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Automotive Calculators

Stability Margin Calculator

2026-09-27 6 min

Static rollover threshold in G from track width and CG height.

Stability Factor (T/2h)
1.29
NHTSA SSF metric
Rollover Threshold
1.29 g
Theoretical tip-over lateral G

Calculator

Track Width(in)
in
CG Height(in)
in
Results update live as you type

Live statistics

Stability Factor (T/2h)

1.29

NHTSA SSF metric

Rollover Threshold

1.29 g

Theoretical tip-over lateral G

Results

Optimal

Stability Factor (T/2h)

1.29

NHTSA SSF metric

Rollover Threshold

1.29g

Theoretical tip-over lateral G

Planning estimate from standard automotive formulas. Validate with dyno, timeslip or datalog data when precision matters.

Visualizations

Results overview

1.3Stability Factor
1.3Rollover Threshold

Rollover Threshold vs. Track Width

Rollover Threshold

1.3g
02

Formula

Tip-over balance: half-track leverage versus CG height.

Threshold = track / (2 x CG height)

Alternative Form

NHTSA Static Stability Factor — higher is more rollover-resistant

Variables

SymbolNameUnitDescription
SSFStability factorTrack over twice CG

Explanation

SSF predicts rollover risk class: cars ~1.3-1.5, SUVs ~1.0-1.2 — ESC and low CGs manage the rest.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Record the inputs.

Track Width:62 in
CG Height:24 in
Result: 2 inputs ready
Step 2

Apply the formula.

Threshold = track / (2 x CG height)
Result: Primary result = 1.29 g
Step 3

Read every derived output.

Stability Factor (T/2h):1.29
Rollover Threshold:1.29 g
Result: Rollover Threshold = 1.29 g
Final Answer
1.29

Worked Examples

See how the calculator works with different scenarios.

Scenario

Crossover rollover audit.

Inputs

Track:62 in
CG:24 in

Calculation

SSF = 62/48 = 1.29

Result

1.29 (tips past ~1.29 g theoretical).

Interpretation

Typical crossover — tires slide (~1.0 g) before tipping, with margin.

Understanding Your Result

Your Result: Stability Factor (T/2h): 1.29

Typical range: Sports cars 1.4+; sedans 1.3-1.5; SUVs 1.0-1.25; lifted 4x4s under 1.1.

What This Means

Tip-over threshold from geometry.

Why It Matters

Grades rollover risk and guides loading (roof weight hurts most).

Professional Interpretation

Treat the primary result as a planning estimate, then validate on a dyno, at the track, or with logged sensor data. If measured numbers disagree by more than ~10%, re-check inputs (units are the usual culprit) before changing parts.

Recommendations

  • •Double-check units on every input before trusting the result
  • •Compare against the worked example below to sanity-check magnitude
  • •Validate with measured data (dyno, timeslip, datalog) when it matters

Learn — fuel economy, deeply

Rollover threshold is track versus CG height.

1 · Where the gallon goes (energy path)

Engine heat

60–70% lost

Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.

Driveline

5–15% lost

Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.

Aero drag

∝ v²

Doubles from 55→78 mph. Roof boxes hurt more than trunks.

Rolling + brakes

10–20%

Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.

4 · Measure like a pro (the 3-tank protocol)

  1. Fill to first click at the same pump, record the odometer (Tank 0).
  2. Drive normally for 2–3 tanks; always refill to first click at the same pump.
  3. MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
  4. Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
  5. Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.

Practical Tips

  • •Keep roof loads light
  • •Wider track (wheels) helps modestly
  • •ESC on, always, on tall vehicles

Common Mistakes

Mixing units (inches with mm, psi with kPa)
Convert every input to the unit shown on its field before calculating.
Trusting a single output blindly
Cross-check with the worked example and, when it matters, a dyno or datalog.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-state model: Formulas assume stabilized conditions; transients, heat soak and traction limits are excluded.
Standard factors: Empirical constants (BSFC, VE, drivetrain loss) use typical values — your combination may differ.

Limitations

Be aware of these limitations when using this calculator:

Estimate, not measurement: Predictions carry real-world scatter of roughly ±5–15% depending on the model.
No transient effects: Shift time, wheelspin, spool lag and heat soak are not modeled here.

Frequently Asked Questions

Answers to common questions about this calculator.

Will my SUV roll over?
Modern ESC plus slide-before-tip geometry (SSF > ~1.0) makes on-road rollover rare without tripping (curbs, ditches).
Does roof cargo raise rollover risk?
Yes — roof pounds hurt CG most per pound. Keep heavy gear low and inside.

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Related Guides

Deepen your understanding with these educational resources.

Glossary

Technical terms used in mortgage calculations explained in plain language.

MPG
Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
L/100 km
Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
MPGe
Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
CAFE
Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
Rolling resistance
Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
Aerodynamic drag
Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
Hypermiling
Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
OBD-II
On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.
SSF
Static Stability Factor: track/(2xCG) — NHTSA rollover-resistance metric.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

EPA Fuel Economy Testing (40 CFR Part 600)CAFE — Corporate Average Fuel Economy Standards (NHTSA)WLTP — Worldwide Harmonised Light Vehicle Test ProcedureSAE J1321 / J1711 — Fuel consumption test proceduresISO 2575 — Road vehicles symbols & efficiency markings

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