# Need to be schooled on how tire 'size numbers' work.....



## ACA L&L (Jan 5, 2007)

ok I dont need to know which tire to buy,I need help determining the tallest tire i can buy for my truck, I thought i had the size thing all figured out then i read something that made me question what i thought i knew. I have 2 trucks, 2011 dodge 2500(stock size says 245/75/17...........chevy 3/4 ton says 265/75/17..........I want to buy a taller size tire, not a wider tire, i thought the 285/75/17 would be best choice for all the trucks, but i read that some people were using 235/717.............What number or numbers determine the height of the tire, i want to buy taller/skinnier tires for year round use/ plowing/towing/driving/ etc. Can some one school me on how to order tires online, i refuse to pay Discount tire prices anymore for something you can buy at treadwright for less than half the price........


----------



## kimber750 (Sep 19, 2011)

ACA L&L;1387153 said:


> ok I dont need to know which tire to buy,I need help determining the tallest tire i can buy for my truck, I thought i had the size thing all figured out then i read something that made me question what i thought i knew. I have 2 trucks, 2011 dodge 2500(stock size says 245/75/17...........chevy 3/4 ton says 265/75/17..........I want to buy a taller size tire, not a wider tire, i thought the 285/75/17 would be best choice for all the trucks, but i read that some people were using 235/717.............What number or numbers determine the height of the tire, i want to buy taller/skinnier tires for year round use/ plowing/towing/driving/ etc. Can some one school me on how to order tires online, i refuse to pay Discount tire prices anymore for something you can buy at treadwright for less than half the price........


If I remember correct 245 would be the width. Now the 75 is a percentage of the 245 which is what the side wall height is. Of course 17 in the wheel diameter. This is until you get to tires that use the actual measurements for tire size. 33x9.5x15, this would be 33 inches tall, 9.5 inches wide on a 15 inch wheel.

This was how it was explained to me many many moons ago.


----------



## ACA L&L (Jan 5, 2007)

kimber750;1387173 said:


> If I remember correct 245 would be the width. Now the 75 is a percentage of the 245 which is what the side wall height is. Of course 17 in the wheel diameter. This is until you get to tires that use the actual measurements for tire size. 33x9.5x15, this would be 33 inches tall, 9.5 inches wide on a 15 inch wheel.
> 
> This was how it was explained to me many many moons ago.


Thank you.....so not using the actual tire numbers ....would a 235 85 17be taller than a 285 75 17? Or does the 285 make it wider and taller? if it does then im on the right track, if not, i may have to go to discount and fake buy some tires, then come home and order them.....Thanks for feedback


----------



## 87chevy (Mar 11, 2009)

285 is gunna be a 33, almost a 34. where the 235 is a 32.


----------



## cubanb343 (Dec 13, 2007)

First number is the width. Second is the aspect ratio which i believe is percentage of the first number gives you the sidewall. and obviously third number is rim diameter.

285 / 75 / 17 would be 285 mm = 11.2 inches width of tire, 75 percent of 285 is 213.75mm which equals 8.42 inches. 8.42 x 2 is 16.84 plus 17 equals 33.84 inches tall, by 11.2 wide i think.

235 / 85 / 17 would be 9.25 inches wide, 32.7 inches tall. Confusing? You bet


----------



## 87chevy (Mar 11, 2009)

cubanb343;1387189 said:


> First number is the width. Second is the aspect ratio which i believe is percentage of the first number gives you the sidewall. and obviously third number is rim diameter.
> 
> 285 / 75 / 17 would be 285 mm = 11.2 inches width of tire, 75 percent of 285 is 213.75mm which equals 8.42 inches. 8.42 x 2 is 16.84 plus 17 equals 33.84 inches tall, by 11.2 wide i think.


11.6 Thumbs Up get it right. jeez.. haha jk man, close enough. Hopefully he gets the point.

It's safe to assume a 285 is gunna be right around 33 inches. a 265 is around 31-32


----------



## IMAGE (Oct 21, 2007)

ACA L&L;1387182 said:


> Thank you.....so not using the actual tire numbers ....would a 235 85 17be taller than a 285 75 17? Or does the 285 make it wider and taller? if it does then im on the right track, if not, i may have to go to discount and fake buy some tires, then come home and order them.....Thanks for feedback


A 285/75/17 will have 213.75mm of sidewall (285x.75). that sidewall x 2 = 427.5mm of tire. There are 25.4mm per inch. So 427.5 / 25.4 = 16.83" of tire. Then add in your 17" of rim. and you get a tire 33.8" tall

A 235/85/17 will have 199.75mm of sidewall (235x.85). that sidewall x 2 = 399.5mm of tire. There are 25.4mm per inch. So 399.5 / 25.4 = 15.73" of tire. Then add in your 17" of rim. and you get a tire 32.7" tall

The 285 tire will be about 2" wider than the 235 tire. I very much prefer the 235 over a 285 for plowing. The skinny tires bite better and handle better in snow/ice.


----------



## IMAGE (Oct 21, 2007)

damit, I got distracted while I was typing and you guys beat me too it!


----------



## ACA L&L (Jan 5, 2007)

I got it!! At least the part about the 285 being taller and wider than the smaller skinnier tire....I have a new respect for the corner tire shop....


----------

