What Tire Pressure Is Too Low?

Tires.

The most important yet most obviously neglected part of everyone’s cars.

In reality, they should be checked every week or so. Yet, most people will only look two or three times per year or perhaps before a long journey.

Tires are the contact point between your car and the road. If the pressures are too low or, even worse, you suffer a blowout, it can be a costly and dangerous situation.

So, what pressures should your tires be? Why is it important to keep them topped up? And what tire pressure is too low?

This guide will answer all your questions. Let’s get started!

What Tire Pressure Is Too Low To Drive On?

Look in your owner’s manual or the metal plate in your driver/passenger doorframe. This will tell you precisely what tire pressures your car’s tires should be, depending on loads. Anything other than these is too low or too high.

The average car generally takes between 28 and 37 PSI, although these can vary from model to model. As mentioned, don’t take that as gospel. Check your owner’s manual!

Don’t read the pressures off the side of the tire wall – this is just the maximum recommended amount for the tire. It’s nothing to do with your specific car, and you’ll end up overinflating it (which can be just as bad).

Front tires are often set to higher pressures than rear tires, especially in front-wheel-drive cars. The front wheels do all the work and therefore wear down much quicker.

Rear tires could be as much as 5 PSI (or more) lower than the fronts.

If your tire pressures are anything other than the recommended amounts in the owner’s manual, top them up. It’s worth purchasing an in-car tire inflator. This plugs into your 12 V circuit and means you can always top your tires up from anywhere. It also saves you a dollar each time you visit the gas station.

Failing to top them up will cause more damage than you might expect!

What Is The Lowest Tire Pressure You Can Drive On?

The lowest pressure you can drive on is whatever your owner’s manual/in-car informational plate tells you. This always applies. Anything other than the optimal would be under or over-inflated. The further away you are from that figure, the more dangerous it is.

Anything below 25 PSI would be considered dangerously low, causing damage to your tires as you’re driving.

If your tire has reached this level, top it up with air and see if it holds the pressure overnight. If it doesn’t, you’ll need to drive – slowly! – to a nearby tire shop. If you can put your spare wheel on, that’s a much safer option.

Failing that, you could try using a callout service. Many companies will now fit your tires on your driveway or at your place of work.

If your tire pressures are too low, don’t risk it. Take the tire to a mechanic so they can check it out.

A mechanic will first have a visual look over your wheel to see if they can spot any punctures or hear any leaks. If they can’t find the problem, they might remove the wheel for some further tests, such as the bubble check. Here, the wheel and tire are submerged underwater. If there are any leaks, they’ll cause air to bubble up to the surface.

Why Are Low Tire Pressures Dangerous?

Check out the above video to see what mechanics deal with daily.

If you run a car with too low tire pressure, the car’s weight puts too much strain on the rubber. This makes it heat up.

Once it gets too hot, the rubber within the tire will start to degrade physically. It doesn’t take long for a sort of black sand to develop within the tire. Once this has happened, you’ll definitely need a new one. There’s no saving it.

As the rubber breaks down, it becomes less and less able to trap the air within. Eventually, it’ll degrade to the point of causing a blowout – a dangerous situation for you, your passengers, and other road users, not to mention damaging your car’s wheels, suspension, and drivetrain.

Signs Of Low Tire Pressure

Low tire pressures are never good. Keeping them topped up with air will save you from the potential signs and consequences listed below.

You can check your tires for obvious pressure losses by simply looking at them and pushing the sides with your thumb. If you feel significant give, they’re too low.

Have a tire pressure gauge in your car at all times so you can check the pressures and know for sure whether they’re too high or too low.

Poor Fuel Economy

When a tire’s pressure is too low, the surface area in contact with the road will drastically increase.

The rubber essentially sticks to the road. It’s supposed to do this. That’s what keeps you on the road most of the time, after all.

However, when too much rubber is “sticking” to the road, it’ll act as an opposing force to your car’s movement. As a result, it takes more engine power to travel at the same speed or accelerate at the same rate.

Because of this, your fuel economy will quickly plummet, especially if multiple tires are significantly low.

