Things to Know About Tires

things-to-know-about-tires
By Eric Peters, Automotive Columnist

The invention of the wheel was a pretty big deal — rolling stuff being a lot easier than carrying (or pushing or dragging) it.

The invention of tires was the next great leap forward. Rubber tires allowed wheels to travel more smoothly on rough/uneven surfaces and at faster-than-walking pace without shaking themselves — and the cart or carriage or (eventually) car to which they were bolted to pieces. They also much improved traction — getting you going on slick/slippery surfaces, laterally (in the corners) as well as when you want to slow down (many people do not realize that a set of good tires contributes mightily to shorter stopping distances).

Ultimately, they’re the last thing between you and the road. So it’s a good idea to know a few things about them. Such as the fact that… .

* Tires age –

Many people assume that if the tread still looks good, the tires are ok. Not necessarily. A tire with 90 percent of its tread left may be close to 100 percent worn out — a failure just waiting to happen. And if it happens at the wrong moment — like when you’re doing 80 on the highway, for instance — it could have catastrophic consequences.

Tires, recall, are made of rubber. Well, rubber bonded with fabric and steel. Rubber loses its elasticity over time as a result of exposure to sun/ozone, which breaks down the rubber. It become less flexible; the tire may become brittle. If you look closely at the sidewall, especially near the rim, you may see small cracks that look like an old lady’s face with too much make-up. At that point the tire is potentially dangerous and ought to be replaced, regardless of the tread left.

Tire life has increased; anti-aging agents mixed with the rubber have helped stave off dry-rot such that tires now last 2-3 times as long as they did back in the ’70s. But they’re not immortal.

Entropy is a mean — and inescapable — bitch.

As a general rule, modern tires more than ten years old should be replaced even if no obvious signs of wear (such as cracking along the sidewall) are evident, especially if the vehicle is going to be used regularly and particularly if it is going to be used for highway driving. So, if you buy a low-miles circa 2005 car that’s mostly just been sitting for the previous six years and so still has its factory original tires, you probably ought to buy a new set, no matter how “new” the tires look.

Lower the interval to six years from date of manufacturer (the data is stamped on the tire’s sidewall; see here for where) if the tires are high-performance/high-speed tires and you are planning to drive the car at high speeds (80 MPH or more) for sustained periods (more than a few minutes at a time) or subject them to high loading such as high-speed cornering. High-speed driving builds up heat — and even tires designed to handle that may no longer be able to safely handle that once they reach a certain age. In Europe — where sustained high-speed driving is legal — the recommended throw-away date is six years, no matter how much tread is left or how the tires look.

Any tire with a bubble or tear on the sidewall should be replaced ASAP regardless of tread or age. The tire may be structurally weak and a sudden blowout (rather than a gradual slow leak) could occur at speed, with an equally sudden loss of control.

To maximize tire life: When you buy, insist on new tires. Not tires that have been sitting on the shelf for the past year. Check the date code on the sidewall (see above link). Always maintain the recommended inflation pressure. And if the car is parked for long periods, move it at least every two weeks to avoid flat-spotting the tires. Rotate the tires per the manufacturers’ recommendations to even out the wear.

* Tires have different “personalities” –

Some are aggressive — — designed to maximize the car’s cornering grip/sharpen steering responsiveness. They are built to cope with sustained high-speed operation … but usually, the heightened athleticism comes at the expense of ride quality and tread life.

Others are rugged — designed to be great when it snows and for romping around off road. But they’re less adroit on dry pavement — and can be obnoxiously noisy, too.

Others are softies — — designed to give your car a very smooth/quiet ride… but they’re not the hot ticket for high-speed driving.

This is why most cars come from the factory wearing all-season tires that are a compromise design, balancing performance, handling/steering responsiveness with ride quality, tread life — and so on.

However, you might want to improve your vehicle’s handling — or its snow-day capabilities. Maybe you’d like a softer ride — and it’d be really nice if the tires lasted for 50,000 miles instead of 30,000 miles. Picking a different type of tire is a fairly easy way to fine-tune your car’s personality — and capabilities — to better suit the way you actually drive — and the way you’d like for the car to drive.

For example, if you have a pick-up truck, SUV or crossover, going with M/S (mud and snow) rated tires vs. factory all-seasons can dramatically improve your vehicle’s ability to not get stuck if you drive it onto a grassy (and wet and muddy) field, or when it snows. And if you’d like your sporty car to feel even sportier, going with a more aggressive “summer” tire will do exactly that.

