How Does Air Pressure Affect Your Tire Performance? Imagine cruising down the highway, feeling the grip of your tires on the pavement, ensuring a smooth and secure ride. But did you know that the air pressure inside those tires plays a pivotal role in dictating the performance, safety, and longevity of your vehicle? Inappropriate tire pressure can be a silent saboteur, leading to a slew of unfortunate consequences. From compromised handling to decreased fuel efficiency and even potential tire blowouts, improper air pressure can literally deflate your driving experience. In this article, we’ll delve deep into the science and mechanics behind tire pressure, unpacking the reasons why maintaining the right tire pressure isn’t just a recommendation—it’s a necessity for every motorist. Stay tuned and prepare to be enlightened on a topic that every driver should prioritize!
Table of Contents
Results: Tire Pressure Effects
Results below were taken from the 2023 Vibilagare Wrong Tire Pressure Test. A total of 3 different tire pressure were tested this time around with a Audi A4 Avant. With a recommended OE tire pressure at 2.4bar (35 PSI), the low & high pressure was set with a 0.7 bar (10 PSI) difference. The graph below shows the comparison between Low Pressure (1.7 bar) vs Normal Pressure (2.4 bar) vs High Pressure (3.1 bar) based on the relevant performance category. The Normal Pressure (2.4 bar) was set as a reference hence at the 100% mark.
Note that for subjective comfort evaluation, we equate 1 point as 5%. While for the noise test we equate 0.1 dB difference as 1%. The tire size of interest is a 245/40 R18 which is a common tire size for Audi A4 & Mercedes C-Class. You can check out our latest tire size table for more information. The testing vehicle of choice is a Audi A4 Avant.
Comparing Wet Performances of Different Tire Pressures
When it comes to tire safety and performance, especially on wet roads, air pressure plays a pivotal role. Let’s dive deep into the comparison of wet performances across three different tire pressures: Low (1.7 bar), Normal (2.4 bar), and High (3.1 bar).
1. Wet Braking:
- Low Pressure (1.7 bar) : 92%, 25.8 meters
- Normal Pressure (2.4 bar) : 100%, 23.7 meters
- High Pressure (3.1 bar) : 100%, 23.67 meters
Observation: The stopping distance shortens as the tire pressure increases, with the high pressure tire having the shortest wet braking distance.
2. Wet Curve (lap time, cornering grip):
- Low Pressure (1.7 bar) : 97%, 11.9 seconds
- Normal Pressure (2.4 bar) : 100%, 11.56 seconds
- High Pressure (3.1 bar) : 99%, 11.64 seconds
Observation: Normal pressure tires provide slightly better cornering grip as evidenced by the shorter lap time. However, the high pressure tire’s performance is quite close.
3. Aquaplaning (slipping speed):
- Low Pressure (1.7 bar) : 89%, 72.3 km/h
- Normal Pressure (2.4 bar) : 100%, 80.8 km/h
- High Pressure (3.1 bar) : 104%, 84.1 km/h
Observation: The resistance to aquaplaning, or the speed at which tires begin to slip on wet surfaces, improves notably with increasing pressure. The high-pressure tire demonstrates a superior aquaplaning threshold.
The Science Behind Aquaplaning and Tire Pressure:
A tire with higher pressure tends to become more rounded, akin to the profile of a bicycle tire. This rounded contour allows the tire to cut through the water more effectively, engaging with the road beneath much sooner than a flatter contour tire. As a result, tires with higher pressures exhibit better resistance to aquaplaning. This is clearly evidenced in the above comparison where the high-pressure tire starts slipping at a significantly higher speed.
Trade-offs with High Pressure:
While higher tire pressure has its benefits in wet conditions, it’s essential to note the trade-offs. A tire inflated to a higher pressure will have a reduced contact patch, leading to uneven and accelerated tire wear. This not only affects the tire’s lifespan but can also compromise other performance parameters over time.
Conclusion:
Choosing the right tire pressure is a balance between performance, safety, and longevity. While higher pressures may offer advantages in wet conditions, it’s crucial to understand the associated trade-offs. Regularly check and adjust your tire pressures to ensure optimal performance across different driving conditions.
