Based on a Speed:Sport:Life article. Several TTAC readers have pointed out in the past that the “dollar theory” of tire traction fails to account for dynamic weight loads, so consider that pointed out up front — JB
It seems like yesterday, as the man sang, but it was long ago. In April of 2008 I ordered a new Audi S5 in a rather unique color — the “Lime Green” used by Porsche in 1973 and referred to as “Lime Green” and “Viper Green”. Not “Signal Green”, mind you: that’s a different color, with more blue, and less cheer, in the mix. The car arrived in September of 2008. I drove it for two years and 38,000 miles before selling it for approximately five grand more than “regular” S5s were fetching.
In the month after I took delivery of the S5, pictures of the car flew around the Internet with a rapidity usually reserved for lucky shots of Britney Spears making a bowlegged departure from Paris Hilton’s McMerc SLR. I received dozens of phone calls and text messages from friends and acquaintances who had spotted the Audi in traffic or sitting parked somewhere. People who saw the car in the metal seemed to be about 70/30 in favor of my choice, while Internet users who saw the car online (where, it has to be said, the color does not photograph quite “right”) are closer to 80/20 against. Some of the negative reactions were fascinating because their authors seem so… well, personally offended by the shiny S5. “I can’t believe Audi agreed to paint the car that color!” was a semi-common response. Well, they did agree, and they will also paint your new Audi in almost any color you like, thanks to their outstanding “Exclusive” program. The problem for most of these people is that they are afraid to own a German car in any color that is not silver, grey, or silver-grey, and the presence of brightly-colored German cars destroys their cherished Autobahn stereotypes. Of course, were they to ever sign off “World of Warcraft”, stumble blinking out into the afternoon light, borrow their parents’ Camrys, drive to the airport, and actually visit the hallowed Fatherland, they would see that the most common cars there aren’t silver Audis – they’re bright blue Lupos and yellow Renault Twingos. Germans like color, too.
Some of the younger Audi-forum readers were absolutely shocked that it’s possible to buy a car from Ingolstadt that isn’t utterly “tasteful” and “reserved”. How do I know that they’re young? It’s simple: they’re obviously too young to have ever seen the interior of a Seventies Audi, or even the seats of an ur-Quattro. The whole idea of “tasteful” German cars is a scam, kids. It was something the marketing people thought up twenty years ago so the dealers could stock a smaller selection of inventory. I grew up surrounded by lemon-yellow Mercedes diesels, brown Porsche 911SCs, pearl-white Audi 5000s, and baby blue big-bumper Bimmers, and believe it or not, none of the drivers of those cars ever died of color overdose. My father almost killed himself a few times pushing his orange Volvo off the freeway after it stalled for no particular reason, but I have no reason to believe that color was involved. Trust me on this one. I know that your local dealer has thirty-six BMWs on his lot and they are all either silver, grey, or black, but if you take out a BMW brochure and flip all the way to the back, past the endless photographs of optional skiing accessories but right before the disclaimer that tells you to obey posted speed limits, you will find little squares of color. While most of them are silver, grey, silver-grey, or black, chances are there will be a red or blue square on the page. It’s okay to go to the dealer, point to that square, and meekly inquire as to whether you might be permitted to purchase a car in that color. I’m not kidding. I even know a guy who bought an “arrest-me red” 740iL a few years ago… and they didn’t actually arrest him! Crazy, I know.
The other objection I heard to my Audi purchase was a little more reasonable, at least on the surface. There are many variants to what my friends said, but it always boiled down to something like this:
”As a racing driver, multiple Porsche owner, long-time car nut, and soi-disant automotive journalist, aren’t you smart enough to know that FWD-platform cars are, like, totally inferior to RWD-platform cars? Don’t you know that cars with overhanging front engines have lousy balance and will always understeer? Can’t you understand that something like a BMW M3 will always be a better drive than an Audi of any stripe? Have you noticed that pretty much everybody in the prestige-car business is moving to RWD? FWD sucks, even if you add a driveshaft to the rear wheels. I mean, don’t you read the Internet? Why would anybody bother with a front-wheel-drive car?”
It’s a fair series of questions. In an era when even Hyundai is pushing rear-wheel-drive as a selling point – a time when the Issigonis-inspired tranverse-engine layout has become inextricably associated with the very cheapest of cars – can there be any compelling reason to choose FWD? The answer is yes. I believe that FWD continues to be the best choice for a purely street-driven car, even if the driver of that car considers himself or herself to be a driving enthusiast. And since I don’t expect you to take that answer on faith, I’m willing to show you how, and why, FWD comes out on top in nearly every real-world driving situation… if, that is, you’re ready to listen. Are you?
