Blowout on Goodyear Tire

SNOKING said:

So Roger can you explain how Carlisle has raise the max speed of their ST tires like the Radial Trail RH? Chris

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Its easy. Just run a drum test for a few minutes and you can claim the tire "passes" the requirement for the speed symbol.

My point is that the fundamental basis for the load formula was developed back in the 60's & 70's when the National Speed Limit was 55 mph. There has not been any substantive change to the formula since then. Even though highway speeds are now much faster than 55. It is also important to remember than in 2002 other tires like LT and P type had a major overhaul of the regulatory requirements to make radials more robust but it is my understanding that the RV industry opposed the application of stricter, modern requirements be applied to ST type tires.

DOT regulatory test requirements for ST tires are over 40 years old and the only requirements for "High Speed" are as follows from FMVSS 571.109
"S5.5 High speed performance.S5.5.1 After preparing the tire in accordance with S5.4.1, mount the tire and wheel assembly in accordance with S5.4.2.1, and press it against the test wheel with a load of 88 percent of the tire's maximum load rating as marked on the tire sidewall.

S5.5.2 Break in the tire by running it for 2 hours at 80 km/h (50 mph).

S5.5.3 Allow to cool to 38° ±3 °C (100° ±5 °F) and readjust the inflation pressure to the applicable pressure specified in Table II.
S5.5.4 Without readjusting inflation pressure, test at 121 km/h (75 mph) for 30 minutes, 129 km/h (80 mph) for 30 minutes, and 137 km/h (85 mph) for 30 minutes."

NOTE the above applies to a new tire only and the inflation in "Table II" is 2 psi below the max on the tire sidewall. Once a tire completes the above without visible failure it is considered to have "passed" the test. You will note the relative short cumulative time and that the test is on a new tire that has never hit a pot hole or curb, or been exposed to sunlight for weeks or months.

SOURCE Here

LT tires must meet the following under 571.139
"S6.2.1.2 Test procedure.

S6.2.1.2.1 Press the assembly against the outer face of a test drum with a diameter of 1.70 m ±1%.
S6.2.1.2.2 Apply to the test axle a load equal to 85% of the tire's maximum load carrying capacity.
S6.2.1.2.3 Break-in the tire by running it for 2 hours at 80 km/h.
S6.2.1.2.4 Allow tire to cool to 38 °C and readjust inflation pressure to applicable pressure in 6.2.1.1.1 immediately before the test.

S6.2.1.2.5 Throughout the test, the inflation pressure is not corrected and the test load is maintained at the value applied in S6.2.1.2.2.
S6.2.1.2.6 During the test, the ambient temperature, measured at a distance of not less than 150 mm and not more than 1 m from the tire, is maintained at not less than 32 °C or more than 38 °C.
S6.2.1.2.7 The test is conducted, continuously and uninterrupted, for ninety minutes through three thirty-minute consecutive test stages at the following speeds: 140 (86mph) , 150 (93 mph), and 160 (99 mph) km/h.

S6.2.1.2.8 Allow the tire to cool for between 15 minutes and 25 minutes. Measure its inflation pressure. Then, deflate the tire, remove it from the test rim, and inspect it for the conditions specified in S6.2.2(a).
S6.2.2 Performance requirements. When the tire is tested in accordance with S6.2.1:
(a) There shall be no visual evidence of tread, sidewall, ply, cord, innerliner, belt or bead separation, chunking, open splices, cracking, or broken cords.
(b) The tire pressure, when measured at any time between 15 minutes and 25 minutes after the end of the test, shall not be less than 95% of the initial pressure specified in S6.2.1.1.1."

Source here.

Note the test pressure in 6.2.1.1.1 is about 5 psi below the max on the tire sidewall.

Also remember that an LT225/75R15 LR-D carries 15% less load than an identically sized ST type tire. I would ask what part of physics allows an ST to carry more load at the same inflation as an LT if all other conditions of use are identical?? Just making the container stronger doesn't result in increased load capacity.

If you want to learn more about the speed rating test tire companies are using I suggest you read This post written by another tire engineer.

