AG Tire Replacement Rule of Thumb

by | Jun 27, 2022 | Ag Tire Answers, Featured | 0 comments



There are a few situations in which you absolutely need to replace an R-1 or R-1W tire immediately: if you see an oblong bulge that indicates a rupture in the casing, or if excessive wear has exposed belt wires or ply fabric.

In the agricultural industry, it is how the equipment is utilized or the inherent operational requirements that will affect the tire replacement cycle.

If you are just using the tractor on very hard surfaces such as concrete or hard pan, where effective traction is not as important as the tire load carrying capability, many times you can delay the replacement decision and let the tires run down closer to a smooth tread.

Old tires with 20% remaining tread depth won’t ‘get a grip’ in the wet field and the fuel efficiency to pull diminishes rapidly.

If the tire has 30% to 50% of its original tread depth remaining, in normal tillage conditions, this is the best pulling tire available.  Save your money.

When it comes to replacing your Ag tires, we highly recommend replacing all tires across the axle with the same brand.

The industry says slippage should be in the 8-15% range with tires. Anything above that is excessive.

Replacing tires provides improved soil compaction (increased yield), increased fuel economy, and a productivity boost.

Trelleborg Wheel Systems
Chris Neidert: Marketing, Training and Development Manager – AG

There are many things to take into consideration when considering replacing tires due to a worn tread. Tire application will be the main driver with the limits and start the decision-making process.

HARD Surface / Soil Work
If you are just using the tractor on very hard surfaces such as concrete or hard pan, where effective traction is not as important as the tire load carrying capability, many times you can delay the replacement decision and let the tires run down closer to a smooth tread.

SOFT Soil / High Torque
On the other hand, using your tractor for field work, like spring planting, some ripping or field bed preparation, the tires need to provide effective traction. If your tractor can display the current wheel to ground slippage you can monitor the amount of slip that is being produced in real time. An acceptable wheel to ground slippage will be ranging between 5% and 15%. You can monitor your slippage and once it goes above 15% on a regular basis, you are starting to lose traction and efficiency. This loss in traction efficiency represents an increase in fuel usage and increased time to do your field work. Tire replacement should start to be considered.

Tread Depth
If your tractor is not equipped with a slip meter, once the tire gets below 25% of the original tread depth you should start to consider tire replacement. As discussed above, additional slipping will start to happen taking more time to complete your work and using more fuel.  Let’s do a quick example calculation using a R1-W tires with an original tread depth of 71/32.  Calculating the tire to be 75% worn or 25% tread depth remaining, that would equal 18/32. In our example of the remaining tread depth is 18/32, you should consider replacing the tire.  You can consult your tire manufacturer sales representative for your tires original tread depth.

Getting as much horsepower as possible transferred from the engine to the ground is the end target. You spend a lot of money on purchasing a high horsepower tractor and you need to be able to transfer that power to the ground. As you can see in the picture below, the power from the engine gets turned into torque which turns into the grip to the ground which then results in traction.

The first thing we need to do is to make sure the tractor has proper ballasting for the tractor engine power, weight distribution between front and rear axle is correct and the air pressure is set correctly. These topics have been discussed in a prior AG Tire Talk.

The ideal slip percentage for field work is between 5% and 15%.

  • Too little slip will put a strain on the equipment and tires.
  • Higher slippage means spending more time than necessary in the field and wasting money on fuel as the tires are forced to spin more
    • Wheel slip of 0% is acceptable only in roading applications.

ONE Tire Needs Replacement due to Field Hazard
Our example below shows that the left tire has been replaced (the drawing is exaggerated for discussion purposes).

If the tractor is going to stay in the field, you may be able to get away leaving the set up as is, due to the soft soil not affecting steering or any other mechanical items. If you are going to road the tractor a lot, more than 50%, we recommend right tire replacement.  If not replaced, this tread depth difference will affect the steering and tire wear especially if this is a front axle setup. Although this drawing is exaggerated, we recommend that if the tread depth difference between the left tire and the right tire is 50% or more, we recommend replacing the right-side tire.  You can use that right side tire for a spare or transfer it to another vehicle. As far as replacing with the same brand, as long as you stay within a certain percentage between the brands, any brand replacement will be acceptable. We will discuss tire brand specification differences later on in this writing.

