AG TIRE TALK KEY TAKEWAYS
YOKOHAMA TWS: “An Out-of-Round tire is not a perfect circle and known as tire radial runout. There is another tire runout, lateral runout, which deals with the side-to-side wobble. We will discuss radial runout.”
MAXAM: “An “Out of Round” tire…when mounted on a working platform can result in increased vibrations, accelerated or uneven tire wear, and increased instability.”
BKT: “Matching the tire and rim together with high spots and low spots can minimize the amount of runout on a tire and wheel assembly and reduce vibration.”
MICHELIN: “Before assuming a tire is out of round, it’s critical to inspect for more common issues: improper mounting, bead damage, and bent or damaged wheel.”
Yokohama TWS
Chris Neidert: AG Marketing, Training & Development Manager for Trelleborg & Mitas Tires – North America
An Out-of-Round tire is not a perfect circle and known as tire radial runout. There is another tire runout, lateral runout, which deals with the side-to-side wobble. We will discuss radial runout.
There is no tire that is a perfect circle, depending on the tire quality, tire manufacturers strive to be as close as possible to a 100% round tire. The closer the tire is to a perfect circle (smaller manufacturing tolerances), the higher the tire quality. The higher the manufacturing tolerance, meaning larger out of round values, the higher the possibility for the wheel to cause an up-and-down hopping motion felt as vibrations when the wheel spins. Excessive radial runout leads to a bumpy ride, irregular wear, and can cause vehicle vibrations.
The higher the speed the equipment is moving, the more noticeable is an out of round tire or rim.
Common causes of radial runout:
Manufacturing – believe it or not, tires are not perfectly round from the factory. The tighter the manufacturing tolerances the lower the out of round and higher the tire quality.
Improper mounting – the tire may not be seated correctly on the rim.
Wheel – like the tire, some wheels are not perfectly round from the factory resulting in an out of round wheel assembly scenario. Another cause by the wheel is a bent wheel. This is often caused from an impact and can cause a tire to appear out-of-round.
Improper Match-mounting – it may also be caused by improper or not match-mounting the tire and wheel assembly. High quality tires and rims are tested before shipping and marked for their low spot and high spot.
Match-mounting involves matching the low spot of the tire with the high spot of the wheel compensating the out of round of both elements.
Let’s talk about Harmonics.
Tire harmonics are patterns of how a tire and wheel slightly change shape as they spin. These changes create small bumps or vibrations while driving. Each “harmonic” is like a rhythm:
The first harmonic (R1H) makes one bump per tire turn.
The second harmonic (R2H) makes two bumps per turn.
Higher harmonics cause even more bumps.
These bumps can affect how smooth the ride feels.
See my diagram below:
R1H (Radial 1st Harmonic)
R2H (Radial 2nd Harmonic)
R3H (Radial 3rd Harmonic)
R4H (Radial 4th Harmonic)
We will discuss the 1st harmonic.
Here is an example of some verbiage that is required from an Original Equipment (OE) manufacturer regarding a particular size tire and radial runout.
Radial Runout:
- RADIAL RUNOUT (PEAK TO PEAK): 4 mm MAX
- MEASURE RADIAL RUNOUT PEAK-TO-PEAK ON TIRE LUG FACE AND CALCULATE THE 1ST HARMONIC DOUBLE AMPLITUDE RADIAL RUNOUT.
- RADIAL RUNOUT (1ST HARMONIC DOUBLE AMPLITUDE): 2.5 mm MAX
What the spec is saying is that as it relates to the 1st harmonic, the radial runout cannot be more than 2.5 millimeters. The particular tire that this spec is dealing with has an overall diameter of 2,186 millimeters (86.1”). If we use a percentage of how close the tolerance is for the roundness of this tire, it is .00114 %. That’s one-hundredth of one percent and that’s pretty round.
The OE manufacturers demand those tight tolerances because if they produce a machine that costs over $500,000, the last thing they want is the customer complaining about the ride.
What kind of out-of-round tolerances could be acceptable, and the tire can still produce a nice ride? Below is a chart showing some harmonic measurements. You can see as the tire diameter gets larger; the acceptable out-of-round measurement is a little more forgiving. The main reason is the larger out-of-roundness is spread out over a larger circle smoothing out the “bump.”
BKT USA, Inc.
Dave Paulk: Manager Field Technical Services
Out-of-round tires can cause vibrations, road noise, and uneven tread wear. With the bouncing and vibration, they can cause a rough ride. With the technology now used, many tires are more uniformly made than in days past. There are some things to check when vibrations occur that don’t necessarily have anything to do with the tire.
Tires and wheels are not made perfectly round. Each has a high spot and a low spot. If the high spot on a wheel is matched up to the high spot on a tire (or low spot to low spot), this can cause a vibration. The high spot of one needs to be matched up with the low spot of the other. Match mounting the tire to the wheel generally ensures the best ride possible.
