O Mito do RWD.
- Iniciador de tópicos SilverArrow
- Data de início
- Estado
Corsa1200Sport
Well-known member
por acaso agora o forum tem andado pacífico no que diz respeito ao ctr. mas ha uns meses atras o k estava a dar eram tópicos sobre o ctr... um até as 50 paginas passou e se fez um comparativo filmado de proposito[}
]
Corsa1200Sport
Well-known member
isso é psicologico pá
. o máximo k podes sentir é em aceleraçao em curva... ou entao o famoso torque steer dos fwd. mas isso nao é propriamente diferença entre esticao e puxao...Eliselotus
Well-known member
concordo com o T5. é possivel perceber a diferença entre os varios tipos de tracçao (FWD e RWD principalmente) a direito sem ser preciso haver rodas a patinar
basta ter ouvidos e ter as maos no volante.
um vibra mais que o outro, um faz um barulho diferente do outro.
edit: se for uma recta com buracos, mais se nota!! subidas idem.
basta ter ouvidos e ter as maos no volante.
um vibra mais que o outro, um faz um barulho diferente do outro.
edit: se for uma recta com buracos, mais se nota!! subidas idem.
Taveirada
New member
Qt ao z4vss2000 acho que poderá haver duvidas, mas eu acredito que o z4 seja mais rapido... qd se mete o boxster ao barulho... isso ja é outra coisa... é um porsche!
Qt ao IS... é novidade para mim... está assimilado!
Já agora... havia um teste da AH ou da automotor que tinha o 320i com melhor comportamento que o lexus... mais um teste da evo que dizia que o lexus nao tinha o comportamento do 320i... por isso falei... mas estou a ver que não são assim tão diferentes..
Talvez digam que o bmw é melhor comportado por esta mesma razão...
Desculpa lá, mas o Traccion Avant quando surgiu era a referência total em termos de segurança a curvar... Sei, porque o meu avô teve um, e conta-me que na altura era espantoso porque o carro praticamente não fugia em curva.
Quanto ao tópico:
Em termos de segurança, principalmente em piso molhado, os FWD não precisam de tanta atenção por parte do condutor.. Isso torna-os mais seguros porque são mais fáceis de conduzir e controlar.
Pessoalmente, prefiro RWD. Não têm problemas de motricidade, têm melhor inscrição em curva e depois há claro as derivas de traseira, que quando controladas são gozo puro [B)]
Acima de tudo, para ganhar espaço (tal como o fez Sir Alec Issigonis no Mini)
Dá-me 1 exemplo disso!
Yeah, right!
Os FWD surgiram por contenção de custos e para ganhar espaço(como de resto, já referi...). Mainada!
[}
][}][}][}][}]Isso não só é mentira, como estou disposto a prová-lo. O meu RWD sem ajudas electrónicas está pronto para um comparativo com o teu FWD
]Zur Besonderen Verwendung
Banido
Errrrrhm...estás a dizer que ao volante não sentes diferença entre arrancar com um FWD e um RWD ?
Essa é que desafia o conhecimento de condução dos dois tipos de tracção!
Zur Besonderen Verwendung
Banido
depende... em recta talvez engane... mas num arranque devagar... mesmo muito linear...
Mas o que é certo é... em recta nao se usa o guiador e sem guiador para que serve conduzir? andar em frente qq um anda!
[/quote]
Não me estou a referir em recta, ou curva, subir ou descer, arranque rápido ou lento, sentado ao volante não consegues distinguir logo o tipo de tracção ?
Taveirada
New member
Não me estou a referir em recta, ou curva, subir ou descer, arranque rápido ou lento, sentado ao volante não consegues distinguir logo o tipo de tracção ?
[/quote]
Parado? ou a andar? e se for a andar como?
Parado os carros são todos iguais... 4 rodas e uma carcaça... mais bonitos ou mais feios... nao se nota pormenores mecanicos que eu saiba! So se for a abertura das portas!
Eliselotus
Well-known member
para ver que é RWD nem é preciso ligar o carro.
as dimensoes do tunel central n enganam. pode é ser AWD, 4x4 ou RWD
as dimensoes do tunel central n enganam. pode é ser AWD, 4x4 ou RWD
Taveirada
New member
citação:Originalmente colocada por Eliselotus
para ver que é RWD nem é preciso ligar o carro.
as dimensoes do tunel central n enganam. pode é ser AWD, 4x4 ou RWD
ia dizer o mesmo... e adicionar atraves do eixo da frente estar mais na ponta do carro... mas isso pode ser forjado atraves do proprio desenho do carro
pmct
Well-known member
Why Front-Wheel Drive Sucks
And why rear-wheel drive is coming back.
