Front steer tire blowout analysis 2

[Cloud_Dancer]

Front Steer Tire Blowout Analysis
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On the video that shows the roll over of the Thor Tuscany motorhome which is pulling a red pickup, the first thing I notice is how this video further perpetuates the MYTH (this video is almost shocking, except that the angle of departure is distorted, which IMO is what makes it almost unbelievable). I used descriptive geometry and arithmetic to discover that the angle of departure (from straight ahead) is only about 18 degrees!! But remember, “We are afraid of those things that we don’t understand”. The myth is that a sudden failure of a front steer tire (blowout) has the capability of pulling the front of a large motorhome to one side and to send it out of control. This myth is also perpetuated by other videos, and also some motorhome drivers/owners who have misinterpreted what really happens whenever a front tire blowout occurs when you’re cruising/driving a big motorhome. Therefore, I will try to explain. BTW, I happen to have knowledge and experience about this subject, but not enough to qualify me as an expert. Yet, the more you know, the better your chances of learning and executing the safe way of handling a blowout. The most important thing to learn is that if this knowledge is already in your mind, you’re not likely to instantly get a brain cramp when you hear the BANG of a blowout and while feeling the serious shaking of the steering wheel. Be aware that a brain cramp puts you out of commission for a few seconds. Beware that in the Tuscany video, it took 4 to 5 seconds for the “healthy” right side tire to reach the grass. This means that if you do NOT go into “brain fade” AND if you only keep doing what you were doing before the blowout, you can just keep on using the steering wheel to stay in your lane. YES, if the ONLY thing you need to do is seamlessly keep using just the steering wheel appropriately, and nothing with your feet, you will have a very good chance of staying in your lane. NOW, the reason this might sound unbelievable is because you have been led to believe that there is a powerful lateral force pulling the front of your motorhome to the side. Neither the blowout itself NOR the flat tire have the capability to do that. Granted, the explanation of what really happens might sound complicated, but IMO by understanding a few important key factors it will mean the difference between loss of control OR not. Therefore I will explain: The blowout allows the air pressure to escape. A flat tire has a much higher rolling RESISTANCE than the inflated tire. How does this affect the steering? Simple: take an old rear- drive beater car to the highway, park and lower the air pressure in one front tire to 10 psi, then get in, and speed up to a constant speed of 40 mph for one or two minutes, get a good feel of the steering wheel, now let go the steering wheel. You will immediately find out the effect of what and how a motorhome will “self steer” when a front tire SUDDENLY fails AND the steering wheel is UN-ATTENDED. So, why does the the driver fail to drive with the steering wheel. It’s simple, he either had a heart attack, or more likely, immediately experienced a brain cramp or a blank out, or brain freeze. In the video it looks like the driver came to his senses AFTER the motorhome went out of control. Most drivers never have the opportunity to learn how NOT to be startled or shocked by something like a front tire blowout. But, some of us are lucky to be professionally trained to handle life and death emergencies . To me, a steer tire blowout experience is similar to a V-1 cut in a high performance twin jet aircraft (in this event the pilot flying MUST instantly and correctly “steer” the aircraft, due to having a flamed out engine on one side,…just as you pass V-1 speed). There’s no time to think, you either perform correctly, or…..disaster. That’s just a small part of the training.
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IMO while cruising on the open highway, if you experience a front tire blowout, if the ONLY ONLY thing you do is to instantly use the steering wheel with authority for the purpose of staying in your lane, you will get a feeling of being in control… (one reason is that you’ll realize you can do it ). I urge you to use all your concentration on steering correctly/appropriately FIRST. The fact is, you have been using the steering wheel for steering since the first time you drove. So, why quit just because of a blowout? Yes, impact torque will be generated on the steering wheel whenever a significant difference in rolling resistance occurs between the two steer tires. It’s nothing new! Just like when one steer tire hits the big puddle of water at high speed. The driver feels it at the steering wheel. It’s just a STEERING ACTION coming back through the steering system. AND, it’s a good thing because this is what tells the driver what to do with the steering wheel. YES, a motorhome CAN SELF STEER right off the road! All it needs is a significant DIFFERENCE in the rolling resistance between the steer tires, PLUS an UN-ATTENDED steering wheel. WHERE is the PROOF that a blowout by itself can “PULL” the front of the MH to the side??? Heck, there’s at least 2 examples, on this forum, of tires blowing out while the MH is standing still. And, the motorhome did NOT move sideways one inch. This is proof enough that too much credit is given to the actual blowout. Analytically, one must look for OTHER cause-and- effect areas of chassis dynamics. For example, MANY drivers will get in their vehicles, and as soon as the engine starts up they start turning the steering wheel, BEFORE the car begins to move. And, when it starts moving it moves in the direction that the steer tires are pointing. So, the vehicle has to generate some momentum for the vehicle to go in the direction the driver chooses. And, the reason the vehicle does not move straight ahead is because a path to the side, of LESS resistance, is offered. AND, if the subject MH is moving forward, it will PUSH, yes PUSH, the front of the motorhome in the direction the front tires are pointing. And, if one steer tire is flat, no matter….the steering system will still work, as long as the rear tires and the inflated steer tire remain on dry pavement (where there is sufficient traction). And, I repeat, if the steering wheel is unattended, it will self steer to the side of the failed tire, by itself. If you do NOT believe it, simply ask the chief steering engineer at a place that has been doing research on the subject of ELIMINATING the onboard human factor. They know exactly what the robot driver has to do immediately upon the first sense of a steer tire blowout… AND, it does NOT include depressing the accelerator. They know that their driver does NOT need more than a few nano-seconds to keep steering and start slowing down. The robot already knows the real-time obstacle map around him. Yes, I know they now have blowout-proof tires, for these driverless delivery vehicles.
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It takes a steering action to duplicate what the subject Tuscany does. The driver would need to quickly turn the steer tires about 15 degrees to the left. Of course, no driver in his right mind would do that at 65 mph. IMO he was NOT in his right mind. For me, it’s the only explanation. Please don’t tell me that a driver would say different. I already know what he’ll say. He’s a smart man. “The force was horribly strong, it took the steering wheel out of my hands.” It’s a good defense. Except that the science of it does NOT agree.
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[Cloud_Dancer]

