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

Everyone who drives in the snow knows 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. & just as changing weather & 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 & tire manufacturers from around the world. Here we found consistent cold temperatures, plenty of snow & well-prepared snow & ice surfaces - ideal conditions for conducting side-by-side tire comparisons. Our evaluation was comprehensive - comparing each tire's ability to accelerate, brake & drive through the snow & 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.

Our evaluation compared three Studless Ice & Snow winter tires, each designed with advanced tread compounds & highly evolved tread patterns to be the best for when winter conditions are the worst. We compared the Bridgestone Blizzak WS60, the Continental ExtremeWinterContact & Michelin's X-Ice Xi2. We used new 205/55R16 tires mounted on 16x7.0" wheels. 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 H&ling

Our subjective snow h&ling 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 & ice base & proved to challenge each tire's ability to accelerate, brake & turn. Our evaluation was conducted with the test vehicle's traction & stability control system switched off so the driver would feel how much grip, & all of the slip, each tire had. ABS brakes were used for consistency & safety.

In our snow conditions, the Continental ExtremeWinterContact provided very good overall traction & stable vehicle balance, delivering responsive steering, good acceleration traction & confident braking capability. The Michelin X-Ice Xi2 demonstrated good overall traction, but could not quite match the ExtremeWinterContact. The Bridgestone Blizzak WS60 was found to be very similar to the X-Ice Xi2 overall, but with slightly less acceleration & braking traction in our dynamic driving conditions.

Snow H&ling

Rating	Bridgestone Blizzak WS60	Continental ExtremeWinterContact	Michelin X-Ice Xi2
Acceleration	6.00	7.00	6.25
Braking	6.00	7.00	6.50
H&ling	6.00	7.00	6.00
Overall Subjective Snow H&ling	6.00	7.00	6.25

 

Performance Drive Ratings - Ice H&ling

The subjective ice evaluation was conducted on a flat 4/10ths mile h&ling 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 & no road salt or traction s& 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 & areas of acceleration & braking challenged each tire's ability to control the vehicle & provide confidence to the driver.

The Continental ExtremeWinterContact delivered very good overall traction & was found to be noticeably superior to the other two tires. Once it did slide, there was good reserve grip & traction recovered quickly - almost abruptly during lift-throttle maneuvers. The relatively high level of steering traction of the ExtremeWinterContact resulted in a small tendency towards modest oversteer in some situations.

The Bridgestone Blizzak WS60 proved very capable & stable, providing good overall grip levels with a small tendency towards gentle & safe understeer. The Michelin X-Ice Xi2 followed close behind with slightly less overall cornering traction & modest understeer when it reached its traction limit.

Ice H&ling

Rating	Bridgestone Blizzak WS60	Continental ExtremeWinterContact	Michelin X-Ice Xi2
Acceleration	6.33	7.00	6.00
Braking	6.25	7.00	6.00
H&ling	6.55	6.90	6.05
Overall Subjective Ice H&ling	6.38	6.97	6.02

 

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 & braking traction. These tests used sensitive, on-board accelerometers & wheel speed sensors to measure just how much acceleration & braking traction each tire had. These tests were conducted on groomed snow, polished ice & clear asphalt surfaces, & averaged multiple samples to eliminate any variability in conditions.

Objective test scores are percentage based, using a popular Studless Ice & Snow tire as the reference (Bridgestone Blizzak WS60 scored as 100%). A score above 100% indicates performance better than the reference tire, while a score below 100% indicates performance below the reference.

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 onboard 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 & calculating the area under the curve for 9-60% wheel spin.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	103.6%
Michelin X-Ice Xi2	100.8%

 

A close look at the data revealed all of the Studless Ice & Snow tires we tested developed very similar acceleration levels, with increasing acceleration force as wheel spin increased, with all reaching a plateau around 45% slip. Less wheel spin generated lower acceleration force while wheel spin greater than 45% produced gradually declining acceleration force. This shows how turning off the traction control in certain situations when using Studless Ice & Snow winter 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 & 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 st&still to 12mph using the vehicle's traction control system to manage wheel spin.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	104.6%
Michelin X-Ice Xi2	104.8%

 

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.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	100.3%
Michelin X-Ice Xi2	98.0%

 

Snow H&ling Lap

This test captured the time required to cover the 1.1-mile snow h&ling course. The test was conducted with the vehicle's stability & traction control switched off. ABS brakes were used for consistency & safety.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	102.6%
Michelin X-Ice Xi2	100.5%

 

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.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	85.5%
Michelin X-Ice Xi2	82.3%

 

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.

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	85.9%
Michelin X-Ice Xi2	84.9%

 

Ice H&ling Lap

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

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	106.5%
Michelin X-Ice Xi2	96.4%

 

Dry Road Braking with ABS

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

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	98.7%
Michelin X-Ice Xi2	96.7%

 

Wet Road Braking with ABS

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

Tire Line	Percent Versus Reference
Bridgestone Blizzak WS60	100.0%
Continental ExtremeWinterContact	101.0%
Michelin X-Ice Xi2	101.4%