By Mickey Kaus
Updated Friday, April 11, 2003, at 4:06 AM PT
Friday, April 11, 2003
Car/sex metaphors are unavoidable, so let's get right to today's: Front-wheel drive cars are like bad sex. Rear-wheel drive cars are like good sex.
Let me explain!
Sometime in the early 1980s, I asked my friend Paul why he drove a crass Chevy Camaro. He said he liked the "balance" of a rear-wheel drive car. I nodded but secretly sneered at him. Everyone knew that front-wheel drive cars were the efficient, sophisticated wave of the future. Audis were front-wheel drive. Saabs were front-drive. GM, Ford, and Chrysler were about to embark on a massive shift to front-drive, resulting in the current Detroit product lineup, in which even the venerable Caddy DeVille is a front-drive car.
The advantages of front-wheel drive (FWD) seem self evident: By avoiding the need for a driveshaft connecting the engine in front with the rear wheels, front-drive cars save space. The entire drivetrain can be packed into a neat compartment in the front, leaving the rest of the car's volume for passengers and cargo. Plus, front-drive cars have better traction in slippery conditions (in part because the weight of the engine is on top of the wheels that are providing the power).
I should have realized the grim truth decades ago when I borrowed a friend's Audi 100 –- the first front-drive car I'd ever driven -- and took it out on Sunset Boulevard. In one of the curves leaving Beverly Hills, near the pink house that used to be owned by Jayne Mansfield, I mashed the throttle, expecting the satisfying "lock in" effect I got in my old rear-drive Volvo – the nose turning in, the car seeming to stop slipping, tightening its grip on the road even as it went around the corner faster. But that's not what happened. What happened is the front tires went all gooey and the car started to head for the living room of a nearby mansion. Only panicked braking calmed things down.
Naturally, my brain did what the human brain tends to do with a bit of aberrant data: I ignored it. All during the '80s and '90s the car magazines assured me, seemingly continually, that in sophisticated front-drive designs you couldn't even tell which set of tires was providing the power. Weren't front-drive Hondas the hippest cars around? Wasn't even Volvo switching, belatedly, to front drive? I also blamed the victim! I must just be a lousy or unsophisticated driver, I figured.
Then, a bit over a year ago, I conducted an abortive test drive of five convertibles. The idea was to sample cars that had at least a semblance of a rear seat. The entrants were Ford Mustang, Chevy Camaro, VW Cabriolet, Chrysler Sebring, and Toyota Solara. And that was the order of finishing (though the test was interrupted by 9/11 before I could drive a final production version of the Toyota). None of the cars was very good – you give up a lot in chassis stability when you chop off the roof, I discovered. But the old, junky, rear-drive Ford and Chevy pony cars were by far the most enjoyable – they rattled and guzzled, but at least they were a blast to drive around corners. The other three cars, all front-drive, were simply pleasant forms of transportation.
Why are rear-drive cars more fun? Every enthusiast may know the answer, but I didn't. So I called up a helpful GM suspension expert, Vehicle Chief Engineer Ed Zellner. There are, I learned, five basic reasons:
1) "Balance": The car rides on four patches of rubber, each about as big as your hand. An ideal car would distribute its weight evenly, so each tire had to bear the same load, and none would give way earlier than all the others. The ideal weight distribution, then, would be split about 50/50 between front and rear (actually, 48/52 to help with forward pitch during braking). "A rear-drive car can typically approach that," says Zellner. Engineers can move the front wheels forward, so that the engine – which doesn't have to be connected to those wheels -- sits behind the front axle. Meanwhile, the driveshaft and rear differential (necessary to send power to the rear tires) add weight in the rear. Front-drive cars, which must connect the engine and transmission to the front axle, typically have their engines mounted way forward and can't do much better than a 60/40 front/rear weight distribution.
2) Center of Gravity: This is the point the car wants to "rotate around" in a turn. On a rear-drive car, it's "about where the driver sits," says Zellner. In a turn, in other words, the car seems to be rotating around you – you're at the center. It's a natural pleasant effect, suggesting you're in control, the way you're in control when you're walking or running around a corner and your weight is centered inside you. (Analogy No. 2: It's like wearing stereo headphones and having the sound centered between your ears!) A front-drive car, in contrast, with its massive front weight bias, wants to rotate around a point in front of the driver. So in a corner, the driver isn't just rotating around his spine. He's moving sideways, as if he were a tether ball on the end of a rope, or Linus being dragged when Snoopy gets hold of his blanket. Not such a pleasant feeling, or a feeling that gives you a sense of natural control.
