September 6, 2009

• What We Liked: Excellent snow and ice traction
• What We'd Improve: A small improvement in dry braking traction
• Conclusion: Even unstudded, this tire delivers excellent wintertime traction in the snow and on ice
• Latest Test Rank: 1st
• Previous Test Rank: Not previously tested

• What We Liked: Enhanced ice traction versus the unstudded tires
• What We'd Improve: Wet and dry road braking traction when using studs
• Conclusion: Studs help slick ice traction, but can give up a little braking traction on dry and wet roads.
• Latest Test Rank: 1st
• Previous Test Rank: Not previously tested

• What We Liked: Solid snow traction
• What We'd Improve: Ice traction when unstudded
• Conclusion: Good snow traction but needs studs for the best traction on ice
• Latest Test Rank: 3rd
• Previous Test Rank: 4th (October '07)

• What We Liked: Solid dry braking traction
• What We'd Improve: A modest improvement in ice traction
• Conclusion: Delivers good snow performance but can't match the ice traction of the best
• Latest Test Rank: 2nd
• Previous Test Rank: Not previously tested

Vehicles Used:
2008 BMW E90 320i Sedan, 2008 BMW E92 328i Coupe

Drivers who live in the snowbelt know that winter road conditions are almost always changing. Every vehicle that passes through new-fallen snow either clears a path by blowing it away, churns it into slush or packs it down into ice depending on the weather conditions. What that means is you never know what you're going to find on the road up ahead. And just as changing weather and road conditions challenge us as we drive, they also prove challenging to conduct meaningful tire comparisons out on the open road.

In an effort to better control winter's conditions, members of the Tire Rack team traveled to Northern Sweden in late January, 2009 during the height of winter season. This region near the Arctic Circle is home to a number of dedicated winter test facilities used by vehicle and tire manufacturers from around the world. Here we found consistent cold temperatures, plenty of snow and well-prepared snow and ice surfaces - ideal conditions for conducting side-by-side tire comparisons. Our evaluation was comprehensive - comparing each tire's ability to accelerate, brake and drive through the snow and across ice. We conducted both objective tests measuring each tire's performance with sensitive on-board instruments, as well as gathered subjective ratings of how each tire felt from the driver's seat.

This evaluation compared several Studdable Winter / Snow tires. Following traditional winter tire design, our group of Studdable Winter / Snow tires all feature deep treads molded in aggressive patterns designed to dig their way through the snow while including molded-in holes to insert optional metal studs for enhanced ice traction.

Many states in the U.S. have banned or seasonally restricted studded tire use in an effort to reduce damage from the constant chipping of the surface of concrete and asphalt roads. Studded tires cause millions of dollars in road damage annually, as well as can increase the risk of hydroplaning in wet conditions due to the resulting ruts. Studded tire use can even contribute to air pollution from the chipped roadway dust in high traffic areas.

This has led to a dramatic reduction of stud use in the U.S., resulting in most Studdable Winter / Snow tires being driven without studs. Our evaluation mirrored this trend, comparing the test candidates without the optional studs installed. To gauge what sort of difference adding studs makes, we also studded a set to test side-by-side with its unstudded counterparts.

We compared the General Altimax Arctic in both unstudded and studded configurations along with unstudded Firestone Winterforce and Pirelli Winter Carving Edge tires. We used new 205/55R16 tires mounted on 16x7.0" wheels. All tires were broken in by driving them on clear roads for approximately 100 miles prior to testing in winter conditions.

Subjective Tests

Performance Drive Ratings - Snow Handling

Our subjective snow handling test is designed to simulate what you might find out in the real world driving on unplowed roads during a moderate snow fall. The 1.1 mile, modestly uphill course was covered with several inches of groomed snow on top of a packed snow and ice base and proved to challenge each tire's ability to accelerate, brake and turn. Our evaluation was conducted with the test vehicle's traction and stability control system switched off so the driver would feel how much grip - and all of the slip - each tire had. ABS brakes were used for consistency and safety.

The General Altimax Arctic delivered impressive overall performance thanks to its excellent snow traction and responsive steering. Front-end authority was good enough to produce a tendency towards modest trailing throttle oversteer if braking was carried too far into the corner. The Firestone Winterforce felt very well balanced without any significant oversteer or understeer tendencies, and provided almost as much overall snow traction as the Altimax Arctic. Pirelli's Winter Carving Edge was also found to provide balanced handling and good overall traction, following close behind the other two. Because studs didn't significantly aid snow traction during our objective tests, we did not evaluate the studded General Altimax Arctic in this subjective evaluation.

