Tires Q&A: Can I replace one or two tires at a time on my car?

Consumers Union held their annual open-house tour on Saturday, October 17 at the company headquarters in Yonkers, New York. Visitors got a chance to tour various stations to hear how Consumer Reports tests different products. It’s always a nice opportunity to talk about how we test tires at this event and as in past years there were a lot of interested visitors looking for more information on tires, particularly on how to buy.

Question: By far, the most common question asked this year was: “Is it OK to purchase just two tires at time?”

Answer: A simple question, indeed, and the simple answer is yes you can in most cases--but there are many considerations.

Most importantly, CR recommends rotating tires routinely following the guidelines spelled out in your vehicle’s owner’s manual, typically every 6,000 to 8,000 miles. The owner’s manual will have a rotation pattern to follow as well. Following the routine rotations will optimize a tire’s tread life and will wear all four tires evenly. Bottom line: when it comes time to replacing the worn-out tires, buy four new ones.

Many drivers may not rotate tires at all or not on a routine schedule. Owners of front-wheel drive vehicles will likely be replacing the front tires two to three times more often than the rear tires --since the front tires are doing most of the work by driving the wheels, doing most of the braking, and steering the car. The rear tires have a much easier life, being generally lightly loaded and free-rolling. In this common scenario, where only two tires are worn out and need replacing, CR recommends at least purchasing new tires of like brand and model as those already on the car, despite the best practice of purchasing a full set of four new tires. Mixing tire brands or even different models may cause handling instability. And when replacing only two, we recommend installing the new tires in the rear and placing the (older but still decent) rear tires in the front. This may help prevent a spinout or oversteer condition on slick roads. Both these recommendations apply to rear-wheel drive vehicles as well.

Finally, if you own an all-wheel drive vehicle, the first step before buying a new tire or pair of tires (short of installing four new ones) is to read the vehicle’s owner’s manual. Many makes of all-wheel drive vehicles will stipulate that all four tires must be of the same size, brand, model, and state of wear. Any deviation could result in an all-wheel drive system failure due to the stress placed on it from rotating dissimilar overall diameter tires.

Now wasn’t that simple?

To see full details on all tire models we tested, check out our Ratings and recommendations (available to subscribers). In addition to our updated Ratings, all site visitors can access our free buying advice for tips on getting started, types of tires we test, features that are important in making a tire purchase, and general tire care. Also, be sure to check out our TireTalk forum to interact with our tire engineers and other drivers.

—Gene Petersen 

2009 SEMA Show: Tire testing and the transformation of the tire industry

Every year Consumer Reports’ tire team attends the Specialty Equipment Manufacturers Association (SEMA) show in Las Vegas to meet all the tire manufacturers under one roof. It is an effective way to have face time with industry members, learn about upcoming developments and products, and shape our upcoming tire programs. With these insights, we will soon have outlined the tire models that we will be testing for the next major tire report due next year. This much we do know: we’ll be covering ultra-high performance models, including summer, all season, and performance winter tires.

The dismal economy shaped this year’s SEMA show. Big names such as BFGoodrich, Bridgestone, Continental, Dunlop, Firestone, Goodyear, Michelin, and Yokohama were noticeably absent. (Read “2009 SEMA Show: Tire coverage.”) 

But not all companies followed that trend. Cooper had a dominant front entrance booth and was creating a big draw from its major sponsorship of the PBR (Professional Bull Riding) rodeo that was in town the week of the show. Pirelli was there, as in previous years, but employees were dressed in refreshing business-casual attire unlike previous years when the mandatory suit almost made the booth seem overly serious. Pirelli was touting green performance this year. “Green” products seem trendy, but Pirelli’s tact was to demonstrate its new Scorpion Verde All Season tire for SUVs and truck—a tire that is energy efficient and has low noise transmission, but supposedly does not compromise tread life and all-weather grip.

Also present was Hankook, a maturing tire company offering a full array of tire products for aftermarket and original equipment markets. Most Americans’ would be shocked to know that Hankook is the seventh largest tire manufacturer in the world, with record sales tallied in 2008. It perceives itself as the next-generation tire company, growing significantly even during these rough economic times. Upcoming companies like Falken, Maxxis, and Nexen also commanded attention at this year’s show as major contenders in the post-recession period. Nexen plans on developing new tire models dedicated for the North America market soon. They created traffic at their booth with a silly 15-series performance tire in a 365/15R24 size they created—think of an elastic band around a wheel.

