Are FWD cars overall superior to RWD cars?

[Alberto Michelatti]

I am a FWD cars enthusiast, and I would like to explain why for me FWD cars are overall superior to RWD cars and, from a certain point of view, to AWD cars also.

1) the engine and the gearbox overall mass directly over the front axle means at the same time more brake power, more control, more directionality, more safety, more space, more stability, more traction.

2) the absence of the RWD longitudinal propeller shaft means at the same time less fuel consumption, less noise, less pollution, less space waste, less vibrations, less weight (up to about 100 kg).

3) with a FWD car, if you apply full throttle when cornering the car becomes understeering and the worst thing that can happen is that the car go straight, colliding longitudinally with the obstacles (take a scale car model and lock with adhesive tape the front wheels, make it run on the floor, and see what happens. Then lock the rear wheels and then all the wheels, and see what happens). Furthermore, on a FWD car generally only the wheel with less grip spins, while the other wheel keeps the directionality. With a RWD car, instead, the car become oversteering and the worst thing that can happen is that the car fishtails, colliding transversally with the obstacles. With an AWD car, instead, understeer and oversteer limits are obviously higher, but if you exceed them the car control recovery could be very problematic for a normal driver, because over a certain limit the car understeer with the front axle and oversteer with the rear axle, all at the same time.

4) a FWD car is very easy and instinctive to control, because if when cornering the FWD car becomes understeering you have just to release the accelerator pedal and, eventually, slightly adjust the trajectory. A RWD car is very difficult and not at all instinctive to control, because if when cornering the FWD car becomes oversteering you have to carefully keep pressed the accelerator pedal and quickly countersteer to keep the trajectory. The behaviour of an AWD car is generally quite similar to an FWD car, but when you exceed its high limits the control recovery could be problematic for a normal driver.

Briefly, I think that the overall best possible solution today available is a FWD car with an open differential, better if with TCS (Traction Control System: electronically controlled artificial limited slip differential actuated by brakes) and ASR (Anti-Slip Regulation: electronically controlled power modulation actuated by the drive-by-wire throttle). Why an open differential? Simple: just because with an open differential while one wheel spins the other wheel can keep the trajectory.

I think that the only real disadvantage of a FWD car is that it is not funny to drive, because the rear wheels are almost always perfectly on their ideal trajectory, short of you use some

like for example the handbrake 180° turn or the Scandinavian flick (pendulum turn). However, it is neither funny to bring your RWD car to a bodyshop for the reconstruction of the rear end, it isn't?

I think that the only two possible rational solutions are FWD or AWD; however, I think that a RWD car makes sense only in presence of huge power, rear engine and, most of all, in presence of very skilled drivers. I think that if you don't live in a territory with very slippery steepy roads, an AWD car is substantially useless... a waste, from a certain point of view. For example, I think that on a snow covered road it is safer to drive a FWD car with M+S tires rather than to drive an AWD car with normal tires.

And now, the curiosities corner.

Did you know what is the most powerful FWD car ever? As far as I know, the most powerful FWD car ever is the existing Pontiac Grand Prix GXP, equipped with a 303 hp SAE net 5.3 V8 engine (307 hp DIN, EU-spec).

They who say that the most powerful FWD cars ever are the 1966÷1970 Oldsmobile Toronado W-34 7.5 V8 (455 in³) and the 1970 Cadillac Eldorado 8.2 V8 (500 in³), both with 400 hp SAE gross (open exhausts, no accessories), are wrong, because when in 1972 there was the SAE gross to SAE net switch, the advertised power of the Cadillac Eldorado, for example, was of 365 hp SAE gross or 235 hp SAE net, while the power of the Oldsmobile Toronado fallen from 350 hp SAE gross to 250 hp SAE net (to convert DIN horsepower to SAE net, simply divide the DIN number by 1.0139).

For the ultimate, I think that the annoying and not dangerous FWD cars' torque steer issue, mainly noticeable on high torque FWD cars, is not depending by the half-shafts length, but instead it is depending by the overall torsional stiffness of the left-side half-shaft and of the right-side half-shaft, no matter if the equal length half-shafts or the unequal length half-shafts system is used. I think that when full torque is delivered by the differential to the half-shafts, the longer half-shaft, due to its weak torsional stiffness, accumulates a delay in torque delivery to the right-side wheel, and this phenomenon makes the car steer to the left-side.