Increased Tire Wear

Tires with low pressure will wear out much quicker than properly inflated tires.

This happens for the same reason: too much tire is “dragging” along the road. It’s literally being stretched and manipulated as it rolls over the asphalt surface.

Watch for wear on both the inside and outside of the tire.

As the rubber tread wears down, the tire’s condition will rapidly deteriorate. This will force you to purchase a new tire (or tires) much sooner than you expected.

Unbalanced or out-of-alignment wheels can also cause different types of tire wear.

Blowouts

The above video is a somewhat extreme example of a blowout. Still, these types can happen in high-pressure tires (for example, those on trucks).

A blowout is when the tire rubber loses its structural integrity and air “blows out.”

These usually happen while traveling at high speeds. The tire is simply under too much stress to cope, leading to a blowout.

Blowouts are often caused by running on a low tire for some time. This weakens the tire wall, eventually to the point that it can’t contain the air pressure.

A blowout is incredibly dangerous, and you might need to fight to maintain control in serious circumstances.

If you suffer a blowout, pull over on the side of the road and call for breakdown assistance.

More Difficulty Turning, Especially At Low Speeds

If your front tires are particularly low, you’ll notice it takes more force to turn the steering wheel. This happens because, again, the tires are “too stuck” to the road.

Too much turning on low-pressure tires could be doing significant amounts of damage, so get air back in as quickly as possible.

Why Do Tires Lose Pressure?

In general, tires are expected to lose some pressure over time.

Although they’re pretty close, most tires don’t have a perfect seal. A small amount of air usually escapes over time, especially when temperatures rapidly change. Cold tires could have fewer PSI than hot tires, even without a leak!

Physics, eh?

If you happen to drive over a screw or a piece of glass, it could cause an immediate puncture and loss of pressure. Sometimes, the foreign body sticks in the rubber and actually reseals the tire, preventing any air from escaping.

However, it still needs to be removed.

When it comes to punctures, you’ll either need a puncture repair or a new tire. This depends on the location. You can get it plugged if it’s in the tread’s center, more than an inch from the tire wall. If not, you’ll, unfortunately, need a new tire.

Tires could also lose air due to slow puncture. This might be a minuscule crack or leak around the bead (where the tire wall pops onto the metal wheel).

Slow punctures mean the air’s escaping slowly, so they don’t present the same immediate danger as a standard puncture. However, they must still be immediately fixed. Drive to your nearest garage straight away.

Tires can also develop leaks through the valve. If the valve cap goes missing, dirt or debris can get in and cause damage. Likewise, the rubber of the valve itself can break down.

How Does TPMS Help?

TPMS stands for Tire Pressure Monitoring System. It’s a system within your car that notifies you of any changes in tire pressure.

It comes in two types: direct and indirect.

Direct TPMS uses an advanced valve containing a sensor that sends a live reading of the tire pressure on each wheel to the ECU. If there’s a sudden change, the car will activate the tire pressure warning light.

Indirect TPMS doesn’t contain any fancy extra valves or technology. It’s wired up to the ABS sensors. When these detect a significant speed difference between the two wheels on each side of an axle, they cause the dashboard warning light to illuminate.

Direct TPMS is far more reliable than indirect TPMS. Indirect TPMS is often incorrect when it causes the light to come on. However, it’s always important to check.

Manufacturers might use either direct or indirect TPMS. While direct TPMS is undeniably more accurate, it’s a much more expensive system. It also means you must always replace tires onto the same wheel they came off.

In short, yes. TPMS does help by informing you of any sudden changes in tire pressures. However, indirect TPMS often thinks there’s a puncture when there isn’t.

Conclusion: What Is Considered Low Tire Pressure?

As with many things, the answer is relatively simple. Consult your owner’s manual, and don’t settle for anything less (or more) than it says.

By keeping your tires at the correct pressures – not too low and not too high – you’ll have much-improved gas mileage, and your car will be much safer to drive.

Finally, when it’s time to get new tires, don’t put it off. It might cost a few hundred dollars, but it could save you thousands.