What the numbers for tire sizes mean, really dumb question..

275 is the amount of millimeters from outside rim mounting surface to inside rim mounting surface. (think of this as tire width...sorta)

60 is the ratio of the 275 width of sidewall rubber to tread rubber. So 60% of the rubber is sidewall, 40% is tread. So an 80 series tire is a taller/skinnier tire and a 30 series is a wider/shorter tire

15 is the size of the rim (in inches) that the tire is designed for.

All these numbers work together. For example.. a 275/50/15 tire is not as tall as a 275/50/16 tire. This is because the sidewall is the same height, but the rim is larger making the overall tire larger.

Here's a great website for what you want to do: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7

70_Nitrous_Eater said:

275 is the amount of millimeters from outside rim mounting surface to inside rim mounting surface. (think of this as tire width...sorta)

60 is the ratio of the 275 width of sidewall rubber to tread rubber. So 60% of the rubber is sidewall, 40% is tread. So an 80 series tire is a taller/skinnier tire and a 30 series is a wider/shorter tire

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these two are wrong.

275 is the section width of the tire when inflated on its design rim width. the section width is measured at the widest point of the tire, the center of the sidewall bulge. in the case the section width is 275 millimeters.

60 is the aspect ratio. this tells you how tall the tire is from the bead to the top of the tread, in this case 60% of the section width.

every tire manufacturer uses a slightly different tread width on their tires, so there is no actual measurement of tread width.

there are a few other numbers and letters you need to be aware of;

traction

temprature

treadwear

load index

traction and temprature use an alpha character IE: a b or c
the higher character the better traction or temprature resistance. a is higher than b.

treadwear is indicated by a number, 100-400 generally
the higher the number the longer wearing the tire.

load index tells you how much weight the tire can handle at its rated tire pressure, and at a specified speed, usually at the speed rating of the tire.

the speed rating is usually included in the tire size. example;
275/60R-15 H
the speed rating is not like the others where the higher the better. an H rating is higher then an S rating for example

sometimes the speed rating is included in the load index, example 92H

any tire shop you go to should have all the information you need to decode the numbers on a tire.

MustangMatt1966 said:

thanks guys, that really helps! so what tire do you recomend for a 1966 coupe on a 15 by 7 rim that fills the wheelwell without any modifications?

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my mustang and my falcon both will get a 205/60-15

Most tire manufacturers have tables on their websites that tell you what size's fit on what rims, tire height, width, speed rating etc.

example: BFGoodrich Radial T/A, this is from tirerack.com

http://www.tirerack.com/tires/Spec.jsp?make=BFGoodrich&model=Radial+T/A

MustangMatt1966 said:

thanks guys, that really helps! so what tire do you recomend for a 1966 coupe on a 15 by 7 rim that fills the wheelwell without any modifications?

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a 235/60/15 or maybe a 245/60/15 depending on the offset

MustangMatt1966 said:

Ok guys, this is a really dumb question and I feel dumb for asking it, but when someone refers to their tire sizes, say for example a 275-60-15, what do these numbers mean...I am getting 2 15 by 7 rear wheels for my car, and need to know what size tire will fit nice on these and be wide...sorry for the dumb question again amnit:

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There are no dumb questions here at StangNet. Sometimes there are some dumb responses.

HistoricMustang
www.historicmustang.com

well i can tell you from pratical experience that a 205/60-15 fits real nice on the 15x7 rim, and that the kuhmo tires i have on my fairmont, and had on my old grand marquis, work real nice thank you, and are not expensive. i got my kuhmo's from tire rack.com for $42 ea, plus $37 for one day shipping for four tires. total paid $205.