Out of the body shop. McGeorges in Ashland, VA did a great job. Dropped it off Tues and picked it up this morning.


Sent from my iPhone using Tapatalk

Looks great.

Yeah👍 Now you can get "on the road again".

Had a blowout also with a GY 614 on left rear just outside Sturbridge MA on I90.DOT code 2011 and in good condition. Called Good Sam roadside and they informed me that they were not authorized to send help because I90 in that section was restricted.They did supply a phone number to call for help and they would reimburse me the cost. Apparently its a state law that only certain companies are allowed on I90.
Anyway....decided to change the wheel myself and was on the road again in less than 45 minutes.Heard the tire blow as it sounded like a shot gun blast so no damage done to anything other that a hole in the inner sidewall of the tire.Tire shop suspects it may of had a slow leak and over heated.Outside temp was around 26c.The truck radio was blasting also but still heard the blowout.

Birchwood said:

Had a blowout also with a GY 614 on left rear just outside Sturbridge MA on I90.DOT code 2011 and in good condition. Called Good Sam roadside and they informed me that they were not authorized to send help because I90 in that section was restricted.They did supply a phone number to call for help and they would reimburse me the cost. Apparently its a state law that only certain companies are allowed on I90.
Anyway....decided to change the wheel myself and was on the road again in less than 45 minutes.Heard the tire blow as it sounded like a shot gun blast so no damage done to anything other that a hole in the inner sidewall of the tire.Tire shop suspects it may of had a slow leak and over heated.Outside temp was around 26c.The truck radio was blasting also but still heard the blowout.

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I assume you are not running TPMS so can only know the inflation when you last checked. Have any good sharp pictures of the tire? Might be able to offer opinion on cause of failure, depending on picture. (Air Loss or belt separation) 2 different conditions with 2 different causes.

tireman9 said:

I assume you are not running TPMS so can only know the inflation when you last checked. Have any good sharp pictures of the tire? Might be able to offer opinion on cause of failure, depending on picture. (Air Loss or belt separation) 2 different conditions with 2 different causes.

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No picture but it was mid sidewall and looked like a tear about 3 inches long

I had a reputable tire guy tell me that a trailer kept in storage for weeks/months can contribute to a tire failure. A heavy trailer sets on one spot on the tire for a long period of time can cause weakness in the tire on that spot. He recommended jacks stands place on the frame to partial left the trailer off the ground, deflate the tires so they are not holding any weight. When you are ready to use the trailer. Inflate to 70lbs (never fully to 80 psi) to allow for an increase in pressure when traveling. Is anybody doing this, or does it make sense that storage for weeks/months can weaken the tire? I think many of us travel during certain periods of the year and then winterize the trailer and let if set for several months before we use it again. I am wondering if tire failures occur more often after the trailer has been setting in storage for a few months?

Garykcpa said:

I had a reputable tire guy tell me that a trailer kept in storage for weeks/months can contribute to a tire failure. A heavy trailer sets on one spot on the tire for a long period of time can cause weakness in the tire on that spot. He recommended jacks stands place on the frame to partial left the trailer off the ground, deflate the tires so they are not holding any weight. When you are ready to use the trailer. Inflate to 70lbs (never fully to 80 psi) to allow for an increase in pressure when traveling. Is anybody doing this, or does it make sense that storage for weeks/months can weaken the tire? I think many of us travel during certain periods of the year and then winterize the trailer and let if set for several months before we use it again. I am wondering if tire failures occur more often after the trailer has been setting in storage for a few months?

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There are all kinds of 'theories' out there . . .

Who really knows for sure . . .

Garykcpa said:

I had a reputable tire guy tell me that a trailer kept in storage for weeks/months can contribute to a tire failure. A heavy trailer sets on one spot on the tire for a long period of time can cause weakness in the tire on that spot. He recommended jacks stands place on the frame to partial left the trailer off the ground, deflate the tires so they are not holding any weight. When you are ready to use the trailer. Inflate to 70lbs (never fully to 80 psi) to allow for an increase in pressure when traveling. Is anybody doing this, or does it make sense that storage for weeks/months can weaken the tire? I think many of us travel during certain periods of the year and then winterize the trailer and let if set for several months before we use it again. I am wondering if tire failures occur more often after the trailer has been setting in storage for a few months?

