Quote:
Originally Posted by Driven5
Says somebody who has either never done the math for themselves, or done it incorrectly.
First, lets talk about the expected steady state cornering scenario. A sway bar is a simple torsion spring. It transmits a torque from one end to the other. So both ends see the same torque. However, due to leverage, the side with the shorter arm will react a greater force into the suspension than the side with the longer arm.
So using simple round numbers, there is 100 ft-lb of torque being provided to each end of the sway bar. And to exaggerate the effect, let's say that one arm is 1 ft while the other is 3/4 ft. This means that the suspension on the side with the long arm experiences 100 lb of force, while the suspension on the side with the short arm experiences 133 lb of force. Now while the same total force (roll resistance) is experienced regardless of which direction the car is turning, consider this:
Turning one direction, the outside tire is being pushed down with 133 lb while the inside tire is being pulled up with 100 lb. Turning the other direction, the inside tire is being pulled up with 133 lb while the outside tire is being pushed down with 100 lb. If you're familiar with suspension design and tuning at all, you'll understand that such an asymmetry DOES produce a biased effect.
Now moving beyond that, let's look at the less expected straight line effects. Again, thanks to the leverage (motion ratio) difference, here is only no preload across the bar at one singular ride height. During 2-wheel bump or accel/decel, the moving the bar ends the same distance will rotate each end of the bar a different amount, imparting a twist on it. This means there will be weight transferred across the bar even when no cornering is occurring.
Now what do you think happens as things get less ideal and more real? As the car is slowing on the way into a corner, or accelerating out of a corner. The effects will add or subtract depending on whether it's acceleration or deceleration, and a left or right corner. More advanced car development, especially in circle track, has been using this effect to their advantage for decades.
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Thanks for explanation.
I previously assumed such, but never investigated or 'did the math' myself to confirm. I've been since told otherwise by more experienced drivers than myself that the effect is not asymmetrical - apparently this was not true and I've parroted what I've been told.
I did do the math, just now, and you were correct. My apologies. And good to know for myself going forward!