Slowly but surely, horsepower is killing front drive.
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Slowly but surely, horsepower is killing front drive.
http://www.caranddriver.com/article....&page_number=1
The Steering Column
Slowly but surely, horsepower is killing front drive.
BY CSABA CSERE
July 2004
There seems to be considerable trepidation in some Detroit circles about the switch from front- to rear-wheel drive in cars such as the Chrysler 300, Dodge Magnum (replacing the Intrepid), and Cadillac STS. And if we believe our spies, most future big sedans from the Big Three will propel themselves via their rear wheels.
Some critics view this switch as little more than a fashion statement, much like raising or dropping the hemline of a woman’s skirt, and designed to juice sales by giving advertisers something to talk about. Others don’t want to lose front-wheel drive’s traction advantages in winter and fret about fishtailing down snowy city streets with a rear-driver. Some even worry about losing the slightly lighter weight and more efficient packaging available with front drive.
Given the enormous expense of replacing a front-drive car with a rear-drive one, no car company would do it just to provide the marketers with a new talking point. On the other hand, a discussion of front drive versus rear drive in slippery conditions is more relevant. There’s little question that by placing between 60 and 65 percent of a vehicle’s weight over its driving wheels, front drive develops more traction than does rear drive—unless the rear-drive car happens to be a Porsche 911. The only thing better is four-wheel drive, which puts 100 percent of a vehicle’s weight on its driving wheels.
Adding traction control into the equation doesn’t alter this traction pecking order. However, traction control does ensure that a vehicle makes the most of its available grip and helps a clumsy driver from losing control because of wheelspin.
Remember, though, that the definition of traction is grip that allows acceleration. Grip for cornering and braking is completely different, and there’s no evidence that front drive provides any advantage in these areas during winter driving. Electronic stability-control systems make the most of the available grip regardless of which wheels are driven, but if you really want secure winter handling, you need to change to snow tires. Four snow tires will improve traction as well as braking and cornering grip to the point where the winter merits of front and rear drive are rendered irrelevant.
Once we get away from the slippery stuff, rear drive has traditionally displayed better handling because it splits the duties of steering, cornering, acceleration, and braking more equitably among the four tires.
During acceleration, for example, although front drive provides more traction the instant you press the throttle, that advantage diminishes as soon as the car begins to accelerate. This action is caused by the inertia of the car’s center of gravity that is about a foot and a half above the pavement. Commonly called “weight transfer,” this effect on an Acura TSX, which has about 60 percent of its weight on its front wheels when standing still, shifts more than 300 pounds from its front to its rear wheels under hard acceleration in first gear.
The BMW 325i, similar to the TSX in size and performance, has a nearly 50/50 weight split. When accelerating, it undergoes a similar front-to-rear load transfer. But whereas traction in the TSX decreases about 20 percent under hard acceleration, in the 325, it increases by a similar amount.
Under braking, a similar load shift occurs, only this time it’s from the rear tires toward the fronts. With a front-drive car, this means that during maximum braking the front tires might be doing more than 80 percent of the stopping. A more even distribution of braking force would be beneficial, which is why rear-heavy cars such as Porsche 911s always stop very well. Obviously, the forward weight bias of front-drive cars is not helpful.
Nor does it help in cornering, where an equal weight distribution works best. In fact, since so much cornering takes place in combination with some acceleration, a rearward weight bias is advantageous, particularly when combined with larger rear tires. A mid-engine layout provides this configuration, which is why it is chosen by all race-car builders when the rules permit.
Okay, most of us are not exploring limit handling on the street, but we’re all familiar with the many ways that applying power can corrupt the steering feel of front-drive cars. Torque steer is the classic problem, causing the steering wheel to twitch in your hands while the car pulls in one direction or the other when you press on the gas. Equal-length half-shafts going to the front wheels have largely eliminated this problem, but others remain.
