Autos Choosing two Wheel Drive or four Wheel Drive
You're buying a new car. You know the style you like. You know the color you want. You know the sound system and all of the bells and whistles that you just have to have. Then, just when you think you are ready to make a decision, someone asks if you prefer two or four wheel drive. Are you ready to answer? There are important personal, financial, and technical considerations that have a bearing on the decision.As the names imply two wheel drive vehicles only send power to two of the four wheels while four wheel drive technologies send power to them all. The additional systems required to power the extra two wheels add extra expense and weight to the four wheel cars in exchange for substantially increased safety and traction in all but optimal driving conditions.Two wheel drive cars are either front wheel or rear wheel drive. The front wheel configuration is by far the most common and provides some additional control in adverse conditions as well as lighter weight and better fuel economy compared to rear wheel drive. However, due to its more even distribution of weight, the rear wheel drive cars handle better on dry roads.Each two wheel drive configuration suffers from its own specific problems with stability in curves and on hard acceleration or braking. The front wheel drive cars may lose traction when the weight of the vehicle shifts to the back during acceleration. They also are subject to "understeer" in sharp curves causing the car to go straight when the driver asks it to turn. Rear wheel drive configurations have most of the weight in the front and the power at the rear wheels. As a result the rear wheels loose traction in a quick stop as the weight shifts forward and oversteer in curves causing the car to fishtail.Four wheel drive cars avoid all of these difficulties. With power at all four wheels it maintains control and balance in both hard accelerations and is less prone to both understeer and oversteer. This evenly distributed power provides additional traction on slippery or very sloped surfaces. In snow or heavy rain it outperforms a two wheel drive car dramatically. Newer systems sense a loss of traction before the driver does and transfer the torque away from the slipping wheel to the wheels that have traction, allowing the driver to regain control more efficiently. Were it not for the additional expense in initial cost, maintenance and gas mileage the two wheel drive car would be relegated to automotive museums.Quantifying the additional cost can be difficult as car companies like to compare the four wheel drive option to a similarly equipped two wheel drive car, but don't always offer the four wheel drive options on less expensive models with four cylinder engines. The automatic upgrade to a six cylinder engine to offset the additional weight of the four wheel drive components may be fifteen hundred dollars by itself. Industry estimates for the four wheel drive alone range from about $1000 on lower end production models to several thousand dollars on more expensive high performance and luxury models. The loss of fuel economy ranges from one to four miles per gallon.Additional maintenance and repair expenses can be significant especially on advanced systems with computer modulated sensors and transfer cases. These sensitive systems can require the rotation of tires every 5000 miles and the replacement of all four tires even if only one is in some way flawed.In the end the trade off is between safety, reliability, and cost. In snowy or mountainous areas the car of choice often appears to be Subaru, a pioneer in all wheel drive technology. In southern Arizona they may not be as popular.
You're buying a new car. You know the style you like. You know the color you want. You know the sound system and all of the bells and whistles that you just have to have. Then, just when you think you are ready to make a decision, someone asks if you prefer two or four wheel drive. Are you ready to answer? There are important personal, financial, and technical considerations that have a bearing on the decision.
As the names imply two wheel drive vehicles only send power to two of the four wheels while four wheel drive technologies send power to them all. The additional systems required to power the extra two wheels add extra expense and weight to the four wheel cars in exchange for substantially increased safety and traction in all but optimal driving conditions.
Two wheel drive cars are either front wheel or rear wheel drive. The front wheel configuration is by far the most common and provides some additional control in adverse conditions as well as lighter weight and better fuel economy compared to rear wheel drive. However, due to its more even distribution of weight, the rear wheel drive cars handle better on dry roads.
Each two wheel drive configuration suffers from its own specific problems with stability in curves and on hard acceleration or braking. The front wheel drive cars may lose traction when the weight of the vehicle shifts to the back during acceleration. They also are subject to "understeer" in sharp curves causing the car to go straight when the driver asks it to turn. Rear wheel drive configurations have most of the weight in the front and the power at the rear wheels. As a result the rear wheels loose traction in a quick stop as the weight shifts forward and oversteer in curves causing the car to fishtail.
Four wheel drive cars avoid all of these difficulties. With power at all four wheels it maintains control and balance in both hard accelerations and is less prone to both understeer and oversteer. This evenly distributed power provides additional traction on slippery or very sloped surfaces. In snow or heavy rain it outperforms a two wheel drive car dramatically. Newer systems sense a loss of traction before the driver does and transfer the torque away from the slipping wheel to the wheels that have traction, allowing the driver to regain control more efficiently. Were it not for the additional expense in initial cost, maintenance and gas mileage the two wheel drive car would be relegated to automotive museums.
Quantifying the additional cost can be difficult as car companies like to compare the four wheel drive option to a similarly equipped two wheel drive car, but don't always offer the four wheel drive options on less expensive models with four cylinder engines. The automatic upgrade to a six cylinder engine to offset the additional weight of the four wheel drive components may be fifteen hundred dollars by itself. Industry estimates for the four wheel drive alone range from about $1000 on lower end production models to several thousand dollars on more expensive high performance and luxury models. The loss of fuel economy ranges from one to four miles per gallon.
Additional maintenance and repair expenses can be significant especially on advanced systems with computer modulated sensors and transfer cases. These sensitive systems can require the rotation of tires every 5000 miles and the replacement of all four tires even if only one is in some way flawed.
In the end the trade off is between safety, reliability, and cost. In snowy or mountainous areas the car of choice often appears to be Subaru, a pioneer in all wheel drive technology. In southern Arizona they may not be as popular.
