Farm Progress

A day with a tire guru

Jodie Wehrspann

November 1, 2004

12 Min Read

Michael Vandel knows ag tires. As one of the on-farm reps for Michelin, he inspects hundreds of them each year on farms.

I meet Vandel at WW Tire, a tire retailer in Watertown, SD, to accompany him on his day of on-farm tire inspections. And one of the first facts he tells me is this: Ensuring proper inflation pressure is the single most important thing you can do to maximize tire performance.

Firestone, Goodyear, and Titan will tell you the same thing. “What air is to a tire, oil is to an engine, water is to a radiator,” says Len Wagner, global field engineering manager with Firestone Ag. “If you don't have it in the proper amount, failure can occur.”

Too much air decreases flexing of the casing and results in a smaller footprint, increased compaction and a rougher ride. Too little air stresses the tire casing and leads to rapid wear. Either extreme hurts performance and can ruin a tire.

Proper inflation, on the other hand, can more than double the life of an ag tire. Longer life means you won't have to buy a new set of tires as often. And that means money saved, especially this year.

Oil, steel and rubber — the main inputs in tires — are priced at all-time highs this year. Tires are expected to follow suit. Current prices are running from $600 to $1,000 per tire, depending on size.

“Tire manufacturers are attempting to hold down prices but are having difficulty when the materials to make those tires are increasing up to 120%,” says Scott Sloan, vice president of engineering and technical services at Titan Tire.

It's Vandel's job to help farmers optimize the performance and extend the life of their ag tires to help them get the most use of their farm input dollars.

Inflation 101

Before we head out to Vandel's first on-farm inspection of the day, he gives me a quick lesson on tires. He diagrams the parts with his pen, talks about aspect ratios and the shows me the difference between radial and bias tires.

“Now let's go over some nomenclature,” he says pointing to a string of numbers on the side of one tire. “This tire's a 380/90R46,” he says, explaining that the 380 means it is 380 mm (14.9 in.) wide, 90 is the aspect ratio or the sidewall height as a percentage of the width, and 46 is the rim diameter.

After the lesson, I accompany Vandel on his first inspection. Jared Cass, assistant manager of WW Tire, comes along. On the drive out, Vandel explains some basics of tire inflation. He says unlike car and truck tires, Michelin ag tires are designed to run at low inflation pressures. A low inflation pressure allows the tire to flex and makes for a larger footprint on the ground to maximize traction and minimize compaction.

“When talking about inflation pressure, some people will generalize and say you need 15 psi,” Vandel says. “Or that you need three to four lugs on the ground.” But the only way to know for sure is to take the air pressure and see if it matches what is recommended for your load and speed.

Each manufacturer recommends its own pressures based on standards set by the Tire and Rim Association, but the steps to getting to that pressure are all basically the same.

Weight and load

The first step is to weigh the tractor and determine the load placed on each tire. “The question always comes, How do I weigh my tractor?” Vandel says. “I advise people to use their grain or truck scale if they have one. Then weigh each axle of the tractor with the implement on it to get the maximum weight.”

If the implement is on a 3-pt. hitch, weigh the front axle with the implement down and weigh the rear axle with the implement up to ensure you get the maximum load on each axle.

Next Vandel makes sure the weight and weight distribution across each axle are correct. This is called “ballasting.” The purpose is to keep the tractor balanced in the field and ensure the maximum traction for the front and rear tires.

The recommended weight split will depend on the size of the tractor (see sidebar). If the tractor is not at that weight, suitcase weights should be added in front or wheel weights should be added in back to get to the desired distribution.

Next, Vandal takes air pressures using a calibrated pressure gauge and records it on his inspection form. Finally, he visually inspects the tires to check for irregular wear, tread depth and any abnormalities such as cracking of the crown and sidewall fatigue.

Factor in roading

After Vandel inspects the tires, he asks the grower some questions: How far are you traveling from field to field? How fast do you travel on the road and in the field?

“Roading is one of the most extreme uses for an ag tire,” Vandal says, “because a tire's worst enemy besides the hard pavement is heat.” So the amount of air you need to add will depend on maximum speed. Different loading tables are used according to the maximum speed of the machine.