During hard acceleration in the lower gears, front-drive cars often lose some directional stability and are easily deflected by bumps, dips, and crowns in the pavement. Rear-drive cars can fishtail when they lose traction, but front-drivers often “fishhead” under the same circumstances.
In corners, particularly slow ones, many front-drive cars lose self-centering under power. The driver can’t easily tell whether this is a front-drive effect or an impending loss of grip. In some cars, such as the Dodge SRT-4, you can let go of the wheel completely in midcorner under power and the steering wheel doesn’t move a degree. And when a limited-slip differential is employed in a front-driver, these effects are sometimes amplified as the diff decides which wheel to favor with power.
Despite these flaws, we’ve found many front-drive cars over the years with terrific handling. But this was years ago, when power was more scarce than it is today.
The first VW GTI sold in America—back in 1983—had all of 90 horsepower and needed 9.7 seconds to get to 60 mph. When Chevrolet introduced its front-drive Celebrity mid-size sedan in 1982, its most powerful engine was a 2.8-liter V-6 with 112 horsepower. That Celebrity replaced the rear-drive Malibu with a standard 3.8-liter V-6 making 110 horsepower. With only a piddling 112 horses, it didn’t matter which end of the Chevy was driven.
But today, Honda Accords and Nissan Altimas come with 240-hp V-6s, and 300-hp luxury sedans are everywhere. At these power levels, front-drive has reached the limit of its competence.
I don’t even want to think about driving a 340-hp Chrysler 300C Hemi V-8 delivering power through its front wheels. In the end, you can have either front drive or plenty of power. But you can’t have both.
The Steering Column
Slowly but surely, horsepower is killing front drive.
BY CSABA CSERE
July 2004
There seems to be considerable trepidation in some Detroit circles about the switch from front- to rear-wheel drive in cars such as the Chrysler 300, Dodge Magnum (replacing the Intrepid), and Cadillac STS. And if we believe our spies, most future big sedans from the Big Three will propel themselves via their rear wheels.
Some critics view this switch as little more than a fashion statement, much like raising or dropping the hemline of a woman’s skirt, and designed to juice sales by giving advertisers something to talk about. Others don’t want to lose front-wheel drive’s traction advantages in winter and fret about fishtailing down snowy city streets with a rear-driver. Some even worry about losing the slightly lighter weight and more efficient packaging available with front drive.
Given the enormous expense of replacing a front-drive car with a rear-drive one, no car company would do it just to provide the marketers with a new talking point. On the other hand, a discussion of front drive versus rear drive in slippery conditions is more relevant. There’s little question that by placing between 60 and 65 percent of a vehicle’s weight over its driving wheels, front drive develops more traction than does rear drive—unless the rear-drive car happens to be a Porsche 911. The only thing better is four-wheel drive, which puts 100 percent of a vehicle’s weight on its driving wheels.
Adding traction control into the equation doesn’t alter this traction pecking order. However, traction control does ensure that a vehicle makes the most of its available grip and helps a clumsy driver from losing control because of wheelspin.
Remember, though, that the definition of traction is grip that allows acceleration. Grip for cornering and braking is completely different, and there’s no evidence that front drive provides any advantage in these areas during winter driving. Electronic stability-control systems make the most of the available grip regardless of which wheels are driven, but if you really want secure winter handling, you need to change to snow tires. Four snow tires will improve traction as well as braking and cornering grip to the point where the winter merits of front and rear drive are rendered irrelevant.
Once we get away from the slippery stuff, rear drive has traditionally displayed better handling because it splits the duties of steering, cornering, acceleration, and braking more equitably among the four tires.
During acceleration, for example, although front drive provides more traction the instant you press the throttle, that advantage diminishes as soon as the car begins to accelerate. This action is caused by the inertia of the car’s center of gravity that is about a foot and a half above the pavement. Commonly called “weight transfer,” this effect on an Acura TSX, which has about 60 percent of its weight on its front wheels when standing still, shifts more than 300 pounds from its front to its rear wheels under hard acceleration in first gear.