You keep talking about a force vector that is lateral. It is NOT lateral.
And, why would anyone want to "lift" the front? Don't you realize that the more traction you have on the healthy, NORMALLY-inflated steer tire the better off you are? The weight does NOT shift to the flat tire, the weight shifts to the tallest front tire. ANother thing, There is NOTHING that's going to take away the ability of the steering system to NOT work, on dry pavement, if the MH is coasting and dissipating speed. How else are you going to slow down? You think it's better to use the brake?
Have you ever figured out why people say, "It's like riding a bicycle...."?
This I learned in aviation school: There are certain methods which can be used to acquire facts and procedures which end up being absorbed by your cerebellum (you never forget it), and steering a vehicle with a steering wheel is one of them. But, depressing the accelerator when you do NOT need it, is NOT,...However, putting your foot on the brake pedal in case of emergency IS. Do you realize how difficult it is to UNLEARN items that are in your cerebellum? Here's how I think: Good luck with teaching a driver to NOT use the brake, and instead you should use the accelerator. I would first make sure, really sure, that you need to depress the accelerator BEFORE you teach it. Personally, I don't see that it's necessary. I couldn't find a single resultant force that it would bring on that is beneficial. Personally, I KNOW for sure, that the absolutely most important thing is to instantly and appropriately and without interruption keep working the steering wheel.
I recommend to all drivers to learn the most effective safe way your MH can be made to change direction. IN other words, why is it, and how is it, that when you turn the steering wheel the MH changes direction? The other thing is, as a driver, what can you do with your motorhome in order to produce a lateral force?

[4x4van]

Planning wrote:
There is no "stomping" in controlling for a blowout. There is a controlled application of thrust sufficient to counteract the force vector; a smooth decisive application of throttle.

To do what? The Michelin video clearly shows the driver "flooring" it; to me that is the same as "stomping" on the throttle; you say tomato, I say tomatoe. In any case, that additional throttle accomplishes nothing measurable. It does not "lift" the front end and reduce the drag, so the drag (force vector if you prefer that scientific "sounding" term) is still there, and in fact may even be increased by any additional speed. It also does nothing to reduce that drag AFTER you have stepped on the gas and decide to then let off and finally start decelerating; the exact same drag is still there, only now you may be going even faster. You've accomplished nothing other than to travel a couple hundred additional feet prior to even beginning to slow down (65mph equals 95' per second). The key to maintaining control of a blowout is to NOT panic, NOT stomp on the brakes, NOT make sudden steering inputs (and we ALL have a good hold of the wheel while driving, right?).

