August 18, 2011
Tires with an emphasis on low rolling resistance for improved fuel efficiency have been de rigueur on environmentally friendly hybrid vehicles for some time. But just as the number of early adopters driving hybrids was relatively small, most tires designed with the same eco-focus were only available in a limited range of sizes that didn't fit the majority of vehicles on the road. But as the world at large continues to place a greater emphasis on being ecologically friendly, a growing number of tires featuring the latest fuel efficient technology are becoming available in sizes to fit a wide variety of mainstream passenger cars and minivans, helping them roll down the road more efficiently than on standard tires of just a few years ago.
One of the most recent eco-friendly tires to become available for the mainstream is Bridgestone's Ecopia EP422 that employs several technologies aimed at reducing fuel consumption and the tire's impact on the environment. Bridgestone has applied their NanoPro-Tech analysis to improve efficiency at the molecular level by controlling the interaction between different rubber components inside the tire. A special rubber compound is used in the sidewall to help reduce fuel consumption by returning more energy as it rolls. The tread compound even uses 5% recycled post-consumer tire rubber.
To get a better idea of how the Ecopia EP422 drives in the real world, we decided to conduct a Real World Road Ride and Performance Track Drive comparing it with two other eco-focused tires already in the marketplace - the Continental ProContact with EcoPlus Technology and Goodyear's Assurance Fuel Max. Both share the Ecopia EP422's emphasis on reducing fuel consumption, and are available in a wide range of sizes to fit a variety of mainstream vehicles. To help us gauge the gains and discover any trade-offs for having an eco focus, we included the Yokohama AVID TRZ to represent the majority of typical passenger tires on the road that were introduced before low rolling resistance became such a high priority. Our evaluation used 2011 BMW E92 328i coupes fitted with new, full tread depth 205/55R16 tires mounted on 16x7.5" wheels.
Our 6.6-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.
Out on the road all four tires delivered comfortable road manners, with the Continental ProContact EcoPlus and Bridgestone Ecopia EP422 both doing a good job softening the edges of sharp bumps and expansion joints. Our team rated the ride quality of the Yokohama AVID TRZ just behind, noting it was also able to soften the jolt of larger impacts. The Goodyear Assurance Fuel Max let a bit more of the road's imperfections find their way to the driver.
The ProContact with EcoPlus Technology produced the least amount of tread noise, rolling down the road in relative quiet. Right behind was the Ecopia EP422, which also did a good job keeping noise to a minimum. The AVID TRZ generated a small amount of audible noise, while the sound from the tread pattern of the Assurance Fuel Max was a little more noticeable as it rolled over the asphalt and concrete surfaces along our route.
The steering feel of the AVID TRZ felt tight and direct, responding quickly to driver inputs. The ProContact with EcoPlus Technology also gave a reassuring feel in the steering wheel as it tracked down the highway at speed. The Ecopia EP422 was just a little slower to respond to driver inputs, but also felt well-connected. The Assurance Fuel Max felt a little disconnected in comparison to the others, with less precision and slower response to driver inputs.
Our 1/3-mile per lap test track course includes 90-degree street corners, a 5-cone slalom and simulated expressway ramps. Run in both dry and wet conditions, the test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers or competition events.
Out on the test track in dry conditions the AVID TRZ carried over its responsive handling along with a stable and reassuring feel making it a subjective favorite with our team. The ProContact with EcoPlus Technology was able to lap our course a little faster than the AVID TRZ, thanks to its superior ultimate traction. The Assurance Fuel Max felt less precise, relying on its grip to get around our test course faster than it felt from behind the wheel. The Ecopia EP422 lacked the ultimate traction of the other tires, feeling somewhat sluggish and out of its element when challenged during rapid transitions and hard cornering.
In the wet the ProContact with EcoPlus Technology easily lead the group, displaying good overall cornering and braking traction and predictable handling. The AVID TRZ followed with noticeably less ultimate grip, but its stable handling made it relatively easy to control. The Ecopia EP422 was further back, feeling somewhat slippery. The Assurance Fuel Max trailed the group with noticeably less traction combined with sluggish handling.
Our Real World Road Ride features a relatively flat 6.6-mile loop of 65 mph expressway, 55 mph state highway and 40 mph county roads along with two stop signs and one traffic light every lap. Our team drove approximately 500 miles over the course of several days. Since we wanted to compare fuel consumption results that typical drivers would experience, our drivers were instructed to maintain the flow of traffic by running at the posted speed limits and sustain the vehicle's speed using cruise control whenever possible. They did not use hypermiling techniques to influence vehicle fuel economy.
