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Old 10-31-2015, 12:46 PM   #71
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Originally Posted by Gyrogearloose View Post
Not dumbing down.
I'm an engineer, so I'm accustomed to the math and physics. I do it all the time. Most people have expertise in other things.

What I'm saying is that the tires on my trailer are pushed to the limit when the trailer is loaded and sitting still on my driveway.

The other thing I'm saying is that whenever I take a curve, the trailer has a tendency to try to lean to the outside of the curve. This adds weight to the outside tires above and beyond what's there in my driveway.

If the tires are fully loaded in the driveway, then they'll be overloaded when the trailer leans on a curve.

The question is by how much, and that's where the math becomes important. The overload appears to be quite large to me.
I to am an engineer and worked many years in the tool & die industry. I get your point and have looked at my tires in the mirror while making a tight sharp turn in our court in front of our home at nearly no speed at all. One tire flexes inward while the other flexes outwards. It is not a pretty sight and have often thought that there has got to be some damage done there. Maybe you could calculate a chart with given speeds and angularity of turns and share here on the forum for others to apply. Do you have any test data?
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Old 10-31-2015, 12:54 PM   #72
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Quote:
Originally Posted by Gyrogearloose View Post
I agree with this.
There may be some bad tires that come out of China, or have come out of China in the past.
But what I see here is not a problem with the tire quality, it's a problem with choice of tire.
Please, China ? Most of the stuff in your home not to mention on your camper is made in China. These rv units when empty are at near maximum weight capacity. As was mentioned before we are stuffing 15 lbs of stuff on a 10 lb allowable amount.
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Old 10-31-2015, 01:54 PM   #73
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Quote:
Originally Posted by OKI Marine View Post
Please, China ? Most of the stuff in your home not to mention on your camper is made in China. These rv units when empty are at near maximum weight capacity. As was mentioned before we are stuffing 15 lbs of stuff on a 10 lb allowable amount.
To be clear, I was agreeing with you....

I'm skeptical of the no-name brand that's on my trailer, but this isn't the point of this discussion. I don't have hard facts that point at the tire manufacturer as being a problem in my failure. I have what I think is a very solid argument that the tires are overloaded in reasonable use on my trailer.
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Old 10-31-2015, 02:10 PM   #74
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Quote:
Originally Posted by OKI Marine View Post
I to am an engineer and worked many years in the tool & die industry. I get your point and have looked at my tires in the mirror while making a tight sharp turn in our court in front of our home at nearly no speed at all. One tire flexes inward while the other flexes outwards. It is not a pretty sight and have often thought that there has got to be some damage done there. Maybe you could calculate a chart with given speeds and angularity of turns and share here on the forum for others to apply. Do you have any test data?
Test data? I wish! It would be fun to generate some test data, but this requires time and instrumentation that I don't have. I'd need a way to measure the forces on the outside tires. I'll have to leave this for the big guys.

What I've done is math and physics, and concluded that there is a likely problem here. (It's hard to be wrong about this if the tires are loaded to the max when the trailer is sitting still)

I have a spreadsheet that shows my calculations and am happy to share if we can figure out how to do that. PM me if interested.

I needed a reasonable benchmark for speeds on curves. What I found is that the advisory speeds are well defined in a way that makes calculating lateral g-forces easy. Advisory speeds are also reasonable speeds to drive comfortably when towing, based on my experience. They're based on readings on a Ball Bank Indicator. Speeds on advisory limit signs are set according to the following table that's in the MUTCD:

35 mph max bank angle 12 degrees
25-30 mph max bank angle 14 degrees
20 mph max bank angle 16 degrees

The Tangent of the bank angle gives the lateral acceleration on the trailer in g's.

Multiply that times the weight of the trailer and you've got the lateral force on the trailer.

Multiply the lateral force on the trailer by the height of the center of mass of the trailer and you have the torque that's working to tip the trailer towards the outside of the curve. Units are ft-lbs in my spreadsheet. I guessed my center of mass is about 4ft off the ground. The first two feet of this is air under the trailer.

Divide the torque by the side to side span between wheels and you have the restoring force on the outside wheels that keeps the trailer from tipping over.

Divide by the number of axles, and you have the added force per tire.
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Old 10-31-2015, 02:33 PM   #75
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For anyone who's interested and doesn't want to bother with math and physics, I think I've mentioned before that Carlisle Tire has a very good document titled "Trailer Tires: Tips & Best Practices". This is a pdf and is easy to find by googling the title.

Carlisle Tire makes the following recommendation:
"The combined capacity of all the tires should exceed the loaded trailer weight by 20 percent"

If you follow this advice, which doesn't involve subtracting tongue weight from trailer weight, my math suggests that you'll be in good shape.
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Old 10-31-2015, 02:55 PM   #76
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NHTSA complaint Info

I suggested that in general, the RV community ise more interested in posting complaints on RV forums than in providing the information NHTSA needs.
If you have a failure you need to do a few things.
1. Record the vehicle VIN
This number is on your registration and on a sticker and plate on each of your vehicles
2, record the full tire DOT serial (including the date portion of the serial)
On the tire sidewall this serial is molded in 1/4" characters The first 4 after the "DOT" and the last 4 are the most important. An example might be
DOT U2LLLMLR5107
Here is a link
with more info

3. Record the correct and complete tire size (15" is not correct nor is 225-14)
In posts I see on tires, the size is many times incomplete. Here are examples of "complete" size designation.
ST235/75R15
LT235/75R15 107/110Q LR-D
Include all the letters and numbers

Here is some info from one of my blog post on "What size is it" of Sept 14 2011 that explaines why knowing all the information is important.