[mich800]

wnjj wrote:

Jim-Linda wrote:
In 2010, driving south on 59 from Livingston, TX, about 20 miles from Livingston, left front exploded. Freightliner MDT pulling 38' HH. Truck immediately entered north bound lane (no traffic), wheel dug in, no tire left. Kept foot on fuel pedal and slowly pulled back in proper lane. Slowed down and made it to shoulder, except for tire, bent rim, headlight bucket missing, left bumper end dangling all was well. In posting this, I am somewhat in disagreement with parts of the above advise. There was immediate movement to the left, steering was at least 40deg to the right, but no way was it in control. Wife was behind in car and when all was stopped, she said, "what in the world were you doing". Felt lucky

Jim

I know someone who had a front blowout on a 70k lb semi. He was an experienced driver and when it blew he was instantly one lane over (multi-lane freeway). Fortunately there were no cars along side. He lost the entire left fender.

My theory is the flat tire causes enough side force that counter steering is required (I,e, the good tire has to scrub some in the opposite direction). So even while attending the wheel, the driver needs to make a turn toward the good tire in order to return to and continue traveling straight. This probably varies greatly with how the tire goes, if you’re riding on the rim, etc,

That was the whole purpose of the post. When bad stuff happens you need to be a driver and not a passenger.

[Cloud_Dancer]

wnjj wrote:
"My theory is the flat tire causes enough side force that counter steering is required (I,e, the good tire has to scrub some in the opposite direction). So even while attending the wheel, the driver needs to make a turn toward the good tire in order to return to and continue traveling straight. This probably varies greatly with how the tire goes, if you’re riding on the rim, etc,"
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It is NOT a theory, it is a fact. It's proved in many videos. The important thing about is that the counter-steer angle of the good inflated steer tire only has to be approximately 4 to 5 degrees...."piece of cake".

[wnjj]

Jim-Linda wrote:
In 2010, driving south on 59 from Livingston, TX, about 20 miles from Livingston, left front exploded. Freightliner MDT pulling 38' HH. Truck immediately entered north bound lane (no traffic), wheel dug in, no tire left. Kept foot on fuel pedal and slowly pulled back in proper lane. Slowed down and made it to shoulder, except for tire, bent rim, headlight bucket missing, left bumper end dangling all was well. In posting this, I am somewhat in disagreement with parts of the above advise. There was immediate movement to the left, steering was at least 40deg to the right, but no way was it in control. Wife was behind in car and when all was stopped, she said, "what in the world were you doing". Felt lucky

Jim

I know someone who had a front blowout on a 70k lb semi. He was an experienced driver and when it blew he was instantly one lane over (multi-lane freeway). Fortunately there were no cars along side. He lost the entire left fender.

My theory is the flat tire causes enough side force that counter steering is required (I,e, the good tire has to scrub some in the opposite direction). So even while attending the wheel, the driver needs to make a turn toward the good tire in order to return to and continue traveling straight. This probably varies greatly with how the tire goes, if you’re riding on the rim, etc,

[Cloud_Dancer]

IMO The source of energy is the momentum of the MH. This force is called the “driver” force. The resistive forces are called “resultant” forces. The resistive force of a flat tire is NOT proportional to the driver force. The “driver” force is far superior to the resistive force of a flat steer tire. Also, the resistive force vector of a flat steer tire is directly opposite and parallel to the bearing line of the driver force. It is not a lateral force. Even when the MH changes direction, the resistive force of this flat tire “pushes” straight back against the forward motion of the MH. And, it pushes back in a line that is parallel to the bearing line of the MH. HOWEVER, if the steering wheel becomes unattended at the time of the blowout, the push back of the flat tire is of sufficient force to turn /steer its spindle, and this turns the spindle of the other steer tire, which has much more traction than the flat tire. THAT’S when the MH changes direction. But, if the steering wheel is properly attended without interruption, the MH will NOT change direction. The Michelin video and the Tuscany video are of these two scenarios. IMO it makes more sense to believe this, otherwise you will always feel insecure when driving your motorhome. I know I would never drive any vehicle if I did not believe this. To me, a blowout is just an expensive inconvenience. That’s the reason I cruise at 65 mph instead of 75 mph. IMO one of the do-not-forget items on your checklist should be that a blowout can happen when you least expect it. But, the majority of them happen in the summertime when driving fast on a hot road surface.
P.S.
I can keep on steering just fine WITHOUT depressing the accelerator. The power steering is all the help I need. The momentum keeps me going as fast as I need, even if the speed is dissipating.

