Grip: braking distance, kinetic energy, friction, traction, speed, aquaplaning and steering is critical for safe driving in all conditions. This article explains how these factors interact and what you can do to optimize grip.
For more on how reaction time and braking distance affect stopping distance, see Reaction time and braking distance.
For more on speed and distance, see Speed and distance.
For practical line choice in bends, see Cornering technique and grip.
For tips on driving in demanding conditions, see Driving in difficult conditions.
Kinetic energy and braking distance
Kinetic energy (E) can be calculated as E = 1/2·m·v^2. Doubling speed gives four times as much energy that the brakes must absorb.
Friction and traction
Friction between tire and road determines how much energy can be transferred to reduce speed. The friction coefficient varies with road conditions:
| Road condition | Friction coefficient | Effect on braking distance |
|---|---|---|
| Dry asphalt | 0.7–0.9 | Short braking distance |
| Wet asphalt | 0.4–0.7 | 30–50% longer |
| Snow | 0.2–0.4 | 2–3 times longer |
| Ice | 0.1–0.2 | 5–8 times longer |
Aquaplaning
Aquaplaning occurs when the tires can no longer push water away from the contact patch. Critical speed depends on water depth and tire pressure:
| Water layer (mm) | Critical speed (km/h) |
|---|---|
| 1 | 80 |
| 2 | 60 |
| 3 | 50 |
Grip and steering
Good grip is also necessary for safe steering and stability. When friction becomes too low, the ability to hold the course is reduced. Tips:
- Choose tires with the right tread depth and rubber compound for the season.
- Maintain correct tire pressure for the load.
- Adjust speed to the road conditions.
- Avoid sudden steering at high speeds.
Summary
- Grip is key to safe braking, acceleration and steering.
- Kinetic energy rises with the square of speed.
- Friction varies with conditions and strongly affects braking distance.
- Aquaplaning risk calls for lower speed on wet roads.
- Proper tire maintenance and technique are essential.