Should all tires have the same pressure?

A vehicle’s tires are one of the most important parts of a vehicle- they are the primary link between the vehicle and the road itself. Tires carry out a number of vital functions ranging from the provision of a proper grip to the management of overall steer and direction. Keeping this in regard, it is essential that the regular maintenance of tires be done routinely to accommodate safe driving. One of the aspects that comes under this topic is the regulation of tire pressures. A question that comes under under this heading is “should the pressures of all the tires be equal?”

The following article seeks to answer this very question while offering a general insight into facts associated with tires as well as bring awareness to the dangers of under/over filled tires.

What is tire pressure and what should its value be?

To put it simply, tire pressure is a measure of the amount of air in a tire. Its value is measured in pounds per square inch or PSI. For 90% of the cars (which have standard passenger tires) the recommended tire pressure ranges between 30 to 35 PSI.

Some cars may have a different pressure on the basis of the manufacturer. To know the exact tire pressure for your model, try to look for a label/sticker which is printed inside your car door. If your car is of an older model, you should be able to find this in the owner’s manual.

Should all the tires have the same pressure?

Or more specifically, “should the front and rear tire pressures be the same”. Normally the pressures in the front tires are higher than the rear ones. However, there are exceptions to this rule. The pressure can change in accordance to many factors, some being:-

1. Powertrain configuration of vehicle

As for FWD (front-wheel drive) models, the layout causes the engine to drive the front wheels only. These vehicles have more weight in the front, not only because of the engine but also due to the additional weight shift to the front during braking. Therefore, in these cars, tire pressures of the front wheels are higher. On the contrary, RWD (Rear-wheel drive cars) have higher pressures in the back, same principles apply. A number of cars also have an appreciable 50:50 configuration; with equal weight on both ends. On the other hand AWD (all-wheel drive) vehicles require a completely unique set of tires, the details of which have been presented in our article Best tires for AWD SUV.

2. The load in a vehicle

Tire pressures can change with respect to the load in a vehicle. Therefore, if you’re carrying lots of passengers or luggage in your car, the pressure of the rear tires must be increased in order to compensate for the decrease in ride height on the rear.

3. Safety prospects

Some manufacturers recommend lower pressures on the front in order to increase the contact area (allowing a better grip). This condition favors the understeer which, as opposed to oversteer, is much safer in most circumstances. Alternatively, other manufacturers (eg: BMW) recommend lower pressures on the rear to favor rear traction. This is to provide better acceleration, handling as well as lowering the chances of uncontrollable over steer.

4. Driving style

Sports cars for example use a higher than normal pressure (40-45 psi) on the front and normal values on the rear. This is done to accommodate the rather haphazard driving style. Normal cars obviously do not require this. Ideally, the owner should adjust the pressures on the basis of technicality rather than generalization.

5. Manufacturer recommendation

It is important to note that minor pressure differences in the tires are not significant unless the manufacturer specifies that they are. Most cars are not set as to require a specific calibration of different tire pressures. Unless the driver plans on driving in special conditions that require particular modifications, it is recommended that one should stick to the manufacturer recommendations.

What are the effects of inappropriate/incorrect tire pressures?

Ensuring correct tire pressures helps in numerous ways. Not only does it increase the life expectancy of the tires, but it also helps in getting good gas mileage. According to the EPA (US environmental protection agency), properly inflated tires can increase fuel efficiency by 3% or more. 

Furthermore, taking care of your tires can prove to be cost-effective over time; as there are fewer punctures/wear out, the owner saves on both fuel and maintenance costs. Enlisted below are the effects of incorrect tire pressures.

1. Over-inflated tires

These tires are more susceptible to damage from road irregularities. Other than reducing vehicle performance they also create a “bumpy” uncomfortable ride. In addition to that, excessive air pressures can distort the shape of the tire, leading to increased wear and tear down.

2. Under-inflated tires

According to the NHTSA (National Highway Traffic Safety Administration), driving on underinflated tires increases a driver’s chance of being in a serious accident by 300%.
Low tire pressure can also cause a car to be less responsive and have less traction, making it more difficult to avoid emergency situations (i.e switching lanes last minute or seeing an old pedestrian crossing the road). They also possess an increased risk of having a blowout. The lowest tire pressure you can generally drive with is 20 PSI. Anything under this puts you at risk for a life-threatening blowout.

Lower pressures also accommodate hydroplaning. This occurs when water seeps into the car tires faster than it can be removed. When this happens the car is said to be raised on a thin film of water effectively causing a loss in traction which then leads to a diminished contact with the road.

Additional Guidelines

-The importance of maintenance checks cannot be further stressed. All car owners must ensure that tire checks are done routinely. If you have a relatively modern car, the monitoring system will alert you, however for those who have an older car model, check your tire pressure at least once a month.
-Do not just “look” at a tire and assume it to be “perfect”. Tire pressure can be lost without a tire appearing under-inflated or flat. Put in the effort or get it checked!
-Do not inflate your tires to the pressure listed on the tire itself. That number is the maximum pressure the tire can hold, anything beyond could result in a potential burst.
In the end, one must be mindful and incorporate strict checks habitually. By being vigilant and taking precautions you not only help yourself, but you also help keep your community safe. After all, if something is risking one’s life, the matter cannot be compromised upon.

If you liked this article, we recommend you read Do new tires improve gas mileage?

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