question about tires

[MarkMoore]

ok.... thinkin about gettin some new rims, and of course new rubber to go with it. Just wanna check on something. take the numbers 205/40/17 for instance... the 2nd # is the offset (40), and the 3rd # is the size of the wheel (17"), right? okay, so what's the 1st #? Is it the thickness of the tread or something? thanks in advance......

[VampireSix]

I believe its the overall diameter of the tire, and the second number is the size of the sidewall

[rayrrod]

no thats not it
here is it

the first number ie 205 is the tires width in mms
the second number is the sidewall size, in percentage of the tire wide, ie 205 40 means the sidewall is 40 percent of 205 mm. ie 205 mm times .40
the last number is the rim, ie wheel size, diameter in inches

so first number in mm
second number in percentage
and third number in inches
there are other specs.
ie treadware, traction, temperature, speed rating, etc
so i can see how some of us can confused.
note that none of the above has anything to do with offset
Offset is a functin of the Wheel not the tire.

[lakersfan1]

Tires aren't offset, anyways........... wheels are.