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Tuesday, July 26, 2016

Unhappy with the quality of the tires on your RV?

Post on an RV forum where there was a thread about "poor tire quality". There was this interchange:

"ST tires may be approved by government regulatory agencies. They still have a 3 year life. When I had tread separations, documenting the event for a government agency was not my focus. Getting new tires and going camping was my focus."

I responded...

First off, there is no government agency that is "approving" tires. The DOT does publish performance regulations that the tire company is "certifying" all the tires they make are capable of passing the requirements. If a tire company wants to game the system and make tires that do not meet the regulations there is no way for the DOT to learn this unless they conduct an investigation. The DOT will not start an investigation without justification or they could be accused of wasting taxpayer money. A major part of that justification is the number of complaints on file.

Sending a complaint to NHTSA not being your focus after a tire failure is clearly understandable. But if you never bothered to record the DOT serial number (S/N) of your tires and simply disposed of them, then you will never be able to file an actionable complaint.

No actionable complaint =>  No Investigation =>  No findings of low quality =>  No recall => No improvement in quality of ST tires.

IMO there are some in the business of low cost tire production and sales who know the average RV owner will never complain. They are playing the odds that there will never be a recall, so with no future penalty there is no incentive to improve quality.

Even if you can't focus on filing a complaint at the time of the failure you certainly could file it a few days later, but that would mean you had made the initial effort to record the S/N for your tires.

If RV owners can't make that minimal effort of recording the S/N and spend the few minutes it takes to file a complaint,  I simply do not understand why they feel they can take the moral high ground and complain about poor tire quality.

Filing a complaint only takes a couple of minutes. Maybe less time than what many are willing to spend complaining on an RV forum.

Have you recorded the DOT S/N for your tires?

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Tuesday, July 19, 2016

Another post on Cold Inflation Pressure and "Ambient" temperature.

Some clarification from a tire engineer. 

First off, I am not going to address what the correct Cold Inflation Pressure ("CIP") is for your RV. We will assume you have read my other posts on how to learn that number. If you haven't, simply look at the list of labels on the left side of this blog and you can review them.

There are different guidelines for Trailers vs. Motorhomes. I want to focus only on setting the CIP

Some people want to refer to a Temperature compensation chart.

Tire Rack was off a bit till they updated their tech page last year after my input. Also Wikipedia definition for Cold Inflation Pressure was also almost correct till I added a clarification aimed at RV owners. The 1 Psi for 10 F is OK if your base inflation is near 40 psi but many RVs use 80 to 110 psi.
The correct "Rule of Thumb" to use is 2% for each 10F.

Tire pressure is not based on any laboratory standard temperature (some claim 70 F) but is based on the tire not being warmed from either use, i.e. being driven in previous two hours, or from being in the Sun for previous two hours. Even partial sun can affect the reading.

Classical "Temperature in the Shade" is the "Ambient" tire engineers are talking about. Not temperature in a theoretical laboratory.

So regarding a situation of setting the pressure when the tires and air is 50 F. That would be fine and we would expect the pressure to increase by about 8% if the Ambient increased to 90 F even without driving or Sun exposure.

It is correct to say, "The ONLY time to check CIP is FIRST thing in the morning BEFORE the day's temp has had a chance to increase and BEFORE the sun has had a chance to shine on the tires and BEFORE you have used the vehicle."

However, if you are driving from the campground on top of Pike's Peak and stop for lunch for two hours in the shade in Flagstaff where it is 90 and check your air, you might find a change of a few psi. You could adjust your pressure before continuing to Phoenix, where it is 120 F, but I don't bother to adjust inflation by the 1 to 3 psi variation I observe day to day. In my mind that is too much work.

NOTE: My personal CIP is  75/80  F/R on my Class-C MH.  Both of these pressures are more than 10% above the minimum pressure needed to support the measured load on each tire so I have a "cushion".

I usually wait till I am home and am getting ready for the next trip before I adjust my inflation to my personal CIP, so I simply monitor the running inflation pressure which goes up and down as ambient temperature, driving and Sun exposure changes the inflation. My TPMS will warn me of air loss, so all is good as I motor down the highway.

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