Benefits
The biggest benefit to rear wheel drive is that
it spreads the loads of the car across all four tires of a car. In a
rear wheel drive car the rear wheels do the pushing while the front wheels are
reserved for the steering duties. In front wheel drive cars the front tires
must perform both functions. Each front tire in a front wheel drive car must
do two tasks. Both the cornering forces and the engine acceleration/deceleration
forces in a front drive car act on the same tire.
So in a front drive the tires capacity can be easily exceeded.
In a rear drive car the rear tires handle the engine acceleration/deceleration
while the front only need to handle the steering forces. Not only does this
balance the load on the tires but it reserves the front tires exclusively for
the all important steering duties.
Other Benefits to Rear Wheel Drive.
O.K., some assumptions : All comparisons are of equal weight
cars without traction control. Braking comparisons assume maximizing the ability
(two feet on the pedal pressing as hard as possible) of a perfectly working
four channel anti-lock brake system.
- Better weight balance. Most rear wheel drive cars have the engine
in the front and the drive components in the rear. Front drive cars have everything
up front. By properly balancing the front and rear of the car you can improve
the handling, acceleration, braking, and thus safety of a car.
- Better acceleration. On all but the slipperiest surfaces rear wheel
drive cars accelerate faster than a front drive car from a stop. This is because
when you accelerate quickly from a stop the weight of the car transfers to
the rear of the car. In a rear drive car this places extra weight on the rear
of the car, essentially jamming the tires in to the road greatly increasing
traction. In a front drive car, when the weight goes to the rear, weight is
taken off of the front wheels. The front wheels spin thus losing traction.
If the wheels are spinning not only does this slow you down but it also makes
it difficult to steer the car. In the rear drive car the front tires are available
for steering even if the rears have lost traction.
- Better Road Holding. The better weight balance of rear wheel drive
allows the car to handle better. The more even weight allows the car to drive
neutrally through a corner. This means both the front and rear of the car
have near equal loads acting upon them. In a front drive car the the heavy
front end causes the front end to have a higher load on it. This will cause
the front tires to eventually lose grip well before the rear tires are fully
loaded. Front tires on front drive cars do much more work than the rears causing
them to wear out much faster. It is best to balance the load as best you can
among the four tires. If you are accelerating or slowing down (engine braking)
these forces will act upon the already heavily loaded front tires of a front
drive car. In a rear drive car the front tires are left for steering even
when accelerating or engine braking. Sharing the work among all four tires
is the key.
- Better Stopping. Because of the better balance rear drive cars brake
better. When you stop a front drive car the excess weight in the front of
the car allows the force on the front tires to exceed the limits of the tires.
The relatively low weight on the rear of a front drive car does not allow
the tires to be used to their maximum ability. When panic stopping weight
will transfer to the front in both rear and front drive cars but there is
more weight left for rear braking action in the rear drive car.
- No Torque Steer. Front wheel Drive cars have a problem known as Torque
Steer. This occurs when the acceleration of the engine effects the cars steering.
Since the driveline is connected to the steering wheels the torque of the
engine applies force to the front wheels causing the car to pull to the right
during acceleration. Rear Drive cars do not have this problem since the engine
is not connected to the steering gear.
- Better Ride and Feel. The light front end of the car allows it to
"turn in" to a corner easier. The car feels more nimble and controllable.
Since the front is not so heavy it is not burdened by needing strong springs
to keep it under control. This allows the suspension to be set up softer while
maintaining good control ability. The absence of drive shafts (half shafts)
and CV joints in the front of the car allows the front suspension to be designed
for maximum steering efficiency. The lower rotating weight of the front wheel
assemblies improves steering response and ultimate grip. Granted that a rear
drive has more weight at the rear of the car but it can be handled by the
underutilized (in a front driver) rear tires.
- Better Serviceability / More Rugged. Ever notice that cops and taxis
avoid front wheel drive like the plague? That is because rear wheel drive
cars are more rugged and easier and cheaper to fix.
- Better Ultimate Ability.. Purpose built race cars are almost always
rear wheel drive. In production based racing series Front Wheel Drive cars
are given a performance advantage to make them equal to Rear Drive Cars. Usually
this is in the form of a weight break. Granted we shouldn't be driving our
cars like race cars on the street but in an emergency having the extra ability
in the car is an advantage I would like to have.
So why do automakers use front drive cars?
Well I guess there are a couple of good reasons I can think of. Anybody else
have any more? If so e-mail me and let me
know.
- Traction in Snow and Ice. When not under hard acceleration front
drive cars have more weight over the front wheels. This gives more traction
for acceleration in very slippery conditions. This is the biggest perceived
advantage to a front drive car. However, today's rear wheel drive cars with
traction control and independent suspension do very good in the snow. For
areas that have extreme amounts of winter weather this may be enough to justify
a front wheel drive car.
- Packaging. In front drive cars the engine and drivetrain can be pre-assembled
as one unit and then popped in to the car during assembly. This probably leads
to a more efficient assembly operation.
- Cost. Due to easier manufacturing and a few less components it may
be cheaper to manufacture a FWD car.
- Passenger/Trunk Space. Since you do not need to run a driveshaft
down the middle of the car you may be able to get more interior room. Funny
that front drive cars have a hump down the middle anyway! Not having a rear
suspension can allow the trunk area to be larger.
- Demand. Until we tell the automakers we want rear drive cars they
won't build them. So let's tell them!