Automotive Maintenance a Guide to Tire Sizes
So does one size fit all, or does size really matter when we begin to talk about rubber. I am talking about tires and their many sizes and shapes. The real mystery about understanding tires or the little bit of letters and numbers that are imprinted on them, is not such a mystery if you know what the numbers and letters mean.
Lets take for example P195 40 R15. M+S
This might not make much sense right now but let me break down the numbers to bring the whole subject to light.
The first number 195; is the width of the tire. This measurement is in the form of millimeters which determines the amount of coverage of rubber on the surface is present. The letter before the number is going to designate the type of tire.
The second number in this case 40; is the profile number. The lower the profile is the shorter the sidewall height will be in respect to the aspect ratio on the tire. This simply means the amount of rubber between the outside edge of the wheel and the surface, or road. This being said, we can ask which profile is better the low profile or the high profile. There have been studies to show that neither profile has any subsequent difference in wearing, but due to the fact that most low-profile tires are high performance they have a tendency to wear out faster.
Next we have the last number R15 which is the actual tire size. This determines the actual size of the tire which also needs to match the specific size of your rim.
Another letter or addition that can be visible is the conditions the tire is suited to drive, for example M+S would mean the tire is suited for all-season driving.
Does one size fit all? This absolutely false, due to tire size is dependent on many factors. It would be a huge mistake to assume your tire choice will suit any rim, or wheel well depth, so it is always recommended to refer to your manufactures specifications before purchasing a new set of tires.
Another good thing to know about tires is that regardless of your size, profile or speed rating, the real important thing to understand is the grip factor. When selecting tires we should always consider the tires ability to hold the road over any other cosmetic aspects. There are many different makes and breeds of tires, but when factoring conditions like wet roads, snow, ice, and even gravel, we must choose our tires to ensure the best handling of any given condition. If you live in the North, but want a low profile high performance type tire, consider a winter tire for the snow laden seasons, and reverting back to your high performance tires once the snow and ice melts. Don't get caught with a tire that doesn't match the surface or you might just be spinning your wheels, or even worse!