LT235/75R15 107/110Q Load Range D
is a different tire than an LT235/75R15 Load Range D

P235/75R15 105S (Standard Load -35 psi @ max load)
2028# 35 psi 112mph on a Passenger car
1844# 35 psi 112mph on a SUV or P/U (no Dual)

LT235/75R15 101/104Q LRC
1985#single 1820# Dual 50 psi 99mph

LT235/75R15 LRC
1512#single 1377# Dual 50 psi 85mph

ST235/75R15 LRC
2340#single 2040# Dual 50 psi 65mph

Note the different speed and load capabilities associated with each size.


4. Record the tire Make & Brand (model name) "Radial" is not a Make or Brand but that is what some provide
Again read the tire sidewall don't just guess
5. Snap a few pictures of the tire in good sunlight and close up
6. Spend the 10 minutes it might take to file a complaint with NHTSA. They don' need to know your travel itinerary or the weather of the day or who you were visiting. Just the facts.
Example #1
Traveling on Highway #45 in Kansas at about 60 mph. Was flagged down by passing motorist and when we found a safe place to pull over we discovered a tire had failed. The Coachmen RV trailer has two axles and the failure was on the driver side rear axle. The tread was missing and only the lower part of the sidewalls remained. We replaced the tire with our spare. Our inflation had been checked two days prior and found to be 65 psi. The Rv suffered damage and the estimate from Acme RV dealer in Ada Kansas was $1850 which includes the cost of a new tire. Roadside service to change the tire cost $85.
We have pictures of the failed tire available if you are interested. The tire pieces have been scrapped

Example #2
Last week when conducting our normal monthly tire inspection we discovered the passenger side front tire on our Rockwood RV trailer had grown in OD by approximately 2". We knew from reading information on RVtireSafety.com that this was a sign indicating a probable belt separation of our tire. We have weighed our trailer and know that the load on the subject tire is about 1495# when fully loaded. We have a TPMS and it was reporting a cold inflation of 64 psi. We normally set the cold inflation to 65 psi. We contacted the local Rockwood RV dealer but they said that they did not offer any warranty on the failed tire. They did not have the name of any local dealership for the "Superbe" brand tires so we could not file a claim for a tire adjustment.
We did a close visual inspection of the other three tires and two showed areas of local tread wear which we have been told might indicate that they had also suffered belt separations. I have pictures of all our tires and have retained the tires. Please advise you you have an interest in examining the failed tires. I will hold the tires for two months then they will be scrapped unless we hear from you.
We are replacing all four tires with tires from XYZ Tire company that offers a warranty on the brand tires they sell.

Example #3
Our junk tire blew out. We want a replacement. This tire failure cost us $250 and spoiled our vacation. The tire was left with the service truck that did the tire change and they even charges us $5 extra for scrapping the junk tire.

NOTE In Example #3 the DOT was not provided. The tire size was reported as a 15" radial, no pictures were offered.
In Example #1 & #2 the full DOT, tire brand and size was provided.
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Old 10-31-2015, 04:34 PM   #77
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Thanks, Tireman. My next question is when is it appropriate to report to the NHTSA? After any flat? Or are there specific indicators?

I feel like I am going off topic. Sorry!
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Old 10-31-2015, 04:53 PM   #78
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I feel like I am going off topic. Sorry!
I don't think so.

Reporting of possible safety issues is key to identifying and fixing real problems like tire overloading. I think this is spot on topic.
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Old 10-31-2015, 06:01 PM   #79
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Yes More leverage on the spindle with a bigger diameter tire. There are ways around that. If you can go bigger in rim diameter but keep overall tire diameter the same.
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Old 11-01-2015, 11:58 AM   #80
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Thanks, Tireman. My next question is when is it appropriate to report to the NHTSA? After any flat? Or are there specific indicators?

I feel like I am going off topic. Sorry!
Excellent question as we don't need to be "crying wolf"

NHTSA has a goal to decrease the number and severity of injury or accident costs due to a failure of an automotive system or component. One way to achieve that goal would be to hold the manufacturer responsible for providing parts that deliver reliable service for normal and expected operating conditions.

One way to hold a manufacturer accountable is to order and require a manufacturer to replace a part that has been found to have an abnormally high failure rate due to either design or manufacturing problems or in the case of tires an improper selection of size and load capacity.

So what data does NHTSA use to decide if a part is defective? Complaints are part of that consideration.

So the question really is.... What should the tire manufacturer be held responsible for?

It is well documented that over half of RVs on the road have one or more tire in an overload/underinflated condition. Should the tire company be held accountable for an overload or low inflation or for a tire loosing air due to puncture or leaking valve?

Bottom Line
If you believe the RV company or the tire manufacturer should be held responsible for the tire failure then you probably should file a complaint.
If you take a few minutes you might even decide the failure was not the fault of the tire company but of the RV company that selected a tire with no margin for any loss of air or load variation.
You still need to provide tire information but in the last case of poor tire selection I would be sure to include statement with actual measured loads and the small reserve load the tire selected provided.
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