what does tread represent when purchasing a tire?

[SEVNT 9]

when purchasing a tire from say summit or jegs i know sec. means how wide the tire is, diameter is overall tallness, rim is recommended width of rim in inches, what does tread mean? how much rubber makes actual contact with road surface? meaning the sidewall is wider than the actual contact

I.E. (JEGS) m/t et street radials = 255/60/15

rim = 7.0
sec.= 10.7
dia.= 27.1
tread= 8.8

does this mean the sidewall is wider than the actual "footprint" by 1.9 about 1" wider on bothsides? 8.8 (subtract) 10.7?????

 

[boostinmalibu]

the sec.(section) width is the overall width of the tire, bulge and all, and the tread is just 8.8"s...so yea the tread is 1.9" narrower than the bulge of the tire

 

[SEVNT 9]

thanks, thats what i thought it was but wanted to be sure

so with a 7" wide rim (which i have) and that tire the m/t et street 255/60/15
i should have a bulge of about (10.7 sec. subtract 7.0 width of rim = total of 3.7 divide 2 =) 1.85 sticking out over each lip of rim correct?

i took some pictures of the current rims on the car that i would like to fit these m/t onto but i dont think the tires will fit on em without rubbing the frame according to my pictures or at least i think they wont i also measured from an outside lil edge of the rim which if i went to the flatest spot i would gain another 1/16-1/8 of an inch did i measure incorrrectly or from the wrong spot? would the tire have to be completly dismounted to get a "true" reading?

left side outter edge of rim to frame about 1 3/8"

another shot left side to frame

close up of left side

this is the bulge of the tire to edge of fender lip left side approx 1 3/8" camera angle displays wrong reading

this is another shot of outter edge of tire/rim to lip left side w/o tape measure

this pic isnt too clear but top of tire to bottom of fender lip left side

and these two are just the right side without measurements

 

[boostinmalibu]

whats on the car?....section width changes with wheel width...so you kinda need to know on what size rim that 10.7 section width was measured

 

[SEVNT 9]

on the car now are 235/70/r15's 15x7 5 spoke camaro rims seen in my avatar not for sure what the back spacing is on them, and the 10.7 reading is from jegs im guessing on a 7" wide rim cuz thats the other dimension given along with the 10,7 sec, 27.1 dia. 8.8 tread, 7.0 rim