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#### 1.8Tabamoura

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Just made an excel spread sheet to calculate the perfect tire and wheel size for my car if someone wants to use it it is here .
I dont even know if someone post it before ok , did not bother looking for one. so dont put repplies like .
someone posted this before and blah blah blah.

don forget to put the original OEM tire and wheel size in the first roll.

http://mysite.verizon.net/vze43twa/Pictures/tirecalc.xls

Fabio

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#### UA_Variant

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Thanks, downloaded Hey, was just wondering is there some book that tells you how to calculate this. I need source for a reference (not www originated if possible). TIA

#### 1.8Tabamoura

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I dont know about the book but this is the info that i based my spreadsheet on.

you don't have data pages or need dimensional information for a tire size, you can calculate nominal dimensions by using the following calculations. Individual tires may vary slightly from these dimensions.

For example, a tire with size 235/60 HR15:
235 is the section with in mm. This tire is 235mm wide.
60 is the aspect ratio. 60% of 235 is the height of the tire.
HR is the speed rating.
15 is the size of the rim in inches.
235 To convert to inches:
Formula:
Section Width in millimetres / 25.4 = Section Width in inches.

Example:
235 / 25.4 = 9.25" Nominal Section width.>

60 To calculate Tire Section Height:

FORMULA:
Section Width x Aspect Ratio Percentage
= Section Height.

EXAMPLE:
9.25" x 60% = 5.55" Nominal Section Height.

15 To calculate Nominal Overall Tire Diameter:

FORMULA:
(Section Height x 2) + Wheel Diameter
=Overall Tire Diameter.

EXAMPLE:
(5.55 x 2) + 15 = 26.1 " Nominal Overall
Diameter.

To estimate Tire Revolutions Per Mile:
FORMULA:
20,800 / Overall Tire Diameter
=Tire Revolutions Per Mile

EXAMPLE:
20,800 / 26.1 " = 796.9 Tire Revolutions
Per Mile.

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