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In my recently started quest to actually learn about cars, I was wondering...

what are the real advantages and disadvantages of FWD, RWD and AWD? (i know this is a complicated question stated simply)

Also, is there a difference between AWD and 4WD?

Help rid the world of ignorance, and start with me! :D
 

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Replying to Topic 'Pros and Cons of FWD/RWD/etc'

QUOTE
Originally posted by JivinFlava


            In my recently started quest to actually learn about cars, I was wondering...

what are the real advantages and disadvantages of FWD, RWD and AWD? (i know this is a complicated question stated simply)

Also, is there a difference between AWD and 4WD?  

Help rid the world of ignorance, and start with me! :D[/b]

FWD

Pro: You go where you steer, safer under bad weather, easy for beginners to control
Con: Doesn't handle power well, usually limited to under 300HP. Understeer. You usually don't get the pin in seat feeling during acceleration.

RWD

Pro: Can handle as much power as you want. Usually more nimble in handling
Con: Oversteer. Harder to control especially under slick road condition.

AWD

Pro: Best of both FWD and RWD
Con: Fuel economy

I not sure what the difference is between AWD and 4WD. I think AWD is sending the power to the from the wheels that slip to the wheels that grip. And 4WD is same power to all 4 wheels no matter under what conditions.

Everyone is joining the AWD bandwagon now. Mercedes now offer 4Matic in every model, BMW is following soon. Volvo S60 has AWD option as well. And Audi is famous for its AWD. I think if the oil prices doesn't go to far up, more AWD offering will surface in the coming decade.
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

I'm sure you'll get several lengthy answers,. I'll keep mine simple since I'm supposedly at work. This will hardly be comprehensive.

FWD is more efficient - it's easier to pull something than to push it. They're also better for keeping traction in slippery conditions. RWD is lousy for it, although donuts in a RWD car are a throttle blip away in snow. :)

RWD provides better overall performance. Hence the reason the vast majority of purpose-built race cars are RWD. Others are AWD/4WD. Many production-based race cars are still FWD.

With RWD, more power can be put to the ground more quickly. The weight transfer of the car from a stop or coming out of a corner shifts extra weight to the rear thereby increasing traction. The opposite occurs in front wheel drive. RWD cars typically handle better - but why is literally a topic unto itself.

Also - with FWD, the wheels both steer and propel the car. There's only so much traction available. With RWD, the tasks are split.

4WD and AWD are different. I'm sure someone else will know for sure, but it has to do with how the power is distributed. This is a gross oversimplification, but I believe AWD is power to all four wheels all the time. I think 4WD systems only apply power (or more power) to the front wheels when necessary.

You can go on and on...
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

I agree with what the above two gentlemen said, but I'll add my own simplistic answer...

FWD: safe

RWD: fast

AWD: safe and fast

-Alt :)
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

Wisely said Alt :)
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

Going around a curve in a FWD vehicle under slick conditions is easier to recover from loss of traction as opposed to RWD. FWD, let your foot off the gas. RWD, pray that amidst the spinning and sliding of the car, it decides to stop before becoming one with a tree, guardrail, or another motorist.
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

I won't say FWD is better than RWD in bad weather, but kyler puts it well (the first sentence, at least. ignore the last). Reufus also has a very good post overall. The bad weather issue is the only thing I won't buy into 100%.

I won't get too into performance, because some of it is debatable, but I will mention some other things to consider:

FWD is cheaper
RWD requires the drivetrain to go from the front to the back (for lack of a better way to put it). This can affect space and seating.
Physics tell us that RWD will handle better and tighter.
FWD gives us torque steer.

Understeer sucks. Torque steer sucks.

While 4WD and AWD are often used interchangeably, they are not the same. True 4WD spins the wheels in such a way that it is a very poor system for roads - it was designed to be an off-roading system. AWD, on the other hand, compensates for that lack in allowing the wheels to spin at different rates (we won't get too technical here - yet. We can if it's desired) and becomes a very good system for all weather and all road use.

AWD is also a very heavy system.
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

Coming from a RWD toyota supra with busted automatic transmission, that was an absolute nightmare. There was a kick in the change from first to seond gear... it would chirp in the dry, in the wet it would fishtail the car. Usually by 90 degrees :p

But it was fun in the dry bringing the car to 5000rpm in neutral, then slamming it down to first. Screeeech, zoom, chirp, zoom... made the car sound tougher than it really was :p

I miss not being able to do a launch, but it's a small price to pay for leather, bose, safety, looks, sunroof, and all the other goodies the M6 gives :)
 

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Replying to Topic 'Pros and Cons of FWD/RWD/etc'

QUOTE
Originally posted by Rainchild


            Coming from a RWD toyota supra with busted automatic transmission, that was an absolute nightmare.  There was a kick in the change from first to seond gear... it would chirp in the dry, in the wet it would fishtail the car.  Usually by 90 degrees :p

But it was fun in the dry bringing the car to 5000rpm in neutral, then slamming it down to first.  Screeeech, zoom, chirp, zoom... made the car sound tougher than it really was :p

I miss not being able to do a launch, but it's a small price to pay for leather, bose, safety, looks, sunroof, and all the other goodies the M6 gives :)[/b]
Gosh, I wonder how that tranny got broken? 5000RPM brake torqueing you say?
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

FWD, when you have traction "pulls" the front into the direction you steer to. But when you loose grip - then you loose all steering (well on a modern car as the 6 with TCS it's less likely to happen). On snow, from a safty point of view, RWD is better since you might oversteeer, the you usually don't go so far. It spins around and stops there. A FWD on the other hand, can "plow'" forward. It's harder to stop, since all motion energy is focused in one single direction.

ON THE OTHER HAND :). FWD is FAR superior in not getting stuck in the snow. Unless you have a Tatra, Porsche or VW, RWD cars have almost no wieght over the rear wheels. Solution is sandbags :) That's a known thing to swedes (the ones I know at least :)). Volvo 745 and two bags of sand in the trunk and it will get moving again :)
 

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Replying to Topic 'Pros and Cons of FWD/RWD/etc'

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Originally posted by applejax

AWD is also a very heavy system.[/b]
A very good point. AWD is nice if you have a torquey engine to begin with. Weak engines (e.g. Audi's 1.8T) are not the peppiest coupled with an AWD layout. Casein-point our beloved MZI engine... it won't feel nearly as fast in an AWD platform. In FWD (light, reasonable drivetrain loss) form, it feels pretty quick.

-Alt
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

Some random thoughts:
I would say that modern traction and braking control systems on most newer cars negate any ill affect weather or ice would have on a RWD vehicle. Between all three I would personally rather have a good RWD setup with TCS and braking control. these systems can get you to 90+ percent of where AWD will get you in terms of safety, now if your going offroad (ie rally racing) thats another story. AWD is expensive, heavy and more of a maintanence hassle if you don't really need it. For smaller engines FWD is better in terms of drive train loss, verses RWD.
 

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Reading Topic: Pros and Cons of FWD/RWD/etc

Try going up a hill with RWD (or FWD) and all the fancy gizmos you want. Even with snow tires, they won't generally make it with the ease that AWD will.
While modern traction control systems and snow tires will be fine for many applications, they still do not compare to the overall benefits of AWD IMHO. TCS and snow tires will get you to about 90% of what AWD will with all season tires. But AWD with snow tires is another level above, in all aspects except for stopping.
I live in an area that's very rainy, and quite hilly. Snow isn't my biggest concern. But it's really nice to know that if it does dump down and I'm caught with my pants down (ie no snow tires) I can still go pretty much anywhere I need to go. If you live in Nevada where it's flat and hot, AWD probably doesn't make sense.
In the end it all comes down to your own priorities.
 

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Replying to Topic 'Pros and Cons of FWD/RWD/etc'

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Originally posted by kenoka

and I'm caught with my pants down (ie no snow tires) I can still go pretty much anywhere I need to go.  [/b]
Do they laugh at you when you arrive and get out of your car with no pants?
 

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Reading Topic: Reading Topic: Pros and Cons of FWD/RWD/etc

Wheels have a 'circle of grip', if you will. Their grip can be used to propel the car forward or laterally, but total grip is divided between these two directions. So if you are accellerating forward, the powered tires will not grip as well laterally as the ones not getting power.

If you throttle too hard in a turn in a FWD car, you'll end up going straighter than you are steering. This is understeer.
If you throttle too hard in a turn in a RWD car, you'll end up spinning further than you are steering. This is oversteer.

In ANY car, accelleration shifts weight to the rear of the car. The weight will help a RWD press its wheels to the pavement so they don't spin out. When a wheel spins, it looses its grip. In a FWD car, the wheels getting power become light, which takes away their grip. That's one big reason why it's impractical to have a powerful engine in a FWD car.

Combine these concepts: RWD will cause a car to oversteer under throttle, BUT under throttle, the rear of the car will grip better. Consequently, RWD cars can be driven harder through turns before they lose their grip.

RWD cars, because of the position of their transmission, typically have a better weight distribution. Ideally, you want as much of the car's weight centered between all the wheels to avoid weight shifts during corners. Less weight in the front of the car helps a car turn quickly since the front moves first. Rear-engine, RWD cars are fantastic.

It is harder to start spinning an AWD system than a simple two wheel layout. Simply, there are more, heavier parts to turn in a larger drivetrain. It requires proportionally more torque to get these parts to rotate. In general, the more (or larger) the axle and drive shafts, the more loss your drivetrain will have. This takes away from the engine power, so FWD engines are typically more efficient than RWD and especially AWD. Consequently, AWD gets poor gas mileage. FWD cars have torque steer because the transmission is not centered in the vehicle, making the drivetrain heavier on one side of the vehicle.

A good AWD vehicle will send its power only to the tires that are gripping by using advanced differentials. Differentials are what allow your tires to spin at different speeds than one another. Every car has one because in a turn, your inside tires do not turn as fast as your outside tires. A limited slip differential prevents this difference from becoming too great, preventing one-wheel spins. AWD cars have an added differential between the front and rear wheels. I don't think 4wd vehicles do this. Hence, if you ever spin all four tires in a 4wd vehicle, your car will drive like it's on ice- no traction in any wheel. This is also why there are no full-time 4WD cars.

The Mazda6 is pretty sweet. If you don't throttle through a turn, it'll oversteer. It's quite an amazing FWD car- unlike any other FWD car I've driven. With the '6, a little throttle in the turns will cause the car to do what's called a 'drift'. This is where all four wheels are just barely not gripping, and is the fastest possible way to take a turn.

Ask AJ about a 'waggle'.

Edit: the whole dang post was revised. If any of that is incorrect, tell me!
 
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