Replace tires by age or Miles?

[Tireman9]

Originally Posted by Robin_M

Tireman,

First of all, thanks for all your informative comments here, and also for the mounds of useful information in your blogs.

Have a question though... I've always thought that damage to sidewalls from ozone (which is always in the atmosphere) is going to cause sidewall damage more quickly than UV rays. Therefore, unless your motorhome spends a significant amount of its life in direct sunlight (as it might if you were full-timing or even half-timing), it really doesn't matter much if you cover the tires, since you are going to be replacing them in 7 or 8 years anyway. Is this faulty thinking?

Yes Ozone can do real damage to tires. I have seen sets destroy because they were parked in a garage that had a leaking Ozonator. BUT Heat is the primary killer of tires.
Ozone and UV can only attack the rubber surface but heat damages the internal components and structure in addition to the surface rubber.
The UV protection test in the link above shows how almost anything can stop the UV damage to tires.

The stuff sold that promises UV protection is like suntan lotion in that it may extend the time you can be in the sun without getting burned but I know of no spray on protection that cuts UV to zero.

Heat accelerates the degradation of the molecular bonds which can lead to belt and tread separations.

I did a test on covers that shows the significant increase in tire temperature. Since the affect of heat DOUBLES with each increase in temperature of 18F this translates to an effective doubling of the "aging rate" of tires (or reducing the tire life).

I cover my tires whenever parked for more than an overnight stay where the tires can be exposed to direct sunlight. The WHITE covers block all the UV and keep the tires at about ambient temperature rather than baking the life out of them.

With proper care:
Washing with same cleaners and cloths I would use on the RV body.
Having the tires "underloaded" by about 20% when setting cold inflation.
Never getting lower that 5% above the inflation needed to carry the load.
Always running TPMS and checking pressure every AM and after each stop.
Using digital gauges that have been shown accurate to +/- 1psi.

I am hoping for 9-10 year life on my Motorhome. If I had a multi axle trailer and took the same precautions I would hope for 5 to 7 year life due to unique loading from suspension design.

[Robin_M]

Originally Posted by Tireman9

Having the tires "underloaded" by about 20% when setting cold inflation.

Tireman,

Thanks for such a complete reply. So you use the white tire covers to protect the tires more from heat in direct sunlight than from UV rays. But of course you are getting the UV protection at the same time. I never thought of that. However, it makes sense - especially in light of your temperature study.

Please allow me to make sure I understand what you are saying with your "underload by about 20%" statement above...

Here is a representative RV inflation chart from Goodyear...

Now, lets say each of your duels was loaded with 5000 lbs, and your front tires were loaded with 5770 lbs each. The "recommended" inflation rate per the chart would be 90 psi for the duels, and 105 for the front. Adding roughly 20% to the weight factor, you would inflate to 110 psi on the duels and 120 psi on the front (rounding to the nearest 5 psi). Is that correct?

[Tireman9]

Originally Posted by Robin_M

Tireman,

Thanks for such a complete reply. So you use the white tire covers to protect the tires more from heat in direct sunlight than from UV rays. But of course you are getting the UV protection at the same time. I never thought of that. However, it makes sense - especially in light of your temperature study.

Please allow me to make sure I understand what you are saying with your "underload by about 20%" statement above...

Here is a representative RV inflation chart from Goodyear...

Now, lets say each of your duels was loaded with 5000 lbs, and your front tires were loaded with 5770 lbs each. The "recommended" inflation rate per the chart would be 90 psi for the duels, and 105 for the front. Adding roughly 20% to the weight factor, you would inflate to 110 psi on the duels and 120 psi on the front (rounding to the nearest 5 psi). Is that correct?

I think you got the concept but made slight error when reading the chart.
Front load is 5770 so the SINGLE inflation would be 100 (what is needed to meet or exceed the load) 120% of 5770 = 6924 so 120 psi is answer
Rears are at 5000# so spec is 90 but 120% of 5000 = 6000# so 105psi.

the 20% is not a rule but knowing that most cars have about 15% "reserve load" and some more I felt 20% would be a nice round number.

