305/75R18 Tire Size in Inches and Millimeters
305/75R18 tires have a diameter of 36" (915 mm), a tread width of 12" (305 mm), and a wheel diameter of 18" (457.2 mm).The sidewall of the tire is 9" (229 mm), and the tire's circumference is 113" (2873.1 mm). This means a 305/75R18 tire will make make 561 revolutions per mile, or 348 revolutions per kilometer.
| Spec | Inches | Metric |
|---|---|---|
| Diameter | 36" | 915 mm |
| Width | 12" | 305 mm |
| Wheel | 18" | 457.2 mm |
| Sidewall | 9" | 229 mm |
| Circum | 113" | 2873.1 mm |
| Revolutions | 561 per mile | 348 per km |
What Does 305/75R18 Mean?
The tire size 305/75R18 is a common size used on many trucks, SUVs, and other larger vehicles.
Here is what each part of the size designation represents:
- 305: This number represents the width of the tire in millimeters. In this case, the tire is 305 millimeters wide.
- 75: This number represents the aspect ratio of the tire, which is the height of the tire's sidewall as a percentage of its width. In this case, the sidewall height is 75% of the tire's width.
- R: This letter indicates the tire's construction type. “R” stands for radial construction, which is the most common type of tire construction today.
- 18: This number represents the diameter of the wheel that the tire is designed to fit on, in inches. In this case, the tire is designed to fit on a 18-inch wheel.
How To Convert 305/75R18 Into Inches
The 305/75R18 conversion is fairly simple. The first number in the tire size, 305, represents the width of the tire in millimeters. To convert this to inches, we divide 305 by 25.4 (since there are 25.4 millimeters in an inch). This gives us approximately 12 inches.
The second number in the tire size, 75, represents the aspect ratio or the height of the tire as a percentage of its width. To calculate the height in inches, we multiply 12 by 0.75, which gives us approximately 9 inches.
Finally, the last number in the tire size, 18, represents the diameter of the wheel rim in inches. Therefore, the tire size 305/75R18 can be expressed in inches as roughly 12 inches wide, 9 inches tall, and designed to fit a 18-inch wheel rim.
Frequently Asked Questions About 305/75R18 Tires
How tall is a 305/75R18 tire?
A 305/75R18 tire has an approximate height, also known as the overall diameter, of 36 inches (915 mm). This height can vary slightly depending on the brand and model of the tire, as well as the amount of air pressure in the tire.How wide is a 305/75R18 tire?
A 305/75R18 tire has a width of approximately 12 inches (305 millimeters). The width of the tire is the first number in the tire size designation, which in this case is “305”. It’s important to note that the actual width of the tire may vary slightly depending on the brand and model of the tire, and the width may also be affected by the amount of air pressure in the tire.Understanding Tire Speed Ratings
When choosing the right tires for your vehicle, understanding the speed rating is crucial. But what exactly is a speed rating, and why does it matter?What is a Tire Speed Rating?
A tire's speed rating indicates the maximum speed a tire can safely sustain over time. It's a manufacturer's assurance of tire performance, marked by a letter on the tire's sidewall. This rating is determined under controlled laboratory conditions and is part of a broader standard established by industry entities like the European Tyre and Rim Technical Organisation (ETRTO) and the U.S. Department of Transportation.Common Speed Ratings Explained
- P-Rated: Up to 94 mph - Suitable for smaller sedans or light-duty vehicles.
- Q-Rated: Up to 100 mph - Often found on SUVs and light trucks with consistent highway use.
- R-Rated: Up to 106 mph - Typically for medium-duty trucks and vans.
- S-Rated: Up to 112 mph - Common for family sedans and larger vehicles with moderate performance.
- T-Rated: Up to 118 mph - Optimal for family vehicles, including minivans and some coupes.
Why is the Speed Rating Important?
The speed rating is not just about how fast you can legally drive; it's about safety and performance:- Ensures Safety: It guarantees that the tire can handle certain speeds without overheating and failing, which can prevent blowouts.
- Optimizes Performance: Higher ratings often indicate better handling characteristics, important for maintaining vehicle stability.
- Legal and Insurance Considerations: Matching the speed rating suggested by your vehicle manufacturer can be essential for insurance and warranty purposes.
Alternate 305/75R18 Replacement Tire Sizes
Upsizing your wheels or tires? Replacement tires must be within 3% of the diametor of the original tire. The following sizes fall within that range - click on any size to see detailed info about that tire and wheel combination.
| Size | Diameter | Width | Wheel |
|---|---|---|---|
| 255/30R30 | 36.1" | 916 mm | 30 mm |
| 275/25R30 | 35.4" | 900 mm | 30 mm |
| 275/80R18 | 35.3" | 897 mm | 18 mm |
| 295/65R20 | 35.1" | 892 mm | 20 mm |
| 305/55R22 | 35.2" | 895 mm | 22 mm |
| 305/75R18 | 36" | 915 mm | 18 mm |
| 315/20R30 | 35" | 888 mm | 30 mm |
| 315/40R26 | 35.9" | 912 mm | 26 mm |
| 315/45R24 | 35.2" | 894 mm | 24 mm |
| 315/50R24 | 36.5" | 926 mm | 24 mm |
| 315/70R18 | 35.4" | 899 mm | 18 mm |
| 325/35R28 | 37" | 939 mm | 28 mm |
| 325/45R24 | 35.5" | 902 mm | 24 mm |
| 325/55R22 | 36.1" | 917 mm | 22 mm |
| 325/60R20 | 35.4" | 898 mm | 20 mm |
| 325/70R17 | 35" | 888 mm | 17 mm |
| 325/80R16 | 36.5" | 926 mm | 16 mm |
| 335/35R26 | 35.2" | 894 mm | 26 mm |
| 335/55R22 | 36.5" | 927 mm | 22 mm |
| 345/45R24 | 36.2" | 920 mm | 24 mm |
| 345/75R16 | 36.4" | 924 mm | 16 mm |
| 355/40R24 | 35.2" | 894 mm | 24 mm |
| 355/60R20 | 36.8" | 934 mm | 20 mm |
| 355/65R18 | 36.2" | 919 mm | 18 mm |
| 355/70R16 | 35.6" | 904 mm | 16 mm |
| 355/70R17 | 36.6" | 930 mm | 17 mm |
| 365/70R16 | 36.1" | 918 mm | 16 mm |
| 375/40R24 | 35.8" | 910 mm | 24 mm |
| 375/45R22 | 35.3" | 897 mm | 22 mm |
| 375/55R20 | 36.2" | 920 mm | 20 mm |
| 375/60R18 | 35.7" | 907 mm | 18 mm |
| 375/65R16 | 35.2" | 894 mm | 16 mm |