Static Rollover Threshold
The static rollover threshold (static stability factor).
Example
You enter
- Track width (in, wheel centerline to centerline) 72
- Loaded CG height (in above ground) 80
- Curve radius (ft, 0 = skip rollover speed) 200
You get
- Static rollover threshold 0.45 g
- Steady-curve rollover speed 37 mph
Details, formula, and sources
The steady lateral acceleration, in g, that lifts a truck's inside wheels, SRT = half-track / CG-height, plus the steady-curve rollover speed sqrt(SRT x g x R). A 72 in track over an 80 in loaded CG is 0.45 g -- on a 200 ft ramp that impends near 37 mph; a low 96 in-track flatbed with a 60 in CG runs 0.80 g, far more stable, while a tanker or high-cube sits lower. A STATIC screen: suspension roll, tire slip, and load shift lower the real threshold, so slow well below this on ramps and curves. The loaded CG height and the truck govern; not a substitute for driving to conditions.
srt_g = (track_width_in / 2) / cg_height_in; rollover_speed_mph = sqrt(srt_g x 32.174 x curve_radius_ft) x 0.6818 (g = 32.174 ft/s^2, ft/s -> mph).
Static stability factor (static rollover threshold), first-principles rigid-body statics; the track width and loaded CG height come from the truck and its load. NHTSA static-stability metric.
The static stability factor is a first-principles statics identity (half-track over CG height); the track width, loaded CG height, and curve radius are user-supplied.
Estimate. AHJ and licensed professional govern.
Field names used by the API: track_width_in, cg_height_in, curve_radius_ft, srt_g, rollover_speed_mph
- Rigid body no suspension roll or tire slip; these lower the real threshold below the static valuestatic stability factor
- Steady curve the rollover speed assumes a constant-radius steady turn; a fast steer or ramp is worsevehicle dynamics