  • We recommend replacing R1-W Tread Depth tire with an R1-W Tread Depth Tire.
  • We recommend replacing R-1 Tread Depth tire with an R-1 Tread Depth tire.

All Tires on ONE Axle Need Replacement

Our example below is showing duals across one axle and the user is just going to replace the OUTER TIRES. In the dual setup you can see our example below that is exaggerated for discussion purposes. If the worn tires have greater than 50% tread depth remaining, you should be OK.

If the worn tires have less than 50% tread depth remaining, we recommend replacement. We recommend replacement because the outside tires, with their deeper tread depth, are now not letting the inside tires make full contact with the ground. This will create a couple of problems. First, the new tires will be carrying all the load and will wear out quicker. Second, the inside tires, because now they are not making firm contact with the ground, will start to produce some irregular wear patterns.

  • We recommend replacing R1-W Tread Depth tire with an R1-W Tread Depth Tire.
  • We recommend replacing R-1 Tread Depth tire with an R-1 Tread Depth tire.

Why do overall tire diameters vary slightly by manufacturer?

The Tire and Rim Association (TRA) and their European counterpart (ETRTO), define the acceptable tolerance for the design dimensions for a new tire size. This allows for difference in dimensions between tire manufacturers concerning tire specifications. As an example, concerning overall diameter, a + or – 2% variance is allowed between manufacturers.

If we use the example of a tire size 480/80R50.

  • Tire A Overall Diameter = 80.5 “
  • Tire B Overall Diameter = 80.8”

The difference is .4% which is well within the allowable tolerance of 2%.

As we don’t know the condition of the remaining tire and tire brand, we always don’t recommend mixing brands or load capacities.

Precision Inflation Systems
Ken Brodbeck: VP of Technology

When Do I Need New Tires?


When the tire:

  1. will no longer hold air.
  2. will not carry and/or pull the load required.
  3. the tire body has cuts or breaks into the body or belt cords.
  4. has bubbles or separations in tire body.
  5. is overloaded and a higher load rating or larger tire is available.
  6. needs to minimize soil compaction, purchase an IF or VF tire to run at lower psi.

In my career with a major Ag tire manufacturer, we tested ½ worn tires against the same brand new tire.  Both times the ½ worn tire out pulled the new tire.

  • If the tire has 30% to 50% of its original tread depth remaining, in normal tillage conditions, this is the best pulling tire available.  Save your money.
  • If you have a wet harvest in truly muddy conditions, at 30% remaining tread depth, you may need new tires.

If one tire fails on a dual axle, check several dealers for a used tire as a replacement.  The same brand is desirable, but not a must, as long as both manufacturers’ new tire diameters are within a ½”.

Michelin Ag
David Graden: Operational Market Manager – Agriculture

Due to the standard with which Michelin manufactures our Ag products, I think you will find the following answer will challenge your average producers’ way of thinking.

You see, natural rubber has a shelf life, much like the loaf of bread in your pantry. Depending on the ambient temperatures, exposure to elements, humidity, usage, etc., you could get as much as 10-14 years of good use out of an Ag tire before the rubber goes “stale,” regardless of tire brand. The big difference lies in the lug design and rubber compounds that make up those lugs.

Lug Design
At Michelin, we are focused on quality and efficiency in the field. Our lug design not only gives you reliable tractive capacity throughout the life of your tire, but in turn, prevents you from wasting time and fuel in the field when that tire is worn out. This is where we begin to challenge your typical way of thinking. Due to the Michelin standard R1W lug depth on all of our Ag tires, and our upright lug-wall design, you are able to keep the biting edges of your lugs until the end of tire life. When that rubber begins to go “stale,” you will notice some cracking in the sidewall. Again, this is by design. We don’t want to see worn out lugs when your tire has reached the end of it’s life.

Per Axle Tire Replacement
Additionally, when it comes to replacing your Ag tires, we highly recommend replacing all tires across the axle with the same brand. Unfortunately, you will find slightly different overall diameter, and even section width, measurements between manufacturers. This is due to the allowable variance in standard tire sizing. Some manufactures will even play this to their advantage to help reduce costs or even make a tire sound narrower than it truly is. Beware of this when matching different brands of tires.

