Paul Walkers car is one of the most difficult car to drive...there were only 1270 carrera GT were built....because its a RMR (Rear Mid Engine/Rear wheel drive)....its very risky to drive on public roads. R.I.P - Paul Walker ! In detail on RMR (source: reddit) If you throw an object with the weight in the front forward, the object will tend to want to follow the weight. In the case of a midengined car, a lot of the weight is behind the driver. Like throwing a carpenters hammer with the head in the back, one can observe it rotate in mid-flight. In a front engined car, when you go around a corner, the front of the car will want to stay in front. In fact, it will resist turning, so that means the car tends to understeer which means it turns less than you want. If you go into a corner too hot, you increase the understeer. That is not good, because you can run off the road with the front of the car. But it is somewhat controllable and you can slow the car down in the turn if you are too fast. The physics of cars is that if you go into a corner too hot in a front engined car and hit the brakes, you slow down and actually can transfer grip to the front tires, since the car experiences more weight shift. You unweight the rear tires, so you can increase oversteer, which may reduce the understeer. In any case, if you wreck, you will probably do so nose first. But you can handle things by slowing the car down with brakes. This is why most production cars are understeer biased. Its safer for the general public. Front engined cars are probably safer also for people who are not skilled also. Now here is the difference in a midengined car. The weight is behind you. And it always wants to be in front. There are some good things in physics about the weight being behind you in racing. The ability of the car to rotate. Weight over the driving wheels. Launching. Weight transfer under braking. All better. The first thing to understand is what we mean when we consider the ability of a tire to maintain traction with the road surface. To keep this under 1000+ words, I will just say that its very important, and when you exceed the ability of the tires, you lose control. Many things come into play that determine what the ability of your tires are. These things may be: Speed or g-forces. Sideways forces take their toll. Weight pressing down on the tires. If you unweight the tire, it will lose grip. Road and stickiness. Ice of course is bad, so is a patch of wet or some gravel, or even a small bump that upsets the weight balance. The main trick with some of those things is to not get too close to your limits of adhesion, because none of us are superhuman and can forsee everything possible ahead of us on the road. You can play with the limits where it is safe to do so. But a public road is not the place. However, what typically happens is this. Driver goes into turn near the limits of the tires ability. We call that driving near 10/10ths. Most non-skilled drivers cant feel the difference between 8/10ths and 11/10ths. Something happens. That patch of wet. Something in the road. Evasive maneuver. A squirrel. Something. Or maybe just realizing you are going into the turn too hot. Probably the most common reason. You can do certain things BEFORE the turn. Remember, the mass behind you wants to go straight in front of you. If you are in a straight line, that is not a bad thing. If you are in a straight line, hit the brakes hard. But in the turn....now you have an issue. The normal driver reaction is to panic. And panic is not good. If you abruptly lift on the throttle, jerk the steering wheel, or worse, slam on your brakes (which most people do).... you cause some things to happen. You transfer weight to the front of the car so now the front increases its grip, but the rear loses grip. And the rear wants to lead. The rear end will start a very bad oversteer where the car starts to spin. Even if you can catch it, often the correction will induce a huge spin in the opposite direction. And if you are spinning, you have almost no control. You will have no idea where you will end up. You can spin into things or opposing traffic. The solution for this is to understand and learn car control. One of the best (safe) places to learn car control and what 10/10ths is, is a local autocross. Here you can spin out over and over. And many people do. Even on a safe racing track, its not always safe to spin out and go off the track. Famous racing quote: Understeer is when the front of the car hits the wall. Oversteer is when you hit with the back.
Posted on: Sun, 01 Dec 2013 13:08:48 +0000
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