Just be aware that improvements here may also result in liabilities there. High-performance “summer” tires, for example, are often as worthless in winter as a bikini in Antarctica. And M/S “knobbies” — though great in the snow — make a racket on dry pavement and will wear fast if you operate on the highway for extended periods.

You’ll want to have a chat with a tire professional before you change shoes.

* You probably haven’t got a spare –

For a variety of reasons — to save weight (fuel economy pressures) and because many modern cars come with huge wheels/tires (hence a spare would take up most of the trunk) — many new cars either don’t have a spare tire at all or they come with a “space saver” spare.

Those without a spare at all have run-flat tires that can be driven on even if they’re punctured and lose all air pressure. The catch is that you may not notice a tire has run flat and if you continue to operate at high speed or subject the car to high-g loading (as when cornering at a speedy clip) you may be made aware of the problem the hard way. Cars with run-flats usually have a dash warning light to alert you to a low-pressure (or flat) situation. But warning lights (and gauges) do you no good if you’re not paying attention to them. If the light comes on — adjust your driving accordingly until you can get to an air pump (if the tire’s just low) or a tire shop (if the tire is damaged and needs to be replaced).

Space-saver tires, on the other hand, are not even really tires at all. They are definitely not equivalent to the tires normally at each of your car’s four corners. What they are is a stop-gap. A life preserver. A means to get the car rolling again — but just barely. Space-saver tires are specifically temporary use only (see the large yellow warnings on the rim). They are typically much smaller (not diameter but width) and this greatly — negatively — affects handling and braking performance. They are specifically not designed for sustained driving at even normal highway speeds. The recommendation is usually no faster than 55 MPH — and for short distances only. They are to get you to the nearest tire shop and avoid a tow truck. That’s it.

PS: If you get a flat, it might be fixable if the puncture damage is on the tread portion of the tire (sidewall damage cannot be repaired). However, high-speed/high-performance tires may no longer be sound for high-speed/high-performance driving once damaged — even if they could be repaired. Their structural integrity has been compromised. Usually, the tire’s manufacturer will have specific details about this.

Read/ask — and know.

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3 Responses to “Things to Know About Tires”

  1. seenmuch says:

    Something I might add about this is That age, wear and type(purposes of design) matter when considering age from build date. These things matter and should be considered over than just blindly replacing tires based on age alone…..

    If a tire has been kept in a dry place out of the sun and weather their life span can be many times longer than ones that were exposed to the elements for that time.

    A vehicle which has spent years safely stored in a fairly controlled environment garage when not clocking miles can safely go years longer without danger of failure related to age when they still have much tread left. As long as these tires are kept inflated properly they can and do go as long as 10+ years in use without worry of failure.

    When compared to the same vehicle which has spent it's entire life stored outside in heat and cold can need replacing years sooner from the rubber aging due to exposure.

    And space saver tires are not only different sized than what might be on the car/vehicle, but are made of differing rubber compounds. Many times the tread wear rating of a good high mile tire is 500-740+ giving many times the service life of a tire tread wear rated 200-400. Many Years more of service!

    While to save cost of the spare they are made of a cheaper mix of materials with a wear rating of 100 or similar which gives them a very limited service life in the best of conditions.

    Point is, using age alone as the measure of when a tire needs replacing is not something that should be blindly followed. Use other info also, like how the tire/vehicle it is on was store, in what conditions it has been driven through and in what temp ranges it has had to live with on a daily basis.

    With these things figured in you can get a better idea of how long year wise your tires can be safely used…..

  2. Jim Walker says:

    Eric has an excellent piece.

    Remember, the correct recommended inflation pressure is found on the sticker in the car, not the inflation pressure on the tire sidewall. The same tire will have different correct inflation pressures on different cars, and also different correct pressures for the same size tire depending on whether for the front or rear position. And the pressures are to be measured with "cold" tires, meaning driven less than about 2 miles. Get a good pressure gauge and measure them in your driveway before moving the car.

  3. Tyrone Ellis says:

    Hello!
    It’s time to start preparing for the perils of winter driving, and commercial tire chains are an important and often overlooked part of this preparation. A lot of truck drivers might simply throw them in the truck