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jjrbus 07-22-2021 05:43 AM

Tire engineering over load question
This is an imaginary scenario it did not happen to me, so exact weights, tire size, temperature do not apply.

So I go and get rig weighted and inflate rear tires to 10% over psi suggested in load and inflation tables.

Driving along and whats that BOOM noise? Got a blow out on the rear. In a miles long construction zone with no exits or place to pull over. Now one tire on one side is way overloaded, on my RV would be about 30% overload.

Question would be how far can I drive on the remaining tire before destroying it or needing to replace?

twinboat 07-22-2021 05:53 AM

Sidewall flexing and the heat it creates destroy tires.
Slow way down, and stop as soon as its safe.

Don't even think about the traffic behind you. If both tires blow, it will be worse.

xrated 07-22-2021 06:28 AM

I'm going to add something else to the "scenario" described above. Unless the rig was weighed with individual weights per tire.....not just the total axle weights for the unit, you would have no way of knowing what the imaginary 10% value would be. If, lets say I had a trailer that shows that I have 10,000 lbs on the axles (assume tandem axles here), that would be, evenly divided to come out to 2500 lb per tire. But, who's to say that the rear axle has more weight on it than the front axle....or vice versa. And to further that thought, who's to say that the left side of the trailer isn't heavier than the right side of the trailer....or again, vice versa. It is very rare indeed that in a scenario like I just described that there would ever be total equity on a 4 tires/wheels. So the only true way to know is getting weighed on a scale that weighs each and every single tire/wheel......and that is just not something that you find everyday and certainly not at any CAT type scale you will ever find. So in my opinion, until you actually know exactly what weights are what on each and every tire/wheel, go with the sticker that is on the unit that tells you what psi cold inflation is...AND monitor those tires with a good TPMS system to make sure of what you have.

And as far as the construction zone predicament....take twinboat's advice.....slow down....way in maybe 10 mph or even less. And if that remaining tire was overloaded like you describe, I would replace it also.

sibe 07-22-2021 10:40 AM

I lost a rear twice on same side.. URGH on same trip.. once going , put spre on.. then on way home spare took a dump..

Had a 7x16 triler on, with about a 600 tongue weight..

Pulled over, drained water, dumped tanks.. moved as much items as we could to the opposite side, reloaded trailer to lighten the tongue way up and took some stuff from RV into trailer,, NOT IDEAL but it helped.
Limped it 91 miles at around 35-40 MPH max , flashers on and praying.. MADE it..

sibe 07-22-2021 10:45 AM

Hence I now buy good tires, not the most expensive.. but good specs , check date codes,, watch PSI nut road trash can kill a tire fast.. I rather replace with fresh after a couple years for various reasons, dry rot and traction since i go into a lot of grass wet fields..

dizcom 07-22-2021 10:46 AM


Originally Posted by jjrbus (Post 5841575)
Question would be how far can I drive on the remaining tire before destroying it or needing to replace?

All the way to the scene of the crash. :rolleyes:

I don't know that there's a real answer to your hypothetical, but I think it would depend on how overloaded the other tires are and how hard you drove it to the next stop. I don't know that I would be able to calculate all that out in my head while stuck like that. I might try to limp it along and I might just get as far to the side as I could and hit the flashers. Either way I think I'd be fairly nervous.

Maybe if I had Rettrobands...:D

Ron Dittmer 07-22-2021 11:20 AM

I would put on my hazard/flashers and drive 30 mph. The tire won't heat up much more at that speed versus 10 mph.

One thing you will need to be "VERY" mindful of is if the blown tire is deformed or shredded from the blowout, thrashing around hitting other things during rotation. If so, you want to stop and remove the shredded tire.

At that point, I would go extremely slow until finding any place to pull over (a construction access point, move construction cones, whatever) to remove the damaged tire. Bolt the other good tire back on by itself, then proceed to the nearest exit at 30 mph max.

Of coarse if you carry a spare, it's the right time to mount it.

I know that my 2007 E350 tires on the original steel wheels weigh 83 pounds with consideration to the wheel covers. I was never gifted with muscles, yet I can handle the tires myself at age 63. Two people can surely handle one tire.

I recently changed 4 of the 6 steel wheels to Alcoa alloys which reduces the weigh of those tires by 20 pounds.

jjrbus 07-22-2021 08:27 PM

I have been trying to get some good solid info on this, and not doing well. I believe this is from a tire enginner but cannot prove it.

