I'm currently running 205/75/R15 on my 92' YJ. All I ever get from anyone is I need new wheels. Alright, so this spring I'm gonna get them. I have no lift on it right now and I see Jeeps that have the big wide tires, can I do that without a lift kit? Whats the biggest I can comfortably run without a lift kit, and can someone get me some picks of what it would look like? I get confused when it goes back and forth between XXX/XX/R15 format the the XX" x XX" x R15 format. Can someone explain that to me too?
Ok, the 215 is milimeters. The 75 is aspect ratio for the sidewall. To convert 215/75r15 into a XX x XX x 15, just convert it from milimeters into inches.
First number first, the diameter.
multiply the width, 215, by the aspect ratio, .75(because it's a percent), then by the number of sidewalls 2(top and bottom of the wheel), then divide that number by 25.4 (because there are 25.4 milimeters in an inch). You should end up with
(215*.75*2)/25.4 = 12.7"
then add the wheel diameter
12.7+15 = 27.7" or 28" diameter.
Now the width:
215/25.4 = 8.5"
Alternatively, find the width first, then multiply by aspect ratio then by 2 to find the diameter.
So your tire in a floatation size is 28x8.5x15.
To take a different tire, say a 33x12.5x15 and convert it into metric, do the opposite.
Let's find the width first.
12.5 * 25.4 = 317.5 which would probably round down to a 315. Now we need to find the sidewall height.
Total height minus wheel height divided by two gives you the height of the sidewall.
9" of sidewall.
Aspect ratio is the percentage where sidewall is divided by tread width. So 9/12.5=72. We know there is no such thing as a 315/72r15, so we'll have to round again. 315/70r15 turns into a 32.4" and 315/75r15=33.6" diameter.
Your guess is as good as mine, but I'd bet on the 315/70r15.
If your springs are in good shape you might be able to get 31x10.5 but they will rub under flex, are you getting new rims? If not the backspacing on the stock ones is not right. They will rub the springs when the steering wheel is turned all the way turned.
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