Tire Talk

[Eric]

My wife had a guy holler at her the other day. Not because she's beautiful (though she is) but because she was driving around on a flat tire.
I am very grateful to that guy.
A flat tire - even a tire that's just low on air - can be more than an inconvenience. It can be a catastrophe.
Think about a table. It sits on four legs. If one leg is shorter than the other, the table wobbles. Apply the same general concept to a car - at 50 MPH.
In a curve.
Tires leak - often slowly. Cars built in the last two years or so have electronic tire-pressure monitors that will warn you - via a dashboard light - when a tire is low on air. Some of these systems monitor indiovidual tires - and give you the exact air pressure (measured in pounds per square inch, or PSI). Others have a simple amber warning light that comes on when any of the four tires is low on air.
But even if your car has an electronic monitoring system - and especially if it doesn't; if you you own an older car without a tire pressure monitoring system) it's very important to regularly check all four tire visually - and then confirm inflation pressure manually.
Ideally, each time you go for a drive, walk around the car and take a good look at all four tires for obvious signs of a problem. Not just one that looks to be low on air, but also for signs of physical damage or deterioration. For example, a bulge on the sidewall, or a tear.
Hairline cracks - dry rot - are another thing to watch for. Pay particular attention to any tire that is more than six or seven years old. Even if the tread is good, a dry-rotted tore can be dangerous and you should probably think about replacing it.
If you see a sidewall bulge or tear, ideally do not drive the car. Call roadside assistance - or your spouse (or a good friend) and have them come pick you up - and have the car picked up by a tow truck and taken to a tire shop. A tire with a bulge in the sidewall - or a torn sidewall - could fail suddenly (and catastrophically) at any time. Rather than a gradual, slow leak, all the air could leak out at once - like a balloon popping. If this happens while you're driving, the car could become uncontrollable - and you could have an accident.
The same rules apply with low-on-air tires, too - just not to the same degree.You may remember the Firestone tire/Ford Explorer debacle of the late '90s. Under-inflated (and, apparently, defective) tires and high speed driving resulted in tires exploding and Explorers rolling. A car with one under-inflated tire may handle strangely, especially if the steering wheel is jerked suddenly to the left or right (as when the driver is attempting to swerve around another car, or avoid an obstacle).
Your vehicle's panic stop braking distance will likely increase, too.
And under-inflated tires are probably more dangerous overall than flat tires because they are "sneaker." A tire may look ok - but be 20 pounds low on air. This is more true today than in the past because of the widespread use of tires with short, stiff sidewalls. If your car has 18 or 19 inch (or larger) wheels and "sport" or "summer" tires, it probably has such tires. Even when they are almost totally empty of air, these tires may look ok to the eye. This is because there is not much sidewall to sag.
However, the same poor handling (and braking) performance issues will arise. It's also easy to damage the tires - and "sport" tires can be very expensive to replace.
Which is why it's important to manually verify inflation pressures regularly.
Ideally, every two weeks - but once a month at least. It is a job that almost anyone can do and doesn't require tools per se - just a pen-type tire pressure gauge, which you can buy at any auto parts store.
Keep it in the glovebox - and get into the habit (once every other week) of checking each tire's pressure with the gauge. The proper inflation pressure will be listed on the tire itself or in your owner's manual. if possible, go with the with PSI (pounds per square inch) recommended in the owner's manual - by the people who designed and built your car. But if this information is not readily available, go with the figure listed on the sidewall of the tires themselves.
You will see a "max inflation pressure" - for example, 42 PSI. It is not necessary to inflate each tire to the maximum recommended pressure - so long as it's in the ballpark. And not below the recommended minimum inflation pressure.
Nor in excess of the recommended maximum listed on the tire sidewall.
Tip: It used to be easy to find free air at gas stations. Today, very few gas stations have free air. Many don't have air pumps at all. But those that do, usually require you to pay for the air… with coins. Forget your iPhone. And also your debit card. Hence, it's a good idea to get at least $1 in quarters and leave them in the car somewhere for "just in case."
Even better, you could buy a mini-compressor and carry around your own air supply. Mini-compressors are powered by your car's 12V power point (in pre-PC days, the cigarette lighter) and though slow, they will fill up your tire - and for free. Or at least, without quarters. Even better, you're not dependent on finding a gas station that has an air supply. You've got yours in the trunk. These handy gadgets are small - about the size of a shoebox - light and very portable. They're also inexpensive. About $30-$50 depending on the model and where you buy.

[Dave Brand]

The proper inflation pressure will be listed on the tire itself or in your owner's manual. if possible, go with the with PSI (pounds per square inch) recommended in the owner's manual - by the people who designed and built your car. But if this information is not readily available, go with the figure listed on the sidewall of the tires themselves.
You will see a "max inflation pressure" - for example, 42 PSI. It is not necessary to inflate each tire to the maximum recommended pressure - so long as it's in the ballpark.

Bad advice there. The maximum pressure figure on the tyre will in most cases be well above the specified pressure for the vehicle; inflating to the max will seriously affect ride, handling & braking.

Somewhere on the car, usually the driver's door jamb, there will be a sticker stating the correct pressures - it's a legal requirement.

Edit: I've just looked at the tyres on my car. The maximum inflation pressure is 51 lb/sq in; the pressure specified by the car manufacturer is 35 lb/sq in. Tyres inflated to 51lb/sq in would be 45% over-inflated - a vehicle with tyres over-inflated to such a degree would be dangerous to drive.