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Willshire 05-28-2013 10:15 PM

New wheels but so lost in terminology
Looking to purchase new wheel for my 2009 jk and would like to stick close to stock size maybe go up in tire size down the road. But i have no idea what the back spacing means or what size the stock rims are. All I know is that the tire size is 255/75/r17 thats all i know cause i read it off the door. Kinda of new to all the wheel stuff but love the look of the tire coming outside the fenders some.

If I buy new wheels do i need new tire pressure monitoring system or can I take the old ones from factory rims. Would want black rims. Have no idea which brand is good or bad like I said pretty new to the whole changing the rims over.

Right now I'm running firestone international a/t and there ok tire want something little more aggressive for the next time. Have to kill these tires off before I buy new again

Any help would be greatly appreciated


mdelguidice 05-29-2013 07:50 AM

No expert here, but maybe I can give a little help. The 255 is your tires circumference, the 75 has to with the height of your sidewalls and the 17 is your wheel size. The larger the first number the larger the tire. Discount tire direct has a pretty good tool to help visualize this. Do a search for Discount tire direct tire calculator.

Hope this helped a bit.


Marmotte729 06-08-2013 09:47 AM


I’m thinking of getting new rims and tires too. I agree, this is confusing. I have learned that in 255/75R17:

225 is the width of the tire thread in millimeters

75 is the height of the tire in % of width. So your tire from rim to thread is .75*225=169 millimeters.

R means radial tire

17 is the diameter of your rim in inches.

In my case, I have 16 inch steel rims now and would like to stick with 16 inch rims but can’t figure out how to tell which alloy rims fit on the Jeep. I’m told some would hit the calipers so going to a 17 inch rim is safer, not my preference.


dawhitesJKU 06-08-2013 10:17 AM

^Close. lol. thats what i thought before until i educated myself.

To help you understand tire sizes, let me give you my example
My toyo at2 is 285/70/17.


1- This is the width of the tire in millimeters. The conversion is 1"= 25.4mm so for our example: 285/25.4= 11.22" width.

2 - This part is the "aspect ratio" of the tire and is a relation of the tire's width to the sidewall height of the tire. My example is '70'. This means the sidewall height is 70% (.70 in calculation) of the width of the tire. (this part of the math i don't know lol)

^edit: 11.22 x .70= 7.85

3 - Your wheel size. (i say wheels...since rims are on motorcycles...its like when people say headers when theres only pet peeve)

In conclusion, a 285/70/17 equates to 11.22 wide and is (7.85x2)+17"= 32.71" tall, or basically equivalent to a 33x11.50R17 if we can call it a standard size.

BUT.....the real measurement takes place once the tire is on the wheel and set to psi. then you could use a measuring tape. mine came up to 32 tall, and a lil over 11 wide taking real measurements for my procal setting.

i hope this helps.

Willshire 06-08-2013 06:51 PM

Yes it does thanks just trying to understand it all and how to get the look I want.

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