FWD-FTW! Safety first!

Alberto.

Edited June 27, 2008 by Alberto Michelatti

[MT]

4) a FWD car is very easy and instinctive to control, because if when cornering the FWD car becomes understeering you have just to release the accelerator pedal and, eventually, slightly adjust the trajectory.

90% of the big accidents that i've seen in front wheel drive cars (especially Corolla Sportivo's) are caused by doing exactly what you have suggested. its called lift off oversteer.

i accept your thoughts but i totally disagree. if you dont drive like an idiot, it makes no difference what wheels are driving the car. however, if i had to, my choice would be

1. All wheel drive

2. RWD

3. FWD

[CAP]

I am a RWD car enthusiast, and I would like to explain why for me RWD cars are overall superior to FWD cars.

1) the engine and driveline laid out in a longditudunal fashion give better overall weight distribution from front to rear, unlike a fwd car which carries most of its mass in front of the front axle line. The better weight distribution on a RWD car translates to stable braking, more control, more safety, more stability, more traction.

2) Comparing the kerb weights of similar sized passenger cars say for example a BMW 116i (1,245kg) and a VW Golf Trendline 1.6 (1240kg), if there is a weight saving advantage in using a fwd layout, the manufacturers haven't utilised it.

3) Understeering in a FWD and colliding head-on into oncoming traffic or stationary objects can in itself be quite dangerous. In a RWD car, if the level of rear wheel grip is exceeded and the vehicle does begin to oversteer, one eases off the throttle and/or applies some opposite steering lock to correct and continue along the desired cornering line. Severe understeer in a FWD car can easily then turn into snap oversteer if the driver backs off the accelerator too quickly or is hamfisted and jumps onto the brakes, as per point one, most of the mass is over the front, leaving the rear end very light in comparison and less stable when horizontal cornering forces are in play allowing the rear end to swing around and end up making the car and driver come to a standstill facing the direction they just came from. Oversteer in a FWD is far more difficult to correct than in a RWD car, but understeer can be corrected as easily in a RWD car as a FWD car can.

4) A RWD car is easier to control. Much more control is available to the driver via throttle input than would be the case in a FWD car. Understeer? Reduce throttle. Oversteer? Reduce throttle. The better weight distribution of the RWD car, with more weight over the rear wheels as well as the fronts keeps the car more stable and therefore the not so skilled driver has a better chance of regaining control of the car rather than spinning out of control, or understeering into objects, the skilled driver will use this balance to actually increase cornering speeds in a way not achievable in a FWD car. Much more so in both cases when a limited slip differential is fitted. Wheelspin? Then ease off the throttle dummy duh?

Am I biased? No I drive a FWD car. But I do prefer RWD any day. If you haven't owned one before or driven one long term, you'll never understand how better balanced they are.

Where a FWD has advantages, is in packaging, allowing for shorter overall designs because of the layout of the engine/driveline, it allows for much shorter bonnet lines which is a big advantage in small car design. The original Mini took full advantage of this trait at the time it was designed. Small cars have since followed the same trend.

A look at the very clever designed Mitsubishi i small car with its rear engine rear wheel drive layout shows not all small cars have to be FWD to have lots of space for their size and shows engineers dont see FWD to be the only alternative.

[selyaT]

90% of the big accidents that i've seen in front wheel drive cars (especially Corolla Sportivo's) are caused by doing exactly what you have suggested. its called lift off oversteer.

Exactly what Carlo and MT said. If you lift off mid-corner to adjust the "trajectory" you will end up in a "transverse" collision before you know it. (Weight transfer to front of vehicle, front grips, rear slips, around we go)

Hence, a "longitudinal" collision is not the worst outcome.

[Dead]

I am a RWD car enthusiast, and I would like to explain why for me RWD cars are overall superior to FWD cars.