Single Tire Replacement
With regard to replacing all tires on both axles when one gets damaged needs replacing, this is not necessary; however, you may need to adjust the air pressures between front and rear axles to avoid road loping or power hop. Road loping is typically caused when the gap between front and rear tires overcomes the mechanical ratio (yes; even when the front power is disengaged). Power hop is typically incurred when front tires have more tractive capacity then the rear (also a mechanical ratio issue). Bottom line, air pressure changes the overall diameter of the tire. When you also change the lug depth by replacing worn tires with new, the overall diameter of those new tires in relation to the worn tires has been also been altered.

When in doubt, don’t hesitate to reach out to your local Michelin Ag Rep with questions or concerns regarding your Michelin Ag tires. We pride ourselves in employing an Ag tire salesforce that carries a set of scales, equipped with the knowledge and expertise to set your air pressures, calculate proper weight distribution and torque transfer, and help you achieve ultimate machine efficiency.

Dave Paulk:  Manager Field Technical Services

The maintenance of tires is just as important as the maintenance to the equipment. Tires should be looked at regularly and air pressures checked often to ensure they are giving peak performance. This can reduce downtime when time is the most critical.

Tires should be checked for cuts, punctures, bulges, and worn-out tread. If cuts or punctures are shallow and do not expose belts or cords, the tires are good to run. If cords or belts are exposed, it may be a good idea to replace the tire before the tire fails. The cords and belts are the foundation of the tire that gives it strength and stability. When these become exposed, they can become damaged by dirt, rocks, etc. and cause the casing to fail. Punctures can cause slow leaks, low air pressure, and over deflection in the tire. This can ruin the tire’s sidewalls and casing. Bulges in the tread or sidewall can be caused by impacts to the tire. Bulges generally indicate that a belt or cord may be broken and that air is pushing through.

Worn out tread can cause excessive tire/wheel slippage, more time in the field, and excessive fuel usage. The extra slipping causes the tire to turn faster than the field speed of the tractor because there isn’t enough tread to allow the tire to grip the ground properly. The industry says slippage should be in the 8-15% range with tires. Anything above that is excessive. A general rule of thumb is that when a tire gets below about 20% of its original tread depth, it may be time to start shopping for new tires depending on the use of the tractor. Soil types and the amount of moisture also play a role in how effective tires are when they start wearing down.

Care should also be taken to protect tires by not driving directly over the stubble in the spring. Stubble damage can chip away the outside rubber in the tread area and expose cords underneath. GMO technology is great for yields, pests, wind, etc., but terrible for tires. Rubber is no match for the hardness of GMO stalks, especially after they have been in the elements all winter.

The overall diameter in radial tires can differ between brands because of maximum growth rates and the +/- specifications per TRA. Metric sized radial tires between manufacturers are generally close to the same overall diameter and rolling circumference and can be inter-changed between brands when needed. Currently with the shortage of tires, this has become a necessity more than a choice. When replacing one tire that has been damaged, the tread depth needs to be matched closely with the older tires. This may require replacing a couple of tires if the older tires are 25% or more worn. When replacing tires and matching to older tires, the same load indexes should be used. Different load indexes recommend different air pressures for carrying capacity. It is best to use the same brand on an axle and match up a tire with the same brand when possible.

With MFWD tractors, the user should make sure the rolling circumferences closely match when using other brands. With radials, brands can usually be mixed. Different brands can be used on the front and the rear if the lead/lag ratio is within limits. If R-1W’s are used on the rear, they should be used on the front. Tread patterns should be close to the same to ensure good traction and mobility.

Bias ply tires can have different overall diameters depending on the manufacturer. If a user is replacing all tires, they can use the brand they prefer. If they are matching up a tire, they need to go back to the same brand they are matching up. Because of the difference in overall diameters in bias tires, the heights across manufacturers can different. Unlike metric radials, the aspect ratio on bias tires can differ causing the difference in heights.

Maintaining equipment and tires regularly is important to reduce downtime and fuel expenses over the long term. This will ensure maximum performance and keep equipment running as efficiently as possible.

Continental Agriculture North America
Dana Berger:  Ag Business Development Manager

Admittedly, working for a tire manufacturer you become a bit of a tire enthusiast; walking through parking lots noticing brands, tread patterns and wear. In the field, it’s almost a requirement to know at least the basics of tires, along with many other skills of course – but what might seem like a simple question, “Does that tire need to be replaced?”, really has a lot to it.