The BMW 325i, similar to the TSX in size and performance, has a nearly 50/50 weight split. When accelerating, it undergoes a similar front-to-rear load transfer. But whereas traction in the TSX decreases about 20 percent under hard acceleration, in the 325, it increases by a similar amount.
Under braking, a similar load shift occurs, only this time it’s from the rear tires toward the fronts. With a front-drive car, this means that during maximum braking the front tires might be doing more than 80 percent of the stopping. A more even distribution of braking force would be beneficial, which is why rear-heavy cars such as Porsche 911s always stop very well. Obviously, the forward weight bias of front-drive cars is not helpful.
Nor does it help in cornering, where an equal weight distribution works best. In fact, since so much cornering takes place in combination with some acceleration, a rearward weight bias is advantageous, particularly when combined with larger rear tires. A mid-engine layout provides this configuration, which is why it is chosen by all race-car builders when the rules permit.
Okay, most of us are not exploring limit handling on the street, but we’re all familiar with the many ways that applying power can corrupt the steering feel of front-drive cars. Torque steer is the classic problem, causing the steering wheel to twitch in your hands while the car pulls in one direction or the other when you press on the gas. Equal-length half-shafts going to the front wheels have largely eliminated this problem, but others remain.
During hard acceleration in the lower gears, front-drive cars often lose some directional stability and are easily deflected by bumps, dips, and crowns in the pavement. Rear-drive cars can fishtail when they lose traction, but front-drivers often “fishhead” under the same circumstances.
In corners, particularly slow ones, many front-drive cars lose self-centering under power. The driver can’t easily tell whether this is a front-drive effect or an impending loss of grip. In some cars, such as the Dodge SRT-4, you can let go of the wheel completely in midcorner under power and the steering wheel doesn’t move a degree. And when a limited-slip differential is employed in a front-driver, these effects are sometimes amplified as the diff decides which wheel to favor with power.
Despite these flaws, we’ve found many front-drive cars over the years with terrific handling. But this was years ago, when power was more scarce than it is today.
The first VW GTI sold in America—back in 1983—had all of 90 horsepower and needed 9.7 seconds to get to 60 mph. When Chevrolet introduced its front-drive Celebrity mid-size sedan in 1982, its most powerful engine was a 2.8-liter V-6 with 112 horsepower. That Celebrity replaced the rear-drive Malibu with a standard 3.8-liter V-6 making 110 horsepower. With only a piddling 112 horses, it didn’t matter which end of the Chevy was driven.
But today, Honda Accords and Nissan Altimas come with 240-hp V-6s, and 300-hp luxury sedans are everywhere. At these power levels, front-drive has reached the limit of its competence.
I don’t even want to think about driving a 340-hp Chrysler 300C Hemi V-8 delivering power through its front wheels. In the end, you can have either front drive or plenty of power. But you can’t have both.
Lexus Fanatic
Joined: Oct 2003
Posts: 94,574
Likes: 265
From: Virginia/D.C. suburbs
I read Csaba's column....just like I do his ( and Pat's and Brock's and John's ) every month in Car and Driver. He did a good job of pointing out the FWD vs RWD characteristics. What he didn't point out, though......and what I think is the real answer to the RWD vs FWD question.......is that AWD is the real solution, especially with today's power levels that help overcome its drag and weight.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
Originally posted by mmarshall
I read Csaba's column....just like I do his ( and Pat's and Brock's and John's ) every month in Car and Driver. He did a good job of pointing out the FWD vs RWD characteristics. What he didn't point out, though......and what I think is the real answer to the RWD vs FWD question.......is that AWD is the real solution, especially with today's power levels that help overcome its drag and weight.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
I read Csaba's column....just like I do his ( and Pat's and Brock's and John's ) every month in Car and Driver. He did a good job of pointing out the FWD vs RWD characteristics. What he didn't point out, though......and what I think is the real answer to the RWD vs FWD question.......is that AWD is the real solution, especially with today's power levels that help overcome its drag and weight.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
Lexus Champion
Joined: Mar 2003
Posts: 3,525
Likes: 1
From: Pennsylvania
in my mind, as in many others, i've always loved AWD, then RWD, then FWD, in that order. i'm not trying to say i don't like the RWD characteristics of my sc, because i love them. there is definitely something to be said for having a little fun with the rear end once and a while. 