1) the engine and driveline laid out in a longditudunal fashion give better overall weight distribution from front to rear, unlike a fwd car which carries most of its mass in front of the front axle line. The better weight distribution on a RWD car translates to stable braking, more control, more safety, more stability, more traction.

2) Comparing the kerb weights of similar sized passenger cars say for example a BMW 116i (1,245kg) and a VW Golf Trendline 1.6 (1240kg), if there is a weight saving advantage in using a fwd layout, the manufacturers haven't utilised it.

3) Understeering in a FWD and colliding head-on into oncoming traffic or stationary objects can in itself be quite dangerous. In a RWD car, if the level of rear wheel grip is exceeded and the vehicle does begin to oversteer, one eases off the throttle and/or applies some opposite steering lock to correct and continue along the desired cornering line. Severe understeer in a FWD car can easily then turn into snap oversteer if the driver backs off the accelerator too quickly or is hamfisted and jumps onto the brakes, as per point one, most of the mass is over the front, leaving the rear end very light in comparison and less stable when horizontal cornering forces are in play allowing the rear end to swing around and end up making the car and driver come to a standstill facing the direction they just came from. Oversteer in a FWD is far more difficult to correct than in a RWD car, but understeer can be corrected as easily in a RWD car as a FWD car can.

4) A RWD car is easier to control. Much more control is available to the driver via throttle input than would be the case in a FWD car. Understeer? Reduce throttle. Oversteer? Reduce throttle. The better weight distribution of the RWD car, with more weight over the rear wheels as well as the fronts keeps the car more stable and therefore the not so skilled driver has a better chance of regaining control of the car rather than spinning out of control, or understeering into objects, the skilled driver will use this balance to actually increase cornering speeds in a way not achievable in a FWD car. Much more so in both cases when a limited slip differential is fitted. Wheelspin? Then ease off the throttle dummy duh?

Am I biased? No I drive a FWD car. But I do prefer RWD any day. If you haven't owned one before or driven one long term, you'll never understand how better balanced they are.

Where a FWD has advantages, is in packaging, allowing for shorter overall designs because of the layout of the engine/driveline, it allows for much shorter bonnet lines which is a big advantage in small car design. The original Mini took full advantage of this trait at the time it was designed. Small cars have since followed the same trend.

A look at the very clever designed Mitsubishi i small car with its rear engine rear wheel drive layout shows not all small cars have to be FWD to have lots of space for their size and shows engineers dont see FWD to be the only alternative.

0W3ND y0

[Simo]

LoLoLoL nice sig rob

/hi-jack

[Hiro]

I am a FWD cars enthusiast, and I would like to explain why for me FWD cars are overall superior to RWD cars and, from a certain point of view, to AWD cars also.

1) the engine and the gearbox overall mass directly over the front axle means at the same time more brake power, more control, more directionality, more safety, more space, more stability, more traction.

Weight transfer during acceleration means you have LESS traction in a front wheel drive car under acceleration than a RWD car. And "directionality", if it is what I think you are referring to, has a lot more to do with suspension setup than driving wheels.

3) with a FWD car, if you apply full throttle when cornering the car becomes understeering and the worst thing that can happen is that the car go straight, colliding longitudinally with the obstacles (take a scale car model and lock with adhesive tape the front wheels, make it run on the floor, and see what happens. Then lock the rear wheels and then all the wheels, and see what happens)

So, so wrong. Notice that model cars are not scale replicas when it comes to weight, and also aren't producing power at the wheels, nor do they have fully working suspension. It would be like pushing a pedal-car into a wall and using that as crash data.

Furthermore, on a FWD car generally only the wheel with less grip spins, while the other wheel keeps the directionality.

This happens on ANY car without an LSD or locked differential. And the thing that you're losing here is the ability to put power through to the ground, not traction for steering. ANY car with an open diff can light up an inside wheel when going through a corner, FWD or not, and still retain steering ability.