Some standard factors fall into the ‘basics of tires’ category, previously mentioned. Those basics would include things you might learn from your father, before driving a car for the first time – tread depth, air pressure, jack location, etc. When you add the complexity and variability of the environment and farming, several other considerations come into play. These influences make it difficult to narrow down one rule to replacing a farm tire.

Skipping through Summer and getting straight to Fall, a season where tillage is a regular task, the weather is dry, the soil is cracked, and an old worn set of tires might make it through the season. A deeper tread pattern would provide little benefit unless there is a change in weather conditions and the equipment requires traction in the field from heavy rain. Old tires with 20% remaining tread depth won’t ‘get a grip’ in the wet field and the fuel efficiency to pull diminishes rapidly.

Then, pass through the holidays and into Spring, a much wetter season when tread is key! Depending on the type of farming, crop or livestock, there are different requirements for tire tread. In a crop operation a deeper tread is used more often, but livestock farmers may be able to get away with a lower tread depth. As an example, a lower tread depth is important when trying to keep the soil and grasslands intact. This thought process led to an active used tire market because the farmers with operations that require deep treads, can sell their partially worn tires to farmers who do not have a deep tread need. It saves the second farmer a few dollars and gives the first a few to buy a new set.

Replacing tires in sets, is usually the go-to, but sometimes one tire is in great condition and the other suffered damage from a field hazard. In a case like this, it is not recommended to have separate brands on the same axle, because the differential drive would be running constantly to neutralize the difference in rolling circumference. Today’s market has challenged that recommendation, but it will almost always be advised to keep axle brands in the family. A combination is acceptable on different axles, as long as the tire size can fulfill the lead requirements of the tractor.

Should two [or more] tires need to be replaced on one axle, it’s always advised to replace with the same brand. That recommendation can take us back to the ‘new’ vs. ‘used’ discussion, which in turn brings us back to type of operation. The resulting rolling circumference is influenced mainly by the belt diameter and in-part, the tread height. Ultimately, combining partly worn tires on one axle with brand new tires on the other is less problematic than having used and brand new on the same axle, but it would not be conducive to combine with worn tires above a 30% wear rate.

Yokohama Off-Highway Tires America, Inc.
Blaine Cox, National Product Manager—Agriculture, Golf and Turf:

There are a few situations in which you absolutely need to replace an R-1 or R-1W tire immediately: if you see an oblong bulge that indicates a rupture in the casing, or if excessive wear has exposed belt wires or ply fabric. Those conditions are unsafe, and must be addressed at once. Ozone cracking, which you can spot by a network of spider-web-like cracks and the loss of elasticity, can also be a reason to replace tires.

When it comes to regular lug wear, the right time to replace an R-1 or R-1W tire can be a more of a matter of taste, economics and the kind of use you expect from the tire. For tires that are used in the field, watch for excessive slip. If you’ve got a slip monitor in your cab, properly inflated tires should slip 10 to 15% in dry soil. If you don’t have a slip monitor, step out and look at your tire prints in the soil. Optimum slip will leave just a little crumbled soil in the center of the tire track, while excessive slip will leave a blurry print or piles of kicked-up dirt.

Of course, tires that may have worn too much for pulling a field cultivator or planter could still work fine pulling a feed wagon across the farm yard or spearing hay. Again, it comes down to where you’re working and how much traction you need.

We have factored wear into our tread patterns, like the two-layer lugs of the Alliance Agri Star II. For the first 40% of the lug, we have a narrower upper layer that arcs straight across the lower layer, forming more biting edges. As you get past the 40% wear level, the Agri Star II rides on the wider portion of the lugs, which have a multi-angle design, putting more rubber on the ground.

When it comes to maximum performance, the most important thing you can do for your tires is inflate them properly. That will ensure that the sidewalls have the proper amount of flex and support, that the contact patch is the optimum size and shape, and that you will get the most even wear. Operating at the proper inflation pressure maximizes tire performance and tire life.

Another aspect of tire engineering is the outer diameter of a tire, which can vary from one design to the next, so not all ag tires in a specific size are exactly the same height. Tread depth differences such as those between an R-1 or R-1W or an R-2 can also cause a difference in overall diameter.

