By Gary Van Dyke
I’ve been fighting a shimmy on my Cardinal RG for a while. I had a fairly significant event on a trip that pushed solving that problem to the top of the list.
We were taking off from Texas Gulf Coast Regional Airport (KLBX) in the Houston area to Lakefront Airport (KNEW) in New Orleans. Just as we got to rotation speed, we experienced a violent shimmy that was so bad it was actually scrubbing speed. I had plenty of runway, so it came down to a decision on whether to abort or to go ahead and take off.
I thought the nose wheel had gone flat. Since we were at rotation speed, I decided to take off.
Photo by Jack FleetwoodThe takeoff went fine. Since KNEW has a good maintenance facility, I decided to make the trip and have the problem fixed once we were on the ground there.
I told my wife that I thought we had a flat tire and that things were likely to get bumpy as the plane slowed but that I was confident everything would be OK.
When we got to New Orleans, I let the tower know that I may have a flat tire and may need to be towed once we got the plane stopped. I did a soft field landing at minimum speed and held the nose wheel off as long as possible.
I had the yoke all the way back when the nose wheel finally touched down and was surprised that there was absolutely no shimmy.
We taxied to the FBO and I did a very thorough look at things once we shut down. With the tail pushed down to get the nose wheel off the ground, everything looked like it should.
We decided to check everything in the nose wheel and steering systems. We pulled the tail down and secured it to a ring I have installed in the floor of my hangar for that purpose. We then pulled the nose wheel and went through all the connectors and settings for the nose wheel and steering system. Everything we checked was in spec.
We had the tire static balanced when I first put it on during last year’s annual, but I thought something might have changed.
I found a local motorcycle shop that had the equipment needed to dynamically balance the nose wheel, so I took the tire to them.
The mechanic they assigned to balance the tire owns and flies a Maule, so he had a good understanding of my issues. He took a quick look at the tire and said something didn’t look right but mounted it to the balancer and started to spin it up. He stopped it quickly and got me to come over to look. Once it was spinning it looked like there was a lump on one part of the tire.
To verify that, he got it spinning then took a grease pencil and lightly placed the tip on the center of the tread. When we stopped the tire, you could clearly see gaps in the mark the pencil left showing low spots.
He went through the balance procedure. It took a full ounce of weight on a spot opposite the high spot to get the tire in balance.
That was causing the tire to bounce at high speed when lightly loaded (my shimmy).
My new friend pointed out that the tire was so lightly worn that it still looked original in most places.
I told him I would replace it anyway, then he showed me a process they use on motorcycle tires to get them back in round and suggested I try that first.
With the tire off the ground, use a belt sander to get it spinning, then carefully touch the tip of a grease pencil onto the tread. Ideally you mark three or four areas across the width of the tread.
Once the tire stops, spin it slowly by hand. If the tire is round, the marks will go around the entire tire. If it’s out of round, you’ll see gaps in the marks on the low spots.
If there are low spots, get the tire spinning with the sander again and then turn the sander 45 degrees to the tire. Sand a little, check progress, and repeat until you get the tire round, or you decide you need to just replace the tire.
I found 120 grit sandpaper worked best. The coarser grits don’t let the tire slip enough to sand the rubber. I had a small scattering of rubber on the floor when I was done but still had very little wear on the tire.
I took the tire back to the motorcycle shop and this time it was in balance with no balance weights applied. I put it back on the plane and haven’t felt any shimmy since. Next time I will start by checking that the tire is round and in balance before doing anything else.
Telling if a tire is out of round is getting harder and harder by the day. Nowadays tire makers produce original equipment (OE) tires. (OE tires are factory tires that a vehicle is originally equipped with.)
Fix The Problem
An OE tire has to meet specific dimensions and weight requirements, along with longevity expectations, speed ratings and handling performance. This being said, an out of round tire is not common.
Read below to determine if you have an out of round tire.
Just because something is not common, doesn’t mean it can’t happen.
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Learn what the numbers and letters mean on your tire here.