I am lucky in that my Class-C is very light weight and I really only need 50psi based on actual loading. The OE tires were LR-D but I opted for LR-E and I inflate to 67 psi (don't ask why the odd inflation as it has to do with one set of special TPMS I am testing) Normally it would be 70 psi. This underloading keeps the tires cool as I normally only see a 3 to 8 psi rise and the tire temperature is normally only 15 to 25 above ambient.

[speedman42]

Just replace my 9 year old Good year 22.5'S with Firestones
$2700.00

[Gordon Dewald]

Originally Posted by Tireman9

I think you got the concept but made slight error when reading the chart.
Front load is 5770 so the SINGLE inflation would be 100 (what is needed to meet or exceed the load) 120% of 5770 = 6924 so 120 psi is answer
Rears are at 5000# so spec is 90 but 120% of 5000 = 6000# so 105psi.

the 20% is not a rule but knowing that most cars have about 15% "reserve load" and some more I felt 20% would be a nice round number.

I am lucky in that my Class-C is very light weight and I really only need 50psi based on actual loading. The OE tires were LR-D but I opted for LR-E and I inflate to 67 psi (don't ask why the odd inflation as it has to do with one set of special TPMS I am testing) Normally it would be 70 psi. This underloading keeps the tires cool as I normally only see a 3 to 8 psi rise and the tire temperature is normally only 15 to 25 above ambient.

This is getting more confusing by the moment.

First I do not understand that tire manufacturers have not already factored in the "20%" or whatever when they produce the tire loading chart. It is foolish for any of us to second guess their engineers and add another safety factor.

Second I wonder where the "reserve load" comes from and why we would factor that into our loading estimations when it is foolish and quite likely illegal to load in that area. Thus if the GVW of my Chevy 6.2 1500 is 7200 I should plan on 8280 by adding 15%??

It seems we are over thinking and over reacting to all of these numbers. I see why it is so confusing for new owners when everyone seems to interpret and advise based on "???". What is wrong with using the ratings and charts in their unadulterated form?

[Tireman9]

Originally Posted by Gordon Dewald

This is getting more confusing by the moment.

First I do not understand that tire manufacturers have not already factored in the "20%" or whatever when they produce the tire loading chart. It is foolish for any of us to second guess their engineers and add another safety factor.

Second I wonder where the "reserve load" comes from and why we would factor that into our loading estimations when it is foolish and quite likely illegal to load in that area. Thus if the GVW of my Chevy 6.2 1500 is 7200 I should plan on 8280 by adding 15%??

It seems we are over thinking and over reacting to all of these numbers. I see why it is so confusing for new owners when everyone seems to interpret and advise based on "???". What is wrong with using the ratings and charts in their unadulterated form?

Since it is the responsibility of the vehicle manufacturer to specify the inflation on the tires on the vehicle most car companies select inflation levels that result is "Reserve Load" of 12 to 20%.

Reserve load is the difference between the tire load capability at the specified inflation and the actual load on the tire. Think of it as a Safety Factor.

If a tire has a load capacity of 3,000# but the actual load is 2,400# the reserve load is 600#

RV companies, especially large trailer manufacturers seem to select the smallest (cheapest) tire possible to meet the legal regulations. This means many tires have a load capacity that is only a few pounds above the actual load and after the owner loads the RV most RVs have a tire with negative reserve load. (The capacity is less than the actual load)

My post was an answer to a question about what I plan to do to get the max life for my tires.