Lead Lap
Joined: Nov 2001
Posts: 4,590
Likes: 97
From: CA, Mid OC
Originally posted by mmarshall
I read Csaba's column....just like I do his ( and Pat's and Brock's and John's ) every month in Car and Driver. He did a good job of pointing out the FWD vs RWD characteristics. What he didn't point out, though......and what I think is the real answer to the RWD vs FWD question.......is that AWD is the real solution, especially with today's power levels that help overcome its drag and weight.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
I read Csaba's column....just like I do his ( and Pat's and Brock's and John's ) every month in Car and Driver. He did a good job of pointing out the FWD vs RWD characteristics. What he didn't point out, though......and what I think is the real answer to the RWD vs FWD question.......is that AWD is the real solution, especially with today's power levels that help overcome its drag and weight.
AWD will probably be either standard or optional on most luxury and high-performance cars within 5-10 years. One company.....Subaru.....( and a lower-price brand at that ).....has already made it standard across-the-board.
Csaba did mention the benefits of AWD in the following paragraph:
"Given the enormous expense of replacing a front-drive car with a rear-drive one, no car company would do it just to provide the marketers with a new talking point. On the other hand, a discussion of front drive versus rear drive in slippery conditions is more relevant. There’s little question that by placing between 60 and 65 percent of a vehicle’s weight over its driving wheels, front drive develops more traction than does rear drive—unless the rear-drive car happens to be a Porsche 911. The only thing better is four-wheel drive, which puts 100 percent of a vehicle’s weight on its driving wheels."
I don't think he regards AWD as the ultimate solution. The cost of moving to AWD for most entry and mid-level production cars is prohibitive, meaning that doing so requires costs that would move those vehicles out of those pricepoints.
I agreed completely with the assertion that 240 hp in an FWD car is at the limit of an FWD car's competency. Actually, when I drove the '02 Altima, I found the torque steer to be very noticable and very disconcerting. Having lived in CA for most of my life, it is easy to dismiss the benefits of FWD cars as they apply to driving in snow and ice. We don't run into that too often down here.
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I agreed completely with the assertion that 240 hp in an FWD car is at the limit of an FWD car's competency. Actually, when I drove the '02 Altima, I found the torque steer to be very noticable and very disconcerting. Having lived in CA for most of my life, it is easy to dismiss the benefits of FWD cars as they apply to driving in snow and ice. We don't run into that too often down here
When I drove the 240Altima, it's ridiculous, the torque steer. Who could take their family for a ride in this car? Then in driving the 6th gen Max, it's just as bad. Audi and Honda don't have it as much though.
When my folks got a RWD 929, it felt totally planted in comparison. I was sold on RWD. Then after the SC 400, I was truly sold on RWD.
I can see myself in AWD though.
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Lexus Champion
Joined: Jul 2001
Posts: 4,330
Likes: 1
From: I wonder why I live alone here...
FWD=tehsux
The concept of transversely mounted engines with 100% of torque being routed to the front wheels is just plain troubling. Why, God, why?
A proper full-time 50/50 AWD system is nice, but I would still take pure RWD if I could. I wish my Subie came with a driver-controlled diff (a la the STi)...that thing would be set on 95% to rear FOR GOOD.
The concept of transversely mounted engines with 100% of torque being routed to the front wheels is just plain troubling. Why, God, why?
A proper full-time 50/50 AWD system is nice, but I would still take pure RWD if I could. I wish my Subie came with a driver-controlled diff (a la the STi)...that thing would be set on 95% to rear FOR GOOD.