If a tire is not properly seated on the rim, this could cause radial or lateral vibration. The bead of the tire should be properly seated on the rim all the way around the rim to eliminate lateral runout and swaying back and forth.
Low-horsepower tractors (less than 100 HP) have a shorter wheelbase and can cause some vibration in the driver’s seat (generally starts at about 20 mph). Sometimes this has can be caused by the wheel not being centered on the hub. Adjustable rims are common on smaller tractors. While these rims are great for adjusting the wheelbase width, they are bad for wheel runout, which can cause vibration.
There are 3 ways to limit runout on a tire.
In production, when tires are made, there is a splice in the building process. Since it’s not possible to eliminate this, the effect on runout can be reduced by manufacturing.
Matching the tire and rim together with high spots and low spots can minimize the amount of runout on a tire and wheel assembly and reduce vibration.
Air pressures can be adjusted to ensure a good ride and minimal vibration based on the weight of the vehicle and the amount of weight carried. Over-inflation can play a big part in excess vibration at higher speeds.
Unless the tire is out of round from the start due to manufacturing, application can play a part in how the tire rides and rolls. Oftentimes, the heavier the equipment (such as combines and large tractors), the longer the wheelbase, and the slower the speed, the less vibration will be felt. The faster and lighter the machine, the greater the chance of feeling vibration at certain speeds.
There is equipment available to check for runout on tires to determine it the runout exceeds the manufacturer’s recommendation. Radial and lateral runout can be checked. Radial runout is the amount of up and down movement a tire shows. This is the most common cause of a problem and can cause a vibration in steering or the driver’s seat. The distance should be close to the same when measuring from the center of the wheel to the outside of the tread around the tire. Lateral runout is a side-to-side motion and is sometimes caused by not properly seating the tire to the rim.
No tire and wheel assembly is perfectly round, so there is always a bit of runout. This should be minimized for the best tire (and wheel) performance. BKT has a tight tolerance for runout and uniformity to minimize vibration problems caused only by tires. Match mounting tires to wheels and ensuring they are mounted properly solves many problems.
Maxam Tire International
Greg W. Gilland: Vice President Global Agriculture
In general, “Out of Round” conditions on an agricultural tire stem from either poor-quality control during manufacturing or poorly managed tolerance management in the tire specifications. In essence an “Out of Round” tire is not “round” due to a distortion in the casing or tread that when mounted on a working platform can result in:
- An unstable tire
- Increased vibrations
- Accelerated or uneven tire wear
- Increased instability when mounted
Ultimately, these results will reduce the tire’s expected service life. In extreme working conditions, out of round tires can also increase the friction of the tread, causing increased rolling resistance, uneven or abnormal wear, and greater fuel consumption due to greater slip rates
Other possible causes that can lead to “out of round” conditions include:
- Poorly mounted tires that are not fully seated on the rims or flanges.
- Poor storage practices like barrel stacking or tires stacked too high distorting the casing on the bottom tire of the stack.
- Uneven storage or ground conditions resulting in distorted or misshapen tires over time.
- Tires that remain in one position for a long period of time without any movement or rotation resulting in a distorted bead, casing, sidewall, or tread area.
- Poorly maintained or damaged wheels when the tires are mounted result in a “out of round” vibration or harmonic.
- Poorly mounted tires on rims where the “high” spots are misaligned.
- Rims that are distorted from excessive use or poorly manufactured quality conditions.
Good housekeeping and best practices in the storage of tires can reduce the risk of tire distortions as described above.
In addition, regular wheel inspections, replacement of damaged wheel components, and wheel maintenance prior to tire mounting can also reduce the impact of an “out of round” tire. In some instances, even new wheels may have issues like “Rim Concentricity,” which occurs when all the bolted wheel components are not round and resulting vibration harmonic when the tire is mounted. Therefore the “out of round” conditions caused by a poor-quality rim or components may only be noticeable when operating on hard grounds or when roading from site to site. In those instances, adjusting the tires’ cold inflation air pressure can also help to mitigate or reduce the resulting vibration.
Most wheel and tire manufacturers minimize the risk of “out of round” by ensuring that tires and wheels are tested at their manufacturing facilities using “run-out” equipment. They will mount the tires on a rim and mark both the tire, as well as the rim’s “high spot”, to ensure alignment of the two spots, at this reduces the incidence of vibration.
Due to the nature of their field work or application, each agricultural platform will either have higher or lower incidence of vibration.
- Roaded Tractors may only experience some vibrations when operating at speeds greater than 15 or 20 mph on hard surface road conditions.
