Wednesday, July 6, 2011

"The Learning Corner or SIY" - Part Two

In this installment of The Learning Corner (aka SIY: Stephen It Yourself), I will be discussing tires.  Having just purchased some myself, for our Ford Explorer, I though some of you might like to hear some facts and opinions about this often expensive and sometimes overwhelming purchase.  When purchasing tires it is always best to do your research.  Remember, tires are the only link between your car and the pavement.  If you purchase a tire that is of poor quality or of incorrect type this can pose a serious safety and handling problem with your vehicle.  

Choosing a tire can be a very difficult decision due to the large amount of options that are continually changing.  One thing you need to ask yourself is how you intend to use your vehicle.  Is it a truck that goes off road, are you going to be doing performance driving in your car, or is it a basic everyday vehicle that needs good traction in multiple conditions?  For most, all season or touring tires are a good choice for a car or van and all season and all-terrain are good choices for trucks and SUV’s.  Don’t go overkill with the all-terrain unless you need it.  These tires tend to have shorter tread life and are generally loud on the highway.  I suggested asking the opinions of friends, employees of the tire shops, and looking online (such as for reviews on tires to help guide your choice.  Also if you are happy with how your last set performed stick with the same tire.  No need to change how your vehicle handles if you do not feel the need for improvement. 

Tire Size:
Most auto manufacturers have a tire size specified for your car. Some may have a few options with a primary suggested size.  It is always best to stay with the suggest tire size.   Tire size looks just like some sort of code to most but I’ll break it down below.

Here is the tire size for the Explorer: LT235/70R15 102T M+S

In front of the size of the tire there is a letter.  This is for its application
·       P – Passenger
·       LT – Light Truck
·       ST – Special Trailer
·       T – Temporary (spare tire)

The actual size of the tire is expressed as series of numbers and letters ie. 235/70R15
·       235 – this first part is the tread width in millimeters
·       70  - this middle number is called an aspect ratio.  This is the ratio of tread width to sidewall height.  The larger the number the taller the sidewall.  Tires with low numbers like 35 and 40 have very short sidewalls and are found on large diameter wheels.
·       R – Radial tire (almost every automotive tire made today is a radial tire)
·       15 – This is the rim diameter in inches in this case 15 inches

Next is the load and speed rating, for our example this is 102T
·       102 – The higher the number, the higher the load rating (In this case its 1000kg or 2205 lbs per tire)
·       T – This is the speed rating.  The lower the letter of the alphabet, the higher the speed rating of the tire.  There were a few new ratings that were added and those are higher in the alphabet.  Best to stick with the manufacturer’s suggestion or with the tire installers.  This is the maximum speed that the tire is rated for traction, handling, and possible failure.

Other letters, such as the M+S:
·       These are different ratings for things such Mud and Snow
·       There are sometimes letters for white sidewalls, white letters, and other tire options.

Tread wear ratings
·       This is a grade given to rate the tread life of a tire. (ie: A, B, C…)  The higher the grade, the longer life expectancy.  Lower grades will not last as long and are typical on performance tires which are usually softer and sticker for better traction.

Tires need to be replaced when there is 2/32 of an inch of tread left or less.  This is the minimum to pass inspection.  You can easily gauge the tread depth by placing a penny upside down in the tread of the tire.  If the tread covers part of Lincoln’s head then it’s ok.  If the top of his head is visible then the tires need to be replaced.  Also if you notice a lot of cracking on the tire or are just suffering from poor traction or tread wear it’s a good idea to replace your tires.  Always replace at least two at a time but it’s best to replace all four.  The average life for most all season tires is 40,000 to 70,000 miles.  Some performance tires will only last 10,000 to 20,000 miles. 

It is a good idea to rotate your tires periodically.  Some oil change places will do this when you come in for an oil change.  Also some tire shops will offer this service for free after you get tires with them.  Its best to rotate every 6,000 to 10,000 miles.  This helps the tires wear evenly.  Another way to promote even wear is to have your car aligned periodically.  This needs to be done after any suspension or steering components are replaced or every two years. 

Proper tire pressure is a must for tread life and safety.  The proper pressure for your vehicle is located on a sticker, usually inside the driver’s door.  Always go by this and not the maximum pressure stamped on the side of the tire.  Always check the pressure when the tires are cold, before driving as the pressure given is a cold pressure.  After you drive the pressure may increase giving an incorrect reading.  A tire that is low can decrease gas mileage, cause increased wear, and an increase in temperature which can lead to tire failure or a blow out.  I usually recommend using a dial type pressure gauge or a digital one because these tend to be more accurate the slide style pressure gauges.  It is best to check your pressure at least once a month but every two weeks is best, especially if you are doing a lot of driving or hauling.

Consider buying your tires online.  I used and was able to save a decent amount.  Between a lower price per tire and no tax I was able to save even with the shipping costs.  Also shop around for shops to mount and balance.  Wal-Mart is the one of the cheapest.  My only problem with them and any tire shop is how tight they tighten the lug nuts.  Sometimes they torque them on too tight or unevenly which can make them difficult to get off or cause the brake rotors to warp faster.  If you are feeling handy then having a cheap torque wrench and checking this yourself after you get the tires installed is a definite plus. 

Happy Shopping,

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