3) "Torque Steer": One of the most annoying habits of many powerful front-drive cars is that they don't go straight when you step on the accelerator! Instead, they pull to one side, requiring you to steer in the other direction to compensate, like on a damn boat. This "torque steer" usually happens because the drive shafts that connect the engine to the front wheels aren't the same length. Under power, the shafts wind up like springs. The longer shaft -- typically on the right -- winds up a bit more, while the shorter left shaft winds up less and transmits its power to the ground more quickly, which has the effect of pulling the car to the left. (This winding-up phenomenon occurs the moment you step on the pedal. After that, the wind-up relaxes, but "torque steer" can still be produced by the angles of the joints in the drive axles as the whole drivetrain twists on its rubber mounts.)
Veer madness?
Engineers try various strategies to control this veering tendency, but even designing shafts of equal length (as in all Cadillacs) doesn't completely solve the problem because the engine still twists a bit in its mounts and alters the angles of the drive shafts. True, some manufacturers -- Audi, for example -- are said to do a particularly good job of repressing torque steer . But even a top-rank company such as Nissan has problems -- its otherwise appealing new front-drive Maxima is said to be plagued by big-time, uninhibited torque steer. Rear-drive cars, meanwhile, don't really have a torque-steer problem that needs repressing. Their power goes to the rear through one driveshaft to a center differential that can a) have equal-length shafts coming out from it and b) be more firmly mounted.
4) Weight Shift: Suppose you just want to go in a straight line. What's the best way to get traction? Answer: Have as much weight over the driving wheels as possible. Front-drive cars start with an advantage -- but when any car accelerates, the front end tips up, and the rear end squats down. This transfers weight to the rear wheels -- away from the driving wheels in a FWD car but toward the driving wheels in a rear-drive car, where it adds to available traction. In effect, the laws of physics conspire to give RWD cars a bit more grip where they need it when they need it (aqui no forum as leis da fisica são um mito[}][}][}]). (This salutary effect is more than canceled out in slippery, wet conditions, where you aren't going to stomp on the accelerator. Then, FWD cars have the edge, in part, because they start out with so much more of their weight over both the driving and the turning wheels. Also, it's simply more stable to pull a heavy wheeled object than to push it -- as any hotel bellhop steering a loaded luggage cart knows. In snow, FWD cars have a third advantage in that they pull the car through the path the front tires create, instead of turning the front tires into mini-snowplows.)
5) "Oversteer" and the Semi-Orgasmic Lock-In Effect: In a rear-drive car, there's a division of labor -- the front tires basically steer the car, and the rear tires push the car down the road. In a FWD car, the front tires do all the work – both steering and applying the power to the road – while the rears are largely along for the ride. That, it turns out, is asking a lot of the front tires. Since the driving wheels tend to lose traction first, the front tires of front-drive cars invariably start slipping in a corner before the lightly loaded rear tires do -- a phenomenon known as "understeer." If you go too fast into a curve -- I mean really too fast -- the car will plow off the road front end first. In rear-drive cars, the rear wheels tend to lose traction first, and the rear of the car threatens to swing around and pass the front end -- "oversteer." If you go too fast into a corner in an oversteering car, the car will tend to spin and fly off the road rear end first.
What's the best way to fly off the road? Safety types prefer frontwards -- understeer. Why? To control an oversteering skid, where the rear wheels are heading for the weeds, you have to both slow down and counterintuitively turn the wheel in the opposite of the direction you're turning. In a front-drive car, with the front wheels slipping, you slow down and keep turning the way you'd been turning to get around the corner in the first place -- a more natural maneuver, since you're pointing the car in the direction you want to go. This is why, for safety reasons, even rear-drive cars sold to average consumers tend to have their springs and other suspension bits set up to make them understeer -- to make the front tires slip first, despite the car's innate oversteering tendency. Only by applying lots of power in a corner can you actually break the rear end of a bread-and-butter rear-drive car like the Mustang loose -- a maneuver favored by sports car freaks, but one you try at your own peril.
