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ROLL STIFFNESS DISTRIBUTION

(Those who used this spreadsheet before 10/14/09 will note that the procedure has been simplified and that less spreadsheet input is required. This is not an error correction. The answers remain the same. I discovered that the calculation could be greatly simplified.)

Using only a set of wheel scales, a tape measure, a jack, and the spreadsheets below, you will be able to determine the roll stiffness distribution.

With the car on the scales, record the readings. These values will go into the "original" boxes in the spreadsheet. The "jacked" side can be either the right or left.

Measure and record the front and rear tracks for entry into the spreadsheet.

front track =

rear track =

original jacked side front =

original jacked side rear =

original opposite side front =

original opposite side rear =

Place a floor jack at approximately the middle of the car and as far toward the jacked side of the car as is conveniently possible. Jack the car until the wheel scale values are appreciably changed. (See the example in the spreadsheet.) Record the scale readings. These values will go into the "after jacking" boxes below.

(For a typical dragster, the front "suspension" is within the frame, so the jack should be placed, fore and aft, as close to the engine mounts as possible for a hardtail and as close to the front of the 4link for a suspended dragster.)

(after jacking) jacked side front =

(after jacking) jacked side rear =

(after jacking) opposite side front =

(after jacking) opposite side rear =

ANSWER:

PERCENT ROLL STIFFNESS AT FRONT =

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