Rear wheel drive???

Question

Why do BMWs have RWD? It sucks on slick roads. I hear it has something to do with the size of the engine. Just curious.

Answer 1

DISADVANTAGES OF FWD:

Front Wheel Drive puts most of the forces of moving the car on the front wheels. The front wheels pull the car, and they steer it. It makes it easier for the total amount of grip available to be exceeded. When that happens, the FWD car will just keep going straight, while you're trying to turn. (This is called understeer...and on ice understeer can be so bad as to be no steering.)

Front wheel drive also puts the differential and transmission close to the front wheels. These are heavy parts, especially in cars with powerful engines. This means that more weight is in front, which makes it harder to turn the car. (This is the case for the same reason that balance is important in a sword or other combat blade) It does give you more traction on ice, but you can get the same effect in a rear wheel drive car by putting weight in the trunk.

FWD cars can be more difficult to service. The engine sits on top of the trans and differential, making access difficult, and making the engine bay more cramped. If it's a V6 or V8, it also means that half of the engine is angled back towards where the hood hinges, making access to that section extremely difficult. Some V6s are designed with this in mind, but others may require one to remove the hood or even the engine to be able to change spark plugs.

FWD cars experience a phenomenon known as torque steer. Due to peculiarities in most FWD designs, when you accelerate, uneven amounts of torque are applied to the left and right wheels, making the car pull to one side. In low-powered economy cars, this is barely noticeable (take your hands off the wheel and floor it and you might see the steering wheel jerk a bit), but in a performance car (most famously, the Saab 9-3 Viggen) it can be downright dangerous.

Because the drive wheels also have to steer, CV joints are required. These are joints that are able to bend while still transferring power through them. They've gotten better in recent years, but in cold climates they are still far more likely to break than the solid axles or U-joints usually used in rear wheel drive cars.

In performance cars, during hard acceleration the weight shifts towards the back of the car, reducing the traction at the front wheels. This isn't a problem on ice, since you can't accelerate fast enough to notice, but in racing or just spirited summer driving, it's HUGE.

ADVANTAGES OF FWD:

FWD powertrains can be lighter. In a small economy car this saves precious space, and fuel.

FWD takes up less space, since the entire powertrain is in the engine compartment. It doesn't require a transmission tunnel (that hump in the middle) running through the passenger compartment, meaning there is more room for people and cargo.

FWD provides more traction on ice because there is more weight over the drive wheels. RWD can do this, by putting weight in the back, but in a small, underpowered economy car, this can noticeably degrade performance.

FWD is cheaper to manufacture, because the entire power train can be installed as one unit, while more steps will be required for RWD. (This is offset by the difficulty in servicing, but that cost mostly goes to the post-warranty owners, not the manufacturer)


DISADVANTAGES OF RWD:

Harder to control on slick surfaces. RWD is more likely to spin, and most people do not know how to react in that situation.

Heavier and takes up more space. In a large, high-powered car, this is not a problem.

More expensive to manufacture.

Takes up more cargo and passenger room. The differential in back robs trunk space, the transmission tunnel robs cabin space.

Less traction for accelerating on ice. This can be resolved by putting weight in the trunk.

ADVANTAGES OF RWD:

Better weight distribution. More RWD cars are closer to the theoretical perfect distribution of 50 percent on the front wheels, 50 percent on the rear. This means that in absolute terms, it is easier for them to turn about their center, because that is also roughly the car's center of mass.

Better distribution of forces on the tires. The front wheels only have to steer, the rear wheels only have to make the car go. Well, they're both actually a little involved in cornering, but they each have their primary task.

Easier to service. There's more room to work in the engine bay, the transmission is easy to remove, the differential is way off by its lonesome and nothing even has to come off to work on it on a lot of cars. Parts may still be expensive, but generally, a RWD car is going to be a cinch to work on.

Weight shifts to the drive wheels during acceleration. This means that as you accelerate, you have more grip with which to accelerate even harder. Very important in performance cars (like most BMWs)


Basically, for what BMWs are, RWD is just better. Front Wheel Drive has its advantages, but not for high-powered performance cars. There are very fast FWD cars (SRT-4, Integra Type R), but they are all good performers IN SPITE OF being FWD, not BECAUSE OF being FWD. It's a disadvantage they overcame because of good suspension and chassis design.