Overall, it seemed like the underlying mission among manufacturers was to make a statement of confidence to tire dealers and attendees, moving forward with new products, and a commitment to succeed despite the poor economic conditions. A threat to the big names missing at the show, maybe, but even the major companies present could see the irony by looking down the hallways of the convention center to see so many newcomers. These companies are not household names yet, but can you imagine someday buying tires with brand names like Sunny, Hankang, Linglong, Triangle, and Wanli? Stay tuned.

For Ratings, recommendations, and buying advice on car, truck, and winter tires, see our tires section.

—Gene Petersen

Also see from the 2009 SEMA show:
Better than expected, future looks greener
Our favorite modified Chevrolet Camaros
New iPhone apps for auto diagnostics
World's fastest Honda Civic circa 1976
All shades of green project cars
Surfrider Toyota Camry hybrid CNG
Kustomizing the Toyota Prius
Hot rodders turning green
Auto aftermarket prepares for show time in Las Vegas

Tires Q&A: Tire rolling resistance

In our ongoing series of Q&A blog columns, we will highlight common and interesting questions posted to our Car forums, with answers from our automotive experts.

Question: I bought four Yokohama Avid TRZ tires just two weeks before the 11/09 Consumer Reports issue arrived. I'd read reviews on the internet but none addressed mileage. As I drive an ‘04 Prius, mileage is very important. I had been trying to figure how new tires would drop my mileage a very noticeable 10 percent (from 53.3 to 48). Had I only known the tire ratings were coming I would gladly have waited and would definitely have different tires today.

Answer: I’m sorry the report did not reach you in time of your tire purchase. Until the State of California or the federal government comes out with rolling resistance regulations and ratings, your only sources for rolling resistance information on tires are from manufacturers’ claims and Consumer Reports. Our testing is comparative among the models tested.

Yes, you could have purchased a more fuel-efficient tire, but the Yokohama Avid TRZ is average among all season replacement tires for rolling resistance. Some were better--such as the top-rated Michelin HydroEdge, and the Toyo Versado LX. One point to consider when replacing tires: As tires wear out, you’ll likely see improved fuel economy since the tires will have less rolling resistance as the tread (mass) is removed from the tire. Installing new tires, identical in brand and model as those removed, and you likely see a reduction in your fuel economy. The new TRZ tires should become more fuel efficient as the tires wear. Also, keep the tires properly inflated and check them monthly to get the optimum fuel efficiency.

To see full details on the tire models we tested, check out our Ratings and recommendations (available to subscribers). In addition to our updated Ratings, all site visitors can access our free buying advice for tips on getting started, types of tires we test, features that are important in making a tire purchase, and general tire care. Also, be sure to check out our TireTalk forum to interact with our tire engineers and other drivers.

—Gene Petersen 

Tires Q&A: Tire-testing vehicles

In our ongoing series of Q&A blog columns, we will highlight common and interesting questions posted to our Car forums, with answers from our automotive experts.

Question: Has CR tried using different cars, but same size tires to see if the relative ranking would change dramatically?

Answer: Our tests are designed to judge tire performance on a comparative basis. Our goal is to use a popular and suitable car and appropriate tire size that also best represents the segment we are evaluating. Hence, we use one car or truck as the test calls for.

From our experience, a car’s natural abilities in terms of handling and ride comfort would influence the results, but it would be an offset in the comparative ratings between one car model to another. Also, differences in vehicle weight, wheel alignment, and drive-wheel configuration could affect a number of tests like snow traction, ice braking, and hydroplaning resistance. But, again, the comparative results should be maintained. The same holds true for our tread life test that’s done on like vehicles under identical conditions and is strictly a comparative test. Rolling resistance is the only test done without a car, performed on a dynamometer, so there is no vehicle effect.

More recently we have seen stopping distance reversals of tire models when used on different cars. This generally happens with tire models that are somewhat close in braking performance, and our data suggests a grippy tire is generally good on a wide variety of cars. But today’s cars have ABS brake systems tuned to a specific peak friction characteristic. To judge the tire’s peak level of grip we now do a “best effort” stop on dry and wet surfaces. A best effort stop has the driver modulate the brake pedal effort to get the shortest stop without wheel lockup, evaluating each tire model to its own peak friction level.