When looking for this rare occurrence, you should focus on determining if your tire is a perfect circle or not. An out of round tire has a weak spot or spots in the tire. These typically look like a subtle flat patch along the tread of your tire.
This patch or spot can be seen when the vehicle is stationary or parked. This weak spot in your tire will deflect differently from the rest of your tire, while the stronger part of the tire will resist bending and remain stiff, causing vibration.
Please note: If vibration can be felt in the seat, this indicates the problem is located at the rear. If vibration can be felt in the steering wheel this is a sign of a problem that is located in the front.
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Out of Round Tire CheckLoud Tire Noise at Highway SpeedsHas your tire been causing your car to shake or vibrate? Or do you have loud tire noises while driving at highway speeds? A bad out of round tire is when the tire is no longer round, this can cause hash vibrations and road noise.
Once a tire is out of round the only thing you can do is replace the tire.
While there are many things that can cause a tire noise such as low tire tread, tire separation, out of balance tires, bent rims, out of round tires is definitely on the list of tire noise. The key is figuring out which noise is causing your harsh car ride.
An out of round tire is also known as tire run out. An out of round tire or tire run out means your tire is no longer perfectly round anymore. This will cause a tire noise or vibration.
There are two different kinds of out of round tire. Read below to understand the two cases.
Highway NoiseThe first and more common of the two is radial runout. Radial runout is when the distance from the center of the rim to your tire tread is different in certain areas of your tire.
Note: The distance from the center of your wheel to your tire tread should be the same distance all the way around.
Radial runout due to its different distances between the center of the rim to the tread of the tire will cause a rather harsh ride such as vibrations, tire noise, steering wheel vibrating/shaking and also bouncing. The worse the tire runout gets the more harsh your ride will be.
Time will heal most things…
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When your tire has some form of a rough ride due to tire runout, this harshness will travel through your tires and up your steering shaft. This vibration causes your steering wheel to shake. Your whole entire car may also shake or bounce, but in minor cases you may just experience loud road noise while driving.
The second type of out of round tire/tire runout is lateral runout. Lateral run out is when your tire has flat spots across your tread. This means your tire is weaker in certain spots on the tread of your tire. (Check for suspension issues)
When you put the weight of your vehicle on a tire with lateral runout, your tires will not be able to distribute the weight evenly.
This type of runout happens between the center of your tread to the edge of your tread. As your tire spins, one part of your tire could be good and right next to it could be weaker.
This form of out of round tire would cause your tire to lean when it hits that certain spot. This lean is due to the improper weight distribution within that tire. Lateral runout could also cause your tire(s) to move side to side like a wobble.
Can you Balance an Out of Round Tire?Usually you can NOT fix an out of round tire. However, you can maybe improve your ride quality by road force balancing your tire. Before we jump into that, let’s dive into a standard balancing.
A tire should be balanced when you put it on a rim. However, even new tires are usually not perfect. There are some spots that could be slightly heavier than the others. Balancing a tire is simply adding weight to your rim to balance out the weight of your tire.
A tire balancer will find the lighter spot on your tire and tell you to add weight in that certain spot on your rim.
Without this procedure being done, you would have a very rough ride.
Having imbalanced tires can also cause more excessive tire wear. Due to excessive tire wear, you can cause a tire to become out of balance. Road force balancing will help a tire that is out of round or has excessive tire run out.
When you throw your tire up on the balancer a big roller will come down and mash your tire as it spins imitating the road. This detects the weaker points in the tire.
Like your tire, your rim also has a runout, so what the machine does is it will have you put a mark on the tire and a mark on the rim. Once you mark the rim and tire you will need to break your tire down and match the mark on the tire with the mark on the rim.
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So, let’s say you have a weak point in the rim, the machine will have you put the stronger part of the tire on the weak spot on the rim.
This will give you a better ride.
However, this process usually doesn’t fix your problem all the time, it simply improves it. More than likely you would just need to buy a set of new tires if you want to ensure that you have the smoothest ride possible.
Time For New Tires?Can You Fix an Out of Round Tire?
