Thursday, August 29, 2013

Are your tires fresh? A quick guide to tire aging: Diagnosis and Prevention

   It seems these days fresher is always better.  Unless you're talking about wine or cheese, that is probably a true statement.  You hear people saying things like "check out the new deli, they have the freshest ingredients!", or "you have got to take a look at the new store in the mall, they have the freshest styles!". Febreeze has made millions by giving our homes that "fresh" feeling.  It is obvious that in society today we value freshness.  So, when it comes to tires, is fresher better?

   I'm sure you've all heard that tires are good for 5 years and after that should be replaced whether they are wore out or not.  I've seen news outlets showing how to read the date on a tire and telling people to check this date and make sure their tires have a current date when they buy them.  While this is good advice in general, in the real world things are not that simple.  Many different factors determine how old a tire is when you finally put it on your vehicle and also the rate at which is ages.

   Just in case any of you do not know where to look to find the age of your tire, I'm going to give you a quick tutorial.  If you look at the sidewall of your tire down close to the rim you will find the letters DOT followed by a series of numbers and letters.

The first 2 letters are the plant code.  This tells you where the tire was built.  73 is the plant code for the Toyo tire plant in White, Georgia.  This tire is a Nitto Terra Grappler which are built by Toyo so that makes sense.  You'll notice 4 numbers at the end of the DOT number and that will tell you when the tire was built.  If you don't see 4 numbers at the end of the DOT number then look on the other side of the tire as the date is only stamped on 1 side of the tire.  In the case of this tire, 0913 stands for the 9th week of 2013.  If your tire only has 3 numbers, such as 158, then it is from the 90's and 158 would stand for the 15th week of 1998.

  Now that we know how to read a tire, I'm going to tell you how unimportant that is!  The only time I really worry about the date stamped on the tire is when a tire manufacturer issues a recall and they specify build dates that fall under the recall.  Looking at how your tire sidewall is aging is a much more accurate meter of the deterioration of a tire.

  Most tires we sell at the shop have a build date that is within 6 months of the current date.  This is fairly quick when factoring in shipping from the manufacturer to a main warehouse, then to a local warehouse, then having to sit in that warehouse while older stock gets moved first, then getting to us and sitting in our warehouse until someone comes in needing that size.  However, if your vehicle uses a less common size, such as a 285/35r18 that is used primarily on Mercedes sports cars, then it is very common to get a tire in that is a couple of years old.  They naturally sit in the warehouse longer before they are sold because they are so rarely sold.  Is this a reason for concern?  Of course not!  Tires that are stored in climate controlled warehouses age extremely slowly!  I've seen tires in warehouses that were 10 years old and are as good as new, while you will find tires on vehicles that may be 2 years old and look much older.  Outdoor elements, such as rain and sun, speed up the aging process significantly.  This means that vehicles that are garage kept or are not driven as often will age tires at a much slower rate than vehicles that are kept out in the elements all the time or are driven a lot.

  The first sign of tire aging is "dry cracking" in the sidewall.  This is the most exposed part of the tire and therefore is the first to deteriorate.  The sun deteriorates the rubber in the tire just like it does your skin!  After enough sun exposure they will start cracking, especially when water is thrown into the mix from rain or dew.  Look at your sidewall for small cracks.  The best place to look is between the rim and the ground where the sidewall is bulged out from being under the weight of the vehicle.  This exposes cracks that can't be seen when the tire isn't being flexed.
  Here is a picture of a tire that we pulled off that is 8 years old.

  You can see that this tire has no cracking in the sidewall and therefore is perfectly safe to run even though it is 8 years old!  We can see from the DOT number that this tire was built the 2nd week of 2005.  This tire was replaced because the tread was wore out but as far as aging this tire had years left in it.
   Here is a tire we can look at that is about 4 years old.

You can see this tire has some slight dry cracking in the sidewall close to the bead, but this tire is completely safe to run.  This is about average for a tire that is 4 years old and has quite a few miles on it.  The dry cracking is very minor and there are no places where you can actually see down into the cracks.
  Here is a picture of a tire that we took off that is 7 years old.