Big American manufacturers (all heavily invested in front drive) like to say that for 99 percent of drivers, driving at normal speeds, FWD's inherent understeer and better traction in the wet makes it preferable -- both safer and easier to drive quickly. It's only the 1 percent of speed freaks who enjoy breaking the rear end loose and then catching it with a bit of "reverse lock." Here's where I emphatically dissent.
It's pretty clear to me, after driving hundreds of different vehicles over several decades, that rear drive offers a big aesthetic advantage to ordinary drivers at ordinary speeds in ordinary conditions. Why? The lock-in effect I mentioned earlier. Suppose you go into a corner in a rear-drive car at a reasonable, safe, legal speed. Nothing's about to skid. But you can still feel the front end starting to plow wide a bit. What to do? Step on the gas! Don't stomp on it -- but add a bit of power, and a miraculous thing happens. The front end swings back in, the car tightens its line. Cornering traction seems to increase. And the car feels locked into a groove, balanced between the motive power from the rear and the turning power in the front.
Hit the brake?
You don't have to be a race driver to feel this. You can be a defensive driver and feel it. You can be driving a 1973 Ford Maverick with leaking shocks and you'll feel it. Accountants feel it on the way to the office and housewives feel it on the way to the Safeway. Even Ralph Nader probably feels it. It's a good part of what makes driving a car a sensual act. (What's happening, technically? None of the tires is at its limit of adhesion. But the added speed is making the front tires --which [since they are undriven] have plenty of surplus traction -- apply more force to the road surface to change direction. Meanwhile, the rear of the car is shifting outward, ever so slightly -- not a Bullitt-style power slide, but a subtle attitude adjustment that cancels the plowing effect. The power "helps you through the corner," as Zellner puts it.)
This doesn't happen in a front-drive car. The best an ordinary driver can hope for in a FWD car is that it "corners as if on rails" -- no slippage at all. No plowing -- but also no semi-orgasmic "lock in." More typically, if you hit the accelerator in a fast corner, things get mushy up front (as they did that evening near Jayne Mansfield's house). The lesson the FWD car seems to be teaching is: Try to go faster, and you're punished. Front-drive cars are Puritans! In a rear-drive car, you hit the accelerator and things get better! Rear-drive cars are hedonists. (This is assuming you don't hit the accelerator too hard.)
No front-drive here
I'm not saying there aren't sophisticated techniques that allow FWD cars to do better. A recent issue of Grassroots Motorsports tested a humble FWD Acura RSX against a classy rear-drive BMW. The Acura actually turned laps a bit more quickly. How'd that happen? The Grassroots people realized that by stepping on the brake hard enough on entering a turn, the rear of the Acura could be made to swing wide, canceling out its inherent understeer. (This is the same effect you get by stepping on the gas in a rear-drive car.) But normal drivers aren't going to mash the brakes and go sliding through turns like a rally champion. Nor does braking to achieve "lock-in" seem as satisfying as accelerating to achieve lock in. I suppose I shouldn't knock it until I've tried it -- but I'm not going to try it! That's the point. Housewives heading to the Safeway aren't going to try it either. The joys of rear-drive are accessible to them -- it's the joys of FWD that are reserved for the skilled Grassroots Motorsport elite.
Explaining SUVs: Now that the goo-goo bien pensant scales have fallen from my eyes, and I recognize the front-drive-for-the-masses movement as the Carter-era energy crisis con it is, several previously inexplicable things become explicable. Why did truck-based SUVs suddenly become popular just as Detroit shifted to front-wheel drive for its passenger cars? Was it (as anti-SUV activists claim) because the SUVs were exempt from various safety and economy standards -- or because the SUVs still had rear-wheel drive, with all its subtle satisfactions? Why do all BMWs (and virtually all Mercedes-Benzes) persist in using rear-wheel drive? Why do my friends, who aren't fast drivers, say that BMWs just feel better?
It's also now clear to me why Acura is in trouble (it only offers FWD sedans), why GM is busy working on a new "Tubular" rear-drive chassis, why the Infiniti G-35 and Lexus IS-300 (both rear drive) are so popular, and why the RWD Cadillac CTS and Lincoln LS are so refreshing to drive.
I'm not saying that any rear-wheel-drive car is better than any front-wheel-drive car, the way, say, any car with plain black tires looks better than any car with whitewalls. But it's close! Front-drive cars can be fun. Even bad sex is fun. But why choose it? 3:39 A.M.
And why rear-wheel drive is coming back.
