P305/40R18 — what does it mean?
- P means "passenger car"
- 305 stands for tread width in millimeters
- 40 is an aspect ration between the tread width and the sidewall in percents
- R means that the tire has a radial construction
- 18 is a wheel diameter (or rim) in inches
How to convert P305 40R18 to inches?
First of all, we need to divide 305 mm (width) by 25.4 (mm to inch conversion), which will give us a width of 12″. Then, 40% of the 12″ will result in 4.8″ sidewall.
To get the total height or tire diameter, we need to sum the 18″ rim diameter with two of the sidewall heights. It will result in a 27.6″ total tire diameter (or height).
For your convenience, below is a table for P305/40R18 conversion to inches:
|Overall diameter (height)||27.6″||701 mm|
|Tread width||12″||305 mm|
|Wheel diameter||18″||701 mm|
|Sidewall height||4.8″||122 mm|
|Revolutions||731 / ml||454 / km|
Alternatives to a P305/40R18 tire
If you're looking to upsize your P305 40R18 tires, try to stay within 3% deviation of an overall diameter for safety reasons.
|Tire||Tire diameter||Width||Wheel Size|