With a RWD car, instead, the car become oversteering and the worst thing that can happen is that the car fishtails, colliding transversally with the obstacles

This can be corrected with proper suspension setup. Most modern cars, RWD or not, are designed to understeer or be neutral at their limit, because of the flexibility of modern suspension designs. Older cars with simpler suspension like solid axles and leaf springs didn't have that ability, and thus were more likely to oversteer at the limit

With an AWD car, instead, understeer and oversteer limits are obviously higher, but if you exceed them the car control recovery could be very problematic for a normal driver, because over a certain limit the car understeer with the front axle and oversteer with the rear axle, all at the same time.

You can't oversteer with one axle and understeer with another at the same time. Understeer and oversteer refer to the angle of the car relative to the steering angle of the wheels. Oversteer is when the car has turned further than the front wheels have turned - understeer is when the front wheels have turned more than the car. Most AWD naturally understeer, and are quite hard to provoke into oversteer (notice the lack of AWD cars in drifting competitions).

4) a FWD car is very easy and instinctive to control, because if when cornering the FWD car becomes understeering you have just to release the accelerator pedal and, eventually, slightly adjust the trajectory. A RWD car is very difficult and not at all instinctive to control, because if when cornering the FWD car becomes oversteering you have to carefully keep pressed the accelerator pedal and quickly conutersteer to keep the trajectory.

Do this once into a corner, experience lift-off oversteer, and then come back and say you understand how cars handle. Saying a RWD is not instinctive to handle is a joke, since no car is _instinctive_ to handle as it is a skill that has to be learnt from scratch.

Briefly, I think that the overall best possible solution today available is a FWD car with an open differential, better if with TCS (Traction Control System: electronically controlled artificial limited slip differential actuated by brakes) and ASR (Anti-Slip Regulation: electronically controlled power modulation actuated by the drive-by-wire throttle). Why an open differential? Simple: just because with an open differential while one wheel spins the other wheel can keep the trajectory.

All these electronic gizmos just to get the thing to handle as well as a car with an LSD. Arguably one of THE best handling FWD cars of all time, the DC2 Honda Integra Type-R, had none of that electronic crap, just FWD, LSD and a well sorted chassis/suspension combination. One of the best handling FWD cars currently available is the Renault Clio Sport 172 Cup, again with no electronic stability control, no ABS,

And now, the curiosities corner.

Did you know what is the most powerful FWD car ever? As far as I know, the most powerful FWD car ever is the existing Pontiac Grand Prix GXP, equipped with a 303 hp SAE net 5.3 V8 engine (307 hp DIN, EU-spec).

And did you know that it handles like an absolute BOAT?

FWD with large amounts of power are extremely hard to get acceptable handling out of. The SAAB Viggen, for instance, only had about 170kw but had MASSIVE amounts of torque steer, and whilst a very good performer in a straight line it would get left for dead in the twisty sections by your average RWD family sedan.

In short, I think there is a LOT you need to learn about car handling, chassis dynamics and suspension tuning. Whilst it is easy to repeat myths and generalisations, actually understanding the theories behind what you are talking about makes a HUGE difference. Being part of a design-and-build racing team at my university for 3 years has taught me immeasurable things about those subjects, coming from the mouths and books of some of the most respected car designers and race mechanics (Carroll Smith, Ron Tauranac for instance)

[SuperDave]

One of the best handling FWD cars currently available is the Renault Clio Sport 172 Cup, again with no electronic stability control, no ABS,

Carroll Smith

I never knew the 172 Cup was still for sale :P (it was only the UK versions that didn't have abs and stability control). The 197 is the new one, but it isn't on sale here yet...

w00t Carroll Smith!

[Dead]

4) a FWD car is very easy and instinctive to control, because if when cornering the FWD car becomes understeering you have just to release the accelerator pedal and, eventually, slightly adjust the trajectory. A RWD car is very difficult and not at all instinctive to control, because if when cornering the FWD car becomes oversteering you have to carefully keep pressed the accelerator pedal and quickly conutersteer to keep the trajectory.

Do this once into a corner, experience lift-off oversteer, and then come back and say you understand how cars handle. Saying a RWD is not instinctive to handle is a joke, since no car is _instinctive_ to handle as it is a skill that has to be learnt from scratch.

Agreed. I'm very cautious through corners ever since I went through 'that circle' on the outskirts of Canberra.