In short the answer is you can NOT fully fix an out of round tire, you may be able to make it a little smoother or better but not entirely fix the issue. Usually this means you need to purchase new tire(s). Get tire discounts by using the link below!
When you have a new set of tires installed you should have a nice, smooth ride. If you are starting to feel vibrations after a couple of thousand miles there is a problem.
If the vibration begins and continues to get worse until the next new set of tires, look into an issue with an imbalance in brake rotors, inspect the pads and rotors and the front struts and/or rear shocks.
Also, ensure the tires are balanced, rotated on schedule, and have the shop do a 4-wheel alignment.
If none of these are making a difference and your tire(s) continue(s) to go out of round after a couple thousand miles, you should inspect the wheel (rim) for imperfections, bumps, dents, bends, cracks, not round, etc.
You may also want to look into buying quality tires that are specified for your particular vehicle to fix this issue.
Symptoms of Out of Round TireSymptoms of an out of round tire are similar to an out of balanced tire. So, before you think your tire is out of round, check for a balancing issue.
Due to the rarity of an out of round tire, because of technological advancements in tire creation, more than likely your tire isn’t balanced.
When determining the problem you are facing with your potential out of round tire(s) consider the following:
With mileage, the technical condition of tires changes, which affects the performance of the car and traffic safety. Therefore, it is important to monitor the uniformity of wear of all tires, and also to prevent the operation of the vehicle, the residual height of the tire tread of which is lower than the minimum allowable. The task of preventing premature wear and destruction of tires is very complex and is associated with the ability to determine their types, accurately identify the cause that caused each specific tire failure. The increased wear of your car tires is influenced by many factors, or, to put it bluntly, violations. The fact is that many car owners do not follow the basic rules for maintaining their own or working car.
This happens either due to ignorance or negligence. Due to the periodic and timely inspection of car tires, you can get complete and necessary information about the condition of the wheels and tires, the degree of wear, identify defects that are dangerous for traffic safety, determine the causes of tire wear and the features of car operation.
In addition to safety, tire condition affects handling, driving dynamics and fuel consumption . The latter is especially important for trucks and car owners with high daily mileage. Some tire manufacturers claim in their flyers that their tires will not only last longer, but will also save fuel. Let's see how tires really affect a car's fuel consumption. In a truck, this is of course more noticeable than in a passenger car, due to the large number of wheels and high loads. The rolling resistance of an entire vehicle consists of a whole list of resistances: air resistance, overcoming inertia forces during acceleration, internal resistance of engine and transmission components, and tire resistance. We will not dwell on all these factors and focus on tires.
The total rolling resistance of tires is also made up of several components. Contrary to popular belief, tire friction on the road surface of is only 5%. A little more (about 15%) falls on air resistance . The lion's share of the energy expended (about 80%) is spent on tire deformation . If the tire is rolled along the road with no load at all, then before stopping, it will move for a long time. But if the tire is loaded so that its lower part begins to deform (compress), after the initial impulse it will stop very quickly. This clearly demonstrates how much energy is spent on the constant deformation of the tires.
Thus, car owners may want to buy tires that will deform minimally, and therefore create less rolling resistance. Now in the market such an option is quite possible to find. As a rule, these are inexpensive budget-class tires. A stiffer carcass, although it gives some fuel economy, at the same time can present an unpleasant surprise in the form of a tire explosion. You just need to run into any object with sharp edges (stone, piece of iron, etc.). By the way, a similar situation can happen with premium tires. Some drivers, mostly trucks, inflate their tires on purpose to save fuel, without realizing that uneven wear will appear.
The chassis geometry of the also has a significant impact on fuel consumption. Even minor deviations entail extra costs. Firstly, tires wear out faster, and secondly, fuel burns more. When the wheels, figuratively speaking, go in different directions, additional energy is spent on their "drag". For example, if at one meter the wheel “leaves” only 2.5 mm, then at a kilometer it turns out that the wheel will “drag” to the side by 2.5 m. 2.5 kilometers at full load.