Comparative testing works well if you can remove or compensate for the vehicle effects as we strive to do. Publishing actual data would be misleading because it applies to the specific vehicle used.

Ratings, recommendations and buying advice on car, truck and winter tires, see our tires section.

—Gene Petersen  

Video: How to choose the best tires

At a glance, all tires look alike. They are black, round, and ringed with tread patterns. But there are significant differences in how they perform and how they wear. Since tires are the only part of the car that touches the road, it is crucial that you make a smart, informed decision about what tire is right for you. And we can help.

As demonstrated in this tire buying video, Consumer Reports runs a comprehensive, year-round tire testing program to ensure it can deliver the advice and ratings you need. To evaluate all aspects of a tire, we put it through a number of objective and subjective tests in the most comprehensive tire-test program of any American magazine or Web site.

We test braking and lateral grip on dry and wet surfaces, handling in our emergency-avoidance maneuver, and hydroplaning resistance, which measures how well a tire maintains contact with the road in standing water. We evaluate how easily a tire can accelerate on moderately packed snow and we rent a local skating rink to test braking on ice. Outside labs evaluate tread life and rolling resistance which is a function fuel efficiency . To ensure consistency, we buy each tire model in the same size and mount them on the same test cars.

Check out our video to see the details on how we conduct these tests. Then see our car, SUV and truck, and winter tire ratings (available to subscribers) to find the models that score well in the areas that matter most to you. All site visitors can access our free buying advice for tips on getting started, types of tires we test, features that are important in making a tire purchase, and general tire care. Also, be sure to check out our TireTalk forum to interact with our tire engineers and other drivers.

—Liza Barth 

Car care: Myths vs. reality

When it comes to maintaining your car, misconceptions abound. And even the best intentions can lead you to spend more money than necessary or even compromise your safety. Here are a few common car care myths that can do more harm than good.

Myth: Engine oil should be changed every 3,000 miles.

Reality: Despite what oil companies and quick-lube shops often claim, it’s usually not necessary. Stick to the service intervals in your car’s owner’s manual. Under normal driving conditions, most vehicles are designed to go 7,500 miles or more between oil changes. Changing oil more often doesn’t hurt the engine, but it can cost you a lot of extra money. Automakers often recommend 3,000-mile intervals for severe driving conditions, such as constant stop-and-go driving, frequent trailer-towing, mountainous terrain, or dusty conditions. Read how to check your car's engine oil.

Myth: Inflate tires to the pressure shown on the tire’s sidewall.

Reality: The pounds-per-square-inch figure on the side of the tire is the maximum pressure that the tire can safely hold, not the automaker’s recommended pressure, which provides the best balance of braking, handling, gas mileage, and ride comfort. That figure is usually found on a doorjamb sticker, in the glove box, or on the fuel-filler door. Perform a monthly pressure check when tires are cold or after the car has been parked for a few hours. See our tips on tire maintenance.

Myth: If regular-grade fuel is good, premium must be better.

Reality: Most vehicles run just fine on regular-grade (87 octane) fuel. Using premium in these cars won’t hurt, but it won’t improve performance, either. A higher-octane number simply means that the fuel is less prone to pre-ignition problems, so it’s often specified for hotter running, high-compression engines. So if your car is designed for 87-octane fuel, don’t waste money on premium. (Read more on how to get the best gas mileage.)

Myth: After a jump-start, your car will soon recharge the battery.

Reality: It could take hours of driving to restore a battery’s full charge, especially in the winter. That’s because power accessories, such as heated seats, draw so much electricity that in some cars the alternator has little left over to recharge a run-down battery. A “load test” at a service station can determine whether the battery can still hold a charge. If so, some hours on a battery charger might be needed to revive the battery to its full potential. (See our car battery ratings and buying advice.)

Myth: Let your engine warm up for several minutes before driving.

Reality: That might have been good advice for yesteryear’s cars but is less so today. Modern engines warm up more quickly when they’re driven. And the sooner they warm up, the sooner they reach maximum efficiency and deliver the best fuel economy and performance. But don’t rev the engine high over the first few miles while it’s warming up.

Myth: A dealership must perform regular maintenance to keep your car’s factory warranty valid.

