Maintaining Control In A Rapid Air Loss Situation (Tire Blow Out)
Blow-outs, even the most experienced commercial vehicle drivers dread them. Some are convinced that it's not possible to maintain control of a rig when a tire blows out.
Experiencing a rapid loss of air from a tire does not automatically mean a driver will lose control of the vehicle. Here is a summary of some important points to consider relative to blow-outs.
The principles for handling a rapid loss of air from a tire are the same for every type of vehicle, whether loaded or unloaded, straight truck, tractor trailer or set of doubles, fire truck or ambulance. They're the same for all weather conditions, all types of roads, even in a curve.
- The laws of physics say that an object going in one direction - such as a tractor trailer on a highway - will keep going in that direction unless it is acted upon by a new force in a different direction.
- When a blow-out occurs or a tire becomes flat, the corner of the vehicle drops, creating a new side force. The strength of the side force depends on factors such as tire-road resistance and vehicle dynamics.
- Unless the driver compensates for the side force, the rig will move in a new direction.
- When something is pulling the rig to the side, the best response is to get power to the drive wheels.
- To compensate for the new side force caused by the blow-out, the driver steps on the accelerator, then makes any necessary steering correction.
- When a tire goes flat, the tire wants to turn in the direction of the flat. As the driver steps on the accelerator, applying power to the drive wheel gives the driver time to make the steering correction. When control is maintained, the driver can then choose where to slow down, pull over and stop.
- Stepping on the accelerator doesn't necessarily mean the driver will pick up significant speed. He or she should be able to diagnose the problem and get the rig stable before picking up significant extra speed.
- Driving against a governor all the time means the driver has no power in reserve. Drivers should always leave themselves with some extra power to enable them to deal with unexpected situations, such as a rapid loss of air.
- Although it may be instinctive or natural to want to brake or stop when experiencing a blow out or flat tire, that's the worst possible thing a driver can do. Taking your foot off the accelerator is the second worst thing to do.
- Stepping on the brakes in an air loss situation means the driver loses the forward force that allows him/her to maintain control. The rig becomes much more vulnerable to the new side force. Without the forward force, the driver is less able to control the rig.
- Front and drive tire air loss situations are handled in much the same way - by stepping on the accelerator. The big difference is in how they feel to the driver and what effect they have on the behaviour of the vehicle.
- When drive tires lose air, the driver still has two good tires to use for steering. In this situation, the driver should get power to the drive tire, but make a steering correction only if necessary. The drive wheels will follow where the steering wheels lead them.
- If a front tire experiences a rapid loss of air, the driver will probably first feel it through his/her hands on the steering wheel. A rear tire blow-out affects the ride, so the driver is most likely to feel it through the seat.
- Drivers should be taught never to give up in an air loss situation. Even if a blow-out or flat tire catches them by surprise, they can still keep the situation under control.
- Use of a seat belt is critical, as it helps maintain driver stability in the seat.
Today's tires are better than ever, and chances are good that drivers won't experience a rapid air loss. Basic techniques - such as a pre-trip inspection of tires, proper seat and hand positions, and good driving habits will help drivers be in a position to better maintain control in the event they do experience a blow-out.
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