Comparing Dry Performances of Different Tire Pressures
Driving conditions, especially those on dry roads, can significantly vary based on tire pressures. It’s essential to understand the nuances that differentiate the performances of tires inflated to Low (1.7 bar), Normal (2.4 bar), and High (3.1 bar) pressures. Here’s a detailed comparison:
1. Dry Braking:
- Low Pressure (1.7 bar) : 101%, 33.01 meters
- Normal Pressure (2.4 bar) : 100%, 33.26 meters
- High Pressure (3.1 bar) : 99%, 33.73 meters
Observation: The dry braking distance is shortest with the low-pressure tire. This is likely due to the larger contact area the tire has with the road surface. When the tire pressure is lower, it flattens out slightly, increasing the area that comes into contact with the road, which aids in better braking performance. However, the difference in braking distances among the three pressures is relatively minimal.
2. Subjective Dry Handling (on a scale of 1 to 5, where 5 is best):
- Low Pressure (1.7 bar) : 90%, 2/5
- Normal Pressure (2.4 bar) : 100%, 4/5
- High Pressure (3.1 bar) : 100%, 4/5
Observation: Both the normal and high-pressure tires score equally in terms of subjective dry handling, significantly outperforming the low-pressure tire.
The Science Behind Dry Braking and Tire Pressure:
Lower tire pressures do offer the advantage of a larger contact patch because of the tire’s slightly flattened profile. This is especially advantageous for dry braking, as a greater surface area equates to more traction. Consequently, the braking distance is somewhat reduced with lower pressures, as evidenced in our comparison.
Impact on Subjective Dry Handling:
While low pressure may benefit dry braking, it has a noticeable downside when it comes to steering response and handling. The sidewall of a tire with lower pressure is not as stiff as that of a fully inflated tire. This lack of stiffness can lead to a sluggish steering response and a spongier feel when navigating turns or sudden maneuvers. Consequently, the subjective experience of handling is less favorable with low-pressure tires. This is clear from our data, where the low-pressure tire’s handling score lags behind the normal and high-pressure tires.
Conclusion:
Every tire pressure setting comes with its set of pros and cons. While low-pressure tires may offer slightly better dry braking performance due to their increased contact area, their handling, especially the steering response, suffers. Understanding these nuances can help drivers make informed decisions about their tire pressures, optimizing them based on their driving conditions and preferences.
Comparing Rolling Resistance Across Different Tire Pressures
Tire pressure significantly influences rolling resistance, which in turn affects fuel efficiency and overall vehicle performance. Let’s break down the numbers for the three different tire pressures:
Rolling Resistance :
- Low Pressure (1.7 bar) : 79%, 11.06 N/kN
- Normal Pressure (2.4 bar) : 100%, 8.72 N/kN
- High Pressure (3.1 bar) : 110%, 7.94 N/kN
Observation: As tire pressure increases, the rolling resistance decreases.
Why Does This Happen?
In simple terms, think of rolling resistance as the “friction” or “drag” a tire faces when it moves on the road.
When a tire has low pressure, it’s a bit flatter on the bottom. This “flattening” means more of the tire’s surface touches the road. With more surface area in contact, the tire faces more resistance when it rolls, similar to how it’s harder to drag a flat balloon across a surface compared to a fully inflated one.
On the other hand, when the tire is inflated to higher pressures, it becomes rounder and less of its surface is in direct contact with the road. With a smaller contact area, there’s less resistance as it moves, making it “easier” for the tire to roll.
Conclusion:
Higher tire pressures lead to lower rolling resistance, making it more fuel-efficient and easier for the vehicle to move. However, while it’s beneficial from a fuel economy standpoint, drivers should always adhere to recommended tire pressures for their specific vehicles to ensure safety and optimal performance. Too high or too low pressures can have other adverse effects on tire wear, handling, and overall vehicle safety.