Reality: As long as the maintenance items specified in the vehicle owner’s manual are performed on schedule, the work can be done at any auto-repair shop. If you’re knowledgeable, you can even do the work yourself. Just keep accurate records and receipts to back you up in case of a warranty dispute on a future repair.

For more on taking care of your car, see our guide to car maintenance.  Talk with others about car maintenance and repair in John's Tool Box forum.

2009 SEMA Show: Tire coverage

Every year Consumer Reports tire engineers trek-out to the Specialty Equipment Market Association (SEMA) show held in Las Vegas usually in the first week of November. The show is the premier industry event for aftermarket automotive products. This non-public event attracts well over 100,000 people who work in the automotive industry.

We go there every year to meet with the tire manufacturers, discuss upcoming tire testing programs (including what tire models to test and trends and challenges facing the industry as a whole), and to view new tire-related products that might be interesting to evaluate. In previous years, nearly every major tire manufacturer would attend, each with their own flashy booth, exotic cars shod with their newest tire models, and sometimes have scantily dressed models to help draw in the floor traffic. 

This year, coming off the heels of the worst recession since the Great Depression, many tire manufacturers are struggling to make a business case to attend the show and as a result many won’t be there. BFGoodrich, Bridgestone, Continental, Dunlop, General, Goodyear, Kumho, Michelin, and Toyo will not exhibit this year. That will put the lime-light on Cooper, Hankook, Pirelli, Maxxis and Nexen.

We’ve seen the automotive landscape change this year in a historic way with the restructuring of GM and Chrysler. Maybe times are a changing in the tire industry, too, as reflected in the companies that will (and will not) be at the show.

We'll bring you the latest tires coverage from this year's SEMA show, which runs from Nov. 3rd through Nov. 6th.

—Gene Petersen 

H-rated tires with shorter life spans become more common

Consumer Reports runs the largest tire testing program in the United States. And one of the main things we’ve found in our testing lately is that keeping fresh tires on your car is getting more expensive.

One reason for the increased cost for rolling stock is that more and more family cars are coming equipped with higher-speed rated tires. Speed ratings indicate the highest speed a tire maker considers safe for that tire to travel and is designated by letters such as Q, S, T, H, V, and Z along with the tire size information on the sidewall. All these ratings cover speeds well above legal limits. The most popular, S, T, and H, are rated for 112, 118, and 130 mph, respectively.

Traditionally, most family cars have used S- and T-rated tires, while tires rated H and higher have mostly been available only in sports cars or upscale sports sedans. But when we tested this year’s group of all-season passenger-car tires, we found a growing number of popular cars are equipped from the factory with H-speed rated tires. Partially, this is because tire manufacturers have an easier time meeting the latest tire safety standards with higher speed-rated tires. Other factors include using performance tires that are better suited to the elevated levels of acceleration, braking, and handling that todays family cars are capable of achieving, and finally, marketing is driving the move to squatting low profile performance tires.

So what should drivers do?

A key lesson here is to be aware of the tires on the vehicles you are considering purchasing. Not only have speed-ratings increased since your last purchase, but so have the overall size. There are family vehicles now, such as the Toyota Venza, that are available with 20-inch wheel diameters—a size considered exotic just a few years ago. Carefully consider the benefits of upsizing the wheels when you buy the car, either from the factory or with aftermarket wheels.

Most vehicles are available with a choice of fitment, often characterized as a base tire/wheel combination and a sportier option. Often the more aggressive tire/wheel combination will enhancing traction and even give the car a more sporty feel, with heavier steering and greater road feedback. However, such upgrades often lead to compromises with a harsher ride and shorter tread life, plus a greater upfront cost. The lesson here is to think twice before upgrading the rubber on your new car.

For owners looking at tire replacement, we don’t recommend downgrading because it introduces a safety risk. Tires with higher speed ratings generally have better steering response and cornering grip than lower-speed rated tires, in addition to being capable of higher speeds. So if your car originally came with H-rated tires, that’s what you should replace them with. After all, the automaker spent millions on testing the car with that specific configuration, including suspension and braking systems.

Sticking with H-rated tires comes at a cost. While we found prices are similar to S- and T-rated tires, H-rated tires didn’t last as long in our treadwear test--an average of 49,180 miles, versus 61,080 for our S- and T-rated tires. V-rated tires had an even shorter tread life of 48,260 miles. Mileages are projected to wear-out, based on Consumer Report 16,000 mile wear tests.

