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Monday, September 3, 2012

Tire Covers - Do they do any good?

Very interesting test by an engineer on whether using tire covers is a good idea. A link to Roger's piece at follows:

June 16, 2011
I have seen some posts and comments about tire covers. One post caught my eye.

The owner was complaining about the cover degrading in the sun so he was of the opinion the cover wasn't worth the cost. I have to wonder how he failed to properly interpret the proof that the cover was protecting his tires. How would he answer the question: Which would you rather have degrade due to being in the sun? Your tires or the low cost cover?

As an Engineer I always prefer to have data rather than just someone's opinion. So I set up a quick test on my own RV.

As you can see I have covers for my tires. They were the second purchase after buying my rig. The first was a Tire Pressure Monitor System.

The Test
With one side of the RV in full shade I checked the temperature of the side of the unit.
You can see I recorded 85.1°F.

Then I took the temperature of the side of the RV in the full sun.

Here we see 107.9°F

Next the temperature of the white tire cover in full sun.

We get 98.6°F
I believe the cover is cooler than the side of the RV because air can circulate behind the cover.

I then removed the cover to see what the tire temperature was under it.

We see 99.5°F
Only 1 degree hotter than the cover.

I then waited 30 minutes to see how hot the black tire got while in full sun.

We see the black tire was at 136.1°F.

There are three things that can "kill" your tires. Ozone, UV and High Temperature. The Ozone & UV directly attack the surface of the tire making it crack when flexed. Temperature works no only on the surface but deep down inside the tire structure.
Increased temperature causes continued and accelerated chemical reaction which "ages" a tire faster than when the tire is cool. A rule of thumb would be that the rate a tire ages doubles with every 18°F increase in temperature. We can see the result of old rubber on the surface. What we don't see is the more brittle rubber of the internal tire structure. As rubber gets more brittle with age it also looses strength.

NOTE Overload and Underinflation can overheat a portion of a tire to the point the rubber and reinforcement materials loose all their strength.

Based on my simple test it would appear that by covering my tires I am significantly reducing the artificial aging for all the daylight hours my RV is parked and the sun is out. If I didn't have covers my tires would be "aging"FOUR times faster than with the covers in place.

I don't have black tire covers so can only guess at their temperature. While they may provide protection from UV I would be surprised if they can offer much temperature protection.

So I will let you answer the question of Tire Covers being a good investment or not.

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