I have read a few posts both here at FMCA as well as on other RV forum sites when the topic of what to do when a tire fails and you don't have a spare. Many times it has been suggested that the person plans on "limping" home or to the tire service center with just one tire in the dual position of their RV.
While on the surface this might seem to be a reasonable approach, there are a few things that need to be considered.
First, unless you have a TPMS that warned you that one of your duals was loosing air, in all probability you have no idea how long you drove with one dual underinflated. If you don't know when the tire started to loose you also have no idea at what speed you drove on one underinflated tire and also on one overloaded tire.
If a tire looses more than 20% of its air it is considered to be "Run- Flat" by tire industry
If you have driven on a "flat" tire it is considered to have been damaged and should not be considered for future safe usage.
What is not obvious when you read the above is that is one tire of a dual goes flat the mate has now been overloaded. I covered some of the info in a post on the Special Considerations for Duals, but there is more that needs to be considered.
If you have one tire punctured and loosing air the mate is "taking up" the load for both tires until it is 100% overloaded. Driving at highway speed will do serious internal structural damage. Most of which cannot be seen with out special equipment like X-Ray so it is simply considered scrap so now you need to replace two tires.
Trying to "limp" means that you need to reduce your speed and according to the special tables in Tire & Rim Association for adjustments for speed, inflation and load your limp speed is not 30mph or 20 mph or even 10 mph but it is limited to 2 mph. That is TWO miles per hour Maximum. Any more and you are damaging your tire beyond repair.
The solution would be to call for service. I would only drive on a single tire for a hundred yards at most to get to a location where I could safely pull off the roadway.

chunker 07-23-2021 07:09 AM

This spring with my toy hauler 5th wheel I had a blowout on the right rear. Not dually tires but tandem axle. I was fortunate to be able to pull over rather quickly even though it was a construction zone and replace the blown tire with the spare. At my next stop I replaced both tires on that side since I had no idea what condition the other tire was having carried the whole load. Yes I had a TPMS but a blowout is sudden. Years ago on a different 5th wheel I had a blowout that I heard, explosive. It took out its partner tire and damage to the RV body. I got the blown one changed with my one spare and drove 15 miles at 20 mph to town to the tire shop and bought 5 new tires. Tires were not old, 2 years, but chinese crap.

f14av8r 07-24-2021 06:03 AM

The answer to your question, “How far can one drive on an overloaded tire without causing damage,” is zero miles. The instant you overload the tire to that degree, you may have caused damage. The only way to know for sure is to have the tire dismounted and professionally inspected. Otherwise, you should replace both tires on that side of the axel.

Ron Dittmer 07-24-2021 08:28 AM


Originally Posted by f14av8r (Post 5844208)
The answer to your question, “How far can one drive on an overloaded tire without causing damage,” is zero miles. The instant you overload the tire to that degree, you may have caused damage.

This is an interesting topic.

Where I live, the street curbs are rain gutters, not raised curbs. If I park our motorhome on the street just right, one outer rear tire will be suspended in the air over the gutter, placing all the weight on the inner tire.

I called the Michelin tire technical hotline specifically regarding leveling ramps. My question to them was.....

Do I need to use leveling ramps to accommodate both rear tires on a particular rear corner?
The tech answer was "Yes".

Then I described my street curbs and parking condition.
The answer was "Don't worry about the outer tire being suspended over the gutter".

Then I asked, What is the difference?
Michelin tech told me there is no difference, but this is Michelin's position.

Here is my street curb.

wolfe10 07-24-2021 08:34 AM


Originally Posted by Ron Dittmer (Post 5844399)
This is an interesting topic.

The answer was "Don't worry about the outer tire being suspended over the gutter".

What a tire can safely support in a STATIC condition is substantially more than it can support while in motion. Think about load on corners, over bumps, etc.

Remember, while driving, load is not constant, but varies with road condition and at times can be well more than static load.

jjrbus 07-25-2021 06:09 AM

Interesting, I had not thought of one unsupported tire. It used to be common to use a ramp for the inner dual if the outer dual was flat, to change outer tire.

chunker 07-25-2021 07:17 AM


Originally Posted by jjrbus (Post 5845288)
Interesting, I had not thought of one unsupported tire. It used to be common to use a ramp for the inner dual if the outer dual was flat, to change outer tire.

I would not be concerned about short term conditions with having the load supported by one tire. Replacing a tire, parked on a curb, etc. isn't going to hurt anything. If I were facing long term storage and parking, I would definitely support all tires. As far as driving with all weight on one, only as short distance as necessary and I would consider the tire that carried the whole load to be damaged and replace it.

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