Why is Tyre Pressure Important?

Tyre pressure is a critical factor for vehicle performance and safety. The incorrect adjustment of tyres can compromise driving safety, increase fuel consumption and lead to economic losses.

Importance for Security Purposes

• Braking distance: Low-pressure tires increase the surface area of the road, but they also extend the distance to stop. High pressure causes the tyre’s centre to wear faster, and the road grip is reduced.
• Cornering safety: An incorrect pressure can cause the vehicle to behave in an erratic manner when turning. This can increase rollover risk, especially for SUVs and commercial vehicle.
• Blowout risk: Extremely low pressure can cause heat to build inside the tyre. This increases the blowout risk.

Performance and Economy

• Fuel consumption: incorrect pressure increases rolling resistance. The engine will use more power.
• Tyre life: Low or high pressure can cause excessive wear on certain parts of the tire. Tires that are inflated correctly can last up to 20 percent longer.
• Driving confort: Underinflated tyres cause the vehicle to sway. Overinflated tyres can make bumps and potholes feel more harsh.

Manufacturer Recommendations

The vehicle manufacturers provide the optimal tyre-pressure values for their models to ensure maximum road holding, comfort and safety. This information can be found on a sticker inside the driver door or in the user manual.

Experts say that even a pressure of 1 bar (14.5 PSI or approximately) below the recommended level can reduce tyre lifespan by 25 percent.

Should the Front and Rear Tyre Pressures of the Vehicle Be the Same?

The pressures in the front and rear tires of a car are normally different. This is mainly due to the weight distribution of the vehicle and its usage. The engine being located mainly at the front of the vehicle, the front tyres are under more pressure. Manufacturers may therefore recommend slightly higher pressure values for front tyres compared to rear tyres.

Why Should It Be Different?

• Weight distribution: In the front section, you will find engine weight, steering weight and driver’s bodyweight. The front tyres are therefore heavier.
• Road holding: A correct pressure differential improves road holding and balance of the vehicle when turning.
• Even wear: Correctly adjusting the front and rear pressure values will ensure that tyres are worn evenly. This extends tyre lifespan.

In Which Situations Are They the Same?

• In some passenger vehicles, the load distribution may be balanced and the tyre values at the front and back are equal.
• In small volume vehicles, the manufacturer may recommend a single value for pressure (e.g. All tyres should be inflated to 2.2 bars.

Differences Based on Load Status

• Unladen vehicle: Front tyres are generally inflated slightly more than rear tyres.
• Fully loaded vehicle: As the load on the rear tires increases, the rear pressure must also increase.

Summary: This chart is available on the door label or in the owner’s manual. This chart can be found on the door labels or in the owner’s manual.

What Should the Tyre Pressure Be?

What is the recommended tyre-pressure in bars? This depends on the type and size of tyre, the load conditions, and how you use your vehicle. The recommended values for passenger vehicles are generally between 2.1 and 2.4 bar (30-36PSI). Nevertheless, it is important to take into consideration the value specified by the manufacturer for each vehicle.

Average Pressure Values

• Passenger cars: 2.2 – 2.4 bar range.
• SUVs: 2.3 – 2.6 bar range.
• Light commercial vehicles: 2.8 – 3.1 bar range.
• Heavy commercial vehicles: 4.5 – 6.9 bar range.

Factors Affecting Pressure

• Tire size: Different sizes of tyres have different pressure values, for example 185/65 R15 and 205/55 R16.
• Load condition: If the vehicle is fully loaded, pressure should be increased 2-3 PSI.
• Seasonal conditions: Temperature changes cause pressure to fluctuate. Pressure changes by approximately 1 PSI for a 10°C temperature difference.

Effects of Incorrect Pressure

• Low pressure: Increases fuel usage and wears the shoulders of the tyre.
• High pressure: Decreases comfort, and wears the centre of the tire quickly.
• Uneven pressure: This causes the steering wheel pull to one side, resulting in unsafe cornering.

The tyre-pressure table is located on the inside of the vehicle’s door. For the most accurate answer, check it.

How to Read the Tyre Pressure Chart?

This chart will give you the best information on the recommended pressures for your vehicle’s front and back tyres. This chart can be found in either the owner’s guide, on a label on the driver’s side door or on the cap of the fuel tank.

Points to Note When Reading the Chart

• Units: Table values will be given in BAR and PSI. 1 BAR = 14.50 PSI
• Vehicle condition: Different pressure values are specified when the vehicle is loaded or unloaded.
• Front and rear tires: The table shows clearly the different pressures for front and back tyres.
• Tire sizes: Different pressure values are assigned to different sizes, such as 185/65R15 or 205/55R16

Ideal Tyre Pressure for SUVs and Passenger Cars

There are differences in the tyre-pressure values of SUVs and cars. The differences are due to the weight of the vehicle, its load distribution, and its intended use. In passenger cars, comfort and fuel efficiency are the most important factors. However, in SUVs weight and balance are more important.

Tyre Pressure in Passenger Vehicles

• Average values: Front and rear tyres are 2.2-2.3 bars, respectively.
• These values are designed to balance fuel consumption with increased driving comfort.
• The front and rear tire pressures of small and medium sized cars are typically similar.

Tyre Pressure in SUV Vehicles

• Average values: Front and rear tyres are 2.3-2.5 bars, respectively.
• SUVs are heavier, and they have a different distribution of load. This means that the pressure on them is greater than it is for passenger cars.
• It is important to increase the rear tyre pressure, particularly in SUVs that are fully loaded.

