At Home Mechanic

But if you go back to the father of modern physics, Sir Isaac Newton, the apple falling on his head and his writings about the principles of bodies in motion, you have the basis of the science of making a car go and stop. I could bore you worse than you are already are but instead I will boil it down to a few basic points: A body at rest tends to stay at rest; a body in motion tends to stay in motion. Throw in some ancient Egyptian discoveries about leverage and you have all need to know to improve the performance of your car. Got that? Good. There will be quiz on this materiel at the end of the week.

So what does this have to do with your car and its performance? Bottom line: It is easier to make a light car go, stop and turn a corner than a heavy car. An American Muscle car that weighs3800 lbs with a 400 horsepower engine has a power to weight ratio of 9.5:1, you only need to create about 300 horsepower in a 2800 lbs. car to get the equivalent power to weigh ratio.

Where the weight is on your car makes a difference also. As an extreme example, think if you had a couple hundred pounds hanging off the front bumper of your car. That weight acts like a pendulum when you turn a corner; your car will want to continue to turn after you straighten the steering wheel due to the momentum of that weight. This example demonstrates the principles of both a body in motion combined with leverage and how they act on your car. So by this example we have learned that we want as much of the cars weight within the wheelbase of your car to fight this pendulum effect.

The height of the weight in your car makes a difference as well. All those SUV's on the road have a very high center of gravity and it is relatively easy to push them over. Again, leverage and the principle of bodies in motion act together to tip over a tall vehicle with its high center of gravity. So clearly, a car with its weight as low as possible is less likely to tip over and can turn a corner more quickly.

As an aside it is easy to determine approximately where the center of gravity (CG) is on your car. Roughly, the CG on a modern car is about the height of the driver's seat bottom cushion. I can judge how well a car will withstand tipping motion by standing next to the vehicle. If the seat cushion is at my knee or lower, the car has a fair chance of being safe and stable in an emergency maneuver. Many SUV's and trucks put the driver's seat bottom at hip level or higher; you can expect those autos to be candidates to roll over much more easily.

As the American consumer base ages, car buyers as a class prefer taller cars that are easier for older, less flexible drivers to get in and out of. Other consumers prefer the view form a higher seat position. This has induced manufacturers to create taller cars that sacrifice stability for comfort. I prefer a low-slung car that has a better chance of safely maneuvering around an obstacle that might suddenly appear on the road.