- High Clearance Self-Propelled Sprayers or Floaters will inevitably experience a higher incidence of vibrations when you have an “out of round” issue either with a tire, the wheel, or the mounted assembly.
- Harvesters may also only exhibit severe out of round issues or vibrations when moving from field to field on harder roads that can be masked at slower speeds (below 10 mph) when working in the field during harvest season.
- In every instance above, checking the tire and wheel components to include the tire mounting, tire alignment to the vehicle, and resulting “camber” of the wheel assembly in each position, can also impact the tires’ resulting vibration or harmonic.
When troubleshooting “Out of Round” conditions below are some recommendations and suggestions to identify the root cause of the Vibrations or Runout (Out of Round) issues:
- Evaluate the Tire and Wheel Assembly Lateral (side to side) runout.
- Evaluate the Tire “Radial” (up and down) runout.
- Use a runout gauge to evaluate both the lateral and radial stability of both the tire and the wheel separately.
- As the tire and wheel are connected as an assembly, it is imperative that both be examined together and then separately to ensure all the component variables are assessed.
- A high spot or heavier spot on a wheel or component like the inner disk can become further amplified on larger tires as the center of gravity is further removed from the spinning center, as a result the vibration force becomes more amplified on the mounted tire contacting the working surface.
- The continuing radialization of the Ag industry has increased the need for tighter tolerances related to the tire and wheel assembly “Runout”.
In every instance, MAXAM’s manufacturing and quality teams use stringent measurement controls to ensure that our tires are “concentrically round” and within acceptable tolerances to deliver the best performance.
Michelin Ag
David Graden: Global Account Manager – Agriculture
In today’s agricultural landscape, especially with high-speed equipment like sprayers and MFWD tractors, ride quality issues are sometimes blamed on out-of-round tires. But in my experience working with Michelin Agriculture and supporting farmers and OEMs globally, it’s important to take a closer look at what’s really going on.
What Is an Out-of-Round Tire?
An out-of-round tire is one that doesn’t maintain a consistent radius as it rotates. This can be radial (up and down) or lateral (side to side). On agricultural equipment, symptoms may include:
- Vibration at specific speeds
- Uneven wear patterns
- Reduced traction and soil contact
- Operator discomfort and fatigue
However, more often than not, the tire isn’t the issue—it’s the wheel. Based on field experience and feedback from our technical engineers, it’s far more common for the wheel to be the source of an out-of-round condition than a Michelin Ag tire. This likely applies to other brands as well, but I can only speak to the Michelin brand.
Michelin does perform uniformity checks on passenger and light truck tires as part of standard quality control. But for agricultural tires, the process is different. In OE (original equipment) applications, we may check for a high/heavy spot or heavy harmonic—typically where the tread rubber seam is located—but this is extremely rare. In those cases, we might mark the tire so the OEM can match it with a low spot on the wheel to optimize ride quality.
Start with the Basics
Before assuming a tire is out of round, it’s critical to inspect for more common issues:
- Improper mounting
- Bead damage
- Bent or damaged wheel
These are far more likely to cause ride quality problems and/or out of round conditions and should be ruled out first.
When and Where It Shows Up
If a vibration issue does occur, it typically shows up during roading—not in the field. Soft ground conditions and torque tend to mask minor imbalances. On the road, especially at higher speeds, those imperfections become much more noticeable.
This is especially true for MFWD machines, which have suspensions that can amplify vibration frequencies. In contrast, 4×4 machines—with their heavier build and different vibration profiles—tend to absorb these issues more effectively.
Harmonic Imbalance: Rare but Real
While Michelin Ag tires are engineered to perform across a wide range of conditions, there is a very rare possibility of a harmonic imbalance. This can be caused by lug count, an out-of-round tire, or more commonly, an out-of-round wheel. When present, it can manifest as road loping and, in some cases, become quite violent.
If both the wheel and tire roundness check out and the issue persists, it may be worth trying a different tire with a different lug count or tread design. Sometimes, the natural vibration frequencies of the machine simply don’t harmonize well with the tire’s pattern. Though rare, this mismatch can lead to noticeable ride disturbances—especially during transport at road speeds.
Final Thoughts
Ride quality matters, particularly as equipment becomes faster and more sophisticated. But when diagnosing vibration or imbalance, it’s essential to look beyond the tire. At Michelin Agriculture, we stand behind the integrity of our products, and based on years of field experience, I can confidently say: if there’s an issue, start by checking the wheel. On the other hand, if the wheel checks out, don’t hesitate to reach out to your local Michelin representative. All Michelin sales representatives are equipped with the tools, knowledge and skills required to diagnose any problem and quickly present you with a solution. They are backed up with well over 100 years of successful experience!
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 & Tire Manufacturer before use. Ag Tire Talk does not recommend anyone conduct tire service work with exception of Certified Ag Tire Dealer Professionals.