While the speed ratings are one more factor to consider in your next vehicle purchase, it is better to be armed with the information before having to visit the tire store earlier than expected.

To find the best tires for your car, check out our tire ratings (for subscribers). Or check out our general advice on tire safety and shopping for tires.

—Eric Evarts

New tire tests and Ratings

Michelin tires top four categories in our latest Ratings of 69 models of all-season (S and T speed ratings), performance all-season (H and V speed ratings) and Winter tires--the largest group ever tested by Consumer Reports.

The Michelin HydroEdge was the top scoring model among S- and T-rated all-season tires, and the Michelin Primacy MXV4 and Michelin Pilot Exalto A/S took top honors among H- and V-rated all-seasons, respectively. The Michelin X-Ice XI 2 topped CR's ratings for winter tires for passenger cars.

CR's tire engineers rated models based on a variety of categories including dry and wet braking, handling, hydroplaning resistance, snow traction, ice braking, ride comfort, noise, rolling resistance, and tread life. Despite top scores, the Michelin models aren't necessarily the best in every area and they are also among the most expensive tires CR tested, but drivers don't have to pay top dollar to get good performance.

Other high scoring all season tires include the Hankook Optimo H727, Nokian WR G2, Dunlop Signature in the all season and H and V speed rated all season categories, respectively. In the winter category, the General Altimax Arctic was a runner-up to the Michelin X-Ice XI 2.

Consumer Reports' testers put tires through a number of objective and subjective tests. Testers measure braking and lateral grip on dry and wet surfaces, handling in CR's emergency avoidance maneuver, and hydroplaning resistance, which measures how well a tire maintains contact with the road in standing water. CR rents a local skating rink to test braking on ice and has outside labs evaluate tread life and rolling resistance. To ensure consistency, testers buy each tire model in the same size and mount them on the same test cars.

CR's latest tire ratings have changed from previous tests. Starting with these tests, CR's ratings are now designed so that readers can compare the individual performance of one type of tire with another. For example, you can compare the ratings of all-season and winter tires to see how much dry and wet grip you give up with winter tires in return for better snow and ice traction. The overall score, however, is still relative to each tire category. Because tread life can influence driving safety, a tread-life rating is included in each tire's overall score.

Investing in better tires can give you a wider margin of safety when driving. A little extra grip, for example, can mean the difference between an accident and a close call. There are a lot of tire choices, and you can't tell by looking at them which ones will perform better. When you buy replacement tires, CR recommends sticking with the same size and speed rating of your car's original tires. You can find the specifications listed on a placard usually located inside the driver's doorjamb.

To see full details on the tire models we tested, check out our Ratings and recommendations (available to subscribers). In addition to our updated Ratings, all site visitors can access our free buying advice for tips on getting started, types of tires we test, features that are important in making a tire purchase, and general tire care. Also, be sure to check out our TireTalk forum to interact with our tire engineers and other drivers.

Tires Q&A: Run-flat tires for Corvette?

In our ongoing series of Q&A blog columns, we will highlight common and interesting questions posted to our Car forums, with answers from our automotive experts.

Question: My first Corvette has Michelin Pilot Sport A/S Plus. I’m considering using the same tires but in a run flat, but I hear bad things about them. Any feedback would be appreciated.

Answer: In short, the virtue of a run-flat tire is extended mobility with no need to worry about being stranded with a flat tire. If you have my luck, the tire will go flat on a rainy, cold night over a dangerous section of road--and you don’t get to choose when a tire goes flat. Run-flat tires can handle a puncture or road-inflicted damage and allow the driver to make it to a service station or final destination. That’s the payoff of having run-flat tires.

Our experience is that some applications work better than others. The Corvette C5 is a perfect candidate for run-flat tires as there’s not much room for a spare tire, let alone room for tossing in a full-size flat tire inside the car. Run-flat tires are stiff by design to support the weight of the vehicle with no air pressure. For the Corvette, which uses stiff, low-profile ultra high performance tires, a run-flat is not much of a trade-off in terms of ride comfort and handling, even when it goes flat. Also, the Corvette was designed to accommodate run-flat tires, so it should be your first consideration when making a new tire purchase.

See our run-flat report to learn more about on the pros and cons of run-flat tires. For Ratings, recommendations and buying advice on car, truck and winter tires, see our tires section.

—Gene Petersen