Getting the Right Tire
Enthusiasts might drive around on giant rims with glorified rubber bands as tires, and to them we say, "Enjoy!" Our goal with this guide is a bit more practical: to help you make the most important decisions when choosing tires, be it as a new-car option or as replacements for existing treads on a car you already own. These decisions depend on the climate in which you drive and on what matters most to you: handling, ride comfort, noise levels, mileage, longevity or cost. We'll also help you choose what kind of spare tire to get — if any.
Key to understanding your choices is recognizing that every tire is a balance of characteristics. If you change one characteristic, such as traction, you're sure to get other changes along with it, for better or for worse. For example, summer tires have superior warm-weather grip but are dangerous in winter and tend to wear out faster than all-seasons. Low-profile tires sharpen handling performance, but they make for a rougher ride and are more susceptible to damage. You get the idea.
Passenger-car tires fall under three main categories: summer, all-season and winter, which you can learn how to spot in Tires 101. We'll start with the most common: all-season.
All-season tires are common for the same reason four-door sedans are: They do everything reasonably well, though they excel at nothing in particular. They won't give you the whiplash-inducing traction of a summer performance tire, but they do a more-than-adequate job on snow and ice, where summer tires fail. They also tend to last longer than single-season tires, and as a result most models come with treadwear warranties. As a class, they also tend to be less noisy than summer tires and have lower rolling resistance. As you might expect, rolling resistance refers to how much the tire resists rolling. High-rolling-resistance tires take more energy to stay in motion than do less-resistant tires, so cars equipped with them will get lower gas mileage. Unfortunately, low-rolling-resistance isn't a tire type — it's a characteristic, and a changing one: All tires' rolling resistance improves as their tread wears down. Even more troublesome, there's no standardized specification that consumers can use to determine if a given tire's rolling resistance is better or worse than another's, though manufacturers do measure it and are increasingly likely to market their tires with this term as efficiency has again come into demand.
As explained in Tires 101, the height of a tire's sidewall is known as its profile or series, and lower profiles mean shorter sidewalls. In terms of sidewall heights, all-season tires tend to fall in the middle. You can get performance-oriented low-profile tires that fit on relatively large wheels, but as a class, all-seasons seek the middle ground between the nimble handling of low-series tires and the comfort of higher-series tires on smaller wheels.
Winter and Off-Road Tires
Winter tires have come a long, long way from the studded bias-ply snow tires that we used to slap on our cars' rear wheels in late fall. Aspects of those tires remain, specifically in the aggressive patterns and deep tread blocks on what we now call winter tires. The deep grooves take a bigger bite than all-seasons do, and the tire's shoulders are usually squared off rather than rounded, providing an edge to dig into snow and prevent lateral sliding as the car turns. The most important difference in winter tires, though, is the rubber compounds they use. Designed to remain soft in frigid temperatures, their grip is superior to that of all-season tires — especially on ice. The problem with winter tires is that this performance almost invariably comes at the expense of wet and dry traction. Stopping distances are increased in these cases, and the deep tread blocks and softer materials make for less-responsive handling. Winter tires also wear more quickly than all-season tires, especially as temperatures rise well above freezing.
People who spend most of the winter driving on dry or plowed roads are better served by all-seasons. Winter tires are a commitment due to the cost and hassle of buying a second set of tires, storing them and having them mounted and removed twice a year. You can't use only two winter tires to save money. As we explain in Tire Maintenance, the best-case scenario is to have the same type of tire at all four corners: same model, inflation pressure and amount of wear — which is why we rotate tires. The performance of winter tires is so different than the other types that having them only on the front or rear wheels makes for an unpredictable and potentially uncontrollable car.
As a class, winter tires are slightly higher in profile than the average all-season tire, and for good reason: Winter weather makes for uneven road surfaces, whether it's chunks of ice or the potholes and pavement buckles that follow, and a taller sidewall can better absorb the shocks — isolating passengers while preventing wheel damage. It's not uncommon for winter tires to ride on wheels that are an inch or two smaller in diameter than the summer tires they replace. So long as the outer diameter, measured at the tire's tread surface, remains the same, the wheel can shrink as the sidewalls grow, and vice versa. To save money and eliminate the risk of damage to nicer rims, tire outlets often sell winter tires on cheap steel wheels, which also save the cost of remounting and balancing seasonal tires to the same four wheels twice a year.