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It's pretty routine to have RVs in storage or at seasonal sites for months at a time without following your tire guy's advice. Except for breakdown of the rubber from exposure to the sun, I've not seen any information supporting the theory that setting on one spot for a long period leads to tire failures.

And from everything I've read, his advice on underinflating the tires runs contrary to advice from the tire manufacturers and tire engineers.

Birchwood said:

No picture but it was mid sidewall and looked like a tear about 3 inches long

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Mid sidewall is almost certainly the result of Run Low Sidewall Flex failure.




In extreme case the tire ends up in 3 pieces


This is the exact situation when a TPMS would have prevented the failure as the RUn Low only occurs after a tire has been run for miles at highway speed while very low on air or the tire is actively leaking.

You can learn more by reviewing the topics on my blog.

- - - Updated - - -

Garykcpa said:

I had a reputable tire guy tell me that a trailer kept in storage for weeks/months can contribute to a tire failure. A heavy trailer sets on one spot on the tire for a long period of time can cause weakness in the tire on that spot. He recommended jacks stands place on the frame to partial left the trailer off the ground, deflate the tires so they are not holding any weight. When you are ready to use the trailer. Inflate to 70lbs (never fully to 80 psi) to allow for an increase in pressure when traveling. Is anybody doing this, or does it make sense that storage for weeks/months can weaken the tire? I think many of us travel during certain periods of the year and then winterize the trailer and let if set for several months before we use it again. I am wondering if tire failures occur more often after the trailer has been setting in storage for a few months?

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I have read some posts about bending of frame by using it to support the trailer. This may be due to the fact that frames are not designed to be jacking pointe so unless the MFG identifies jacking points on the frame you may do damage. What does Heartland say?

As an actual tire design engineer and not someone that has just sold tires I can suggest that all that work is not really necessary.

I have a post specifically on how to maximize tire life with minimal effort.

The idea of only inflating to 70 on a Load Range E tire (80 psi rating) is not supported by the physics of tire construction. To minimize the Interply Shear trailer tires experience (extra 20% shear forces) you should always inflate tires to the sidewall inflation. You should always confirm your actual measured load on each tire in no more than 85% of the tire max. Don't forget that very few RVs have the load equally split axle to axle or even side to side on an axle.

JohnD said:

There are all kinds of 'theories' out there . . .

Who really knows for sure . . .

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Without getting too pedantic, "Theories" are developed and updated based on their ability to accurately predict future outcome.

So when I suggest that a tire that is run very low on air at highway speed for a few miles, the heat from the excessive sidewall flexing can melt the Polyester sidewall cord, my analysis and prediction is based on the examination of thousands of tires whose sidewall cord looks like this.

and the tire may look like this


With the additional conditions in Innerliner abrasion and external sidewall wear as additional physical evidence.

Not sure what you mean by 85% of the total load capacity? If Tow Maxx tires are rated at 3,500 lbs each and 4 are on the trailer that would equal 14,000 lbs, the gross allowable weight of the trailer. Do you mean that 85% of that total or 11,900 should be the total weight, that would be impossible.

Garykcpa said:

If Tow Maxx tires are rated at 3,500 lbs each and 4 are on the trailer that would equal 14,000 lbs, the gross allowable weight of the trailer.

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Do a search on Towmax (also known as 'Blow Max') here in the forum . . .

You'll find that their tow rating means nothing as they are junk tires.

If you have them . . . get rid of them ASAP!

Roger that I got rid of them already - but trying to understand the meaning of the 85% capacity statement and the 3500 lbs rating makes the math easier. Goodyear Marathons are 3420 per tire and the GY G614 are 3750 lbs per tire, so what does the 85% of capacity mean? If the original tires on the trailer where Tow Maxx before I replaced them, 85% would mean the factory gave us tires that did not cover the weight of the trailer if the max capacity is 85% of there total capacity.

