What do tire size numbers mean?

[redneckgames]

for instance 245/75 ? I believe the r is the rim size right? I am needing to find out how tall this tire is for part of a homework assignment due tomorrow. I think that 75 pertains to the height but is it in Centimeters or something? Please help me understand this. Thanks guys



Brad

[redneckgames]

lt 245/75 r16 to be more specific

[largekid]

245 is the width, 75 is the percent of sidewall or something like that, r is a speed rating...they have a few with z being the best and the last size is the rims size....let me find a link for you



edit:



he ya go

auto.howstuffworks.com/tire2.htm (http://auto.howstuffworks.com/tire2.htm)



<font size=1>[ This message was edited by: largekid on 2005-07-24 17:24 ]</font>

[grimpuppy]

p245/75r15 - P = Pasenger, LT would be light truck/ 245 is the width of the tread in millimeters/ 75 is the height of the sidewall in percentage of the width. For example, this tires height from the bead to the tread would be 183.75 mm. (75% of 245) This is for 1/2 the tire. Now to get total height take 183.75 x 2 = 367.5 mm take this number and divide by 25.4 (there are 25.4 mm in one inch) and you get 14.46 inches (we will round this to 14 1/2 inches) now take 14 1/2 inches total sidewall heigth plus 15 inches (r15 in the tire number) for the size of the rim and you get a tire that is 29 1/2\" tall.

Hope I explained it clear enuff to understand.

[tracker]

the r stands for radial . the speed rating is located in a different section of the sidewall.



245 is width in millimeters

75 is the aspect ratio ( sidewall height in relation to tire section width. not tread width. big difference.

r is for radial

15 is the rim diameter.



section width is sidewall to sidewall when mounted and inflated on the proper wheel

[redneckgames]

thanks guys. That is great! It always pays to have connections. thanks again.

Brad

[mzoomora]

I always thought the 245 is the measurement from one bead up the side and around to the other bead, then the 75 is the percentage of that that is sidewall (so 25% tread width). That is why a 75 is taller and narrower than a 60 series tire.

[grimpuppy]

You are right tracker, it is section width....

Tire Number Breakdown (http://www.sbcc.ca/tech/tires1.htm)