Tire rapid air loss
This is a great article from RV Life Magazine. Make sure you watch the second video lower down the page on vehicle control. The first one is scary but the second one will help safe your life. blowo...
Forum Discussion
Regarding the two real-life videos of motorhomes experiencing a front steer-tire blowout, and the Michelin instruction video on what to do in event of a tire rapid-air-loss,.....here's what I wrote:
The Michelin video does not explain where the force comes from that makes the vehicle suddenly yaw in the direction of the failed tire.
Nor, does it explain the source of the two available forces which can be called upon to counter the offending said force,....allowing the driver to maintain directional control of the vehicle.
The first force in question is easy to explain. It's a frictional force caused by the larger footprint of the failed flat tire together with the higher rolling resistance of this tire. This force "pulls" the nose of the vehicle to the same side as the failed tire (the vehicle yaws to the side of the failed tire).
If the driver of the vehicle never loses his grip of the steering wheel, he/she can induce an opposite frictional force by turning the steering wheel in the direction opposite the side of the failed the failed tire. However, this has to be done in the first one or two seconds of the blow-out event. BUT, since this action might not be sufficient to gain complete control of the vehicle,....THIS is the reason that the Michelin video demonstrates that at the same time the driver is working the steering wheel, he/she HAS to also be depressing the power pedal quickly and completely. The explanation as to why this helps in regaining directional control of the vehicle can only be understood if you know that the differential gears inside the drive axle can vary the ratio of power transmitted between the right and the rear drive tires,....AND that you know that more power is transmitted to the drive tires on the side that is carrying a heavier load (than the other side). YES, in event of a blown left side steer tire, the left rear drive tires will produce more forward thrust when you stand on the throttle. AND, it's THIS force that helps the driver stay in control of the vehicle with the blown left front tire. This is a propulsion force (thrust). This now-asymmetrical forward thrust(more on the side of the failed front tire) is the force which helps yaw the front of the vehicle to the side opposite of the side of the failed front tire.(The “weight shift” occurs as a result of the failed tire becoming shorter than the other tires on the vehicle. This shorter tire(flat tire) forces the other tires to bear the load that it can no longer support. Primarily, the weight shifts to the other front tire, and to the rear drive tires on the same side as the failed front tire. And, because of this added load, and due to the internal design of the differential gear system, the engine power at the driveshaft is bias to the drive tires on the side of the failed tire.)
*
Now, if you view the second half of the Michelin video, you will see that the author assumes that the driver always had a tight grip of the steering wheel and was constantly steering it in order to stay in the same lane and on the pavement. THIS assumption of continuous tight grip is the reason this author talks about the FIRST step is to stand on the throttle (the other two first steps are already done).
Finally, it all makes sense to me. And, I hope I can be "spring-loaded" for it when/if it happens to me.
The Michelin video does not explain where the force comes from that makes the vehicle suddenly yaw in the direction of the failed tire.
Nor, does it explain the source of the two available forces which can be called upon to counter the offending said force,....allowing the driver to maintain directional control of the vehicle.
The first force in question is easy to explain. It's a frictional force caused by the larger footprint of the failed flat tire together with the higher rolling resistance of this tire. This force "pulls" the nose of the vehicle to the same side as the failed tire (the vehicle yaws to the side of the failed tire).
If the driver of the vehicle never loses his grip of the steering wheel, he/she can induce an opposite frictional force by turning the steering wheel in the direction opposite the side of the failed the failed tire. However, this has to be done in the first one or two seconds of the blow-out event. BUT, since this action might not be sufficient to gain complete control of the vehicle,....THIS is the reason that the Michelin video demonstrates that at the same time the driver is working the steering wheel, he/she HAS to also be depressing the power pedal quickly and completely. The explanation as to why this helps in regaining directional control of the vehicle can only be understood if you know that the differential gears inside the drive axle can vary the ratio of power transmitted between the right and the rear drive tires,....AND that you know that more power is transmitted to the drive tires on the side that is carrying a heavier load (than the other side). YES, in event of a blown left side steer tire, the left rear drive tires will produce more forward thrust when you stand on the throttle. AND, it's THIS force that helps the driver stay in control of the vehicle with the blown left front tire. This is a propulsion force (thrust). This now-asymmetrical forward thrust(more on the side of the failed front tire) is the force which helps yaw the front of the vehicle to the side opposite of the side of the failed front tire.(The “weight shift” occurs as a result of the failed tire becoming shorter than the other tires on the vehicle. This shorter tire(flat tire) forces the other tires to bear the load that it can no longer support. Primarily, the weight shifts to the other front tire, and to the rear drive tires on the same side as the failed front tire. And, because of this added load, and due to the internal design of the differential gear system, the engine power at the driveshaft is bias to the drive tires on the side of the failed tire.)
*
Now, if you view the second half of the Michelin video, you will see that the author assumes that the driver always had a tight grip of the steering wheel and was constantly steering it in order to stay in the same lane and on the pavement. THIS assumption of continuous tight grip is the reason this author talks about the FIRST step is to stand on the throttle (the other two first steps are already done).
Finally, it all makes sense to me. And, I hope I can be "spring-loaded" for it when/if it happens to me.