Why is it important?

• Low pressure in SUVs can cause the sidewalls of the tyres to stretch excessively, increasing the risk of a blowout.
• High pressure in passenger cars compromises comfort, and wears out the center of the tyre quickly.
• Correct pressure reduces the braking distances in both types of vehicles and increases cornering safety.

Note: There’s no one answer to the question “What pressure should I use on my SUV’s tyres?” The best information comes from the manufacturer’s recommendations, which are usually found on the inside of the door.

What Does a Car Tyre Pressure Warning Mean?

Tyre Pressure Monitoring System (TPMS), found in most modern cars, continuously monitors each tyre’s pressure and alerts drivers in the event of a critical fall. The car tyre warning that appears on the dashboard is displayed as a yellow circle with a tyre or exclamation symbol.

The Meaning of the Warning

• Low pressure: One or more tyres have a pressure that is below the recommended level.
• Sudden pressure drop: The tyre may have a puncture or leak.
• Temperature effect: Sudden changes in the air temperature may also cause a sensor to warn.

What Should You Do When a Warning Appears?

• Parki the vehicle in an area that is safe.
• After parking the vehicle for 3 hours, measure the pressures of cold tires.
• The table of the vehicle manufacturer will tell you how much air to add or how much air to release.
• Visit a service center if the pressure continues to drop.

Important Points to Note

• The TPMS system warns the driver early, but it does not replace manual inspections.
• The warning light cannot be turned off by simply resetting the computer. It is necessary to fix the underlying problem.

Summary: The “tyre-pressure warning” is more than just a light. It’s a reminder to drive safely. The warning light should not be ignored and the tyres should be checked as quickly as possible.

How Should Pressure Be Adjusted When New Tyres Are Fitted?

The performance and life of the tyres can be severely affected if the air pressure when fitting new tyres is incorrect. Correct pressure increases road grip and ensures the tyre is properly seated on the rim.

Steps to Ensure Correct Pressure Settings

• Cold Tyre Measuring: Measure the pressure of your tyres when they are cold. The vehicle must be parked at least three hours.
• Check the Manufacturer’s Chart: Base the values listed on the label of the manufacturer according to the tyre type, vehicle and load conditions.
• Check the pressure in the first 24 Hours: After fitting the new tyres, check the pressure again within 24 hours. When the tyre has been fully seated, there may be some slight differences.
• Use the values listed in the table if you are travelling long distances, or carrying a heavy load.

Why is it important?

• Low pressure: This forces the sidewalls on new tyres and causes premature wear.
• High pressure: Reduces comfort, and wears out the tyre quickly in the middle.
• Incorrect pressure: negatively affects steering control, braking distance and brake distance.

Additional Recommendations

• On newly fitted tyres, the pressure and balance settings should be checked.
• The pressure values for different sizes can vary, such as the 185/65 R15 and 205/55 R16. Therefore, a single standard is not correct.

It is important to note that adjusting the pressure correctly after installing new tyres can extend tyre lifespan by up 20%. This will also ensure safe driving.

The engine fault light is often illuminated in vehicles with advanced engine technology such as the Mercedes-Benz W205 C180. This indicates that there may be a mechanical or electronic issue. A motor that starts to run rough, misfires in the cylinders and error codes P0354/P0300/P0304 on the OBD device are all signs of a serious situation.

Definition of Fault Codes

P035413 – Ignition Coil A Circuit Open Circuit (4th cylinder)

This code indicates that there is a continuous interruption or loss of signal in the coil circuit attached to cylinder 4. This is caused by:

• Contact in the coil socket is poor
• The wiring harness has a break or short circuit
• The ECU is unable to send the signal to coil

P030085: Random Cylinder Ignition Fault

This code indicates that there is an irregular firing of multiple cylinders. Causes:

• Fuel system pressure fluctuations
• Spark plugs, coils or injectors can cause problems
• Combustion chamber problems such as vacuum leaks or compression loss

P030485 – Continuous Ignition Failure in Cylinder 4

This code points directly to the cylinder number 4. This code indicates that the coil and spark plug have been replaced.

• Injector failure
• Wear on piston rings and valves
• Fuel distribution problems

Interventions Performed

• 4 spark plugs replaced
• Renewing 4th cylinder coil
• The fault was cleared, but it recurred

There are other points to be checked

What should be done?

• It is important to read the fault codes again and record them.
• OBD Live Data should be used to check the injection and ignition timing for the 4th cylinder.
• A cable tester should be used to measure the coil socket and wiring harness.
• To see if it helps, swap the injector from the 4th to another cylinder.
• It is important to perform a compression test. If the compression is low, mechanical interventions are required.
• Check the ECU software. In rare instances, software-based errors can occur.

The cause of engine vibration can be more than just a component failure. It may also be the result of the interaction between multiple systems. A problem in a sensitive engine like the Mercedes W205 can cascade to affect other components. Therefore:

• Replace parts only if the fault code is present.
• The system should be analysed holistically, and backed up by live data.

Replacing just one part may not be enough

In most cases, ignition problems (P0300-P0354) on C180 W205 engines can be resolved by changing the coil or sparkplug. If the problem persists this is not enough. This is especially true if the problem persists on the same cylinder.

• Injector test
• Electrical system inspection
• Test of cylinder compression

The rules must be followed without exception.