Performance Drive Ratings - Ice Handling

The subjective ice evaluation was conducted on a flat 4/10th mile handling course covered in natural ice. The mottled texture of the ice was chipped rough then lightly polished, much like the ice-covered Swedish roads found in the surrounding area where studded tire use is common and no road salt or traction sand is applied after the fresh snow is plowed. This leaves the local roads ice-covered for nearly the entire winter season. On the test course, the combination of sweeping corners and areas of acceleration and braking challenged each tire's ability to control the vehicle and provide confidence to the driver.

Even without studs, the General Altimax Arctic felt sure-footed on the rough ice surface of the test course. Its relatively high grip level and good feedback meant the driver always knew what and where the tire's traction limits were. Subjectively, both the Firestone Winterforce and Pirelli Winter Carving Edge weren't able to match the overall grip of the unstudded Altimax Arctic, and took a little longer to regain traction once wheel spin, brake lock-up or a cornering slide began. The studded set of Altimax Arctic tires were clearly superior to any of the unstudded tires with noticeably better acceleration, braking and cornering traction.

Objective Tests

In an effort to quantify the subjective impressions felt by our drivers, we also conducted a number of instrumented objective tests to evaluate differences in acceleration and braking traction. These tests used sensitive on-board accelerometers and wheel speed sensors to measure just how much acceleration and braking traction each tire had. These tests were conducted on groomed snow, polished ice and clear asphalt surfaces, and averaged multiple samples to eliminate any variability in conditions.

Objective test scores are percentage based, using a popular Studdable Winter / Snow tire as the reference (General Altimax Arctic scored as 100%). A score above 100% indicates performance better than the reference tire, while a score below 100% indicates performance below the reference.

Unstudded Versus Studded Tire Performance Overview

Our test results confirm the addition of studs to the General Altimax Arctic had little to no influence on snow traction, but did have a significant positive effect on ice performance. Also of note, ABS braking performance on dry and wet roads was negatively affected somewhat with the addition of studs.

Snow Acceleration Traction without Traction Control

This test measured each tire's wheel spin during hard acceleration without traction control or throttle modulation by the driver. An on-board accelerometer measures the longitudinal force as a wheel speed sensor measures slip at the drive wheels. Scores were generated by graphing acceleration force over wheel spin, and calculating the area under the curve for 9-60% wheel spin.

Close review of the data captured during this test showed the aggressive tread designs of the Studdable Winter / Snow tires reached their maximum acceleration force around 45% wheel spin. Faster wheel spin resulted in relatively constant acceleration as it passed 60% slip. This shows how turning off the traction control in certain situations when using Studdable Winter / Snow tires can be helpful, such as when trying to maintain vehicle momentum when churning through deep snow, or when attempting to get a vehicle unstuck by rocking it back and forth. Most vehicle traction control systems will not allow enough wheel spin to utilize a winter tire's peak acceleration traction found at relatively high wheel spin levels.

Snow Acceleration with Traction Control

This test measured the time required to accelerate from a standstill to 12mph using the vehicle's traction control system to manage wheel spin.

Snow Braking with ABS

This test measured the distance to stop from 25mph on a groomed snow surface, using the vehicle's Antilock Brake System to control wheel lock up.

Snow Handling Lap

This test compared the time required to cover the 1.1 mile snow handling course. The test was conducted with the vehicle's stability and traction control switched off. ABS brakes were used for consistency and safety.

Ice Acceleration Traction with Traction Control

This test measured the time to accelerate a given distance on polished ice using the vehicle's traction control system to aid the driver in minimizing wheel spin.

Ice Braking with ABS

This test measured the distance to stop from 10mph on a polished ice surface, using the vehicle's Antilock Brake System to control wheel lock up.

Ice Handling Lap

This test captured the time required to complete a lap of the 4/10th mile rough ice course. The test was conducted with the vehicle's stability and traction control switched off. ABS brakes were used for consistency and safety.

Dry Road Braking with ABS

This test measured the distance to stop from 50mph on a dry asphalt surface, using the vehicle's Antilock Brake System to control wheel lock up.

Wet Road Braking with ABS

This test measured the distance to stop from 50mph on a wet asphalt surface, using the vehicle's Antilock Brake System to control wheel lock up.