40 km/h in a turn - how many g does the car pull?

    Enter speed, turn radius and vehicle mass. The calculator returns centripetal force in Newtons, lateral acceleration in m/s squared and g-force. Formula: F = mv squared / r.

    At 40 km/h, the lateral g-force depends entirely on the turn radius. A tight roundabout at 40 km/h generates far more g than a sweeping highway curve at the same speed. Enter 40 as your speed, then set the turn radius and vehicle mass. The calculator shows centripetal force in Newtons, lateral acceleration and whether your tires can handle the load.

    Parameters

    Enter data for calculations

    Turn entry speed (e.g. city roundabout: 30-50 km/h, highway: 80-120 km/h, track: 100-200 km/h)

    Turn radius (e.g. roundabout: 10-20 m, country road: 30-100 m, highway: 300-1000 m)

    Vehicle mass (e.g. VW Golf: 1,400 kg, BMW M3: 1,730 kg, SUV: 1,900-2,200 kg)

    Form progress0 / 3 fields

    💡 Fill in all required fields to unlock the calculate button

    A car turning at 60 km/h through a 30-meter roundabout pulls 0.94 g

    One number separates a comfortable cruise from a white-knuckle slide: lateral g-force. Enter speed in km/h, turn radius in meters and vehicle mass in kg. The calculator returns centripetal force in Newtons, lateral acceleration in m/s2 and g-load. It classifies the turn severity and shows the maximum safe speed for street tires (0.8 g limit) and sport tires (1.2 g limit). The formula is F = mv2/r - force grows with the square of speed, so doubling your speed quadruples the force trying to push you off the road.

    Key numbers at a glance

    Four scenarios, four very different loads on your tires.

    City roundabout
    Speed: 30 km/h | Radius: 15 m
    G-load: 0.47 g | Force: 6,481 N
    Comfortable for passengers, well within tire grip on dry road
    Highway curve
    Speed: 100 km/h | Radius: 500 m
    G-load: 0.16 g | Force: 2,778 N
    Barely noticeable - highway curves are engineered for high-speed comfort
    Fast roundabout entry
    Speed: 60 km/h | Radius: 30 m
    G-load: 0.94 g | Force: 13,066 N
    Near the grip limit of street tires - on wet road this slides
    Track hairpin
    Speed: 80 km/h | Radius: 25 m
    G-load: 2.01 g | Force: 23,704 N
    Only possible with racing slicks or heavy downforce - street tires slide at 1.0 g

    The centripetal force formula

    Core equation:

    F = m * v^2 / r

    F = centripetal force (N) | m = mass (kg) | v = speed (m/s) | r = turn radius (m)

    G-load: g = v^2 / (r * 9.81) - mass cancels out, so a Miata and a Range Rover pull the same g in the same turn.

    Speed must be in m/s. Divide km/h by 3.6 to convert. A car at 60 km/h moves at 16.67 m/s. Force grows with the square of velocity - going from 40 to 80 km/h quadruples the centripetal force.

    G-force classification table

    G-load range Classification Typical scenario Tire requirement
    Below 0.3 g Very comfortable City driving, gentle highway curves Any tire
    0.3 - 0.6 g Normal road turn Country road, roundabout at moderate speed All-season OK
    0.6 - 0.9 g Dynamic turn Spirited driving, track day warm-up Premium summer
    0.9 - 1.3 g Grip limit Sport tires on track, racing conditions Cup 2, AD08R
    Above 1.3 g Beyond street grip Slick tires, downforce, F1 cornering Racing slick

    Tire grip limits - dry vs wet

    Tire type Max lateral g (dry) Max lateral g (wet) Max speed in r=30 m (dry)
    Budget all-season 0.70 g 0.40 g 51.7 km/h
    Premium summer (PS4, P Zero) 0.95 g 0.60 g 60.3 km/h
    Max performance (Cup 2, AD08R) 1.15 g 0.55 g 66.3 km/h
    Racing slick 1.50 g N/A 75.7 km/h

    Facts you might not expect

    Mass does not affect g-load
    An 800 kg Miata and a 2,500 kg Range Rover at the same speed through the same turn feel the exact same g-force. Mass only changes the force in Newtons - heavier cars stress tires more.
    Double speed = 4x force
    Force grows with the square of velocity. Going from 40 to 80 km/h in the same turn quadruples the centripetal force and g-load. That is why speed kills in corners.
    Wet roads cut grip by 40%
    Street tires on dry asphalt hold 0.8-1.0 g. On wet pavement that drops to 0.4-0.6 g. The same turn becomes dangerous at a speed that felt safe ten minutes ago.
    F1 drivers sustain 5-6 g laterally
    Aerodynamic downforce pushes the car into the track, giving tires far more grip than weight alone provides. No road car can match this without wings generating thousands of Newtons.

    FAQ - Frequently asked questions

    What is centripetal force?
    Centripetal force is the net inward force keeping an object on a circular path. For a car in a turn, this force comes from tire friction against the road. Without enough friction, the car slides outward - understeer in FWD cars, oversteer in RWD cars. The force equals F = mv^2/r.
    What is the difference between centripetal and centrifugal force?
    Centripetal force is real - it is the tire friction pulling the car toward the center of the turn. Centrifugal force is apparent - passengers feel pushed outward because their body wants to continue in a straight line (Newton's first law). In physics, centrifugal force is called a fictitious force that only exists in a rotating reference frame.
    Why does vehicle mass not affect the g-load?
    G-load equals v^2 / (r * 9.81). Mass is not in the equation. A heavier car needs more force in Newtons to hold the turn, but its tires also press harder into the road (more normal force = more friction). The effects cancel out. G-load depends only on speed and radius.
    How do I find the turn radius on a road?
    Use Google Maps: zoom in on the turn, right-click the center of the curve to drop a pin, then measure the distance to the outer edge. For roundabouts, the radius is half the central island diameter plus lane width. Typical values: city roundabout 10-20 m, suburban 20-40 m, highway ramp 50-150 m, highway curve 300-1000 m.
    What is the maximum safe speed for a given turn?
    For street tires on dry pavement (0.8 g limit): v_max = sqrt(0.8 * 9.81 * r) * 3.6 km/h. A 30-meter roundabout: max safe speed is about 55 km/h. A 100-meter highway curve: about 101 km/h. On wet roads, reduce by 30-40%.
    Does road banking (camber) affect cornering force?
    Yes. A banked road tilts the car inward so gravity provides part of the centripetal force, reducing the load on tires. Highways bank curves at 3-7 degrees. NASCAR tracks bank at 24-33 degrees, allowing much higher cornering speeds. At the ideal banking angle, tires provide zero lateral force.

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    See also

    G-Force at 30 km/h - Centripetal Force in TurnsG-Force at 50 km/h - Centripetal Force in TurnsG-Force at 60 km/h - Centripetal Force in TurnsG-Force at 80 km/h - Centripetal Force in TurnsG-Force at 100 km/h - Centripetal Force in TurnsG-Force at 120 km/h - Centripetal Force in TurnsG-Force at 150 km/h - Centripetal Force in TurnsG-Force at 200 km/h - Centripetal Force in Turns

    Calculator verified by the LiczGrupa.pl team

    Content, formulas and results have been reviewed for accuracy and relevance by our team of specialists.

    Krystian Szyszka

    Reviewed by: Krystian Szyszka

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