I'm looking at Maxxis 8008's for our Prowler . . .

The Goodyear Marathon's are not much better than the BlowMax tires, according to reports I've read here and at other RV chat boards.

However, I've also read that there is a new version of the Marathon's coming out that are supposed to be much better than the current ones.

Garykcpa said:

Roger that I got rid of them already - but trying to understand the meaning of the 85% capacity statement and the 3500 lbs rating makes the math easier. Goodyear Marathons are 3420 per tire and the GY G614 are 3750 lbs per tire, so what does the 85% of capacity mean? If the original tires on the trailer where Tow Maxx before I replaced them, 85% would mean the factory gave us tires that did not cover the weight of the trailer if the max capacity is 85% of there total capacity.

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If the tire sidewall says 3520 lbs at 80 psi, inflate to 80 psi. 85% of load means 85% of the 3520 lbs which would be 2,992 lbs. If equally distributed on the wheels, that would allow 11,968 lbs on the wheels, plus some weight on the hitch. A trailer with GVWR of 15,500 lbs will have approximately 20% of that weight on the hitch, or 3,100 lbs. That leaves 12,400 lbs on the wheels, which is loading at about 88% versus the 85% load that Tireman9 recommends.

But weight is never evenly distributed. And 20% is a planning number. Actual weight on the hitch could be anywhere from 15-25% leaving less or more weight on the wheels.

Garykcpa said:

Roger that I got rid of them already - but trying to understand the meaning of the 85% capacity statement and the 3500 lbs rating makes the math easier. Goodyear Marathons are 3420 per tire and the GY G614 are 3750 lbs per tire, so what does the 85% of capacity mean? If the original tires on the trailer where Tow Maxx before I replaced them, 85% would mean the factory gave us tires that did not cover the weight of the trailer if the max capacity is 85% of there total capacity.

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Lets start at the beginning.
1. You need to know the actual load on each tire. Driver side front has no idea what the load is on Pass Left.

2. Lets assume the RV company did what most do and get tires with zero reserve capacity. If your axle GAWR was 6,500 that does not guarantee that each tire is loaded to 3,250. It is entirely possible you have 3510 on right end of the axle and 2990 on the left but the total is exactly 6,500 so you think you are OK and set your pressure to support 3,250. What are the chances you would see an early failure of the 3,510 side?

3. In general LT tires are rated for about 85% of what the same size ST tire is. Since it is the air pressure that supports the load what is the magic in putting "LT" on a tire sidewall rather than "ST" that allows the pressure in the LT tire to support more load?

4. Side tilt loading from road crown, cornering and side wind can shift about 500# load from one side to the other. This is why we suggest you have a load capacity margin of about 15% based on actual static loading on each tire.

5. All tires on an axle (or all tires on multi axle trailer ) should have the same inflation as this affects stopping distance and cornering forces.

6. Interply shear is lowered when you run higher inflation so run the inflation on the tire sidewall.

If you really care about the facts I suggest you review the posts on my blof with "Inflation, "Trailer", "Load" and "Interply Shear" as labels as I simply cannot re-post all 250+ posts here.

There is no "Magic". Overload a tire and it will fail sooner, Underinflate a tire and it will fail sooner. Rin faster and it will fail sooner.

ST tire load formula are based on 50 year old technology and highway speeds of about 50 mph for trailers that maybe weighed 4 to 6,000# total and the DOT regulations are about the same age.

LT & P load formulas and regulatory test requirements were updates in 2002 - 2005 time frame.

The new (2016) speed rating for ST tires were done to avoid import tariffs. No regulations for better speed performance were made for ST tires sine 1970.

I can think of absolutely no technical reason for ST tires to be rated to carry more load than LT of the same size when they are now expected to run the same speeds. In fact the Interply Shear loading makes an excellent case for - de-rating any ST tire by at least 10% if not more.

When I bought new tires for my truck a couple of months ago I was asking about putting some LT tires on our 5th-wheeler, and the tire shop guy (Tire's Plus) told me that they won't install LT tires on a trailer.

He told me it was company policy and wouldn't give me any other reason.