer applications work well both roading and in the field, as this is a self-propelled machine.
I also highly recommend sticking with the manufacturer’s intent and using sprayer tires for sprayers and tractor tires for tractors, ensuring safe trouble free optimum performance.
NORBERTO HERBENER, OE applications engineer, Trelleborg Wheel Systems: Let’s start with some basic definitions. A tractor is a vehicle designed to provide a high tractive effort - or pulling force - at slow speeds in order to haul a trailer or machinery used in agriculture or construction.
Agriculture sprayers are complete spray systems engineered for generating pressure to drive spray fluid from a tank out to the sprayer’s nozzle(s) onto crop or soil. Sprayers are most often used for the administration of water, insecticides, pesticides, herbicides and fertilizer. Sprayer tires need to pass over soil and crops.
Obviously these two definitions are very different. Consequently, these machines will need very different tires. However, in today’s farming climate, there are times where a sprayer tire size can be used on a tractor and a tractor tire size can be used on a sprayer.
Let’s talk about various differences between tractor tires and sprayer tires. The need for higher productivity in the world’s agricultural industry drives the professional and extensive use of modern sprayers. New generations of fertilizers and self-propelled, high-powered sprayers require a significant upgrade in tire technology to cope with new, high-demand applications through high-load, stability and reduced fuel consumption.
Current sprayers and spreaders’ normal working speed is between 25 and 30 miles per hour.Transport speeds are up to 45 miles per hour. Sprayer-specific tires must at least have a speed symbol of D. This enables the speed to comfortably carry its rated load at 40 miles per hour.
Another major difference between a tractor tire and a sprayer tire is tread depth. A tractor tire needs to pull, whereas a sprayer tire needs to float on the ground and provide some traction. But flotation and stability are its main contributors.
Sprayer tires normally have an R-1 tread design, where as a tractor tire normally has an R1-W tread design. The main difference is an R1-W lug design is 20% taller than an R-1 and assures a higher traction transfer from the tractor to the ground.
Over the years, applications have become quite sophisticated. End users now will often use two kinds of sprayer tires.
Sprayer tires feature VF technology. VF technology enables the tire to carry up to 40% more load at the same air pressure. It also allows the tire to be used at up to 40% less air while carrying the same load. This while maintaining the 40 miles per hour speed capability.
BLAINE COX, national product manager - agriculture, golf and turf, Yokohama Off-Highway Tires America Inc.: Like so many segments in the tire industry, sprayer tires have become very specialized. It’s really the opposite of a one-size-fits-all market. But there are some common denominators.
For instance, applicators need to protect crops, whether it’s by running between the rows of standing crops or by minimizing soil compaction, especially if they are running on wet, compaction-prone soils. They need precise, reliable steering, without the squirrely wobble that many older-style tires can create. Good roadability is an absolute must to cover as many acres as possible in a day.
That’s critical to maximizing income or return on investment and also to react with protection when the crops need it. And applicators and managers have come to recognize the value of a smooth ride to help maximize productivity.
Finally, they need to handle heavy loads, which has driven a lot of enthusiasm for our VF sprayer tires. VF technology permits up to 40% more weight at the same inflation pressure as conventional radials of the same size or allows applicators to reduce inflation pressure by up to 40% to carry the same load as a conventional radial.
Yokohama Off-Highway Tires America Inc. offers a wide range of tread patterns and constructions for sprayers of all kinds to help farmers and custom applicators match their tires to their business model, soils, crops and even the time of the season.
Choosing the best sprayer tire takes a little consideration, but it’s time well-spent. The right tire can help maximize the productivity and impact of an application rig at times when the stakes are high and the crop or an applicator’s bottom line are at stake.