Confused about tire sizes? What do those numbers or combinations even mean? When you look at tire size, all you see is a bunch of numbers. These are not random numbers but tire size indexes. They tell you several factors about a tire.
Here in this article, we will discuss tire size index in such a way that you can learn about the size of a tire just by looking at the numbers.
Maybe you are confused about two tire sizes. 305/70R16 vs 285/75R16 Tire Size: What’s the Difference? By the end of this article, you will be able to decide the suitable tire size for your vehicle. This article will also inform you if the tires are interchangeable or not.
To begin with, let’s learn the tire sizes right away.
What Is 305/70R16 Tire Size In Inches?
The numbers of a tire size index tell us the exact tire size of that tire. The tire size of 305 70R16 is 12.01 inches in Width, which is .The Sidewall Height of the tire is 8.41 inches. This tire is designed to fit a 16-inch wheel rim.
What Is 285 75R16 Tire Size in Inches?
The tire size of 285 75R16 is 11.22 inches in width.The Sidewall Height of the tire is 8.42 inches. This tire is designed to fit a 16-inch wheel rim.
As you can see, there is a very slight difference in size between the two size tires. But can you interchange them? Find out how 305 70R16 and 285 75R16 differ considering 4 aspects and get your answer.
305/70R16 Vs 285/75R16: In-Depth Tire Difference Considering 4 Aspects
The tire size index of a tire tells us about 4 factors of that tire – Width, Aspect Ratio, Construction Type, and Rim Diameter.
Let’s say, the tire size index 305 70R16 is fragmented, then we get this 4 information –
- 305 stands for – Tire Width in Millimeters
- 70 stands for – The Aspect Ratio of Height/Width
- R stands for – Construction Type
- 16 stands for – Rim Diameter in Inches
Comparing these factors, you can decide whether two tires are interchangeable or not. Let’s find out if 305 70R16 and 285 75R16 tire sizes are interchangeable or not.
The first thing you can learn from a tire size index is the Width of a tire. The first three digits indicate the Width.
As you can see, the first three digits of 305 70R16 are 305. It means the Width of that tire is 305 millimeters. