RWD vs FWD

[Chapman2233]

Well i am a first year mechanic apprentice, was just wondering about why there was the move to FWD, was it primarily for fuel economy via placing the engine and transaxle in the front, there is no large transmission housing or driveshaft tunnel running through the passenger compartment and the engine being placed in transversely?

Although times change and now RWD is probably the same in fuel economy and most other ways.

Thanks

[saikou27]

there was a move to fwd for packaging simplicity to make cars cheaper to build and easier to manufacture

[aaronng]

Cheaper to manufacture, more spacious cabin, easier chassis design, more reliable because of less moving parts, able to make smaller cars and less power loss through the drivetrain.

[ajbm]

Here's some of the pro's and con's for each transmissions system:

FWD
Advatages
- Increase fuel efficiency, by their reduction in size (weight)
- most engines were positioned transversely to reduce the size of the engine bay
- Commonly with 60% of its weight at the front, 40% at the back, fwd holds an advantage in slippery conditions such as ice or snow as more weight is over the drive wheels reducing slip during acceleration
Disadvatages
- as most of the weight in up front, a fwd car is not as well balanced therefore it doesn't handle quite as well
- as the vehicles power increases, handling of FWD cars becomes a problem
- Torque steer (when the steering wheel pulls to one side during acceleration) is a serious issue with many front wheel drive cars that exceed 250hp

RWD
Advantages
- having the front wheels do the steering, and the rear wheels driving the car, you get a better-balanced vehicle (can eliminate torque steer)
- RWD offers better weight distribution (much closer to 50/50 than fwd), which in turn offers more predictable handling
- also most cars today have the AWD options
Disadvantages
- more size, hence more weight
- Poor handling in slippery conditions. However, the addition of traction control and stability management systems, virtualy reduces FWD advantage in slippery/wet conditions.

[e240]

FWD so that the Honda Boys can cheese off the RWD brigade...

[EK1.6LCIV]

BMW has a good explaination as to why they have never or will ever build a fwd car, worth a read it's a good 3 paragraphs

other ads are as followed

http://www.bimmerfile.com/wp-content/uploads/2009/10/bmw-front-wheel-drive.jpeg

[Gio]

^^^ i dont get it lol.

Ps my ek has torque steer lol

[vtecing]

apparently there was too many old ladies crashing their ke70s into trees when it was raining

[MWAKU]

lol the bunnys big legs are at the front

thats not right

its meant to be at the back..

get it?

(fwd, its not right, its meant to be rwd)

[Gio]

ahhhh i seen that but it didnt click, getting late at uni eeek

Edit; THAT RABBIT LOOKS WAY MORE LETHAL WITH HUUUUUUGE FRONT LEGS

[V73C]

Does that rabbit have vtec now ?

[ajbm]

^^^ i dont get it lol.
Ps my ek has torque steer lol

LOL, you only have to worry about torque steer if U drive ur car to the limit
(i.e. high speed cornering or in the track) and have loads of power in that little EK of urs.

There are other causes of torque steer:
- Uneven half-shafts between the transaxle and wheels.
- Open differentials
- Damaged suspension/steering components (bushings, trailing arms, etc)
- Tyre defects

Open differentials may not equally distribute the torque between the two driveshafts. When excessive torque is applied, one shaft flexes more than the other, thus causing one wheel to momentarily spin slower than the other, and the tendency for the slower wheel to receive more torque.

This is where U can appreciate Limited slip differentials (LSDs).
It helps FWD vehicles reduce/eliminate the amount of torque steer and improve cornering at high speed. :thumbsup:

[Troy]

Rabbit with VTEC FTW!

This thread is one reason why I love the Mini so much, it revolutionised the industry. Read up more on Alec Issigonis' masterpiece, there's plenty of info out there on it that is completely relevant to this topic.

[curtis265]

oh and with RWD, you get better straight-line acceleration characteristics, as weight transfer will put more traction on your rear wheels.

FWD's will gradually lose grip (but as long as it doesn't slip,it's ok)
FWD's have wheel hop.

[ajbm]

here's an example of NA FWD vs RWD battle on the track...
enjoy!
gNjT99yMhSc

[redefine]

oh and with RWD, you get better straight-line acceleration characteristics, as weight transfer will put more traction on your rear wheels.

FWD's will gradually lose grip (but as long as it doesn't slip,it's ok)
FWD's have wheel hop.

tbh im suprised it took this long for someone to mention this :confused:
IMO its one of the biggest advantages for rwd, among balance

[curtis265]

Probably too basic, lol

[string]

... one of the biggest advantages for rwd, among balance

This is commonly cited but rarely accompanied by supporting arguments.

A standard Honda Integra has more than 60% of the weight over the front wheels. A standard Porsche 911 has more than 60% of the weight over the rear wheels. Non-static balance is determined by the suspension geometry and is as adjustable as your creativity allows.

So my question is - when people hear or use the word "balance", what is meant?

[redefine]

This is commonly cited but rarely accompanied by supporting arguments.

A standard Honda Integra has more than 60% of the weight over the front wheels. A standard Porsche 911 has more than 60% of the weight over the rear wheels. Non-static balance is determined by the suspension geometry and is as adjustable as your creativity allows.

So my question is - when people hear or use the word "balance", what is meant?

usually when people talk about a rwd car being "balanced" theyre talking about FR cars....RR has the same weight distribution problems as FF. just as hondas are known for understeer, the 911 is also known to be tail happy.

fr is much easier to get 50-50 front and rear, or similarly 25% to each wheel. honda is a great example of that. an integra has more then 60% on the front. whereas an s2k with a 60kg passenger and driver has 25% to each wheel.

in fact, to aid this balance, most supercars are MR. though i assume that when most people say "balance" its a combination of weight distribution, and that the wheels each have their own job (acceleration dosent effect steering like it does in FF. etc.) among a few other little things.

imo the topic should really be FF vs FR. RR is often forgotten about when talking about rwd.


also....thats a 20B fd there :O

[string]

imo the topic should really be FF vs FR. RR is often forgotten about when talking about rwd.

That depends entirely on who you talk to. One could argue that any serious performance discussion would forget all but MR/RR.



RR has the same weight distribution problems as FF

What are the inherent problems associated with a non-mid-wheelbase centre of mass?



though i assume that when most people say "balance" its a combination of weight distribution, and that the wheels each have their own job (acceleration dosent affect steering like it does in FF. etc.)

Acceleration affects steering no matter what the layout or weight distribution. "Each have their own job" is a more acceptable articulation, but certainly a stretch in the definition of "balance" :)

[redefine]

That depends entirely on who you talk to. One could argue that any serious performance discussion would forget all but MR/RR.

yeah, i get that :p i meant in terms of the fwd rwd argument, it often turns into a FF/FR argument, cause there are so many more FR street cars then there are RR or MR (though there are a few, the rx7 Can be considered FMR.)


What are the inherent problems associated with a non-mid-wheelbase centre of mass?

well less "balance"?? :p
i guess the 911 has the opposite problem as other FF cars. though you can tune an FF car to be tail happy, if you have an entirely even suspension, a RR car will be tail happy and a FF car will be prone to understeer. non-mid-wheelbase cars have the majority of their weight unevenly distributed. while that is excelent for a dedicated RR drag car (most of the weight pushing the rear/driven wheels into the ground) its not so good for track/sprint/touge etc...as the engine has more inertial mass around corners then is necesary. in RR, any part of the engine behind the rear axle is moving the opposite direction to the direction you are turning, also, extra weight in the rear is harder to turn in RR leading to a tail happy car as the lighter front is easier to turn. in FF the further forward the engine is, the more the engine has to move to turn a desired angle, putting extra pressure on the front tires/suspension. of course, again in a FF drag car, having the engine as far forward as possible increases leverage on the front/driven wheels. \


so while they have separate effects, they come from the same basic design problem. eg. uneven weight distrobution.


Acceleration affects steering no matter what the layout or weight distribution. "Each have their own job" is a more acceptable articulation, but certainly a stretch in the definition of "balance" :)

i thought i'd add that in, cause the average daily driving joe wouldnt have a good idea of exactly what performance specific terms mean :p

[curtis265]

when they talk about balance, i have a suspicion theyre talking about the characteristics - even amouts of over and understeer when pushed to the limit..? :S

I have no idea btw, just throwing an idea out there..

oh and a non wheelbase centre of mass... how is that even possible - cars would be tipping over!

[aero]

BMW has a good explaination as to why they have never or will ever build a fwd car, worth a read it's a good 3 paragraphs

other ads are as followed

http://www.bimmerfile.com/wp-content/uploads/2009/10/bmw-front-wheel-drive.jpeg

i read that bmw has announced that they will be producing a new series below the 1 series which will be fwd. although they say it will be coming in 2014 lol

[Troy]

Proof?

[aero]

http://www.autoblog.com/2010/02/01/report-bmw-to-launch-two-cars-below-1-series-by-2014/

http://img3.auto-motor-und-sport.de/BMW-Megacity-f498x333-F4F4F2-C-bfc8918c-302487.jpg

[Mikecivic78]

IMO it all depends on the chassis/weight distribution and suspension setup.

A well tuned FWD car can handle very well indeed.

I agree with this article:http://autospeed.com.au/cms/title_Automotive-Myths/A_111396/article.html

Heres an excerpt:Myth 2: Front-Wheel Drive Cars Don’t Handle

Bizarrely, this myth has been around for decades. Yet it’s now eons since a front-wheel drive car (the Mini) outright won major motor races and rallies, and since that time, plenty of front-wheel drive cars have out-handled their direct rear-wheel drive opposition.

Let me put the myth differently: if you’re a bad driver, you might find that you can be faster around corners in a rear-wheel drive car than a front-wheel drive. For anyone who is competent, FWD vs RWD is a non argument.

Now you might well argue that some FWD cars don’t handle very well. Of course! That’s just like making the point that some RWD cars don’t handle very well. But it’s another thing altogether to suggest that for ‘real handling’ you need RWD.

If you’re one of the ‘old school’ that deeply believes that RWD is somehow much superior, perhaps get into a good handling FWD and do an advanced driving course so that you can learn how to drive a FWD properly.

Me? I don’t care whether it’s RWD, FWD or AWD. There are lots more important aspects of a car that affect its handling than which wheels are driven