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Old 12-30-2017, 11:55 AM   #1
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Front Tire Blowout Findings

I couldn't find John Anderson (He's retired, to his farm in NE Kentucky). I wanted to ask him a couple of questions. But, I did other research, plus I have experience and knowledge, and would like to help.
There’s a need for more information. Understanding unbalanced forces will help you become a safer driver. It has to do with how is it that you can steer the front of the motorhome. You gotta start from the beginning, with the motorhome sitting still on flat pavement, with engine running and parking brake applied. The force of gravity and a fore/aft motion resistance is at play. The forces at play are balanced. To move forward, less resistance and the force of propulsion is needed. You get moving due to the fact that the force of propulsion is greater than all the forces which were holding the motorhome still. It moves straight because the side forces are balanced. If you want to turn, you introduce a frictional force plus a path of less resistance in the direction that you want to go. And, you do this just by turning the steering wheel. Then you balance the steering forces and go straight, on the straight and level highway, at cruise speed, on cruise control. The unbalance force is the force of propulsion. Plus you now have momentum and inertia. And, Newton’s first law of physics tends to keep you moving in a straight line (unless an unbalanced force is introduced at the front). Also, to slow down you decrease the force of propulsion PLUS increase the rolling resistance(apply the brakes). So, what happens if a front tire suddenly fails?
You need to immediately NOT release your grip on the steering wheel, plus articulate the steering wheel appropriately, PLUS do NOT touch the brake. The problem is that you need to do all THREE immediately and simultaneously! IF you use your analytical mind, and really study all the instructional blowout videos (use stop action, over and over), several things will become evident: the inflated steering tire offers significantly MORE traction that the flat tire, and by just using the steering wheel in a timely, aggressive and appropriate manner, ANY dangerous force can be defeated (if you do NOT touch the brake). IMO in event of a front tire blowout, the most dangerous force is the one that comes from the rolling resistance of the flat tire. This is the force that the driver feels on the steering wheel, BUT if you do NOT let the engine RPM drop, you will have the full force of the power steering, which can easily defeat the “dangerous” steering forces. Staying in your lane, under control, is all about immediately and appropriately using the steering wheel in order to have BALANCED FORCES acting on the steering system.
In physics, the term is “net force” or “unbalanced force”. The rolling resistance of the flat tire is what initiates a potentially dangerous net force that acts on your steering system. And, it’s only the driver who can decide to DEFEAT this dangerous force. The videos show how easy it is to defeat this force. The most I see the steering wheel turn is about 15 degrees, and it’s just momentarily.
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Old 12-30-2017, 12:12 PM   #2
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The idea of a front tire blowout in my MH keeps me up at night. Intellectually, I know what I should do when it happens. I had a sidewall failure on a TT tire a few years ago which I sensed somehow, and slowed before the tire lost any air. It lost the sidewall but still held air. No loss of control at all.

From the intellectual to the practical, I would defer to those who have unfortunately have had to deal with such a traumatic event. There is not much time to think in these cases. I do not wish a tire failure on anyone!

F you are looking for data, can you discover how many folks have been able to stop under control vs rollovers?

And I for one wonder why our MH do not come equipped with a 'safety cage' at each front wheel position to prevent the tire from taking out the front steps, hydraulics, wiring and body damage in the event of a tire failure.