To understand when, and why, FWD can be better, we have to start with how, and when, it is worse. In his book A Twist Of The Wrist, Keith Code explains the “dollar theory” of tire traction. Consider, if you will, that each tire has a fixed amount of traction available at any given time, and assign the value of one dollar to that traction. We can spend that entire dollar on cornering, as we would on a skidpad; we can spend the dollar on braking, as would be the case when doing perfect threshold braking before corner entry, or we can spend it on acceleration, as a skilled drag racer would when leaving the line. We can also split that dollar any way we like. When we brake and turn at the same time, we can spend fifty cents on braking and fifty cents on turn-in, or we can spend ninety cents on braking and ten on turn-in. What we cannot do is spend $1.05. When we ask for more than a dollar’s worth of combined traction from a tire, we’ll be “overdrawn” and the car will slide. Understeer is the condition you get when the front end is overdrawn; oversteer is when the rear end is using more than a dollar’s worth of traction per tire. Keith invented the dollar theory for motorcycles, but it holds true for cars as well. Ross Bentley tell us: “You can only use 100% of the available traction – and make sure you do.”
The basic advantage of rear-wheel-drive is this: you can accelerate out of a corner earlier. Since you aren’t relying on the front wheels to both steer and accelerate, you can hit the gas sooner. There’s a secondary advantage – you can maintain corner speed slightly better because you can accelerate just enough to eliminate the braking effect of the turned front wheels without “overdrawing” the front tires – but at that point we’re into 10/10ths driving and serious racecraft, so we’ll forget about that for now. Earlier acceleration is what makes RWD the racer’s choice.
That’s the only dynamic advantage strictly linked to RWD, but there are two other disadvantages of traditional front-drivers which we should consider. It’s worth noting that these disadvantages also apply to all-wheel-drive cars which are based on traditional FWD layouts, such as Audi Quattros or SH-AWD Acuras. First, weight distribution. FWD cars tend to have more than fifty percent of the weight on the front wheels, and often the bulk of that weight is ahead of the front wheels. Having more weight on the front end needs you need more tire to control that weight, and most sanctioning bodies frown on having wider front tires. (Those of us who race FWD cars have all sorts of ways to make up for this, from arm-thick rear swaybars to crazy toe settings, which is why my Neon ends up naturally oversteering on corner entry. It’s not for the timid, trust me.) Pontiac is the only manufacturer in modern times to address this problem on a street car, offering a tire package for the V8-powered Grand Prix with slightly wider front tires, but customers tend to be actively repelled by the idea of having wide front tires. I’m not sure why, but there you go.
The second, and more important, dynamic disadvantage of a front-engine layout is polar moment of inertia. The more weight you can place at the center of the car, the quicker and easier it is to turn; think of a figure skater pulling her arms in during a spin and speeding up as a result. Placing weight at either end of a car affects its willingness to change direction, for the same reason that a heavy arrowhead makes an arrow fly true: the weight has effective “leverage” and is better able to resist sideways force. Rear-engined cars tend to have a slow-turn in, which is one of the three reasons why a typical 911 understeers on corner entry, (and someday we’ll discuss them all) but a front-engined car with big weight ahead of the front axle is even worse. It’s exactly like the arrow in our analogy. It wants to fly straight. Reluctance to turn is, of course, not a desirable condition in a race car, unless it’s a drag race car. The less polar moment of inertia – which is to say, the more weight you have at the center of the car, relatively speaking – the better, which is why all true race cars are mid-engined. It’s also why BMW makes such a big fuss about having most of the engine behind the front axle, and why Nissan is so fond of their so-called “front mid engine” layout. Getting the weight between the wheels reduces the inherent stability of the car, making it easier to turn.
You’ve heard all of this before, of course. You’re probably intimately familiar with all the reasons RWD is better. I’ve raced both FWD and RWD cars, and have experienced these advantages at the very limit myself. So why would anybody buy an FWD car, or a car with an overhanging front engine? The answer is simple: the reasons which argue against FWD for racecars actually support FWD in the real world.
Let’s start with The Dollar Theory. It still holds true in the real world, with one important caveat: it’s utterly irrelevant. On the street, we “performance drive” for our own enjoyment. There’s no clock against which to run, no competitor to outbrake you into the next turn. We’re looking for satisfaction, and that can be had just as easily in an FWD car. Some of the most satisfying canyon carvers in history have been FWD cars. The fellow who tells you that all FWD cars are “understeering pigs” is really telling you that he doesn’t understand how to trail brake. Furthermore, since we aren’t competing in a real race series with fixed rules, we can do anything we like. Are you dissatisfied with your Acura’s cornering ability? Get more tire. Want a faster corner exit in your MINI? Put a limited-slip diff in there. There are no sanctioning bodies to satisfy, so that minimal RWD corner-exit advantage is meaningless. We can make up for it in other ways.
