Enter Vehicle Parameters
Use direct lateral acceleration for track or test data. Use speed-radius mode when you know the steady-state turning speed and radius.
Example Data Table
| Parameter | Example Value | Unit | Engineering Note |
|---|---|---|---|
| Total vehicle mass | 1600 | kg | Representative midsize vehicle. |
| Sprung mass | 90 | % | Used to estimate roll moment. |
| CG height | 0.55 | m | Higher CG generally increases roll angle. |
| Lateral acceleration | 0.70 | g | Steady-state cornering input. |
| Front / rear roll stiffness | 950 / 850 | N·m/deg | Controls total roll and axle split. |
| Front / rear track width | 1.60 / 1.58 | m | Affects lateral load transfer per axle. |
| Body roll angle | 3.020 | deg | From roll moment divided by total stiffness. |
| Net cabin angle | 1.020 | deg | Includes a +2.00° inward bank offset. |
| Critical wheel-lift threshold | 1.419 | g | Approximate quasi-static reference only. |
Formula Used
ay = v² / rLateral acceleration comes from steady turning speed and radius.
Mroll = ms × ay × hCGSprung mass, lateral acceleration, and CG height create the chassis roll moment.
φbody = Mroll / (Kφf + Kφr)Total roll stiffness is the sum of front and rear stiffness values.
φnet = φbody - βPositive inward banking reduces the cabin angle the driver feels.
ΔWfront = (Kφf / Kφ,total) × Mroll / tfrontΔWrear = (Kφr / Kφ,total) × Mroll / trear
Roll gradient = φbody / ay[g]Rollover threshold ≈ tavg / (2 × hCG)This threshold is a simple geometric reference, not a full dynamics simulation.
How to Use This Calculator
- Select Direct lateral acceleration if you already know cornering g-force from test data or simulation.
- Select Speed and turn radius if you want the tool to derive lateral acceleration from steady-state turning conditions.
- Enter total vehicle mass and sprung mass percentage. The calculator uses the sprung portion to estimate roll moment.
- Enter CG height, front and rear roll stiffness, and front and rear track widths with consistent units.
- Add road bank angle if the road is positively banked into the turn. This reduces the net cabin angle shown.
- Submit the form to view body roll angle, net cabin angle, roll gradient, load transfer, balance tendency, and threshold indicators.
- Use the CSV or PDF buttons to export the full engineering summary and graph for reporting.
- Compare multiple runs by changing stiffness, CG height, or track width to see how each design choice changes roll behavior.
Frequently Asked Questions
1) What does vehicle roll angle represent?
Vehicle roll angle is the body tilt produced during cornering. It shows how far the sprung mass rotates relative to the road surface, usually in degrees. Lower values often feel flatter, but damping, tires, and compliance still influence handling feel.
2) Why are front and rear roll stiffness entered separately?
Separate axle stiffness values let the calculator estimate roll couple distribution and the split of lateral load transfer. That split affects balance. More front share usually pushes the setup toward understeer, while more rear share can increase rotation.
3) Does road banking change the result?
Yes. Favorable inward banking reduces the cabin angle the driver feels and can lower the tire force needed for the same path. Negative or opposite banking increases effective lean and can make the vehicle feel less settled.
4) Is this a rollover simulation?
No. This is a quasi-static engineering estimate, not a full multibody dynamics model. It does not include transient damping, nonlinear tires, compliance steer, active systems, or detailed roll-center migration through suspension travel.
5) Should I enter total mass or sprung mass?
Enter total vehicle mass and the sprung mass percentage. The tool estimates the sprung portion automatically because the body roll moment mainly acts through the sprung mass supported by the suspension.
6) Which units should I use for roll stiffness?
Use newton-meters per degree for both front and rear roll stiffness. If your source data is in newton-meters per radian, divide it by 57.2958 before entering it here.
7) Why can net cabin angle be smaller than body roll angle?
Net cabin angle subtracts road banking from body roll. A positive inward bank can partially cancel chassis lean, so the vehicle may feel flatter even while the suspension still develops significant roll moment and load transfer.
8) How accurate is speed-radius mode?
It is accurate for steady-state kinematics because lateral acceleration equals v²/r. Real roads, steering corrections, tire slip, grade changes, and transient weight transfer can still shift the actual result from this simplified estimate.