Front-wheel drive versus rear drive

The mechanical systems in vehicles are as varied and complex as their owners and operators. Optimum care for humans requires some knowledge of our makeup, along with proper operation and maintenance. Learning about our cars and trucks is a responsibility that we drivers must take to successfully and safely operate our vehicles. What follows is a primer on front and rear drive systems — in this case, a little knowledge is a good thing!

We’ve all heard one thing or another about front-wheel drive vehicles and rear-wheel drive vehicles. In our region, much of the debate has to do with the pros and cons of winter driving with each type of system. Generally, discussions and articles tend to tout the front-drivers as superior to their rear-driven counterparts. Well, yes and no.

First, as many of you know, a front-wheel drive vehicle is propelled by engine power transferred to only the front wheels — the rear wheels are just back there for the ride. Rear-wheel drive vehicles have engine power directed to the two rear wheels, and besides turning left and right, the front wheels just roll along. This creates double duty for the front wheels on a front-drive car, as they must move the car and steer it. As a result, tire wear is greatest for the front tires on a front-drive car, where wear is up to three times greater than the rear tires of such a vehicle. Rear-wheel driven cars use up tires at about the same rate on the front as the back, but the wear pattern is different for the two positions. That is why periodic tire rotation is important for either drive system, to even out different patterns and rates of wear.

Now here are some facts on that winter driving stuff. Yes, front-wheel drive vehicles have a traction advantage over rear-drivers on snow and ice when it comes to climbing a grade, or taking off from a stop. This is for one reason only — the majority of the weight (engine and transaxle) is directly over the drive wheels. For those who remember how well an old Volkswagen Beetle could climb a hill, the same theory applies, except it is because the VW engine is over the rear-drive wheels — rear engine, rear-wheel drive. This traction advantage, however, puts the FWD (or rear engine, RWD) car at a disadvantage compared to front-engine, RWD cars when it comes to overall stability in highway driving, turning, and stopping. This disadvantage is due to an inherent balance shortcoming of the engine-over-drive-wheel designs. Ideally, a good handling vehicle should strive toward a 50/50 front/rear weight balance. That means you could make a seesaw out of a perfectly balanced car by placing a fulcrum right under its middle. Only the best sports cars achieve this desirable balance, and none of them are FWD.

This is not to say that FWD cars are ill handling — they are not. Within normal driving situations, the added traction for our winter driving is a welcome exchange for performance handling. Within the speed limits and under most conditions, FWD works quite well — it’s just that when pushed to handling limits, and while driving at speed in adverse conditions, RWD is more stable and predictable.

To make this case, one need not look far — virtually all true performance cars are RWD (or now all-wheel-drive — another topic), such as Corvette, BMW, Mercedes-Benz, or new American models like the Pontiac GTO. Racecars are typically RWD vehicles with a 50/50 balance, and even the Washington State Patrol cruisers are nicely balanced, big rear-driven sedans. That last example really confuses the issue of FWD winter superiority, since State Patrol officers travel all of our roads in all weather. It’s amazing what some quality traction tires, coupled with some driving skill, can accomplish.

Aside from early Oldsmobile and Cadillac models, American manufacturers began producing FWD vehicles for the masses in 1980 with the introduction of the Chevrolet Citation — import automakers had already been doing it with models like Audi, Volkswagen, Subaru and Honda. Automotive engineers who I know suggest that the impetus for the American movement to FWD was for ease of assembly — the entire drive train package (engine and transaxle) can be fully assembled, installed in a sub-frame, and bolted under the body as the car rolls down the line. By contrast, it takes many more steps to put together a car with the engine in the front, and the transmission in the middle, connected via a drive shaft to the differential at the back.

So, a side benefit that we derive from this manufacturer convenience is getting FWD cars with a distinct traction advantage for climbing hills and taking off from a stop during our winter driving. But don’t shy away from well-balanced, good handling RWD cars, because with a good set of traction tires and some astute driving, these models will work as well, and in certain instances, better.

Now you’re not only armed with a bit of knowledge for your next car shopping excursion, but you know a little more about what’s happening underneath your vehicle as you drive.

In a Roundabout Way

The popularity of intersection roundabouts is increasing in our country, and right here in Spokane. Al Gilson, public information officer with the state Department of Transportation, informs me that the state is building a modern example at the intersection of SR 206 and Bruce Road, and that the city is constructing one at Wellesley and “A” Street. These projects are in response to safety concerns at these intersections. There is some very interesting info at the state’s Web site: http://www.wsdot.wa.gov/Projects/SR206BruceRoadRoundabout.