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Old 07-01-2010, 03:33 PM
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BillyShope BillyShope is offline
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With a beam axle, both wheel rate and roll stiffness must be taken into account. When one wheel drops into a pothole, the situation is quite different from hitting a speed bump. The speed bump situation is akin to that which I referenced when I said the spring rate is equal to the wheel rate. Unless a hefty sway bar is used (which increases manufacturing cost), however, a compromise is necessary. This results in spring rates which cause you to lose your fillings when you hit a speed bump, but are otherwise acceptable when a pot hole is encountered. At the front of the car, steering requirements move the leafs close to the car's centerline, resulting in a greater compromise (and higher spring rates) than at the rear.

Since I hate trips to the dentist, I'd go to a lower rate at the front and sneak in a sway bar.

The following is a post from another thread:

A very popular reference book among suspension engineers is Race Car Vehicle Dynamics by William and Douglas Milliken. (It can be purchased through Amazon.)

On page 582, ride frequency ranges for different vehicle types are given. For a sports car, the range is from 70 to 90 cycles per minute. For a passenger car, 30 to 50 cycles per minute.

With an 800 pound corner weight, the 150 pound per inch wheel rate would put you right in the middle of the sports car range.

For greater convenience, the ranges can be expressed as a multiplier, which, when multiplied by the corner weight, gives you the wheel rate. For sports cars, from 0.139 to 0.23; for passenger cars, from 0.026 to 0.071 .
http://www.racetec.cc/shope
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