by Athanasios Pantginis

Created on: January 13, 2007   Last Updated: April 23, 2007

Here are some basics about tire life, tread wear and performance. The tire is one of the biggest marvels of the 20th century just imagine the abuse they undergo everyday and still maintain a round shape, one of the most important safety features of the automobile and yet one the most neglected features and, an item when replaced is replaced most of the time on price and not performance. Lets get into it shall we?

First we'll start with tire size and performance rating. The size of the tire is very important to a cars performance. The manufacturer spends many man hours to find the correct size so altering it for appearance and or performance gains might not work to your best interest. Let me explain the size of a tire for example the most common method is P-Metric like 195/65R15 89H.
The 195 is the section width in millimeters from edge of one sidewall to another not the width of tread that is why certain tire of same size can appear wider if your looking at the tread.
The 65 is called aspect ratio. This measurement is the sidewall height in percentage to section width so in this case the sidewall has a height of 65% of 195mm.
The "R" means radial steel belted tire.
The 15 is the rim diameter in inches
The 89 would be the load rating (weight carrying capacity)
The "H" is performance rating commonly called speed rating (we'll get into this later on in the article).
Buying new tires should not be a punishment, like a major tire manufacturers slogan said, "...so much is riding on your tires". You don't have to buy the most expensive but avoid the cheapo's also. Purchase the correct size, do not change unless the manufacturer has an option, for example a late model base equipped 4 cylinder Honda Accord will come with the 195/65R15 89H but a loaded V-6 sport coupe will have a 205/60R16 89V so you can upgrade the width of your base tire to a 205mm but you must adjust sidewall height as well to 60 aspect ratio to compensate this is called the +1 -1 method, you will take a smaller percentage of a wider tire to achieve same overall rolling diameter. Going to a wider then recommended size can hinder traction in snow and rain. A wider tire will disperse the vehicle weight over a wider surface area making it easier for it to hydroplane which means the rain or snow is actually get underneath the tire and lift it off the asphalt. By the way thats not a good thing!
The performance or commonly known as speed rating is the letter at the end of the size in the example size above

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