Finding the correct tire pressure for your car, especially if you’ve changed out your stock tires, is an important safety step. Having tires that are accurately inflated makes you safer and helps to keep your tires from wearing out too quickly.
Your recommended tire pressure depends on several factors, which is why there is no absolutely correct answer to “what tire pressure should my Mustang be at?” Your individual model and tire selection can all affect what the ideal tire pressure is for you.
Tire Information Sticker
Most manufacturers put a sticker on the inside of the driver’s side door that tells you what the correct inflation is for the stock tires. You may also find this placard on the inside of the glove box, or even in the trunk.
This should tell you your original sized tires and the pressure that they should be inflated to in order to support your vehicle’s load. It’s important to use this number rather than the number that’s printed on the tire. Tires are all printed with their max pressure number, which can be useful, but fails to take into account the load that they’ll be under. The manufacturer’s number takes that into account.
On the tire pressure sticker, you should see an ideal tire pressure for the stock tires and also a load capacity. When you’re swapping to new tires, you’ll want to find what tire pressure they’ll have the same load capacity at and fill them accordingly.
How to Read a Tire Pressure Gauge
There are a lot of different types of tire pressure gauges. A digital one will simply tell you the psi. The simple stick gauges work essentially the same way, though they are less precise.
It’s easiest to get an accurate reading on your tire pressure when your tires are cold, ideally after they’ve been parked for at least three hours. Remove each tire’s valve cover and check them individually. With a standard handheld gauge, a little pressure bar will shoot out the bottom and show you the tire’s current pressure, though there are fancier looking handheld options as well.
Digital gauges make this process even easier by giving you a screen reading of your tire’s pressure. Either add compressed air or release air to get to the desired inflation.
Ideally, you should be checking your tire pressure every time the temperature changes by ten degrees or every thirty days.
But what happens if you choose to ignore the warning light and just drive with tires that have a lower pressure, or decide to overinflate your tires in preparation of the coming weather change?
Tire Pressure Is Too Low
Though there are times when you might want to under inflate your tires (track and off-roading are both good examples) most of the time driving on underinflated tires is incredibly dangerous for a variety of reasons.
With a lower tire pressure, more of your tire is making contact with the road (if you look at your car from behind you’ll notice that the tires slightly flare out as they touch the road). More tire contact means that more friction is being conducted. Though this is exactly what you’re going for in a beach driving or off-roading scenario, it’s not ideal for highway driving.
Underinflated tires cause those tires to overheat and subsequently fail. This can end in a blowout—if you’ve ever seen the carcasses of fallen tires hanging out in the highway you know what we’re talking about. It can be very dangerous to blow out a tire on the highway, for you and the other cars driving around you.
Another potential safety hazard associated with under-inflated tires is the loss of handling that comes from underinflated tires. This can put you in a position where you are more likely to have an accident.
Tire Pressure Is Too High
The most immediate loss you’ll notice with overinflated tires is a loss of traction. With less rubber gripping the road beneath your car, you’ll feel distinctly less grippy. This lack of traction can lead to more slipping and sliding, especially in bad weather, and your risk of hydroplaning goes up significantly. You’ll also notice a bumpier ride. Literally. Usually, the slight bounciness of your tire allows it to absorb some of the minor bumps you drive over on a day to day basis. An overinflated tire is stiff and thus is unable to absorb these bumps in the same way.
Though some people purposely overinflate their tires to get better fuel economy, the cost-benefit analysis on that choice doesn’t quite add up. With only a small patch of the tire actually touching the road, there will be distinct splotches of overly worn spots on your tires. This can lead to you needing to buy tires much more frequently, a not trivial expense. Overinflating your tires to save money on gas is spending a dollar to save a penny, it doesn’t make sense and you’re making driving less safe for yourself and the other cars on the road.
When the Problem is the Sensor
It is possible for your car to be at the right tire pressure and for the tire pressure monitoring system to be flawed. These systems get out of calibration and sometimes age poorly. Read through your owner’s manual to find out how to reset your tire pressure sensor. It can be as easy as pushing a reset button on a dash or slightly more complicated depending on your car’s model.
Before resetting your tire pressure sensor be sure that you’re at the ideal tire pressure though. Whatever it’s set to when you hit the reset button will essentially be recalibrating and setting zero. If your tire pressure is incorrect then your sensors will be as well.
By checking your tires regularly and keeping them at the recommended psi, you'll improve your car's handling and traction, ensure your tires don't wear irregularly and get better fuel efficiency. All of which are good reasons to check before you see an alert on your dash.