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Tires

What's in a Number? (What Tire Numbers Mean)

Jan 01, 2021

You've probably never paid much attention to the writing on the sides of your tires, but they contain a wealth of information.  There's a long combination of letters and numbers that can tell you a whole lot about what tires your vehicle was designed to be riding on.  Let's check out this example found on an SUV: P245/70R17 108T.

The first letter, P, means it's intended for passenger vehicles.  If there's no letter, it means it's a metric tire.  If there's an LT at the beginning or end that means a tire designed for light trucks.

Moving on to our example, the 245 shows how wide the tire is in millimeters from sidewall to sidewall.  The number that follows in our example, 70, means the height of the tire is 70% of its width.  The letter after that in our example, R, describes the type of tire (on this vehicle, radial).  Following that is the diameter in inches, in our SUV example, 17 inches. 

How much load the tires' sidewalls are designed to take is what that next number is all about (108 in our example).  The higher the load index, the more weight the sidewalls can take.  And the last letter is the speed rating of the tire, in our example, T.  The further along in the alphabet that letter is, the higher its speed rating.  So now you know what those letters and numbers mean.  But why are they important?

When you are getting ready to replace those tires, those numbers are telling you what the original equipment was when your vehicle was new.  Sticking with the same rated tires is always a good idea.  If you don't know what you're doing, trying different sized tires and wheels can cause real issues when it comes to performance and safety, considering all the computerized systems now found on vehicles.  When in doubt, consult your service advisor when it comes to buying new tires.  He or she knows what those tire numbers and letters mean… and a whole lot more.

The Car Doctors of the Antelope Valley
226 West Avenue I
Lancaster, California 93534
661-949-8484
http://cardoctorsav.autovideotipsblog.com



No Fountain of Youth (Aging Tires)

Dec 13, 2020

Can you think of anyone who enjoys aging?  Wrinkles where you don't want them, gray hair, eyes that won't focus any more, no stamina. 

Believe it or not, your tires age, too, and they don't get better the older they get.  And here's the important thing to know, even if they can still pass a tread depth test, they may simply be too old to be safe 

Here's the best way to understand this.  Have you ever found an old deck of playing cards with a rubber band wrapped around them?  Try stretching the rubber band.  SNAP! It's all cracked and brittle.  And you haven't stressed that rubber one bit since the time you put them in that drawer.

Now you know what's happening to your tires.  Rubber ages.  Just like us, the day we come into the world, we start to go downhill (no pun intended).  Oh, engineers are able to make a tire last longer than ever before.  But that gas that keeps us alive—oxygen—seems to love to chemically mix with some components in rubber.  Oxidation causes rubber to become hard and brittle.  The rubber band test.

Is there an age test that can tell you when a tire is tool old to roll? Well, not really.  They don't all age the same.  Hot climates can make tires wear out more quickly.  Some experts say a tire can last up to 10 years but should be inspected every year after the age of five.  Others say tires should have an expiration date at six years old.

Since no one would ever ask a tire its age, how do you know how old one is? Believe it or not, tires made after the year 2000 have a date code stamped on either the inside or the outside of the sidewall.  It's a four-digit numbers; the first two tell you the week, the second two tell you the year. So if it has the number 1916, it was made in the 21st week of 2016. 

Another way to find out if your tires still have enough life in them is to have your vehicle service facility inspect them.  They look for signs of age, such as developing cracks in the rubber, the condition of the sidewalls and, of course, that old standby: tread.  If it's time to "retire" them, discuss options with your service advisor.


The Car Doctors of the Antelope Valley
226 West Avenue I
Lancaster, California 93534
661-949-8484
http://cardoctorsav.autovideotipsblog.com




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