What are Flat Spots on Tires?

Most drivers know that maintaining their vehicle is crucial in ensuring longevity, optimal performance, and cutting running costs. However, few people take care of their tires and assume that they will do the job fine, regardless of the way they are treating them.

Well, the tires on your car also require special care to ensure optimal performance and longevity. Only in this case, their well-being is even more important, as it's directly correlated to safety. A badly-treated tire can seriously worsen the handling performance of your vehicle and might even lead to a blowout while you are driving on the highway.

A very common issue with tires is flat spots. These spots are a flat part of the tread that is worn more than other areas due to various issues. And while you would think that flat spots are benign, they can be a real safety concern. In most cases, you will actually need to replace the tire that has a flat spot, which also has financial consequences.

Understanding Flat Spots

Let's get into more detail and see what flat spots are, how you can prevent them from happening, and of course, what you need to do if you spot a flat spot on one of your tires. 

1. What are Flat Spots on Tires?

Flat spots on tires refer to areas on the tire's surface that have become flattened or deformed due to certain conditions or actions. In that sense, flat spots are a type of uneven wear, where some parts of the tread wear faster than others. A tire with regular wear would have all the tread wearing down evenly.

These irregularities typically manifest as a pronounced thumping noise or unusual vibrations when driving, particularly at high speeds. You can also spot more severe flat spots on one of your tires.

2. The Science Behind Flat Spots

The pneumatic radial tire is essentially a reinforced rubber casing filled with air, designed to carry the weight of your vehicle, absorb shocks, and deal with the forces of driving (acceleration, braking, cornering).

Tires are specifically designed to be used, i.e., to cover miles. Driving distributes all forces across the tire, ensuring regular wear. Moreover, it helps with the tire's flexibility by redistributing the essential oils and keeping them at working temperature.

However, if the tire isn't used for prolonged periods, it will start to lose its flexibility, and it might start to wear irregularly or deform. Usually, not using your tires results in flat spots.

Main Causes of Flat Spots on Tires

Flat spots are a common issue on trailers and motorhomes that were parked for longer periods, but they can also arise on regular cars. Let's dive into more detail.

1. Vehicle Parked for Prolonged Periods

One of the most common causes of flat spots is prolonged parking or storage. When a car is left parked for an extended period, the tires carry the weight of the vehicle on a particular spot, leading to the creation of flat spots.

Flat spots are even more likely to happen in colder temperatures. Remember the flexibility that is so important in keeping your tires from deformation? Well, if the ambient temperature is lower, the tires will become stiffer, increasing the risk of flat spots appearing.

Even parking for the night in extremely cold conditions could cause temporary flat spots, usually referred to as 'morning flats.' However, these are typically temporary and round out after a few minutes of driving as the tires heat up and regain their pliability.

2. Extreme Braking

Although a less common occurrence on modern vehicles with ABS systems, extreme braking can also cause flat spots. This is especially true for old cars without ABS, where under extreme braking, only one part of the tread will touch the ground.

The skidding that occurs under braking creates higher friction on a certain spot of the tread, accompanied by an increased temperature. This heat can soften the rubber in the tread, and when combined with the abrasive action of skidding, it can wear off, creating a flat spot.

However, the ABS system in modern cars largely alleviates the issue, as it prevents the wheels from locking up under braking by pulsating them. This helps mitigate flat spots, but it's also crucial for safety, as it ensures the vehicle is still drivable.

Spotting the Symptoms of Flat Spots

1. Visual Indications

Severe flat spots can be clearly visible with the naked eye, though you can also spot less severe flat spots upon closer inspection. Look for one section of the tire that is visibly flatter or more worn out than the rest of the tire's circumference. The tread in that area could be visibly reduced, hinting at unusual wear, i.e., a flat spot.

You can also use a tread depth gauge to measure various areas of your tire. If one horizontal area has a shallower tread depth than the other, it indicates that a flat spot has started appearing. With this gauge, you can also spot other irregular wear issues.

However, there is no denying the fact that a professional tire technician will notice these things much more easily. This is particularly true if the tire is removed from the rim and put on the balancing machine, which will immediately show irregularities in the weight distribution.

2. Feeling the Flat Spots Through Driving

Aside from the visible signs, you can detect the presence of flat spots while driving. You will need to be concentrated and engaged in spotting the tactile feedback the tires give you if the flat spot just starts appearing.

Look for an uneven ride and vibrations that can be felt in the steering wheel, especially at higher speeds. If your vehicle starts to shimmy or shake when you hit a specific speed, it could be due to flat spots. However, this behavior could also indicate a badly balanced tire. Thus, I recommend inspecting the tire visually after feeling the symptoms to ensure it's a flat spot.

Furthermore, a loud rhythmic thumping or rumbling noise can also be caused by flat spots. This noise is created by the flattened part of the tire hitting the road, creating a thump for each rotation. The faster you go, the quicker the thumping.