Maxam Tire International
Greg W. Gilland:  Business Development & Ag Segment Manager

In the agricultural industry, it is how the equipment is utilized or the inherent operational requirements that will affect the tire replacement cycle. As agricultural tires are considered off-road and not US Department of Transportation (DOT) regulated, there are no firm rules to determine when an ag tire absolutely needs to be replaced.

Below are some general guidelines that can help a farmer or grower determine his next move or predict the removal of his tires. In all cases, MAXAM recommends utilizing ag tires for the longest possible time regardless of the type of tire R1 or R1W, if the tire can be safely utilized to meet operational requirements and therefore achieve the most value for the tires in question.

General Tire Replacement Guidelines for Farmers & Growers:

Tire Operational Condition Root Cause Recommended Action
Increased Tire Slip Adjusted tire inflation not working or tire tread depth (increased wear) reducing operational traction, great fuel consumption, or increased machine slip. Tires may be too worn for the soil condition or crop conditions of the operations. If tires are exceeding a 15% slip rate, MAXAM suggests replacing the tires to improve traction and fuel efficiency.
Constant Air Leakage or Loss of Air Loss of traction due to poor air valve maintenance or tire cuts resulting in constant air loss. Tire damages or cuts from operational use are degrading via leakage of the required air pressure to operate the tire effectively. In this case, MAXAM suggests replacing the tires.
Excessive Damages or Cuts in the Tread or Sidewall Tire cuts, exposed casing cables, large damage, or deformities on the tread/sidewall are indicative of external or internal damages that could impact the safe operation of the tires. Evaluate the tires for damages that could impair operations or result in equipment damage while in operation. This situation can result in imminent failure or loss of tire integrity, MAXAM suggests replacing the tires
Uneven Tire Wear


Tires exhibiting uneven tire wear or more than a 10% difference in tread depth on the same axle can result in a loss of traction, increased slip, increased fuel consumption, or can impact gear ratios. Tires have uneven wear that can precipitate a loss of traction or increased fuel consumption and /or can also impact the gear ratio of a front wheel assist tractor. MAXAM suggests replacing the tires on the axle in this circumstance.
Tire Diameter Differences Tires that have more than a 5% difference in overall diameter that are operating side by side or on the same axle can lead to a loss of traction, increase slip, generate gear ratio issues, and increase soil compaction as the load will shift to the larger diameter tire. Tire diameters need to be as closely matched as possible to prevent excessive slip and limit any gear ration mechanical issues. Anytime where larger tires are used side by side due to overall diameter differences the axle load will shift to the larger tire which can increase soil compaction and limit your gross tire flat plate or footprint. MAXAM suggests replacing tires on an axle at the same time to limit this occurrence.
Ozone Deformities or Dry Rot Tires stored or equipment parked in the open achieving excess sunlight or ozone cracking/wear that will degrade tire casing integrity. Inspect tires in open storage or parked equipment for ozone cracks that expose internal materials such as working belts or casing materials. If materials are exposed, MAXAM suggests replacing the tires as needed.


All the above can be considered resulting conditions of extreme fieldwork and or poor maintenance/storage. In all cases MAXAM recommends the following operational parameters being employed regularly:

A. Monitor normal tire slippage by tractor type:

  • 2WD Tractors = from 10% up to 15% slip rate
  • MFWD Tractors = from 8% up to 12% slip rate
  • 4WD Tractors = from 8% up to 10% slip rate

B. Verify tractor gear ratio for MFWD Tractors and ensure tires selected have the appropriate tire diameter front to rear (RCI) to maintain the 5 to 1 engine gear ratio required for MFWD type tractors and minimize any extreme tire wear.

C. Set the correct tire cold inflation pressure based on the actual axle load (tire weight) and the number of tires being employed by tire size.

D. Regularly check tire inflation pressures for the specific implement or load being carried. If necessary, weigh the machinery to ensure proper cold air inflation settings for improved wear and performance.

E. Employ the best weight distribution possible by adjusting axle load ballast using suitcase weights, wheel mounted weights, or tire liquid ballast (not recommended) for the pulled or towed implement to ensure improved tire wear.