This tire has some extreme dry cracking in the sidewall and I would not consider it safe to run.  You can clearly see down in the cracks of the tire and there is no way to tell how deep the cracks go.  If the deterioration has gotten this deep into the sidewall it could weaken the walls to the point of blowing out, especially when under extreme heat caused by hot pavement during the summer or running the tire with low air pressure, or both.

  Tread depth is normally the main concern when looking at your tires to determine if they need replaced or not.  I'm not going to go into much depth on that because I think most everyone knows that tread depth is important.  I will stress that it is a good idea to get down and look under your vehicle at the tread on the inside of the tire. Most people walk around the vehicle and glance down at the outer tread, but the inner part of the tread wears much quicker on a lot of vehicles, especially if they are not aligned correctly.
Here is a picture of a tire where the outside tread looked great, but upon further inspection the inside tread was completely wore out.

I've seen people run tires like this, thinking that their tread was fine, until they blew out on the inside because they were wore out and the customer never looked at the inner part of the tread.
At what tread depth should you replace your tires?
  Some of our customers run their tires until they are about to pop!  Others prefer to replace them when they get to about 1/2 tread.  It is a matter of personal preference and if you have the means it is nice to have a new set of tires because they handle so much better, especially in bad conditions such as rain or snow.  While many have their own preference, and there is nothing wrong with that, a good general rule for everyone to go by is to look at the wear bars on your tires.  Every tire is made with these wear bars that are about 3/32's of an inch thick, basically telling you that after your tread passes this point your tire performance will be significantly diminished.
Here is a good picture of a tires wear bars.
You can see the small rectangular blocks in the 4 tread grooves. This tire still has a little ways to go before it gets to the wear bars.  Once the tread gets even with those bars, I would highly recommend replacing the tires!

How do you prevent premature aging of your tires?
  If tires are taken care of properly, they will almost always wear through the entire tread before you ever have to be concerned about tire aging.  Keeping your air pressure at the correct level will help.  Low air pressure causes the sidewall to flex more, which creates friction in the sidewall, which in turn creates a lot of heat.  This heat speeds up the aging process significantly.  Low air pressure or high air pressure also can cause the tires to wear too much on the outside or in the middle of the tread, reducing your tread life. In general, too little air causes the outer edges of the tread to wear faster and too much air causes the center of the tread to wear faster.  It is important to check your air at least once a month to make sure you are at the correct pressure.  When running the factory size tires on your vehicle, the factory recommended air pressure can be found on the placard in the front driver side door jam.

Here you can see that the recommended air pressure for my 4Runner with factory size 265/65r17 is 32 psi.
Whether you use regular air or nitrogen you will still experience pressure loss over time and it is important to stay on top of it.  At Custom Automotive we offer free air pressure checks anytime to help motivate customers to keep their tires aired up!
  Using a sidewall protector such as Mothers Protectant can help protect your sidewalls from deterioration.

 This product is available on our shelves at Custom Automotive.  We apply this solution to the tires on every car that comes into our shop whether it's for new tires, used tires, wheels, or just a rotation.  This helps moisturize the tire and protect it from the elements and also works great on interiors as well!  Smells great too!  Mothers has some great products and this is one I make sure I have plenty of at home!  I always follow a wash with a wipe down of the tires and interior with this stuff.

  So in summary, we've covered how to determine the age of your tires using the stamped sidewall DOT number, how to determine the condition of your tires by looking at sidewall cracking and tread depth, and how to prolong the life of your tires by keeping the correct air pressure and protecting your sidewalls.   Whether your tread wears out or your sidewalls deteriorate first, it is important to know what to look for when deciding when you should replace your tires.  If you have any concerns, it is always best to play it safe and ask someone you trust at a local tire store whether your tires are safe to run or not.

-Dustin Brown
Custom Automotive
Calvert City, KY

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