UV protection for tires. Still important, and the facts haven't changed in 7 years

 This is a reprint of a post I did in 2014. The facts and data have not changed.

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 one day in April. 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.

BOTTOM LINE
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.

##RVT1006