By Mickey Kaus
Updated Friday, April 11, 2003, at 4:06 AM PT
Friday, April 11, 2003
Car/sex metaphors are unavoidable, so let's get right to today's: Front-wheel drive cars are like bad sex. Rear-wheel drive cars are like good sex.
Let me explain!
Sometime in the early 1980s, I asked my friend Paul why he drove a crass Chevy Camaro. He said he liked the "balance" of a rear-wheel drive car. I nodded but secretly sneered at him. Everyone knew that front-wheel drive cars were the efficient, sophisticated wave of the future. Audis were front-wheel drive. Saabs were front-drive. GM, Ford, and Chrysler were about to embark on a massive shift to front-drive, resulting in the current Detroit product lineup, in which even the venerable Caddy DeVille is a front-drive car.
The advantages of front-wheel drive (FWD) seem self evident: By avoiding the need for a driveshaft connecting the engine in front with the rear wheels, front-drive cars save space. The entire drivetrain can be packed into a neat compartment in the front, leaving the rest of the car's volume for passengers and cargo. Plus, front-drive cars have better traction in slippery conditions (in part because the weight of the engine is on top of the wheels that are providing the power).
I should have realized the grim truth decades ago when I borrowed a friend's Audi 100 –- the first front-drive car I'd ever driven -- and took it out on Sunset Boulevard. In one of the curves leaving Beverly Hills, near the pink house that used to be owned by Jayne Mansfield, I mashed the throttle, expecting the satisfying "lock in" effect I got in my old rear-drive Volvo – the nose turning in, the car seeming to stop slipping, tightening its grip on the road even as it went around the corner faster. But that's not what happened. What happened is the front tires went all gooey and the car started to head for the living room of a nearby mansion. Only panicked braking calmed things down.
Naturally, my brain did what the human brain tends to do with a bit of aberrant data: I ignored it. All during the '80s and '90s the car magazines assured me, seemingly continually, that in sophisticated front-drive designs you couldn't even tell which set of tires was providing the power. Weren't front-drive Hondas the hippest cars around? Wasn't even Volvo switching, belatedly, to front drive? I also blamed the victim! I must just be a lousy or unsophisticated driver, I figured.
Then, a bit over a year ago, I conducted an abortive test drive of five convertibles. The idea was to sample cars that had at least a semblance of a rear seat. The entrants were Ford Mustang, Chevy Camaro, VW Cabriolet, Chrysler Sebring, and Toyota Solara. And that was the order of finishing (though the test was interrupted by 9/11 before I could drive a final production version of the Toyota). None of the cars was very good – you give up a lot in chassis stability when you chop off the roof, I discovered. But the old, junky, rear-drive Ford and Chevy pony cars were by far the most enjoyable – they rattled and guzzled, but at least they were a blast to drive around corners. The other three cars, all front-drive, were simply pleasant forms of transportation.
Why are rear-drive cars more fun? Every enthusiast may know the answer, but I didn't. So I called up a helpful GM suspension expert, Vehicle Chief Engineer Ed Zellner. There are, I learned, five basic reasons:
1) "Balance": The car rides on four patches of rubber, each about as big as your hand. An ideal car would distribute its weight evenly, so each tire had to bear the same load, and none would give way earlier than all the others. The ideal weight distribution, then, would be split about 50/50 between front and rear (actually, 48/52 to help with forward pitch during braking). "A rear-drive car can typically approach that," says Zellner. Engineers can move the front wheels forward, so that the engine – which doesn't have to be connected to those wheels -- sits behind the front axle. Meanwhile, the driveshaft and rear differential (necessary to send power to the rear tires) add weight in the rear. Front-drive cars, which must connect the engine and transmission to the front axle, typically have their engines mounted way forward and can't do much better than a 60/40 front/rear weight distribution.
2) Center of Gravity: This is the point the car wants to "rotate around" in a turn. On a rear-drive car, it's "about where the driver sits," says Zellner. In a turn, in other words, the car seems to be rotating around you – you're at the center. It's a natural pleasant effect, suggesting you're in control, the way you're in control when you're walking or running around a corner and your weight is centered inside you. (Analogy No. 2: It's like wearing stereo headphones and having the sound centered between your ears!) A front-drive car, in contrast, with its massive front weight bias, wants to rotate around a point in front of the driver. So in a corner, the driver isn't just rotating around his spine. He's moving sideways, as if he were a tether ball on the end of a rope, or Linus being dragged when Snoopy gets hold of his blanket. Not such a pleasant feeling, or a feeling that gives you a sense of natural control.