What about weight balance? At low speeds, in low-traction conditions, FWD cars are better, because they have more weight on the wheels that accelerate, steer, and stop. There’s a reason BMW and Mercedes fit such wonderful traction-control systems to their RWD cars – they are necessary in many parts of the country. Under, say, forty miles per hour, FWD cars are better in the rain, better in the snow, better any time the condition of the road is in doubt. Racing drivers rarely find themselves driving up a slippery hill in the snow – but that’s a real-world condition that many of us experience every year. Of course, AWD cars are better still, but the funny thing is that Audis, Acuras, and other “natural FWD” cars are still better in the snow than AWD variants of “natural RWD” cars like Bimmers and Benzes, because they have that extra weight on the wheels that turn and stop.
We don’t all live in the snow belt, though, so what about high speeds? What about the freeway? Believe it or not, that’s where FWD really shines. Remember my analogy of the arrow with the heavy arrowhead? It’s hard to turn. It wants to fly straight. It’s stable – and that’s exactly what we want during freeway driving. To begin with, a stable car is inherently more restful for a long drive. I love my Boxster and 911, but over the course of a ten-or-twelve-hour drive, I do get a bit tired of the constant minor corrections needed to keep them pointed straight. When the camber of the road tilts, the Porsches want to follow it off onto the shoulder; when there’s a dip on the freeway, it unsettles them far more than it would a front-engined car. For long hauls, particularly at high speeds (like – gosh! – the Autobahn) you want a car which is stable by default.
”Sure,” you reply, “but what about emergency maneuvering?” Now we come to FWD’s finest hour. Most drivers steer too much in emergency freeway maneuvers. They unsettle the car beyond the point where they can control it. That’s why they spin, flip, or roll off the road. The perfect freeway car would be stable during the avoidance maneuver, and would naturally return to a straight-line balance when steering input was removed. Guess what kind of car does that best? Nope, it sure as hell isn’t a 911, or even a BMW M3. It’s the front-engined, FWD car that has the most predictable emergency handling and the quickest return to stability. This even benefits those of us who consider ourselves to be “skilled drivers” or “racing drivers”. We may be capable of steering a fast-moving Ferrari 430 around a crash… in daylight on dry pavement. Put us behind the wheel for six hours, get us tired, crank up the stereo, let our passengers start talking, put some rain on the road, take the light away… and pretty soon even a superhuman driver becomes merely human.
There are other popular objections to FWD, many of them centering around “refinement”, ride quality, and that sort of thing, but one drive in a Bentley Flying Spur, which is an FWD car under the skin, proves that most of those objections are pretty worthless. In the modern engineering era, it’s possible to make FWD-platform cars behave just as well as the RWD competition. If you doubt me, go test-drive a Lexus ES350 and IS350. Surprise! The FWD car rides better and feels more refined.
If FWD offers real-world safety, security, and comfort benefits, and I would contend that it certainly does, why are manufacturers in such a hurry to convert everything more “upmarket” than a Dodge Avenger to RWD? Why did Toyota and Hyundai expend such massive effort to make their flagship cars spin the back wheels? Why is GM endlessly flip-flopping between future plans for RWD or FWD Cadillacs?
As always in this industry, it’s a question of marketing. Front-wheel-drive is associated in the public mind with cheap, crappy little cars, while rear-wheel-drive is the land where BMW and Mercedes-Benz dwell. It’s about prestige, it’s about perception, it’s about that bloody Autobahn. It’s about journalists pretending to be racers, and racing journalists forgetting that, contrary to the advertisments, not every day is race day. It’s what Donald Fagen might call “The Royal Scam”, where we all pretend to see and feel things which don’t really exist. It sells magazines and generates clicks on banner ads, but there’s no substance behind the sizzle.
Even iconoclastic, wonderful Audi has finally fallen into the trap of being ashamed of FWD. I have been solemnly assured that the modern range of Quattro-drivetrain automobiles has “rear-biased” AWD, and that the new flip-flop differential arrangement has moved their engines slightly farther back in the car. They say it’s for sound engineering reasons, but I suspect it’s that old marketing mojo at work, trying to add some of that RWD-style frosting on a solid FWD cake. It doesn’t matter to me. The end, in this case, justifies the means. To misquote Bob Seger one more time, front-wheel-drive may not rule the ‘Ring, but it has the advantage — down on Main Street.