As for slick roads, they don't suck. They're just different, not what most drivers are used to. I learned to drive in RWD on ice. With bad tires. Give a RWD good snow tires and it can be as easy to drive as any FWD car. Plus a RWD car can be driven sideways, from a stop. Try that in your FWD. (Actually, don't, because you can't.)

Answer 2

It all has to do with BMWs stature.
BMWs are considered to be an 'enthusiast car'.
while, 95% of americans are ignorant to what fwd and rwd even is, i would guess 80% of bmw buyers are looking for rwd. They want a rear wheel drive performance luxuary car.
Take the chevrolet impala for example. For 38ish years impalas were rear wheel drive. A very popular car in there time. Then in 2000, GM did the unthinkable, they made a fwd impala, and what happened... BOOM. The car was a success.
Those buyers could care less what wheel drive their car is. They just want to get from here to there without knowning how an engine even works. FWD cars are more fuel effecient, because they generally weigh less.
So theres your answer.

And the reason enthusiast prefer rwd to fwd, is for the drive.
A rwd car feels much more balanced; When you drive hard into a turn, you know that rwd will keep you from loosing control; and its alot more fun to drive.
A side note, i dont think there is an enthusiast out there who wouldnt say a mid engined (sitting behind the front axle) awd , 4 wheel steering isnt the best feeling drive out there...

Answer 3

Front wheel drive for me. OK you can do some serious drifting in a rear wheel drive car but apparently can go into a spin fairly easily if pushed a bit too much on normal roads. Also,in this snowy weather I would prefer front wheel as the weight is at the front with the steering wheels. BUT, this is just an opinion.

Answer 4

Size of the engine and the way BMWs are designed all play a role. BMW is known for their 3 series, and most 3s have the inline-6 engines, not V-6. Inline-6s have longer blocks, therefore they won't fit in a FWD configuration.

Also, BMW focuses on handling, not just power, unlike your typical "Meatheads" American muscle cars. To be able to handle spirited driving, you MUST have RWD. If you lose traction during a turn in a FWD, there's no way you'll be able to savage the turn. You're going whereever the car is going. FWD also induces excessive torque steer (the way your front wheels jerk to one side when you punch the gas) and understeer (the tendency of the car wanting to keep going straight when you turn, i.e. harder to turn)

Look at any serious sports car companies and tell me if there are any FWD cars? No FWD cars from Ferrari, BMW, Mercedes, Porsche, or Jaguar.

RWD cars aren't bad on slick roads. Like any bad road conditions, you have to slow down and drive with caution. If you constantly drive on icy or snowy roads, BMW also offers AWD cars, like their X5, X3, 330xi, and 530xi. All are excellent winter vehicles.

FWD belongs on econo cars and daily drivers with owners of mediocre driving abilities. True driving machines have power going to the rear or all wheels.

Answer 5

Rear wheel drive cars do not suffer from torque steer under hard acceleration as front wheel drive cars do and so can offer better handling.

Front wheel drive cars usually have better traction because the mass of the engine is above the driving wheels and most rear drive cars suffer because the back end is to light.

Most BMW's are well balanced with around 50/50 weight distribution providing superb handling on dry roads, on wet roads you just have to slow down and pray!

Answer 6

The reason for this is because BMW cars are designed for better handling and in order to give the driver a better " FEEL " of the road, RWD makes much more sense than say FWD which is much better for in the snow.

Answer 7

Not so much the SIZE of the engine as the POWER of the engine. RWDs plant much better on take offs, and are very predictable when it comes to their handling characteristics. Personally I would go AWD, but that is my opinion. I mean even the Porsche and Lamborghini are AWD now.

Answer 8

Because a BMW is a REAL car. Engines were never meant to go sideways and its the cheaper tin can cars that are made on a front wheel drive structure.

The mechanics on a front wheel drive car are not practical and being that european cars are designed to be practical, it makes more sense.

Answer 9

rwd is wayyy beter then fwd its more sporty all high end cars are rwd if you put tht much power in the front weels it would drive bad. Today they are mnakin cars AWD this is the best of both good traction n profromance.

Answer 10

Rear wheel drive is preferrable for high speed driving, which is why all race cars are rear wheel drive (a few are all-wheel drive). BMWs are built for high performance, so they are one of the few comapnies that haven't given in to front wheel drive.

Go to drivers school (I'm serious) and you'll appreciate what you have!

Answer 11

I live in New England and was told when I bought mine that studded snow tires are a must for the winters, and have never had a problem in snow, sleet, or freezing rain. In the spring and summer I put good all season radials on and it's fine.