Normal tire wear
Tire inspection provides you with information about the condition of the tires and wheels, how the vehicle is used, possible defects, and driving style. So, for example, a sporty driving style leads to a different tire wear pattern than a relaxed one. For a correct assessment, it is necessary to inspect all the wheels. This is especially evident in the example of a passenger rear-wheel drive car, since the load is distributed differently between the driving and steered wheels in it.
Tire wear as a function of air temperature
Tire wear as a function of driving speed
While driving, tire wear is determined by measuring the remaining tread height. Tire wear must be uniform over the entire circumference; when the minimum tread height is reached, the tire is considered completely worn out and must be replaced. Tire wear is primarily determined by driving style. Hard acceleration and braking wears out the tire faster than steady motion.
Drive and steer wheels have different wear patterns due to different loads. Steered wheels wear more on the sides, since it is on this part of the tire that the main load in the turn occurs. Tires on drive wheels wear more in the middle , since it is this part of the tire that contacts the asphalt and transmits the rotation of the wheel to the road. On vehicles with front-wheel drive, the wear is "cumulative" - in this case, the entire tire wears out evenly and its central part and sides.
One-sided wear (possible reduction in wear from 15% to 30%) - occurs more often than others, since there are several reasons for its occurrence. One-sided tire wear can be caused by an error in suspension geometry. To determine the cause in this case, it is necessary to check the toe-in and camber. Wear on the outside of the tire can be caused by excessive positive toe or camber . Wear on the inside of the tire, on the other hand, causes excessive negative toe or camber. Driving with zero camber results in even but increased tire wear. In addition, it increases the tire's rolling resistance and increases fuel consumption . In addition to the tires of the steered axle, tires of other axles can also be subject to one-sided wear - again due to problems with the geometry. This is either a lack of alignment, or deformation of the axes themselves. On steering tires for tractors, one-sided wear may appear due to the operating conditions of the vehicle. Another reason is cornering at high speeds. To prevent one-sided wear, you need to monitor the condition of the chassis, periodically check the geometry and abandon the aggressive driving style.
Bilateral and central wear (possible reduction in mileage from 5% to 10%) appear for the same reason - tire pressure mismatch. When the pressure is below normal, the tire begins to wear more at the edges, and bilateral wear is obtained. The same thing happens during overload - the tire, even with normal pressure, rides as if it were lowered. Fans of pumping tires get a different result: the load on the contact patch is not distributed evenly, but closer to the center, which means that the tire wears out faster in the central part of the tread. Anyone who monitors tire pressure and does not overload the car does not encounter such problems.
Multiple wear around the circumference
Patchy wear (possible 10% to 20% reduction in mileage) is a direct result of imbalance. It is especially characteristic of steering axle tires, but can appear on all axles. If such wear has become visible to the naked eye, the problem is obvious. Balancing will correct the situation, but only partially: a wheel that has lost its roundness will wear out more intensively. Therefore, it is more expensive to ignore balancing when buying and installing new tires. Repeated wear spots around the circumference of the tires can cause suspension failure (arms, dampers, springs). After diagnosing and repairing the suspension, the tire must be replaced, since this wear pattern no longer ensures its uniform rotation, and the wheel will “beat”.
Spot wear
Spot wear in one spot is the result of emergency braking with a locked wheel. The uniformity of rotation of the wheel in this case is also broken and the tire will have to be replaced. If you leave the car for a long time in the parking lot, then there is a risk of flat areas on the tires, which then during the movement will cause the wheels to vibrate. It is recommended to increase the pressure in the tires if you leave the car for a long time. A similar effect can also be caused by stopping the car after intense sports driving - heated tires are easily deformed at the points of contact with the road surface and practically “freeze” in this state. This defect is easy to fix - after warming up the tires, they will again acquire a round shape.