TPMS, as required on all pass vehicles since 2007 would go a long way to reduce tire failures.
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Old 12-30-2017, 12:28 PM   #3
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I blew a steer tire on my Peterbilt running 70 mph with 14500 on my steers. It took the right fender off, But I didn`t realize it until I seen the fender flying away. I first thought I blew a drive tire. Never ever hit your brakes.
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Old 12-30-2017, 01:59 PM   #4
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We blew a front tire at 60mph and had no problem controlling it.
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Old 12-30-2017, 02:51 PM   #5
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Quote:
Originally Posted by Cloud Dancer View Post
I couldn't find John Anderson (He's retired, to his farm in NE Kentucky). I wanted to ask him a couple of questions. But, I did other research, plus I have experience and knowledge, and would like to help.
There’s a need for more information. Understanding unbalanced forces will help you become a safer driver. It has to do with how is it that you can steer the front of the motorhome. You gotta start from the beginning, with the motorhome sitting still on flat pavement, with engine running and parking brake applied. The force of gravity and a fore/aft motion resistance is at play. The forces at play are balanced. To move forward, less resistance and the force of propulsion is needed. You get moving due to the fact that the force of propulsion is greater than all the forces which were holding the motorhome still. It moves straight because the side forces are balanced. If you want to turn, you introduce a frictional force plus a path of less resistance in the direction that you want to go. And, you do this just by turning the steering wheel. Then you balance the steering forces and go straight, on the straight and level highway, at cruise speed, on cruise control. The unbalance force is the force of propulsion. Plus you now have momentum and inertia. And, Newton’s first law of physics tends to keep you moving in a straight line (unless an unbalanced force is introduced at the front). Also, to slow down you decrease the force of propulsion PLUS increase the rolling resistance(apply the brakes). So, what happens if a front tire suddenly fails?
You need to immediately NOT release your grip on the steering wheel, plus articulate the steering wheel appropriately, PLUS do NOT touch the brake. The problem is that you need to do all THREE immediately and simultaneously! IF you use your analytical mind, and really study all the instructional blowout videos (use stop action, over and over), several things will become evident: the inflated steering tire offers significantly MORE traction that the flat tire, and by just using the steering wheel in a timely, aggressive and appropriate manner, ANY dangerous force can be defeated (if you do NOT touch the brake). IMO in event of a front tire blowout, the most dangerous force is the one that comes from the rolling resistance of the flat tire. This is the force that the driver feels on the steering wheel, BUT if you do NOT let the engine RPM drop, you will have the full force of the power steering, which can easily defeat the “dangerous” steering forces. Staying in your lane, under control, is all about immediately and appropriately using the steering wheel in order to have BALANCED FORCES acting on the steering system.
In physics, the term is “net force” or “unbalanced force”. The rolling resistance of the flat tire is what initiates a potentially dangerous net force that acts on your steering system. And, it’s only the driver who can decide to DEFEAT this dangerous force. The videos show how easy it is to defeat this force. The most I see the steering wheel turn is about 15 degrees, and it’s just momentarily.
Here we go again.
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Old 12-30-2017, 03:00 PM   #6
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Quote:
Originally Posted by hohenwald48 View Post
Here we go again.
Maybe not a long life this time.......
Every tire failure will bring different events based on condition's.......
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Old 12-30-2017, 04:07 PM   #7
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[QUOTE=Cloud Dancer;3966060 The rolling resistance of the flat tire is what initiates a potentially dangerous net force that acts on your steering system. [/QUOTE]


Sorry to have to disagree with you on this point, bit I don't think it's the flat tire that causes the dangerous net force you talk about. If it was, all flat front tires would react the same and in reading the posts on the forum, some have real problems steering after a blowout and others don't.

I'm a firm believer the difference is in the alignment settings on the coach. Conventional thinking is that settings should be between x degrees and y degrees. On many coaches, camber can't be adjusted, other than frame shops. Toe in is about the same on everything, I like 1/32 total or .04 degrees total toe. The setting left is caster and conventional thinking is to set it at the max. My Freightliner XCM specifies 4 1/2 to 6 degrees. If I were running 6 degrees and had a left front blowout, I'd expect a wild and strong turn to the left of the steering system. That's what a big caster setting will do for you and that can easily be demonstrated in a classroom environment. My thoughts are based on what can actually be physically demonstrated, not theory. Also a big caster setting will allow a side wind force to more easily move the coach over in the lane and will result in you doing more counter steering to correct the movement. Big caster settings also make the steering wheel harder to turn, even with power steering, and takes more effort in all your driving.
Some have said they wish their motorhome drove more like their toad drives. Possibly they need to align their motorhome up more like their toad is lined up. That's the approach I've taken in the last three motorhomes and won't be changing anytime soon. First item to be done on my current motorhome when we got it was to change the alignment. Alignment tech's don't want to do it because they don't understand it and you'll have an argument on your hands in order to get done. I had to argue my way through two guys at the local Freightliner shop to get my coach adjusted. Caster needs to be set according to the amount of "trail" you want to run. Trail is measured where the rubber meets the road. Determine the trail setting, calculate backwards to determine the caster setting needed. My coach is set at about 2 1/4 degrees caster which gives me about 3/4 inch of trail. The goal was 1" when we started but adjustments are made with shims so you just get close, not exact.

Bottom line is the force that instantly shows up towards the blown out tire is from alignment settings, not a bunch of theory. Physics, yes, but not what is described above.

Let the flames start, remember I can demonstrate my opinions.
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Old 12-30-2017, 04:50 PM   #8
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Some of the things I"ve done would turn your tighty whities brown but a front tire blow out on the MOtor home is ont (yet ore ever if I can prevent it)_ on the list.

