Roll Stiffness & LLTD Calculator
Dial in your Lateral Load Transfer Distribution (LLTD) and total roll stiffness by dialing your spring rates, anti-roll bars, and motion ratios.
Suspension Limitations
This is a simplified steady-state roll stiffness model. Caveats:
- Roll center heights alter dynamic LLTD drastically vs geometric LLTD
- Tire stiffness is omitted (assumed infinitely rigid)
- Chassis torsional rigidity assumed perfectly rigid
- Does not account for rising rate/progressive linkages or bump stops
Methodology
Wheel Rate: Spring_Rate × Motion_Ratio²
Roll Stiffness (per axle): 0.5 × Track_Width² × (Wheel_Rate + ARB_Rate) ÷ 57.3
LLTD: Front_Roll_Stiffness ÷ Total_Roll_Stiffness
Frequently Asked Questions
What is LLTD?
Lateral Load Transfer Distribution (LLTD) defines what percentage of chassis roll resistance comes from the front axle vs the rear. A 60% LLTD means the front suspension handles 60% of the body roll restraint, meaning the outside front tire will get highly loaded in corners.
How do I fix understeer?
Reduce your front roll stiffness (softer front ARB or springs), OR increase your rear roll stiffness (stiffer rear ARB or springs). This shifts the LLTD percentage lower, increasing mechanical grip at the front axle.
What is a motion ratio?
Because springs aren't mounted flush to the wheel hub, a lever arm exists. A 0.85 motion ratio means for every 1 inch the wheel moves up over a bump, the spring only compresses 0.85 inches. Squaring this ratio gives the wheel rate reduction.
Disclaimer & Legal Notice
All tools and calculators provided by Lapsite are for informational and educational purposes only. While we strive for mathematical precision, these results are approximations and should not be used as the sole basis for critical engineering, financial, or safety decisions. Lapsite Ltd and its creators provide no warranty, express or implied, regarding the accuracy or fitness of these calculations for any specific use.Always double-check calculations independently, especially for safety-critical components such as brakes, suspension, or structural changes. By using these tools, you agree that Lapsite Ltd is not liable for any mechanical failure, financial loss, or injury resulting from the use of this data.
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