Comb (sawtooth) wear (possible reduction in mileage from 10% to 20%) is a form of uneven wear. It can often be seen on drive axle tires with a block tread pattern. It is caused by the fact that during the movement the tire is deformed - at the point of contact with the road, the tread is pressed inward (the blocks are crushed and dragged along the road surface), and as the wheel rotates, it straightens again. This leads to the fact that the tread wears more on the front edge than on the back. The result of this wear is an increase in tire rolling noise. It is impossible to avoid the appearance of comb wear, but with the help of permutations, its negative effect on tire mileage can be leveled. Drivers can also influence the situation: if you step on the gas pedal as smoothly as possible, comb wear will be minimal. To even out this wear, tires are usually swapped, as tires on a non-drive axle are more susceptible to this wear. Low tire pressure also increases sawtooth wear.
Driving with the wrong tire pressure
Insufficient tire pressure causes the tire to flex in the middle and wear out at the edges as a result. Excessive pressure in the tire leads to the opposite effect - its middle part wears out. It is authentically known that it is impossible to create an ideal tire. If you make it economical, it will be too rigid and unsafe. Conversely, a soft, durable tire with good grip will inevitably have increased rolling resistance. Manufacturers strive to find the best solution, but in any case it will be a compromise between durability, reliability, safety and economy.
Source: www.avtoregion36.ru/information/article/iznos
Irina Zverkova
Estimated reading time: 4 minutes
RIA Novosti
Tires are one of the most important components of a vehicle to ensure driving safety. Proper use of summer and winter tires during the season improves handling and saves the car owner money. But some drivers not only postpone changing tires depending on the weather, but also continue to use the same tires for several seasons. At the same time, wheel wear becomes more and more, and the threat that the tires will not cope with holding the car increases.
The tire tread is responsible for connecting the car to the road. This is the outer layer of rubber, which contains a certain pattern, suitable for different operating conditions. For summer tires, the removal of water from the contact patch is relevant, for winter tires - improved grip on slippery surfaces, for off-road tires - maximum cross-country ability. Regardless of the purpose of the tire, one of the important characteristics of the tread is its height or depth. This is the distance from the outer edge of the tire to the "bottom" of the groove. For new modern car tires, the height starts from 5 mm. For ordinary summer passenger tires, this value is 6–8 mm, for winter tires it is 8–10 mm, for SUVs it is 15–20 mm.
When the tread wears out (reducing its depth), the driving properties first of all suffer: the car is more prone to aquaplaning. Winter tires lose some of their properties, which are provided by special sipes and studs. It is important to consider that different brands and models have different rubber composition, so some wheels “run” longer. The driving style also affects wear - more aggressive starts and active braking shorten the life of the tire.
9 is considered critical for tire wear0115 tread height of 1.6 mm for summer tires and 4 mm for winter .
Height can be measured using the ruler with the depth gauge or caliper.
Those who do not have such tools can use a regular 10-kopeck coin placed in one of the grooves. If the word "kopecks" is hidden, it means that the tire is almost new and does not require replacement. If the tread covers only the floral ornament on the winter tire, then it will soon need to be changed; if it’s in the summer, the replacement will have to wait. If only the rim of the coin is hidden, you need to urgently install new tires.
On the left is a worn tire, on the right is a nearly new tire. Photo: AiF / Irina Zverkova Many modern manufacturers make wear indicator on tires (this is a protrusion located perpendicular to the axis of rotation of the tire) or lay a special colored layer that becomes visible when the tire is erased. Their manifestation serves as a signal for the car owner to change tires.
It is important to monitor not only the tread depth, but also the wear uniformity . To be sure that the wheel is in good condition, it is better to measure the tread depth at different places around the circumference along the entire width of the tire. If the inner or outer part is worn out more, then the wear of the tread is taken into account at a minimum value, and it is better for the owner to check the wheel alignment / collapse of the car.
If the vehicle has frequently been driven on bumpy roads, climbed curbs, or the tires have been run half-flat, the sidewalls may have dents, cuts, or cracks that are not completely broken through. It is better to check their condition at the tire shop before the wheel is flat at the most inopportune moment. For example, it may not withstand the loads in a turn, burst and provoke an emergency. You should be especially careful about such damage on low-profile tires.
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