[Planning]

Cloud Dancer wrote:
IMO if there is no source of energy, there can NOT be a mysterious lateral force.

It is not mysterious new energy, it is a transfer or redirection of force caused by the now increased drag from the added friction of the deflated tire. It is not "pushing" the vehicle in another direction, it is the addition of drag which changes the force vector from predominantly forward, to forward with the addition of lateral. Prior to the blowout there was one vector, there are now two. Both together equal the total of all momentum.

Controlled application of forward thrust helps to compensate for the friction induced drag which is producing the lateral force vector. This maneuver is performed to enhance maintaining or regaining stability and control and then controlled deceleration to a safe location.

[Cloud_Dancer]

Here's the obvious. In the case of the subject video vs all the instructional tire-blowout videos, IMO if there is no source of energy, there can NOT be a mysterious lateral force. If depressing the accelerator for the sake of maintaining control is truly necessary, whatever helpful force is produced, which has not been identified, apparently is not needed when you experience the same speeds when you decide to slow down.
All of the many internet videos which show simulated blowouts, all of them show how easy it is to steer and stay in your lane. What I would like to see are questions from some RV drivers who are not convinced that they can safely deal with a steer tire blowout.

[Planning]

There is no "stomping" in controlling for a blowout. There is a controlled application of thrust sufficient to counteract the force vector; a smooth decisive application of throttle.

[4x4van]

I, too, have experienced RV tire blowouts while driving, at least 2 on the front. One of those at 65mph, and another at 55-60 on a downhill freeway offramp while decelerating. Never did the RV try to pull me off the road; it was simply a matter of retaining hold of the steering wheel to counter the "drag" of the blown tire and gently applying the brakes to slow the RV to a stop.

I vehemently disagree with the often-linked Michelin video on dealing with a front blowout that claims you must immediately stomp on the accelerator in order to maintain control. The key is to NOT panic and stomp on ANYTHING, gas or brake.

[fj12ryder]

Jim-Linda wrote:
In 2010, driving south on 59 from Livingston, TX, about 20 miles from Livingston, left front exploded. Freightliner MDT pulling 38' HH. Truck immediately entered north bound lane (no traffic), wheel dug in, no tire left. Kept foot on fuel pedal and slowly pulled back in proper lane. Slowed down and made it to shoulder, except for tire, bent rim, headlight bucket missing, left bumper end dangling all was well. In posting this, I am somewhat in disagreement with parts of the above advise. There was immediate movement to the left, steering was at least 40deg to the right, but no way was it in control. Wife was behind in car and when all was stopped, she said, "what in the world were you doing". Felt lucky

Jim

Don't forget, the OP says specifically "I happen to have knowledge and experience about this subject, but not enough to qualify me as an expert.", so you pretty much have to take all the advice with the knowledge that it is an opinion, by a self-professed non-expert.

[Jim-Linda]

In 2010, driving south on 59 from Livingston, TX, about 20 miles from Livingston, left front exploded. Freightliner MDT pulling 38' HH. Truck immediately entered north bound lane (no traffic), wheel dug in, no tire left. Kept foot on fuel pedal and slowly pulled back in proper lane. Slowed down and made it to shoulder, except for tire, bent rim, headlight bucket missing, left bumper end dangling all was well. In posting this, I am somewhat in disagreement with parts of the above advise. There was immediate movement to the left, steering was at least 40deg to the right, but no way was it in control. Wife was behind in car and when all was stopped, she said, "what in the world were you doing". Felt lucky

Jim

[ajriding]

I have had front blowouts in a class-C twice!
Never had any issues with van doing anything except make a very, very loud boom.
I kept motorhome driving perfectly straight and had no issues controlling it or steering it to the side of the road.
I suspect that is is not the flat tire causing the vehicle to wander, but the driver jerking the wheel from shock and being untrained, or mentally unprepared to handle anything unusual that might happen on the road.
I have a hard time believing that the motor home, on its own, jerked to the side like that. I would have to see a simultaneous camera inside showing the driver to believe this was not driver caused.
Yes, if you did not have your hands on the steering wheel then this is possible, but holding the wheel straight will keep the steering straight enough, period. Some correctional steering will be necessary, but is not difficult at all, no different in my experience, than hitting a deep patch of water on one side.

[Cloud_Dancer]

Driving a big motorhome is a more responsible job than what most drivers want to realize. I delegate most of the sight seeing to my wife.