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Lexus Fanatic
Joined: Oct 2003
Posts: 94,574
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From: Virginia/D.C. suburbs
Originally posted by wantAnewLex
FWD=tehsux
The concept of transversely mounted engines with 100% of torque being routed to the front wheels is just plain troubling. Why, God, why?
A proper full-time 50/50 AWD system is nice, but I would still take pure RWD if I could. I wish my Subie came with a driver-controlled diff (a la the STi)...that thing would be set on 95% to rear FOR GOOD.
FWD=tehsux
The concept of transversely mounted engines with 100% of torque being routed to the front wheels is just plain troubling. Why, God, why?
A proper full-time 50/50 AWD system is nice, but I would still take pure RWD if I could. I wish my Subie came with a driver-controlled diff (a la the STi)...that thing would be set on 95% to rear FOR GOOD.
Unless you want to do powerslides (which can be dangerous if you are not skilled at them), there are a lot of good things to the 50/50 AWD mix....more even tire wear, more even traction front-to-rear, more even handling balance, and more even braking.
Lexus Fanatic
Joined: May 2003
Posts: 7,864
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From: Massachusetts
I think the perfect solution is to have an electonic option to
switch from RWD to AWD when needed. Currently, the G35x
sedan electronically does it by itself, however I would like to be
given the control. In dry weather I would have it in RWD mode,
then when the snow arrives I would swtich to AWD. Ideally, I
think all cars should be built this way. No FWD necessary.
switch from RWD to AWD when needed. Currently, the G35x
sedan electronically does it by itself, however I would like to be
given the control. In dry weather I would have it in RWD mode,
then when the snow arrives I would swtich to AWD. Ideally, I
think all cars should be built this way. No FWD necessary.
RWD ROXXORS YOUR BOXXORS!!!
Someone had to say it
I owned one FWD car as my first car... and the rest have been ALL RWD except for one AWD Talon...
I will never own a FWD unless its a cheap beater car... NEVER EVER as a performance vehicle
Someone had to say it
I owned one FWD car as my first car... and the rest have been ALL RWD except for one AWD Talon...
I will never own a FWD unless its a cheap beater car... NEVER EVER as a performance vehicle
Lexus Champion
Joined: Jul 2001
Posts: 4,330
Likes: 1
From: I wonder why I live alone here...
Originally posted by JLSC4
I think the perfect solution is to have an electonic option to
switch from RWD to AWD when needed. Currently, the G35x
sedan electronically does it by itself, however I would like to be
given the control. In dry weather I would have it in RWD mode,
then when the snow arrives I would swtich to AWD. Ideally, I
think all cars should be built this way. No FWD necessary.
I think the perfect solution is to have an electonic option to
switch from RWD to AWD when needed. Currently, the G35x
sedan electronically does it by itself, however I would like to be
given the control. In dry weather I would have it in RWD mode,
then when the snow arrives I would swtich to AWD. Ideally, I
think all cars should be built this way. No FWD necessary.
I give BIG-UPS to Subaru for being the only car manufacturer to:
-Offer true, even, full-time 25x4 torque distribution AWD on all (manual) models as standard (their auto AWD systems vary depending on model)
-Offer all longitudaly-mounted boxers, all of the time
-Offer a turbo-charged variant of each model
-Offer a manual transmission with each model, including all turbo-charged variants
-AND keep the prices of most turbo models well below $30K
-Building the Imp-based models in Japan doesn't hurt either
They're really a stand-out manufacturer, and other companies should get a clue. Develop one really good drivetrain and a performance motor with several variants, which will lend itself not only to keeping costs down, but resulting in a great vehicle. Subaru has totally nailed performance+value.
EDIT: Oh yeah, as many of you know, Japan gets AWD Camrys, Corollas, Accords, etc. Granted, they're FWD-biased, but it's better than 100% FWD. So they really can't whine and use the cost of developing an AWD system as an argument. Toyota's been making AWD variants of many of its models for years (Hello...Calling AllTrac), and I'm sure there would be a market for them here in the US. Jeez, at least they could make the ES models with AWD standard.
