4/10/2023 0 Comments Inboard suspension(Too) Soft springs can do this, as can poor choice in ARBs and many other factors. And, sometimes it happens so fast we only have time for the expletive before we're in the dirt. If a significant unload results, and the car is cornering, it'll try and spin. In most cars, a lift causes a weight shift which unloads the rears with respect to the front. By comparison, in a lift, the weight shifts forwards. This would result from an accelerative force compressing the rear. The snap oversteer from RRR is more caused by compression at the rear which, as it firms, becomes skate board like and loses any compliance, hence the oversteer. Solly, others are more knowledgeable than me at this, but, with that caveat, I don't think rear rising rate suspension would cause what you are describing. His books are great reading for non-engineers (me) and (I suspect) engineers alike. He found, for example, that having a steeply rising rate suspension at the rear of the car led to chronic (fast, unpredictable) oversteer. Smith's experience guided him to indicate about 20% rising rate at the front was reasonable and somewhat less at the rear. Of course there are modified (progressive) springs where people try and simulate increasing rate suspensions.Ĭarroll Smith's illustration led me to compare the 308 front upper shock mount point (inline with the A arm pivot) with the 360 (higher than the upper shock mount). Whether a car has rising rate or decreasing rate suspension is driven by the pick up geometry. The corresponding situation where the first inch requires 200lbs and the second inch 180 lbs is decreasing rate. For example, it make take 200 lbs of force for the wheel to travel the first inch, but 240 lbs of force to travel the next inch of compression. For each inch of movement, the force exerted on the spring either increases or decreases depending on the motion ratio. Imagine 1 inch increments in wheel movement in compression. If the exit is onto a long straight, the average speed running down this straight will increase saving time and should result in lower lap times. The advantage occurs if one can exit a corner at a higher speed. The increase in natural frequency also depends on the spring rate. Saving 10 pounds of unsprung weight on a suspension corner that may weigh 30 pounds is a lot. Saving 20 lbs on a 2000 pound competition car will increase accelleration about 1%. Real roads and tracks are not perfectly smooth. If the road is perfectly smooth there is no benefit. Ultimately, this provides more grip on the pavement and increases cornering speeds. A link tube is much smaller in diameter than a shock/spring assembly and also lighter so local air flow is improved, which reduces drag and improves heat transfer to down stream radiators, and unsprung is reduced, which increases the natural frequency of the supension.Ģ) A reduction in unsprung weight increases the natural frequency of the suspension allowing it to move more quickly and remain in contact with the road longer. 1) Repositioning of the shock inside the body work improves local aerodynamics.
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