Lean angle calculator
Enter speed and corner radius to calculate ideal lean angle. Use the second card to calculate speed from angle and radius.
Speed + radius → lean angle
Enter numbers within the field limits. Speed: 0–100 km/h; angle: 0–60°; radius: 5–200 m.
Required friction μ ≈ —
Lean angle + radius → modelled speed
Enter numbers within the field limits. Speed: 0–100 km/h; angle: 0–60°; radius: 5–200 m.
Required friction μ ≈ —
What the numbers mean
In a steady turn on level ground, friction supplies the centripetal force mv²/r while the normal force balances weight mg. Thus tan θ = v² / (g · r). Speed in km/h is divided by 3.6 before calculation. The angle describes the combined centre of mass of bike and rider; frame lean can differ when the rider moves their body.
The required friction coefficient is μrequired = tan θ. Available grip must be at least this high in the model. The calculator does not measure road grip or give a safe maximum speed. It omits braking, wind and road banking, among other effects. Pedal clearance depends on bike geometry and crank position; there is no universal strike angle.
Frequently asked questions
How is cycling lean angle calculated?
For a steady turn on level ground, θ = atan(v² / (g × r)). Use speed in metres per second, radius in metres and g = 9.81 m/s². The result describes the combined bike and rider balance.
What lean angle does 30 km/h in a 15 m radius require?
The ideal model gives 25.3° from vertical and a required friction coefficient of about 0.47. These numbers do not measure available road grip.
Can I calculate speed from lean angle?
Yes. The second calculator uses v = √(g × r × tan θ). For 25° and a 15 m radius it gives about 29.8 km/h. This is a modelled speed, not a safe maximum.
Does rider weight change the result?
Mass cancels in this ideal model. Rider position can still change the frame angle relative to the combined centre of mass.
Does the calculator account for wet roads or pedal strikes?
No. It calculates required grip, not available grip. Tyres, surface, braking, road banking and pedal clearance need separate consideration.