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Page Nomenclature

H = height of c.g. above datum, in. SF = rollover safety factor, %
T = wheel track, in.  

 


Stability Table

By itself, safety factor is a quantitative measurement. The higher the SF, the more tip-resistant a vehicle is. Theoretically, anything over 0% SF will not tip, but there is more too it. The Stability Table below, Fig. 6, rates SF into categories which can be used to evaluate the predicted performance of a vehicle.

STABILITY TABLE

SAFETY FACTOR, SF, percent

RATING

Less than or equal to zero (<or=0) Fails test! Extraordinarily unsafe.
0 to 21 Unsafe
22 to 33 Marginal
34 to 50 Acceptable
51 to 75 Very safe
Greater than 75 (>75) Extremely desirable but not attainable*

Fig. 6

*State laws limit width of passenger cars to 80 inches. This places a limit on SF.

As you recall from the example of Case 1, a compact station wagon, the SF was 38%, which the chart indicates a rating of "Acceptable". To get this car up to 50%, approaching "Very safe", the track would have to be widened to 70 inches, an H to T ratio of 1:2.5. This ratio where T = 2.5 x H will hold true for any car. If T could be widened ever farther, out to close to the legal maximum for passenger cars, SF of 75% could be achieved. Fig. 7, below, will help the viewer visualize the Stability Table.


Fig. 7

Fig. 7 represents Case 1, the station wagon, with H fixed, but T variable. As the track is varied, SF will also vary, going through all the color codes, from red (unsafe) to dark green (very safe). The actual wheel track of Case 1 would place the wheel in the light green zone, which rates the car as acceptable.

 

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