One thing you won't see are winter tires that are significantly wider than the summer- or all-season models they replace. Intuition tells us that a wider tire gives better traction in snow, but in this case intuition is wrong. In most conditions, a narrower tire will dig down into snow and gain traction, where a wider tire is more likely to ride up onto the snow like a toboggan. Look to any racecar to see that intuition is back in force in the case of dry roads: When cornering on a track, wider is definitely better. Tire noise tends to be louder with aggressive tread patterns, as it is with studded winter tires. Many states have outlawed studded tires because they can damage roads, but you can still get winter tires with metal studs in the treads — or a choice of studded or studless versions of the same model. Tests have shown studded tires to have an advantage on ice but not necessarily on snow, and the studs can extend stopping distances on dry or wet pavement.
Off-road tires for SUVs and pickup trucks share some of the characteristics of winter tires, such as big-bite treads, deep grooves and high profiles, though they tend to be pretty wide. You can now get winter tires for practically any model, including true off-road vehicles, but the same tradeoffs exist here as they do for cars, including diminished warm-weather and dry traction and increased treadwear, so off-road and all-terrain (on/off-road) tires might be the more versatile choice for most buyers. We've even driven outrageously low-profile winter tires on supercars like the Audi R8, which has the added benefit of all-wheel drive.
Note the term "added," which shows that four-wheel drive is beneficial for low-traction surfaces, but that doesn't make it a "substitute" for all-season or winter tires.
By now you've caught on that tread patterns and compounds vary among the seasonal tire types, and summer performance tires are different than winter and all-season types. Their tread does have grooves intended to shed water and prevent hydroplaning, but the main goal is to maximize the surface area that contacts the pavement, so the channels are narrower and often shallower. For the same reason, grip on dry surfaces tends to increase with wear, even with all-season tires.
Also crucial to performance-tires' traction are the rubber compounds, which are softer than all-seasons and better able to mold into the pavement's rough texture. The tradeoff is lower treadwear ratings and a shorter lifespan. Soft compounds might sound similar to winter tires, but the chemistry is wildly different: Winter tires are softer at sub-freezing temperatures, but they're too soft at higher temps. Summer tires are soft when it's warm but go hard as a rock in low temps, blowing the traction advantage they'd had on dry and wet pavement and making them downright dangerous on ice and snow. All-wheel drive won't save a car equipped with summer tires in a winter storm.
To provide the sharp steering response and higher grip desired by sport-driving enthusiasts — as well as the large-wheel appearance — summer performance tires come mostly in low-profile sizes. The tradeoffs here are many. A main one is ride quality, which gets firmer as sidewalls get shorter, all other things being equal. Both this and issues of construction make some performance tires very noisy. One exception is the noise the tires make — or don't make — when they lose traction. Where all-season tires might squeal as the car starts to slide, summer tires tend to be more discreet.
With low-series tires also comes higher risk of wheel or even suspension damage: The tire is less able to absorb hard shocks, and that means the rim and suspension components do, along with the driver's spine. Low-profile tires put the wheels closer to the ground, which exposes them to damage when parking along a curb. With normal tires, the sidewall absorbs any contact and typically rebounds unscathed.
If you're still not sure that any of the three tire choices meets your needs, you're in luck. The lines have blurred to a degree never seen before. There are now ultra-high- as well as high-performance summer tires, all-season performance tires and winter performance tires. The capabilities of all-season tires now stretch well into performance levels once known only to winter and summer tires. You can't get everything you want in any one tire, but you can get more than ever. Returning to the sedan analogy, luxury sport sedans are actually excellent performers — in addition to being roomy and luxurious — and some even come with all-wheel drive, which suits them better for winter driving. You can get a tire that has above-average performance in many areas, too, but just like the sport sedan, the more you get, the more it's gonna cost you.