3) "Torque Steer": One of the most annoying habits of many powerful front-drive cars is that they don't go straight when you step on the accelerator! Instead, they pull to one side, requiring you to steer in the other direction to compensate, like on a damn boat. This "torque steer" usually happens because the drive shafts that connect the engine to the front wheels aren't the same length. Under power, the shafts wind up like springs. The longer shaft -- typically on the right -- winds up a bit more, while the shorter left shaft winds up less and transmits its power to the ground more quickly, which has the effect of pulling the car to the left. (This winding-up phenomenon occurs the moment you step on the pedal. After that, the wind-up relaxes, but "torque steer" can still be produced by the angles of the joints in the drive axles as the whole drivetrain twists on its rubber mounts.)
Veer madness?
Engineers try various strategies to control this veering tendency, but even designing shafts of equal length (as in all Cadillacs) doesn't completely solve the problem because the engine still twists a bit in its mounts and alters the angles of the drive shafts. True, some manufacturers -- Audi, for example -- are said to do a particularly good job of repressing torque steer . But even a top-rank company such as Nissan has problems -- its otherwise appealing new front-drive Maxima is said to be plagued by big-time, uninhibited torque steer. Rear-drive cars, meanwhile, don't really have a torque-steer problem that needs repressing. Their power goes to the rear through one driveshaft to a center differential that can a) have equal-length shafts coming out from it and b) be more firmly mounted.
4) Weight Shift: Suppose you just want to go in a straight line. What's the best way to get traction? Answer: Have as much weight over the driving wheels as possible. Front-drive cars start with an advantage -- but when any car accelerates, the front end tips up, and the rear end squats down. This transfers weight to the rear wheels -- away from the driving wheels in a FWD car but toward the driving wheels in a rear-drive car, where it adds to available traction. In effect, the laws of physics conspire to give RWD cars a bit more grip where they need it when they need it (aqui no forum as leis da fisica são um mito[}
][}][}]). (This salutary effect is more than canceled out in slippery, wet conditions, where you aren't going to stomp on the accelerator. Then, FWD cars have the edge, in part, because they start out with so much more of their weight over both the driving and the turning wheels. Also, it's simply more stable to pull a heavy wheeled object than to push it -- as any hotel bellhop steering a loaded luggage cart knows. In snow, FWD cars have a third advantage in that they pull the car through the path the front tires create, instead of turning the front tires into mini-snowplows.) 5) "Oversteer" and the Semi-Orgasmic Lock-In Effect: In a rear-drive car, there's a division of labor -- the front tires basically steer the car, and the rear tires push the car down the road. In a FWD car, the front tires do all the work – both steering and applying the power to the road – while the rears are largely along for the ride. That, it turns out, is asking a lot of the front tires. Since the driving wheels tend to lose traction first, the front tires of front-drive cars invariably start slipping in a corner before the lightly loaded rear tires do -- a phenomenon known as "understeer." If you go too fast into a curve -- I mean really too fast -- the car will plow off the road front end first. In rear-drive cars, the rear wheels tend to lose traction first, and the rear of the car threatens to swing around and pass the front end -- "oversteer." If you go too fast into a corner in an oversteering car, the car will tend to spin and fly off the road rear end first.
What's the best way to fly off the road? Safety types prefer frontwards -- understeer. Why? To control an oversteering skid, where the rear wheels are heading for the weeds, you have to both slow down and counterintuitively turn the wheel in the opposite of the direction you're turning. In a front-drive car, with the front wheels slipping, you slow down and keep turning the way you'd been turning to get around the corner in the first place -- a more natural maneuver, since you're pointing the car in the direction you want to go. This is why, for safety reasons, even rear-drive cars sold to average consumers tend to have their springs and other suspension bits set up to make them understeer -- to make the front tires slip first, despite the car's innate oversteering tendency. Only by applying lots of power in a corner can you actually break the rear end of a bread-and-butter rear-drive car like the Mustang loose -- a maneuver favored by sports car freaks, but one you try at your own peril.
Big American manufacturers (all heavily invested in front drive) like to say that for 99 percent of drivers, driving at normal speeds, FWD's inherent understeer and better traction in the wet makes it preferable -- both safer and easier to drive quickly. It's only the 1 percent of speed freaks who enjoy breaking the rear end loose and then catching it with a bit of "reverse lock." Here's where I emphatically dissent.
