What is a Static Stability Factor (SSF)
The Static Stability Factor (SSF) of a vehicle is an at-rest calculation of its rollover resistance based on its most important geometric properties. SSF is a measure of how top-heavy a vehicle is.
A vehicle�s SSF is calculated using the formula SSF=T/2H, where T is the "track width" of the vehicle and H is the "height of the center of gravity" of the vehicle. The track width is the distance between the centers of the right and left tires along the axle. The location of the center of gravity is measured in a laboratory to determine the height above the ground of the vehicle�s mass. The lower the SSF number, the more likely the vehicle is to roll over in a single-vehicle crash.
What is a good Static Stability Factor (SSF)?
A higher SSF value equates to a more stable, less top-heavy vehicle. SSF values across all vehicle types can range from around 1.00 to 1.50. Most passenger cars have values in the 1.30 � 1.50 range. Higher-riding SUVs, pick-up trucks, and vans usually have values in the 1.00 � 1.30 range.
Many of the higher-riding vehicles of previous model years are being redesigned to ride lower and with a wider track width, thus improving their rollover resistance and yielding a higher SSF rating.
How do Dual Rear Wheels Increase SSF?
Well, first off, it just makes sense that the wider something is, the harder it is to tip over. It's always nice when science confirms our common sense. When you add dual wheels, you are increasing your track width. This is the T in the equation above. If you increase T, then you are increasing the SSF, making your vehicle more resistant to rollover.
WHAT CAUSES A ROLLOVER?
2003 Ford E-350 15 Passenger Van W/Dually Conversion