  • 2WD tractors weight distribution: 25-30% front axle & 75%-70% rear axle
  • MFWD tractors weight distribution: 40-45% front axle & 60%-55% rear axle
  • 4WD tractors weight distribution: 55-60% front axle & 45%-40% rear axle

F. Inspect ag tires regularly for damage, cuts, loss of air, or any indication of uneven wear or ozone cracking replace tires as necessary especially as you move from season to season and when you start or stop equipment after long periods of use or storage.

Differences between ag tires made by various tire companies on the size dimensions or specifications are always linked to the fact that not all tire fabrication steps, quality, efficiency, or production controls are the same between manufacturers. As a result, manufacturer’s processes and tire geometry will vary for the same tire size within industry tolerances due to material or casing component differences that will lead to specific variances between tire brands. MAXAM, therefore, does not recommend mixing brands on machinery axles to ensure the best uniformity in terms of tire diameter, performance, traction, and value.

Rick Harris: Region Sales Manager

The American agriculture producer requires high performance tractor tires to maximize their tractor’s capability and effectiveness.  Many agriculture producers use a tractor daily for multiple purposes on their farm. Worn tires struggle providing optimum traction, increasing fuel costs, and limiting productivity.

Producers across the nation who keep a tractor around for years, is eventually faced with the decision to replace tires. There is no standard rule in determining agriculture tire replacement however, below are signs to consider when making the decision to replace your tractor tires.

Tread Depth
Significantly worn drive tires increase a tractors fuel consumption as high wheel slip due to poor traction wastes fuel. Frequent use wears tire tread at a more rapid pace. Depending on the condition and type of terrain (wet, dry, flat, hilly, loom, clay, etc.) your farming impacts wear on varied soil conditions and moving between different surfaces.  Transporting on asphalt or concrete roads regularly wears down the tread more quickly.

A common cause of tire damage is punctures. There are varied ways tractor tires are punctured (deer horns, fence posts, stubble).  GRI tires are manufactured to withstand regular encounters with such, although older worn tires have less rubber which is a first line of defense against punctures. When a puncture, tear, or cut exposes body plies or belts (which provide a tire stability and strength), it’s time for a new tire.

Impact damage caused by a rock or inferior road condition can potentially result in a bulge on the tire. A bulge indicates tire casing is damage. Bulges are not repairable and you should replace a bulging tire as soon as possible, as it can fail at any time causing frustrating downtime or pose a serious safety risk.

When you see cords, it’s time to replace the tire.  Damage on the shoulder needs to be evaluated or repaired.

If it’s time for new tires on an older tractor with bias tires, consider upgrading to radials as they significantly improve performance.  The upfront investment is higher, but it’s offset by longer life and pays for itself two or three times. Fuel efficiency improves, soil compaction improves, and the ride is smoother.  When converting to radials avoid internal fluid for ballast, as it negatively impacts the radial tires ability to flex reducing the contact patch.  Convert to cast iron wheel or saddle weights.

Air Pressure
Tire performance and, subsequently a tractor performance, is directly related to tire air pressure. Keeping a leaking tire at the optimal air pressure, which effects footprint (soil compaction), fuel efficiency, ride comfort, and productivity is time consuming. Tractors tires should be checked daily with a tool that can measure the pressure.  The best time to check a tractor’s tire pressure is in the morning before the tires warm up.

Wheel slip is indictor the tires are turning faster than the speed the tractor. Tractors are designed to operate with some wheel slip to reduce drivetrain strain, however, too much slip wastes fuel and power and also wears the tires. Some tractor manufactures recommend 3-7% slip, others 3-10%  every 1% beyond optimal slip, forfeits 1% productivity and energy efficiency.  Late model tractors come equipped with wheel slip indicators to easily monitored in the cab.

Dry Rot
Dry rot is caused by excessive exposure to the sun, arid climates, and/or herbicides and pesticides chemicals.  Dry rot makes the tire brittle creating cracks which degrades the structure and eventually unusable. Replace a tire with dry rot.

All information is provided in this blog solely to provoke thought. All deductions made from information on this site must be confirmed by Certified Ag Tire Dealer and tire manufacturer where specified before use. Ag Tire Talk does not recommend anyone conduct tire service work with exception of Certified Ag Tire Dealer Professionals.