It's pretty clear to me, after driving hundreds of different vehicles over several decades, that rear drive offers a big aesthetic advantage to ordinary drivers at ordinary speeds in ordinary conditions. Why? The lock-in effect I mentioned earlier. Suppose you go into a corner in a rear-drive car at a reasonable, safe, legal speed. Nothing's about to skid. But you can still feel the front end starting to plow wide a bit. What to do? Step on the gas! Don't stomp on it -- but add a bit of power, and a miraculous thing happens. The front end swings back in, the car tightens its line. Cornering traction seems to increase. And the car feels locked into a groove, balanced between the motive power from the rear and the turning power in the front.
Hit the brake?
You don't have to be a race driver to feel this. You can be a defensive driver and feel it. You can be driving a 1973 Ford Maverick with leaking shocks and you'll feel it. Accountants feel it on the way to the office and housewives feel it on the way to the Safeway. Even Ralph Nader probably feels it. It's a good part of what makes driving a car a sensual act. (What's happening, technically? None of the tires is at its limit of adhesion. But the added speed is making the front tires --which [since they are undriven] have plenty of surplus traction -- apply more force to the road surface to change direction. Meanwhile, the rear of the car is shifting outward, ever so slightly -- not a Bullitt-style power slide, but a subtle attitude adjustment that cancels the plowing effect. The power "helps you through the corner," as Zellner puts it.)
This doesn't happen in a front-drive car. The best an ordinary driver can hope for in a FWD car is that it "corners as if on rails" -- no slippage at all. No plowing -- but also no semi-orgasmic "lock in." More typically, if you hit the accelerator in a fast corner, things get mushy up front (as they did that evening near Jayne Mansfield's house). The lesson the FWD car seems to be teaching is: Try to go faster, and you're punished. Front-drive cars are Puritans! In a rear-drive car, you hit the accelerator and things get better! Rear-drive cars are hedonists. (This is assuming you don't hit the accelerator too hard.)
No front-drive here
I'm not saying there aren't sophisticated techniques that allow FWD cars to do better. A recent issue of Grassroots Motorsports tested a humble FWD Acura RSX against a classy rear-drive BMW. The Acura actually turned laps a bit more quickly. How'd that happen? The Grassroots people realized that by stepping on the brake hard enough on entering a turn, the rear of the Acura could be made to swing wide, canceling out its inherent understeer. (This is the same effect you get by stepping on the gas in a rear-drive car.) But normal drivers aren't going to mash the brakes and go sliding through turns like a rally champion. Nor does braking to achieve "lock-in" seem as satisfying as accelerating to achieve lock in. I suppose I shouldn't knock it until I've tried it -- but I'm not going to try it! That's the point. Housewives heading to the Safeway aren't going to try it either. The joys of rear-drive are accessible to them -- it's the joys of FWD that are reserved for the skilled Grassroots Motorsport elite.
Explaining SUVs: Now that the goo-goo bien pensant scales have fallen from my eyes, and I recognize the front-drive-for-the-masses movement as the Carter-era energy crisis con it is, several previously inexplicable things become explicable. Why did truck-based SUVs suddenly become popular just as Detroit shifted to front-wheel drive for its passenger cars? Was it (as anti-SUV activists claim) because the SUVs were exempt from various safety and economy standards -- or because the SUVs still had rear-wheel drive, with all its subtle satisfactions? Why do all BMWs (and virtually all Mercedes-Benzes) persist in using rear-wheel drive? Why do my friends, who aren't fast drivers, say that BMWs just feel better?
It's also now clear to me why Acura is in trouble (it only offers FWD sedans), why GM is busy working on a new "Tubular" rear-drive chassis, why the Infiniti G-35 and Lexus IS-300 (both rear drive) are so popular, and why the RWD Cadillac CTS and Lincoln LS are so refreshing to drive.
I'm not saying that any rear-wheel-drive car is better than any front-wheel-drive car, the way, say, any car with plain black tires looks better than any car with whitewalls. But it's close! Front-drive cars can be fun. Even bad sex is fun. But why choose it? 3:39 A.M.
pmct
Well-known member
About The Calculations Elapsed Time
The programs used are based on formulas (see the box to the right) in the "Auto Math Handbook" by John Lawlor. They were based on tests conducted by Patrick Hale, who distributed computer software called Quarter Jr which calculated 1/4 mile acceleration and took into account factors such as aerodynamics, gearing, etc. The QUARTERjr. formulas were derived empirically (via experimentation), and have been used with confidence by professional drag racers for years.
