| THE BASICS - DYNAMICS 1 |
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| STATIC: CAR AT REST - WHEEL PAIRS ARE EVENLY LOADED |
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| The vehicle above is at rest, or in a 'static state'. |
| Each wheel pair is evenly loaded meaning each front wheel has the same amount of weight on it, and each rear wheel has the same amount of weight on it. The car's body is parallel to the road surface. The total load on each wheel pair will vary based upon the weight distribution of the vehicle. |
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| PITCH: LONGITUDNAL WEIGHT TRANSFER, FRONT TO BACK AND BACK TO FRONT |
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| Forward pitch is known as DIVE, which occurs as a result of braking. The car above is displaying 2 degrees of Dive. |
Rearward pitch is known as SQUAT, which occurs as a result of acceleration. The car above is displaying 2 degrees of Squat. |
| The key elements to note are that the front wheels are more heavily laden or loaded as the vehicle weight is transferred forward. Although the front tires have more overall grip as a result of increased load, Dive is not desirable because there is less available grip for turning. Also, because of weight transfer, the rear wheels are 'unloaded' and as a result, there's less overall grip on those as well, which makes things worse. |
The key elements to note are that the rear wheels are more heavily laden or loaded as the vehicle weight is transferred rearward. Unlike the negative affects of dive, the rearward weight transfer and resultant increased load is desired. Since we're accelerating, we're getting increased grip on the rear wheels, which in the case of RWD (acronym) cars is not a bad thing. Note we also have less grip on the front wheels which isn't good, especially in the case of a FWD (acronym) car. |
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| ROLL: LATERAL WEIGHT TRANSFER, LEFT TO RIGHT AND RIGHT TO LEFT |
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| 2 DEGREES OF BODY ROLL - TURNING RIGHT |
2 DEGREES OF BODY ROLL - TURNING LEFT |
| The car above is experiencing an increase in lateral load transfer to the outside wheels, in this case, the left side front and rear. The good news is that the increased weight on the left side has increased the grip of the laden wheels. The bad news is the unloaded inside wheels (front and rear right) have less traction. The end result is that as pairs, they have less total tractive capacity than they would if equally loaded. |
The car above is experiencing the same, but in the opposite direction. The control of body roll is desired for the most part on a race car. Body roll is mainly controlled by the anti-roll bars. The spring/shock combination controls body roll as well. It should also be realized that the lateral loading of the wheels is not as much caused by body roll as it is the reduction of it. This little known fact is greatly misunderstood in vehicle dynamics. Loading is mostly due to the degree of anti roll stiffness, not body roll. |