Spare Tire Types: What to Consider if Given a Choice
Full-size spare tire: The full-size spare tire has the fewest shortcomings in the event of a flat tire. Its cons are present even if it's never used: It's large, heavy and relatively expensive. Not all cars are designed to accommodate a full-size spare in the trunk. Those that do have gotten better at making the remaining space usable, by means of molded plastic covers that turn otherwise wasted space alongside the spare and inside the wheel into storage bins.
Temporary "donut" spare tire: Almost the opposite of the full-size spare, the ubiquitous "donut" spare is cheap, small and light, and its shortcomings come into play when it's put into use: mileage limits, speed limits, ineligible when towing a trailer and the potential — because of its small diameter — to undermine speedometer operation and such safety features as antilock brakes, traction control and electronic stability control.
See the detailed warnings below about using small spare tires.
Temporary full-height "bagel" spare tire: A relatively new idea, this temporary spare has some of the donut's advantages — narrow and lighter than a full spare — in a tire of full height. Because its circumference is the same as the main tires, it keeps the speedometer honest and doesn't interfere with the ABS, traction control, electronic stability control or all-wheel drive. As a temporary, its range, speed and load bearing are limited, and it shouldn't be used when towing a trailer. The nickname "bagel" comes from the fact that it's larger than a donut, as all respectable bagels are. You won't see the term used widely for this type of spare tire, but we have high hopes.
Inflatable temporary spare tire: Inflatable, or collapsible, temporary spares have begun to appear, sometimes referred to as super-space-saver spares. Mercedes-Benz is one of the European automakers to adopt this strategy, in its small roadsters. The tire itself comes deflated and takes up even less space than a donut, at least in terms of its diameter; Mercedes' tire actually has a wider tread than most donut spares. The system requires the spare to be inflated before use, with a supplied compressor that runs off the car's cigarette lighter. In terms of its weight, the whole system seems to be between that of a donut and a full spare.
See the warnings below about using small spare tires.
Run-flat tires: Run-flats are not spare tires but a type of regular tires that do away with spares altogether. Their thicker sidewalls allow one to continue driving even if they have no air pressure at all, typically for up to 50 miles. Because they don't actually flatten, cars with run-flats have always been equipped with tire pressure monitoring systems (now required on all new cars), which alert the driver if one of the tires loses pressure. One of run-flats' drawbacks is typically higher replacement cost.
Run-flat tires also tend to have a stiffer ride and are heavier than conventional tires, factors for which automakers must account when tuning the car's suspension — and one reason they aren't easily added to vehicles that didn't come with them originally. When run-flats were in their infancy, some automakers shunned them because they felt that conventional tires performed better. In time, improvements in the tire designs and the way manufacturers integrate them have broadened their acceptance. They now are employed widely on performance vehicles.
Spare Tire Warnings
Don't exceed speed and distance ratings The primary reason temporary spares have speed and distance ratings is that the wear of extra mileage and the heat generated by excessive speed can cause the tire to fail. If you think having a tire fail is a drag, imagine a second one failing on the same day.
Small spares can damage the vehicle, too
Important: Small spares can damage the vehicle itself if used for too many miles. For two tires to work together on the same drive axle requires a differential, the job of which is to let the wheels turn at different speeds. When the vehicle travels in a straight line, the differential is effectively dormant. If one wheel is smaller than the other, however, the differential is working constantly, for which it was not designed. Driving 200 miles on a small spare can put the equivalent of tens of thousands of miles on this set of gears, causing premature wear. Certain all-wheel-drive systems also can sustain damage from this size mismatch. Follow your owner's manual's instructions carefully.
Small spares, speedometers and safety equipment
Small spares may undermine a car's speedometer operation and such safety features as ABS, traction control and electronic stability control. All these systems depend on equal rotation of all the wheels in straight-line driving, often using wheel-rotation sensors that are calibrated to work with a full-size tire. A smaller tire may throw off the speedometer reading or disable one of the other systems, all of which affect safety.
Your owner's manual should explain if your car may suffer these consequences when employing a small spare tire.