I do not know if they exist here but on anotehr family of forums I visit )(Sorry no link) there is a post
Watcihing these videos may save your life"

Believe it.. the video was produced by an agreement between, as I recall, Mitchlen and an insurance company (Aeon?_ and if you take the safe driver class at an FMCA rallly.. they include it.
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Old 12-30-2017, 05:35 PM   #9
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alank,
Caster authority is a function of the vertical load on the spindle. And, there is a significant decrease on the vertical load on the spindle with the flat tire.
What I am claiming is not a theory. BOth John Anderson and Benny Parson have demonstrated in the their instructional videos that the proper minding of the steering wheel by the driver, while the full power of the power steering is present, is the most effective tool the driver has in maintaining control of the motorhome with a blown front tire. Clearly, these drivers were in complete control at cruising speed when the blowout occurs, during the deflation of the tire, during the speed-up, during the slowing down,....in short throughout all the different speeds of the total event.
The best explanation that I have for those drivers who have lost control is that they had a few seconds of incapacitation,.... and that was all the time it took for the multiplied force that is initiated by the rolling resistance of the blown tire to take the steering wheel from their hands,.....AND steer the motorhome OFF the pavement into the rail or the median. Yes, that is MY theory and I'm sticking to it. It has happened to me, and except for the significant damage to the fiberglass, it was a non-event. I never lost my grip nor my control of the steering wheel.
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Old 12-30-2017, 05:58 PM   #10
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Quote:
Originally Posted by palehorse89 View Post
Maybe not a long life this time.......
Every tire failure will bring different events based on condition's.......
I think what you are calling "different events" is actually called a variable asymmetrical thrust vector anomaly.
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Old 12-30-2017, 06:03 PM   #11
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Originally Posted by hohenwald48 View Post
I think what you are calling "different events" is actually called a variable asymmetrical thrust vector anomaly.
Well.........All Righty then........
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Old 12-30-2017, 06:42 PM   #12
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The thing to remember in those videos is the driver new the “blow out” was coming. It would make a huge difference.

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Old 12-30-2017, 06:53 PM   #13
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"cruzbill"......Do you know what will help alleviate your fears of a blowout......just watch some of the junk motor homes going down the road at 70 mph.....you know the ones, rotting apart with the curtains blowing out the side windows on a 95 degree day.

Just look at them, think about how well you take care of your coach and tell yourself.....if they can drive that thing like that and make it to their destination....I'll be just fine!

It always works for me when I start aggravating about an issue with the RV.
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Old 12-30-2017, 10:31 PM   #14
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[sQUOTE=Cloud Dancer;3966530]alank,
Caster authority is a function of the vertical load on the spindle. And, there is a significant decrease on the vertical load on the spindle with the flat tire.

I would agree with this statement, although a specific definition of the vague term "caster authority" may change my mind. If you continue your thinking along the lines of your statement above, you will eventually come to my point of a high caster setting causing the significant turning force towards the blown out tire.


"What I am claiming is not a theory. BOth John Anderson and Benny Parson have demonstrated in the their instructional videos that the proper minding of the steering wheel by the driver, while the full power of the power steering is present, is the most effective tool the driver has in maintaining control of the motorhome with a blown front tire. Clearly, these drivers were in complete control at cruising speed when the blowout occurs, during the deflation of the tire, during the speed-up, during the slowing down,....in short throughout all the different speeds of the total event."

If this is the video I watched, I am positive the driver had a "white knuckle grip" on the steering wheel before, during and after the blowout demonstration because he knew exactly when it was coming. I for one don't drive that way and think may others don't either. As pointrow stated above, if the driver was relaxed, driving with one hand and observing some scenery at the time of blowout, the outcome may have been quite different. They pointed out in the video the mysterious side force towards the blown out tire that occurs, but had no explanation of the source of the force or what could be done to minimize the force. I don't think they understood the force at all, just that it existed.


"The best explanation that I have for those drivers who have lost control is that they had a few seconds of incapacitation,.... and that was all the time it took for the multiplied force that is initiated by the rolling resistance of the blown tire to take the steering wheel from their hands,.....AND steer the motorhome OFF the pavement into the rail or the median. Yes, that is MY theory and I'm sticking to it. It has happened to me, and except for the significant damage to the fiberglass, it was a non-event. I never lost my grip nor my control of the steering wheel.[/QUOTE]"

I've been beside one semi when a tire blew, and at the back end of the trailer when another tire blew, both on interstates. It was quite loud even in another car and it could rattle anybody to a few seconds of incapacitation if it happens right below your seat. Possibly to a point it would be too late to regain control. I don't agree that the rolling resistance of he blown tire would steer the motorhome off the pavement. Getting the caster setting to attain about 1" of trail will make the coach steer easier, get pushed around by the wind less, and minimize the force of the "caster authority" which causes the coach to want to turn towards the blown tire.
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