@ 15,000 Miles
|% vs. Most Efficient|
|Bridgestone Ecopia EP422||27.9||537.6||--|
|Continental ProContact with EcoPlus Technology||27.3||549.5||-2.20%|
|Goodyear Assurance featuring Fuel Max Technology||27.6||543.5||-1.09%|
|Yokohama AVID TRZ||27.3||549.5||-2.20%|
|*Our evaluation used Linear Logic ScanGauge II automotive computers to record fuel consumption and Race Technology DL1 data loggers to record true distance travelled.|
Three of the four tires in this test were designed with low rolling resistance as a high priority, and we did find a modest difference in observed vehicle fuel economy. The 0.6 mile per gallon difference between our lowest and highest recorded fuel economy measurements would result in an annual difference of just under 12 gallons of premium gasoline at a current cost of about $47 (at $4/gallon) for drivers traveling 15,000 miles a year.
It's important to note our test's fuel consumption measurements follow consistent procedures designed to minimize variables that could influence the results, however they do not represent an exhaustive long range fuel consumption study. While our procedures require the test vehicles in each convoy to run under the same prevailing conditions, the week-to-week differences in ambient temperatures, barometric pressures and wind speeds that we experience over a season of testing can influence vehicle fuel consumption and prevent the absolute mpg values of this test from being compared directly against those of others.
Larger differences in consumption between tires may indicate a difference that might be experienced on the road, while smaller differences should be considered equivalent. As they say, your mileage may vary.
Winter weather is often unpredictable, and road conditions can change so fast that it's hard to know what waits for you around the next corner. For consistency, our snow testing is done at a dedicated winter test facility in Northern Sweden, and ice testing is done at a local hockey rink to simulate the glare ice often found at intersections and in other high-traffic areas. We measure each tire's ability to accelerate and brake in both conditions, as well as gather subjective ratings of how each tire feels from the driver's seat while driving through several inches of groomed snow on a handling course.
Offsetting its underwhelming wet performance was the Bridgestone Ecopia EP422, this time showing impressive snow traction while feeling stable and composed. Right behind was the Goodyear Assurance Fuel Max which also delivered impressive results, especially under braking. The Continental ProContact with Eco Plus provided reasonable traction with just a hint of understeer, while the Yokohama AVID TRZ showed competitive, but lower overall snow traction than the others.
Tire manufacturers continue to find ways for their tires to help vehicles achieve better fuel efficiency. But there is no free lunch. At least for now, it appears there are trade-offs in some areas of tire performance when trying to maximize capability in others. The Bridgestone Ecopia EP422 and Goodyear Assurance Fuel Max both deliver on the promise of being fuel efficient, but trail when it comes to wet weather traction. The Continental ProContact with EcoPlus Technology and Yokohama AVID TRZ both give up just a little at the fuel pump for noticeable gains in wet traction.
Bridgestone Ecopia EP422 (H- or V-Speed Rated) (Grand Touring All-Season): The Ecopia EP422 is one of Bridgestone's ecologically oriented Grand Touring All-Season tires developed for the drivers of coupes, sedans, minivans and small crossover vehicles looking to combine year-round traction, handling and comfort with reduced environmental impact. Ecopia EP422 tires are designed to enhance vehicle fuel economy by reducing tire rolling resistance along with the vehicle's carbon dioxide (CO2) emissions while delivering year-round, all-season traction, even in light snow. Read more.
Continental ProContact with EcoPlus Technology (Standard Touring All-Season): The ProContact with EcoPlus Technology is Continental's Standard Touring All-Season tire developed for coupes, sedans, minivans and crossover vehicles. The ProContact with EcoPlus Technology is designed to enhance driving pleasure, save fuel and maintain wet braking grip while providing long wear and all-season traction, even in light snow. Read more.
Goodyear Assurance featuring Fuel Max Technology (Passenger All-Season): The Assurance featuring Fuel Max Technology is Goodyear's mid-tier Passenger All-Season tire designed for the drivers of cars, coupes, vans and crossover vehicles looking for affordably priced tires offering long wear, wet traction and low rolling resistance as some of their top priorities. The Assurance Fuel Max is designed to provide year-round confidence in wet, dry and wintry weather conditions, including in light snow, as well as offers lower rolling resistance to enhance vehicle fuel economy over the tire's lifetime. Read more.
Yokohama AVID TRZ (Standard Touring All-Season): The AVID TRZ is Yokohama's Standard Touring All-Season tire developed for the drivers of coupes, sedans and minivans. The AVID TRZ is designed to provide comfort, longevity and driving satisfaction across a wide range of road conditions, including in light snow.
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