Once Vandel collects the required information, he pulls out his laptop and goes to the company's technical data book, which can be found on the Internet at “The data book is a tire man's bible,” he says. “It lists weight capacities and air pressures along with speeds. So if you are going 2 mph and you want to carry this much weight per tire, the data book will show you need to set your pressure at this level.”

Vandel finds the loading table that corresponds to the size of the tires. “It shows you that your front tires need to be set at this pressure for this weight and speed, and your rear dual tires need to be at this pressure for this weight and speed,” he explains. “And there you are optimizing your performance.”

On-farm inspection

After 30 miles, we arrive at the farm of Roger Kreutner outside of Revillo, SD. In the last 25 years of farming, Kreutner has had tires fail before they were worn out. “So I want to maximize the life of the tire with the right tire pressures,” he says.

Kreutner has three machines he wants Vandel to check. The first is a John Deere 7420 front-wheel-assist tractor with John Deere 741 loader. “I use it in many different ways, from the snow blower to the Haybine to the baler,” he says. “I move a lot of hay, so there is a lot of weight on the back. Same way in the front because I use the loader as a forklift and use it for other farm chores. So I want the tires checked for pressure and to see if the tractor is ballasted right for all my different uses.”

Vandel weighs the tractor and provides the recommended weight splits for each of the applications. However, he cannot give recommended inflation pressures on all the tires because the tires are made by different manufacturers and Vandel is only authorized to give recommendations for Michelin tires.

Next we move to a John Deere 4650, which Kreutner uses to pull his grain cart and chisel plow. “Those are the two main implements I use that tractor on,” he says. “So I want to see where I am at for tire pressure to justify the weights and the tires I have on.”

Vandel does a quick walk-around inspection. “The 4650 is a weight and ballasting issue,” Vandel says. “The tractor has a full suitcase up front and a rock box to add additional weight. The problem is the weight he could add in the rock box is actually more weight than it might seem because it is on a fulcrum. So the farther the weight gets out in front, the more total weight is added to the front axle.”

He can also see by the irregular wear on the front tires that Kreutner is roading a lot. As with the other tractor, Vandel weighs the front and rear axles and calculates the correct weight splits for each application. He also gives the recommended inflation pressures for the tires made by Michelin.

The third machine is a Rogator 854 row-crop sprayer, which Kreutner recently equipped with Michelin Agribib row-crop tires. “I want to know how to extend the life of the tires and get a good ride down the road,” Kreutner says. “When you get up to 32 mph, you want a good ride without being too hard.”

Vandel inspects the sprayer and records the weights and air pressures. Then he pulls up the technical data book and goes to the high-speed cyclic loading table. “What we are looking to do is set the correct tire pressure by weight and speed for a 1995 Rogator 854,” he says. Vandel calculates the recommended pressures, which are 20 psi in front and 33 psi in the rear. Both numbers are lower than the actual pressures in the tires.

“The tires are overinflated by weight,” Vandel says. “And if they are overinflated, you don't get the flexing of the sidewall, which means you don't have the correct footprint. So the weight is being distributed over a smaller area. And you are going to get rapid wear.”

Vandel advises Kreutner to pull the core out of the tires and drop them to the recommended pressure.

Check tires often

On the drive back, Vandel explains that ensuring proper inflation pressure is something farmers don't do often enough. “Some might check it once per month or once per operation,” he says. “Some have their servicing dealer set the pressure when they buy the tire or tractor and never check it again.”

However, the whole process can take less than an hour per tractor. And once producers know how to weigh the tractor properly and read a data page on a tire, they can do it themselves very effectively, Vandel says.

Vandel advises that, once you know the recommended pressure, you should check air pressures once a day, preferably in the morning before your tires heat up. Warm tires can have two to three pounds more pressure than cold air. And inflation recommendations are based on cold air pressures.

He also recommends inspecting the tire for cracks, damages and irregular wear. “If there is an issue, it is more economically efficient for the farmer to catch an issue early than it is to wait,” he says. “And all of a sudden we have a situation where he is down in the field.”

