I have a 1999 for ranger XLT. the tires are P225/70 R15 S100.
What do all those numbers mean exactly. and can the tires be interchanged with say P205 or P215 as i can find a better deal on these than on P225s?
This website shows what the S100 stands for (top speed and load capacity) but does the load capacity refer to each tire (giving 7056 lbs of load capacity for everything. the truck, the load and the passengers) the load just in the bed or what.
Using your example of a P225/70 R15 S100,
The “P” at the beginning indicates a passenger vehicle tire. “LT” is used to denote a light truck tire.
The 225 indicates the tire width, in millimeters.
The 70 indicates the sidewall height, as a percentage of the tire width. In your case, 70 percent of 225, which is 157.5 millimeters.
The “R” indicates that it is a radial tire.
15 is the wheel diameter, in inches. Thus, the overall diameter of your tire is (1525.4)+(2157.5)=696 millimeters, or 27.4 inches.
The S100 is, as you indicated, the load and speed ratings.
When did Americans invent the word ‘tire’ to use in lieu of ‘tyre’?
and who did it?
The question is more properly phrased as “Why did the Brits invent the word ‘tyre’ and who did it?”
According to the Merriam-Webster’s and dictionary.com sites, tire in the sense of a wheel covering, is derived directly from the Latin
Tyre, on the other hand, is listed as a “variant of tire²”
The proper tire width is based on the width of the rim. Usually you can safely go up or down one size (from a 225 to 215, or 225 to 235) but it is best to check with the rim or tire manufacturer to be sure. I would think a quaified tire dealer would be able to tell you what sizes safely fit our vehicle.
Since the sidewall height is a percentage of the tire width going a 215/70R15 will have a shorter sidewall then a 225/70R15, but the difference is small so it should not be a problem. Here is a great site for checking how the sidewall height and overall diameter will change with different size tires – http://www.miata.net/garage/tirecalc.html
but what does the load capacity mean? does that mean each tire can handle XXX lbs? if so then my current ones are probably rated too high. 4 100 tires = roughly 7000 lbs. better too high than too low though but its about a 4000 lb truck (from what i understand) with a 500 lb load capacity and i never tow with it.
thanks for your responses people.
That’s the maximum load each tire is designed to support. Due to many variables, such as inflation pressure, tire age, possible sidewall damage, etc., you should allow a considerable safety margin when selecting new tires.
http://www.yokohamatire.com/utspeed.asp
There’s also a substantial difference between static load and transient loads caused by (e.g.) hitting a rock or speed bump, turning, etc. At best, tire designers can only estimate a reasonable range of transient loads for a given static load. All the more reason to play it safe.
Not to mention static loads on uneven surfaces (such as going up into a driveway at an angle) which can significantly unload one or two of the tires, transferring the bulk of your 4000 pound truck’s weight onto three or even two tires.
I don’t think any reputable tire shop would mount tires that did not meet the minimum load range. It is possible that the truck came with different wheels or tires depending on options. As long as the tires you buy have a load range equal or better than that of the lowest rated tire that came on your vehicle you should be OK.