Is 285/75/16 = 33's?
08-04-2008, 01:23 PM
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JK Freak
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Is 285/75/16 = 33's?
i thought so, becuase the tire description says overall diameter 33". The guy at tire shop corrected me and said a true 33 is 305/75/16.....
Can anyone shed some light?
Can anyone shed some light?
08-04-2008, 01:28 PM
#2
JK Jedi Master
I use this tool:
procomptires.com/conversionchart.htm
It says that the 305s are 34s. However, I know that if I put a tape across my 285/75R16s that they are not 33" in diameter--they are a bit smaller. I actually put 31.25" into the Hypertech programmer to get the speedometer correct (which is smaller than they actually measure, BTW). So, I think it depends on who's defining what is "true".
procomptires.com/conversionchart.htm
It says that the 305s are 34s. However, I know that if I put a tape across my 285/75R16s that they are not 33" in diameter--they are a bit smaller. I actually put 31.25" into the Hypertech programmer to get the speedometer correct (which is smaller than they actually measure, BTW). So, I think it depends on who's defining what is "true".
08-04-2008, 01:33 PM
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08-04-2008, 01:49 PM
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Yeah, what they said. I like the Miata tire calculator as well. I have it saved in my favorites
And here's some FYI just so you can check other sizes with a calculator:
Example: 285/75/16
285 = the width of the tread in mm
75 = the height percentage of the sidewall in mm (285 width x .75 = 213.75mm)
Divide mm by 25.4 to get inches
So..... 213.75 x 2 sidewalls = 427.5mm (divided by 25.4 = 16.831")
16.831" + 16" wheel = 32.831" approximate tire diameter.
Also like Mark said, some tires are not the exact advertized size. They seem to vary by manufacturer. For instance, I have been looking into Nitto TerraGrapplers and on their website they give the actual diameter of each tire size which is not exact per the above calculation.
HTH,
GK
And here's some FYI just so you can check other sizes with a calculator:
Example: 285/75/16
285 = the width of the tread in mm
75 = the height percentage of the sidewall in mm (285 width x .75 = 213.75mm)
Divide mm by 25.4 to get inches
So..... 213.75 x 2 sidewalls = 427.5mm (divided by 25.4 = 16.831")
16.831" + 16" wheel = 32.831" approximate tire diameter.
Also like Mark said, some tires are not the exact advertized size. They seem to vary by manufacturer. For instance, I have been looking into Nitto TerraGrapplers and on their website they give the actual diameter of each tire size which is not exact per the above calculation.
HTH,
GK