[Mitchyb]

Originally Posted by SeattlePirat

Or you can live in Washington State on the west side where the sun never shines

You know call it crazy but that's not a totally crazy point In my view here In bc we don't get the heat the temperature is very steady I would hedge to geuss that climate is a big factor to tire life

[SteveSkinner]

Came back to Australia and noticed my wife's car tires were split around the bead, split around the outside of the tread.
I suspected someone had been driving the car with low inflation.
They were Pirelli P7 low profiles.
No at 5 yrs they had failed but the Brigestones on the back were not perished.
Reality is 5 yrs retire your car tires especially low profiles
At 7 yrs retire your Motorhome/truck tires it will give you peace of mind and keep the economy turning

[Dogpatch]

I just had new Hancook - AH12's - 275/70r22.5 tires put on my Beaver. $2450 out the door, all in.

Nice ride and no issue at any speed for the 2200 mile trip home.

[docj]

Originally Posted by dogpatch

I just had new Hancook - AH12's - 275/70r22.5 tires put on my Beaver. $2450 out the door, all in.

Nice ride and no issue at any speed for the 2200 mile trip home.

Just curious, where did you buy them? Are they Load Range J? I've used Hankooks on my cars for several years and have been very pleased with them.

[Dogpatch]

Originally Posted by docj

Just curious, where did you buy them? Are they Load Range J? I've used Hankooks on my cars for several years and have been very pleased with them.

I had the dealer arrange it when I picked up the coach.
They were purchased at Purcell Tire in St. Louis. These are a load range H. The price was the dealers price and from what I can tell, not bad compared to what I've seen for the same tire. The Toyo M154's I put on previous coaches cost me $3250. I liked the Toyo's but couldn't get them in St. Louis in time.

I'm pleased with the Hancook AH12's though and now have another tire I like to choose from.

[bgsc]

Time to replace them we had an inside dual blow out on our coach last fall it did $4,000.00 worth of damage to the coach plus the cost of a new tire, our coach is a 2008 and the date code on the tires was 2007. Had the 5 tires replaced with the Michelin XZE 275/80R 22.5 my cost per tire installed was $590.00 that was done in Ontario Canada in the US FMCA have a good program with Michelin the cost there was $540.00 plus installation. We now feel a lot better riding on new tires.

[Tireman9]

Originally Posted by bgsc

Time to replace them we had an inside dual blow out on our coach last fall it did $4,000.00 worth of damage to the coach plus the cost of a new tire, our coach is a 2008 and the date code on the tires was 2007. Had the 5 tires replaced with the Michelin XZE 275/80R 22.5 my cost per tire installed was $590.00 that was done in Ontario Canada in the US FMCA have a good program with Michelin the cost there was $540.00 plus installation. We now feel a lot better riding on new tires.

IMO
7 years is too old for the cause to be a basic design or manufacturing defect assuming you had many thousand miles on the tire.

7 years is too young for just age as the cause of the failure.

I suspect some other external cause such as puncture, impact or valve related issue.

If valve or simple puncture, your TPM should have issued a warning way before the tire started to come apart.

Now an impact can cause damage that does not result in immediate air loss till the sidewall finally does fail and the hole is large enough to let all the air out in less than a minute. This post shows how an impact can damage a tire but not cause immediate failure.

Learning the real reason for a tire failure can be a challenge, especially if the tire has been driven on after it failed which I suspect happened in your case due to the level of damage.

Glad you are happy with your new tires.

If you are going to Redmond, OR in Aug stop in at my seminar on tires.

[kkriepke]

Well, after I did a really close inspection of the 'steer' tires, I found many, many cracks in the tread area and inner sidewalls. Some were several inches long. Many were in the area where tread separation could occur, so I decided to change tires. I ordered a set from my local Michelin dealer, A&E Tire in Commerce City, CO thru the FMCA tire program. The XZA3+ tires arrived in 3 weeks and all were no more than 2 months old.

Installation was done in 1.5 hours and the price including rim inspection, mounting, spin balance, and new EZ access metal stems was only $387.30. Quite reasonable IMHO. They showed me several cracks on the inside casing of the old tires and verified that the tires had reached their practical end of life.

I have not yet gotten the bill from FMCA so I don't know what the tires cost will be... it has been over a month now so the bill should show up soon I would think...

Ken