Wednesday, April 16, 2014

UV Tire protection. The FACTS

For some time I have been reading posts and advertisements about tire covers and UV protection. As an engineer I prefer FACTS over sales PR.

This investigation has taken more time than I originally wanted as I needed a reasonable way to measure UV and a day with full Sun.
 - Not something easy to find in NE Ohio-

As they say it all came together today April 16 2014. While it was cold 24°F last night and we had an inch of snow yesterday, it is bright and sunny today with only a little haze in the sky.

The test uses a Hawk2 UV meter. This unit is intended to help you judge how much sun you are getting while at the beach but I felt it would serve my purposes as we are not trying to measure an absolute value in milliwatts per square centimeter but a gross relative level of shielding of different materials used to cover tires.
If interested you can learn more about UV HERE and more about the UV Index HERE

I set up a test using my RV.
As you can see the UV of 6 years here in Ohio,  has pretty much destroyed the cheap vinyl used by Coachmen for the side decoration. Anyway the front tire has my normal white vinyl tire cover and there is a standard blue tarp, a roll of window screen and some black cloth backed vinyl similar to what is used in black tire covers.

I will show the meter readings for each "shield".
Full Sun gives a reading of 9 which is considered "HIGH"

 while in full shade the reading in zero.

Under the white cover the reading is zero

 and even under the black cover the reading is zero


  but the screen only reduced the UVI to level 5

I interpret these results to indicate that anything that is not in direct sun or that shields all direct sunlight will provide adequate protection from UV damage for tires.

I would not be worried about reflected light going under the RV to the back side of the tires as this is full shade. After all, tires are designed to be outdoors and we are not trying to protect tires for 20 years but only to get past a normal vehicle usage of 4 to 5 years to the 8 to 10 year range for many RVs. I would not consider open mesh as used in some "tire covers" complete protection but it is probably better than nothing.

NOTE I did not address the effects of heat on tires in this post. I did cover in THIS post and that clearly shows that white covers are the ones to use if you want to keep your tires cooler so they age more slowly.

If you want to protect your tires to give you the longest life possible you need to cover them with white solid covers such as cloth backed vinyl being a most reasonable option.

Friday, April 4, 2014

Another post on "Calculating" inflation to avoid a blowout or tread separation

It seems this will be a never ending task of explaining the "Why and How" of setting tire pressure on RVs.

Quick answer:
A. Trailers should follow the placard which is probably the tire sidewall pressure unless the size or type has been changed. BUT they should also confirm that no individuakl tire is overloaded due to un-balance.
B. Motorhomes should run the tire placard inflation unless they know the actual load on each tire.
C If a Motorhome owner knows the actual corner load he should consult the load inflation charts from the tire manufacturer for his brand in RV use. Select the inflation needed to exceed the actual load of the heaviest side of each axle and then inflate all tires on that axle to the minimum inflation plus 10%
D, If the tires on the trailer have been changes then the individual loads for each tire need to be known. Using load inflation tables select a tire with sufficient Load Range to carry that load and then set the cold inflation to the inflation shown on the tire sidewall.

Following the above should decrease the damage done by running a tire in overload and under-inflated condition. Hopefully this will also prevent Tread separations and Blowouts.

 I try and follow a few RV forums. Some are general and others are focused on a single brand or manufacturer. I would prefer it if I could simply post a few links to this blog so I don't have to spend time saying the same stuff over and over but some sites will not allow a link to this blog. (If you are reading this you should know that you can post a link to this blog but as the Blog writer I am not allowed to.)

Here is a recent post on a thread titled "Calculating the correct tire pressure". This forum is 95% trailer oriented.

 "A while back, we weighed our travel trailer on the CAT scales and got a total weight of 7,300 pounds, rigged for towing. Rigged for towing means with a full water tank, all of the misc. junk that we normally carry and weight distribution bars tensioned, but no clothing or food on board. On average, this translates to 1,825 pounds per tire.
Today, we were able to obtain individual wheel weights using portable scales. The results are (rigged for towing)

Left Front - 2,000 pounds Left Rear - 1,900 pounds

Right Front - 1,900 pounds Right Rear - 1,700 pounds

We can immediately see the unbalance in this trailer with the heavy tire having 27% of the total. We also learn that the TT was not fully loaded with food or cloths which would add more weight. We also see that when the owner simply used the original CAT scale weight he assumed equal weight distribution of 1825# per tire.

In this case the owner was not aware of the special loading seen by trailer tires.

In this same thread we found one owner that switched from ST235/75R15 LR-D to P23575R15/XL ! giving up about 23% of the load capacity. This thread is at 85 posts and counting.

Clearly the need for more knowledge on care and maintenance of tires in RV application is needed. I hope I have provided helpful information here and in my seminars. Please spread the word. If you have a specific question you can send a question to   Tireman9   at  Gmail  dot com