Tires

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

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.

PDR
1008 N. Cunningham Avenue
Urbana, Illinois 61802
217-367-9481
http://www.pdrauto.com

A Not-So-Straight Story (Vehicle Pulls to One Side)

A vehicle should travel straight down a straight road with the steering wheel centered.  But time and travel can take their toll and soon you may find your vehicle pulling to the left or right.  Those are not good signs and should be taken care of fairly quickly.

One thing that you should note is when this is happening: if it is all the time, only when you brake, only when you accelerate. If you describe these symptoms to the service adviser or technician, it may help them pinpoint the cause more quickly. 

Many things can cause a vehicle to pull to one side, one of which is that it's out of alignment.  If so, you could be doing damage to other components of your vehicle if you keep driving with it this way. If your tires show signs of uneven wear on the treads or if your wheels squealing, that is another clue.

Improperly inflated tires can also cause your vehicle to pull in one direction.  Your service facility can check to see if your tires have the pressure recommended by your vehicle's manufacturer. 

When steering linkage wears out or a wheel bearing goes bad, both of those can cause a vehicle not to track straight. When components age and loosen up, they can present a safety hazard and premature tire wearing. 

Maybe you notice the pulling only when you are braking.  That points to a failure of your braking system, perhaps a sticky brake caliper.

When your vehicle was brand new, it went straight unless you guided it on a different path. It's best to have it checked out if it is showing some of these symptoms.  It could save you money in the long run and you'll be driving a safer, better performing vehicle.  That's what they mean by steering you right!

PDR
1008 N. Cunningham Avenue
Urbana, Illinois 61802
217-367-9481
http://www.pdrauto.com