rims
I wrote this up a while ago in faq2...
So a 235/75/16 is a 29.88 x 9.25 inch tire, which would fit just fine under a stock 4x4.
How to decipher metric tire sizes
The first number is the section width of the tire in millimeters. This is not the bead width nor the tread width, this is the width of the widest part of the tire.
The second number is the aspect ratio. This is a ratio of the height vs the width. This number as a percentage of the first number gives you the sidewall height.
The third number is the bead diameter (rim diameter) in inches.
*NOTE* 25.4 millimeters = 1 inch
Example) 235/75/15
Width = 235mm = 9.25". Height = 235*(75%) = 176.25mm = 6.94"
Total diameter = (6.94*2) + 15 = 28.88 inches
Converted to standard size, this is a 28.88 x 9.25 x 15 tire.
The first number is the section width of the tire in millimeters. This is not the bead width nor the tread width, this is the width of the widest part of the tire.
The second number is the aspect ratio. This is a ratio of the height vs the width. This number as a percentage of the first number gives you the sidewall height.
The third number is the bead diameter (rim diameter) in inches.
*NOTE* 25.4 millimeters = 1 inch
Example) 235/75/15
Width = 235mm = 9.25". Height = 235*(75%) = 176.25mm = 6.94"
Total diameter = (6.94*2) + 15 = 28.88 inches
Converted to standard size, this is a 28.88 x 9.25 x 15 tire.
Actually, offset doesn't matter as much as backspacing! If you go with a wider than factory rim, you need to keep it around the same backspacing as factory, which means the offset will have to be different.
https://www.rsracing.com/tech-wheel.html
Offset and backspace are two sides of the same coin, scroll down to the offset to backspace conversion part...
Offset and backspace are two sides of the same coin, scroll down to the offset to backspace conversion part...
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To sum up that article, I'll tell you in a nutshell about width, backspacing, and offset....
First of all, wheel width is measured bead to bead, not flange to flange. The standard measurement of a wheel flange is a 1/2 inch, and each side has one, so add 1 inch to the advertised wheel width to get the flange to flange measurement.
Offset is a measurement from the centerline of the wheel to the mounting surface of the wheel. Positive is toward the outside, negative is toward the inside.
Backspacing is a measurement from the mounting surface of a wheel to the inner flange. (Remember that 1/2 inch is added to the wheel width.) So on an 8 inch wide wheel with 0 offset, backspacing is actually 4.5 inches.
If offset is not 0, convert offset from millimeters to inches (1 inch = 25.4 mm) and add or subtract that number from the neutral backspacing (backspacing at 0 offset) of the wheel. For example, an 8 inch wide wheel with a -12 offset (-12mm converts to ~1/2 inch).... The -12 offset would put the wheel mounting surface closer to inside flange, so backspacing would become less (which is why its negative), so 4.5 inch neutral backspacing minus 1/2 an inch offset gives a 4 inch backspace.
So to explain what I said back in post #4...
If you change rim width, you still need the same (or as close to the same as possible) backspacing to ensure you clear the inner fender wells, frame, and control arms. A higher backspacing will lead to tire rub pretty quick! So like I said, offset will end up being whatever it needs to be for you to use a given width rim and have the proper backspacing for clearance.
So yes, offset and backspacing go hand in hand, but its the backspacing that is the more important of the two numbers.
I copied this to FAQ2 for future reference.
First of all, wheel width is measured bead to bead, not flange to flange. The standard measurement of a wheel flange is a 1/2 inch, and each side has one, so add 1 inch to the advertised wheel width to get the flange to flange measurement.
Offset is a measurement from the centerline of the wheel to the mounting surface of the wheel. Positive is toward the outside, negative is toward the inside.
Backspacing is a measurement from the mounting surface of a wheel to the inner flange. (Remember that 1/2 inch is added to the wheel width.) So on an 8 inch wide wheel with 0 offset, backspacing is actually 4.5 inches.
If offset is not 0, convert offset from millimeters to inches (1 inch = 25.4 mm) and add or subtract that number from the neutral backspacing (backspacing at 0 offset) of the wheel. For example, an 8 inch wide wheel with a -12 offset (-12mm converts to ~1/2 inch).... The -12 offset would put the wheel mounting surface closer to inside flange, so backspacing would become less (which is why its negative), so 4.5 inch neutral backspacing minus 1/2 an inch offset gives a 4 inch backspace.
So to explain what I said back in post #4...
So yes, offset and backspacing go hand in hand, but its the backspacing that is the more important of the two numbers.
I copied this to FAQ2 for future reference.
Last edited by 95_318SLT; May 24, 2010 at 11:38 AM.