Last edited by SecPole14; Jun 25, 2004 at 06:27 PM.
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Joined: Jul 2003
Posts: 51
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From: California
Originally posted by wantAnewLex
Yeah, the G35 has a nice AWD system. At first I thought the "R" Volvo models were cool, but then I learned Haldex usually means 100% up front. And that means it's lame.
...
Yeah, the G35 has a nice AWD system. At first I thought the "R" Volvo models were cool, but then I learned Haldex usually means 100% up front. And that means it's lame.
...
Your Volvo info is a bit off. Lesser Volvos use Haldex I (just like Audi and others.) The Volvo Rs use Haldex II. (Further, Volvo's latest Haldex I implementations are very good - they react and distribute power in 1/7th of a wheel rotation.)
Haldex II is the only AWD on the market so far that distributes power based on ACCELERATION in addition to wheelslip. This means if you stomp on it from rest you will actually feel the car bog for an instant as it pushes all the power to the rear. Further, this setup is the only one designed to oversteer entering a corner, exhibit neutral handling at the apex, and understeer on exit. Once you learn to use it properly (and short of a track environment you will never have the guts to find the edge of the envelop in these cars as they have extraordinary grip and it takes a LOT to unstick one) you can corner with this setup faster than a comparable S4, M3, etc.
Based on reviews and my experience Volvo Rs have the best AWD system out there when it comes to performance (it really does antiquate a simple static mechanical differential like Torsen.) Based on technical details on paper, I suspect Honda's upcoming Super Handling AWD will trump the Volvo Rs and Infiniti AWD systems. Time will tell...
Lexus Champion
Joined: Jul 2001
Posts: 4,330
Likes: 1
From: I wonder why I live alone here...
Originally posted by rdollie
Your Volvo info is a bit off. Lesser Volvos use Haldex I (just like Audi and others.) The Volvo Rs use Haldex II. (Further, Volvo's latest Haldex I implementations are very good - they react and distribute power in 1/7th of a wheel rotation.)
Haldex II is the only AWD on the market so far that distributes power based on ACCELERATION in addition to wheelslip. This means if you stomp on it from rest you will actually feel the car bog for an instant as it pushes all the power to the rear. Further, this setup is the only one designed to oversteer entering a corner, exhibit neutral handling at the apex, and understeer on exit. Once you learn to use it properly (and short of a track environment you will never have the guts to find the edge of the envelop in these cars as they have extraordinary grip and it takes a LOT to unstick one) you can corner with this setup faster than a comparable S4, M3, etc.
Based on reviews and my experience Volvo Rs have the best AWD system out there when it comes to performance (it really does antiquate a simple static mechanical differential like Torsen.) Based on technical details on paper, I suspect Honda's upcoming Super Handling AWD will trump the Volvo Rs and Infiniti AWD systems. Time will tell...
Your Volvo info is a bit off. Lesser Volvos use Haldex I (just like Audi and others.) The Volvo Rs use Haldex II. (Further, Volvo's latest Haldex I implementations are very good - they react and distribute power in 1/7th of a wheel rotation.)
Haldex II is the only AWD on the market so far that distributes power based on ACCELERATION in addition to wheelslip. This means if you stomp on it from rest you will actually feel the car bog for an instant as it pushes all the power to the rear. Further, this setup is the only one designed to oversteer entering a corner, exhibit neutral handling at the apex, and understeer on exit. Once you learn to use it properly (and short of a track environment you will never have the guts to find the edge of the envelop in these cars as they have extraordinary grip and it takes a LOT to unstick one) you can corner with this setup faster than a comparable S4, M3, etc.
Based on reviews and my experience Volvo Rs have the best AWD system out there when it comes to performance (it really does antiquate a simple static mechanical differential like Torsen.) Based on technical details on paper, I suspect Honda's upcoming Super Handling AWD will trump the Volvo Rs and Infiniti AWD systems. Time will tell...
Magazine racing is one thing. Reality is another.