The Impact of Flat Spots on Vehicle Performance

Flat spots can significantly impact the performance of your vehicle and make it less enjoyable to drive, less safe, and more expensive to run.

1. Compromised Handling

A tire with flat spots does not have a uniform contact patch with the road, which can negatively affect the handling, particularly when cornering.

Namely, since one part of the tread is worn down more significantly, it could result in a sudden loss of grip in the corners, which could destabilize your vehicle. This is particularly true in wet, snowy, and icy conditions, where the shallower tread grooves will lead to much less traction.

Steering response and precision might also take if a flat spot appears on your front tires. Namely, the steering will be irregular and unresponsive at times, which leads to worse precision.

2. Safety concerns

Light flat spots only reduce grip and traction, which is a safety concern in itself, but severe flat spots can lead to blowouts. Namely, the excessive wear on the flattened section weakens the tire's structural integrity, making it more vulnerable to damage and puncture. The increased wear can also lead to tread separation, wires becoming visible, bulges and cracks appearing.

The real problem with all these scenarios is that they usually appear at higher speeds, during hard braking, or fast cornering. And when they happen, there is usually no previous notice – it all happens in an instant. Blowouts will spin your car out of control, which could result in a costly accident where people can get seriously injured.

3. Effect on Fuel Economy

Although it seems counterintuitive, the science says that flat spots can also detrimentally affect fuel economy. Namely, the flat spot on the tread of your tire creates added rolling resistance, which makes the engine work harder to maintain the same speed, increasing fuel consumption.

Rolling resistance is directly related to the amount of contact between the tire and the road surface. As such, the more severe the flat spot, the greater the rolling resistance and, consequently, the higher the fuel consumption. This means that ignoring flat spots can lead to higher costs at the pump over time.

Can Flat Spots be Fixed?

Like with every other damage on your tires, the potential to fix flat spots depends on the severity of the issue.

Most of the time, minor or temporary flat spots caused by your vehicle sitting for a few days in the parking lot will resolve by just driving the car. This usually happens when drivers leave their vehicles at the airport for a week or so and then go on a holiday.

Of course, the temperature plays a big role here, and if it is too low, the tire might not return to its original, rounded shape.

This is unlikely to happen if your vehicle has been parked for a week, but leave it for a month, and the flat spots will almost certainly stay there, even after driving for hundreds of miles. These are called permanent flat spots, which can also be caused by extreme braking.

Fortunately, in some cases, permanent flat spots can be fixed using a process known as "force variation balancing" or "road force balancing," which can help. This procedure is only available to professional technicians, who use specialized equipment that applies pressure to various parts of the tire while it rotates, essentially 'massaging' out the flat spot.

With that said, the technique doesn't always work. Therefore, it's crucial to talk to your tire technician for the best course of action, as he will be able to tell if you can repair the flat spot or whether you'll need a new tire.

Preventative Measures Against Flat Spots

You can, fortunately, minimize the chances of flat spots appearing on your tires. Follow these simple rules, and your tires will last you for years!

1. Avoid Long Periods of Inactivity

Your car is meant to be driven, so make sure you drive it at least once every few days. That way, you will ensure that flat spots won't appear on the tires, but driving also helps all other components lubricate and prolongs their lifespan.

2. Use Flat Stoppers

Flat stoppers are a cheap and ingenious solution that distributes the weight of the car over a larger tread area, reducing the pressure over one spot. Just make sure that you buy flat stoppers for your particular tire size for the best performance.

3. Put Your Car on Jack Stands for Long-Term Storage

Flat stoppers are a great gadget, but they only work for up to a month. If you have a classic car that you don't intend to use in the coming months, the best course of action would be to lift it and put it on jack stands. This would take the weight off the tires entirely and completely eliminate the chances of flat spots developing.

4. Maintain Proper Tire Pressure

Underinflated tires are at a higher likelihood of flat spotting as they have a larger contact patch with the ground when stationary. Therefore, always ensure your tires are inflated to the manufacturer's recommended pressure. This will not only ensure their longevity but also ensure the most optimal performance.

5. Rotate Your Tires Regularly

Regular tire rotation can greatly minimize any type of irregular wear appearing, including flat spots. I recommend rotating the tires at 5,000-8,000 miles or at each oil change for convenience.

6. Avoid Hard Braking

Sometimes you might need to brake hard, but most drivers do panic stops when there is no reason for that. Braking gradually or at the limit of traction will give you similar stopping distances yet ensure that no flat spots appear.

Conclusion

Flat spots can be a nightmare and a serious safety concern if you don't tackle them on time. For that reason, look at your tires once in a while and be attentive while driving. Listen to the noises coming from your vehicle's underpinnings and feel the vibrations – it is your duty as a driver!

But what is your experience with flat spots? Have you ever had one? If yes, how severe was it, and was the tire technician able to repair the flat spot? Tell us in the comments below!