Comparing Interior Noise Across Different Tire Pressures
When driving, tire noise is a factor that influences our driving comfort. Let’s evaluate the noise results across the three different tire pressures:
Interior Noise (80 km/h)-Smooth asphalt :
- Low Pressure (1.7 bar) : 107%, 64.1 dB
- Normal Pressure (2.4 bar) : 100%, 64.8 dB
- High Pressure (3.1 bar) : 86%, 66.2 dB
Interior Noise (110 km/h)-Smooth asphalt :
- Low Pressure (1.7 bar) : 108%, 67.5 dB
- Normal Pressure (2.4 bar) : 100%, 68.3 dB
- High Pressure (3.1 bar) : 91%, 69.2 dB
Interior Noise (70 km/h)-Groove asphalt :
- Low Pressure (1.7 bar) : 108%, 69.4 dB
- Normal Pressure (2.4 bar) : 100%, 70.2 dB
- High Pressure (3.1 bar) : 94%, 70.8 dB
Observation: At all speeds and road surfaces, as tire pressure increases, the interior noise levels also increase.
Simple Scientific Explanation:
Think of the tire as a speaker. When a tire rolls on the road, it creates vibrations. These vibrations are what we hear as noise inside the car.
When a tire has low pressure, it’s softer and a bit flattened. This softness allows the tire to absorb more of the vibrations, similar to how a soft cushion might absorb sound. As a result, less noise is transmitted into the vehicle.
Conversely, a high-pressure tire is harder and rounder. Because it’s harder, it doesn’t absorb the vibrations as well. Instead, it transmits more of those vibrations, which translates into increased noise levels inside the vehicle. The harder surface of the tire essentially amplifies the vibrations caused by the interaction between the tire and the road, making it louder inside the car.
Conclusion:
While higher tire pressures may offer benefits like reduced rolling resistance, they can lead to increased noise inside the vehicle. This is a trade-off drivers might need to consider when optimizing tire pressures for comfort and performance. As always, it’s essential to maintain pressures within the recommended range for safety and overall vehicle performance.
Tire Wear and Its Connection to Tire Pressure
Tire wear is a critical aspect of vehicle maintenance. The longevity of your tires, and by extension, your safety on the road, can be significantly influenced by tire pressure. Though we don’t have specific test results to reference right now, countless studies in the past have indicated a clear relationship between tire pressure and wear.
Let’s delve into this:
- Under-Inflation (Low Pressure) Simple Explanation: Think of an under-inflated tire as a squished balloon. The sides (or edges) of the balloon touch the ground more than the center. Scientifically Speaking: When a tire is under-inflated, it doesn’t retain its perfect round shape. Instead, it flattens out a bit, causing the outer edges of the tire to make more contact with the road than the center. This results in accelerated wear on the edges or shoulders of the tire.
- Over-Inflation (High Pressure) Simple Explanation: Now, think of an over-inflated tire like an overly full balloon. The center bulges out more than the sides. Scientifically Speaking: An over-inflated tire becomes too round, causing the center portion of the tire to protrude outwards slightly. This means the center of the tire bears more of the vehicle’s weight and consequently comes into contact with the road more than the edges. This leads to faster wear in the middle section of the tire.
In Essence:
Tire pressure affects how the weight of your vehicle is distributed across the tire’s surface. Ideally, you want an even distribution for uniform wear. Both under-inflation and over-inflation disrupt this balance, leading to uneven and premature tire wear.
Conclusion:
Ensuring the right tire pressure isn’t just about vehicle performance or fuel efficiency; it’s also about maximizing the lifespan of your tires and ensuring safety. Regularly checking and adjusting tire pressures to remain within the manufacturer’s recommended range is crucial for every driver.
Conclusion from a Tire Expert’s Perspective:
Having been in the world of tires for years, I can’t stress enough how crucial the right tire pressure is. It’s a fine balance – not too much and not too little. Every tire tells a story, and those that have been maintained with proper pressure narrate tales of longevity, safety, and optimal performance. Conversely, those neglected sing a lament of premature wear, compromised safety, and inefficient fuel consumption.
If there’s one piece of advice I’d give any driver, it’s this: make it a habit to check your tire pressures. And not just sporadically or when you remember, but diligently, at least once a month. It’s a small act, but one that could save you money, extend the life of your tires, and most importantly, keep you safe on the road.
Stay safe, and keep those tires in check!
Dr Edwin Pang