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Thread: Weight transfer

  1. #1

    Default Weight transfer

    When driving a car, weight transfers can occur in the longitudinal (front to back) and lateral (side to side) directions. Depending on how and when the weight transfer occurs, it can be a help or a hindrance when on the road or track.
    The best way of understanding the effects of weight transfers is to consider a car with very soft suspension. So before driving this....

    You'll need to understand this...

    There are three ways that weight transfers can occur:
    • Acceleration
    • Deceleration
    • Steering
    Acceleration rear weight transfer

    When you accelerate, the weight of the car is thrown backwards (see Figure 1). This causes the rear suspension to compress slightly and increases the available grip at the rear tyres (see our grip section for more information).
    Figure 1 - Rear weight transfer due to acceleration

    Advantages of rear weight transfer

    1. Pulling away in a rear wheel drive car

    If you're trying to get a good start, rear weight transfer will be to your advantage in a rear wheel drive car, as the resulting increase in rear grip will provide you with more traction and reduce any wheelspin.
    In a front wheel drive car, however, you're more likely to get wheelspin off the start, so an extra smooth throttle application is important.
    2. Preventing oversteer in a front wheel drive car

    Oversteer is caused by a lack of traction at the rear wheels, but if you accelerate in a front wheel drive car as oversteer is occurring, the resulting rear weight transfer can increase the available grip at the rear wheels and aid recovery.
    Note: Oversteer in a rear wheel drive car is rarely helped by acceleration, as this will increase the traction demands of the rear wheels, and leave less available grip to oppose the sideways motion.
    Disadvantage of rear weight transfer

    - Can cause understeer

    Understeer results from a lack of traction at the front wheels. If you're accelerating into a corner, the levels of grip at the front wheels will be reduced due to the rear weight transfer, and be more prone to continuing in a straight line despite your steering inputs.
    Deceleration forward weight transfer

    Cars can brake much harder than they can accelerate. Weight transfers under braking are thus more likely to affect the balance of the car (see Figure 2).

    Figure 2 - Forwards weight transfer due to braking

    Advantage of forward weight transfer

    - Prevention of understeer
    If you're hurtling towards a corner, turn the wheel and find yourself ploughing straight on, you've probably approached too quickly. But all might not be lost - easing off the throttle will result in a forwards weight transfer which will increase the available grip at the front wheels. Hopefully this should correct your course. If you're already off the gas, then a light dab on the brakes should help.
    Disadvantage of forward weight transfer

    - Reduction of traction at the rear wheels
    If you stamp rapidly on the brakes, you'll find that the rear wheels (in a car without any clever technology) will tend to lock up first. This is the reason almost all cars have smaller brakes at the rear. Despite this fact, the rear wheels are still the most likely to lock when using the brakes aggressively. Braking in a corner should be avoided for the same reason, as this can result in oversteer.
    Transitions in weight transfer

    To get the best times on the track you need to be either accelerating or braking - any coasting means you're not going as fast as you could. When transitioning between accelerator and brake you'll get exaggerated weight transfers which can further upset the balance of the car.

    It's important to consider sideways weight transfers when cornering. If you turn into a corner progressively rather than 'chucking it in', this will transfer the weight to the outside wheels in a gradual manner. As the outside wheels provide most of the cornering effort, the resulting progressive increase in grip can help you take corners at a greater speed before traction is lost. However, if you throw the car into a corner, the sudden weight transfer can unsettle the vehicle and cause the wheels to break traction suddenly.
    The moral again ladies and gentlemen is smoothness.

  2. #2
    Join Date
    Feb 2006

    Default Re: Weight transfer

    Nice post!

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