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Many people are drawn to all-wheel drive's promise of improved winter driving traction, but what these people don't know may hurt them (or you).

An article titled "What Price Traction?" in the May 1999 issue of Car and Driver magazine answered a very simple question: "Which gives better traction, all-wheel drive, or two-wheel drive with snow tires?"

The following is a quick summary of their surprising findings:

• all-wheel drive helps in accelerating or climbing hills, but hinders braking and turning ability due to the extra weight.
• winter tires are a better solution for most people.
• winter tires make a bigger difference on front wheel drive cars than rear wheel drive cars.

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The Test in Greater Detail

The test was conducted using four cars with their stability control systems disabled and their anti-lock brake systems active:

1. Audi A6 2.8 FrontTrak (front wheel drive)
2. Audi A6 2.8 quattro (all wheel drive)*
3. Mercedes Benz E320 (rear wheel drive)
4. Mercedes Benz E320 4MATIC (all wheel drive)*

Both all-wheel drive systems added roughly 200 pounds.

Cost of Audi quattro option: $1650 (before luxury tax).
Cost of Mercedes-Benz 4MATIC option: $2790 (before luxury tax).
Cost of set of winter tires mounted on dedicated wheels: $300-$1200

*Note that "all-wheel drive" is used to describe many systems that deliver power to all four wheels.

Hill Climb
All-wheel drive was the clear winner in hill climbing ability.
Both all-wheel drive cars could scale the 30% snow-covered grade.
The two-wheel drive cars could not climb the 17% grade.

Straight-line Acceleration (0-50 mph)
on Snow:
Using the front-wheel drive A6 as a baseline:
Adding winter tires made the car 30% quicker. (9.7 seconds)
Adding all-wheel drive resulted in a 45% improvement. (7.6 seconds)

Using the rear-wheel drive E320 as a baseline:
Adding winter tires made the car 36% quicker. (10.5 seconds)
Adding all-wheel drive resulted in a 51% improvement. (8.1 seconds)

Braking (50-0 mph)
Using the front-wheel drive A6 as a baseline:
Adding winter tires shortened stopping distances by as much as 64 feet.
Adding all-wheel drive increased stopping distance by up to 12 feet.

Using the rear-wheel drive E320 as a baseline:
Adding winter tires shortened stopping distances by as much as 37 feet.
Adding all-wheel drive increased stopping distance by up to 18 feet.

Cornering
Winter tires offered twice the improvement in grip that all-wheel drive did
front-wheel drive: .28g
all-wheel drive: .31g
front-wheel drive+winter tires: .34g
all-wheel drive +winter tires: .34g

rear-wheel drive: .30g
all-wheel drive: .32g
rear-wheel drive+winter tires: .34g
all-wheel drive+winter tires: .37g

Slalom Under Acceleration
once again, winter tires offered twice the improvement in grip all-wheel drive did

Using the front-wheel drive A6 as a baseline:
Adding winter tires made the car 5.5% quicker.
Adding all-wheel drive resulted in a 12.6% improvement.

Using the rear-wheel drive E320 as a baseline:
Adding winter tires made the car 2.5% quicker.
Adding all-wheel drive resulted in a 4.7% improvement.

Slalom Under Deceleration
The all-wheel drive A6 was slower (by 3.5 mph) and more difficult to control (it tended to slide sideways) than the front-wheel drive A6 on winter tires.

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Still with us? We're impressed.

As a bonus, we offer you this: the Car and Driver test failed to address the difference in fuel economy - usually about 2-4 mpg.

And for more on the topic, read "Snow tires still beat four-wheel drive", written by Car and Driver magazine's editor in chief, Csaba Csere.

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