Checking the air pressure in your tires once a day and inspecting them will increase their life and decrease your overall expense. And it doesn't take a lot of time. “To go around your tractor with a calibrated pressure gauge takes five minutes,” Vandel says. “In five minutes you can avoid $1,000 worth of heartache.”

Dos and don'ts of tire inflation

Firestone, Goodyear, Titan and Michelin offer the following tips to ensure the life of your ag tire.

Do: Check air pressure often, ideally once a day or at minimum every two weeks during the working season.

Do: Use a calibrated pressure gauge to measure inflation.

Do: Take tire pressure in the morning before you operate the machine.

Do: Ballast your tractor each time you change implements.

Don't: Put fluid for weight in radial tires. Fluid prevents the sidewall from flexing and reduces the tire footprint and ride comfort.

Do: Use cast or suitcase weights in front and wheel weights in back when needed to ensure proper weight distribution between the front and rear axles.

Don't: Underinflate. Underinflation causes the sidewall to deflect more than it was designed to do and will cause premature failure.

Don't: Grossly overinflate. Although slight overinflation is sometimes needed to accommodate severe service conditions, gross overinflation makes the sidewall stiff and prone to impact breaks.

Do: Look for the characteristic “belly” on radial tires, which is a sign of proper inflation.

Do: Visually inspect tires every day for cracks or irregular wear.

Tire pressure

Take these steps to determine the optimal inflation pressure of your tractor tires.

  1. Weigh the tractor. Determine the front and rear axle weight and the weight per tire.

  2. Determine the total tractor weight and number of pounds required per horsepower to transmit wheel torque efficiently. Weight requirements are determined by the horsepower of the engine and the type of tractor. For instance, according to Firestone, a 2-wd tractor should weigh 145 lbs./pto hp; a 4-wd should weigh 105 lbs./pto hp; and a MFWD tractor should weigh 130 lbs./pto hp.

  3. Make sure the tire size is right for the engine horsepower. The tire industry recommends tire sizes based on engine horsepower.

  4. Determine the proper weight distribution required for the front and rear axles. If needed, use cast weights to ensure the proper weight distribution on each axle. In general, the following weight distributions are recommended:

    2-wd: 25% of weight on front axle, 75% on rear

    MFWD: 35% front, 65% rear

    4-wd: 55% front, 45% rear

  5. See the manufacturer's load inflation tables or ask your local tire dealer to determine the recommended inflation pressure for your load and speed.

Radial roundup

Here is a sampling of tires in the R1W category made by the four major farm tire manufacturers.

Michelin Agribib for multipurpose, medium-horsepower tractors

  • Deep tread that contributes to exceptionally long tire life

  • Strong but flexible sidewall casing to allow for a longer footprint

  • Self-cleaning hinge between lugs for pulling power in wet conditions

  • Sharp, vertical lug design to reduce wear and retain traction

  • 45° lug for improved ride and comfort

  • Price of the 18.4R38: $750

Goodyear Optitrac Farm Radials available in a wide range of sizes

  • Optimized tread and carcass design to decrease vibration, increase tread life, promote even wear and increase traction

  • Reinforced bead area to withstand high-torque applications

  • Supported material and workmanship warranty; a field hazard and stubble damage warranty; and a 12-month no risk guarantee

  • Wide servicing dealer network

Titan Low Sidewall (LSW) Tire 20.8R50

  • Offers the same advantages of low-profile automotive tires in the ag market

  • Keeps the outside diameter of the tire the same and increases the wheel diameter. The aspect ratio is lower to give improved performance.

  • Eliminates power hop and road lope

  • Company is exclusively devoted to the manufacture of ag tires.

Firestone Deep Tread 23, a premium radial rear tractor tire

  • Low, 23° bar angle designed for better traction than is possible with competitive tires with 45% lugs

  • 30% deeper tread depth than the standard R1 tire for better traction and road wear

  • Heavy carcass to withstand field hazards

  • Two-year field hazard warranty

Subscribe to receive top agriculture news
Be informed daily with these free e-newsletters

You May Also Like