We did our own survey and found that the calculations were a little generous in that every car was faster than it should have been. For more accuracy, the weight and horsepower data for 25 cars was entered in a spreadsheet. The numbers were crunched (eliminating the two highest and the two lowest) and averaged into a more accurate formula, which basically redefined the 5.825 factor. The front wheel drive and rear wheel drive figures, which are based on Car and Driver road tests, are available.
Why seperate formulas for front and rear wheel drive cars? In a word (two words, actually): weight transfer. When a car accelerates, the rear wheels are pushed into the ground (more weight) and the front wheels are pushed away from the ground (less weight). For rear wheel drive cars this is an advantage as the extra weight means more traction and they "hook up" better. It is also why it is so easy to chirp the front tires on a front wheel drive car, even those with low horsepower. The same phenomena can be seen at a dragstrip as the front tires immediately jump from the surface on acceleration.
Play around with these calculations and you will soon discover an old racers adage: "To go faster, add lightness." Put another way, it is often easier to gain speed by taking away weight instead of adding horsepower. A rule of thumb amongst drag racers is that removing 200 lbs. will add 0.1 seconds to the 1/4 mile time. That is why when manufacturers come out with a serious racing version of a car, a weight loss program is part of the package.
The WebCars! calculations do not take into account a number of factors, such as aerodynamics, gearing, elevation, transmission and many other factors. Even tire size can make a difference, as big horsepower cars will slip at the beginning, slowing down the car. Temperature, humidity and elevation affect horsepower and are also factors.
The programs used are based on formulas (see the box to the right) in the "Auto Math Handbook" by John Lawlor. They were based on tests conducted by Patrick Hale, who distributed computer software called Quarter Jr which calculated 1/4 mile acceleration and took into account factors such as aerodynamics, gearing, etc. The QUARTERjr. formulas were derived empirically (via experimentation), and have been used with confidence by professional drag racers for years.
We did our own survey and found that the calculations were a little generous in that every car was faster than it should have been. For more accuracy, the weight and horsepower data for 25 cars was entered in a spreadsheet. The numbers were crunched (eliminating the two highest and the two lowest) and averaged into a more accurate formula, which basically redefined the 5.825 factor. The front wheel drive and rear wheel drive figures, which are based on Car and Driver road tests, are available.
Why seperate formulas for front and rear wheel drive cars? In a word (two words, actually): weight transfer. When a car accelerates, the rear wheels are pushed into the ground (more weight) and the front wheels are pushed away from the ground (less weight). For rear wheel drive cars this is an advantage as the extra weight means more traction and they "hook up" better. It is also why it is so easy to chirp the front tires on a front wheel drive car, even those with low horsepower. The same phenomena can be seen at a dragstrip as the front tires immediately jump from the surface on acceleration.
Play around with these calculations and you will soon discover an old racers adage: "To go faster, add lightness." Put another way, it is often easier to gain speed by taking away weight instead of adding horsepower. A rule of thumb amongst drag racers is that removing 200 lbs. will add 0.1 seconds to the 1/4 mile time. That is why when manufacturers come out with a serious racing version of a car, a weight loss program is part of the package.
The WebCars! calculations do not take into account a number of factors, such as aerodynamics, gearing, elevation, transmission and many other factors. Even tire size can make a difference, as big horsepower cars will slip at the beginning, slowing down the car. Temperature, humidity and elevation affect horsepower and are also factors.
pmct
Well-known member
PArece que não estas a ler bem este topico, ja por varias vezes, te disse quais são as vantagens do ponto de vista da fisica.
Eu sou portugues e tambem digo que são mais divertidos, portanto ja tens uns ingleses e pelo menos um Portuga
Exactamente aquilo que as maioria dos FWD não é tirando algumas excepçoes .
A Alfa é uma marca a serio, e como tal esta a planear o regresso ao RWD.
Tracção total são alguns audi, os que usam diferencial torsen, e não é so vantagens, pois aos ganhos em arranque linear e curva com piso escorregadio, contrapõe a maior dissipação de energia, que chaga a ser superior a 20%
Se for Diferencial HAldex, é pouco melhor que um FWD.
No poto anterior tens a formula Generica,, have fun com ela.
Quanto aos acidentes todoa a gente sabe que quando choive os biommers andam de comboio
- Estado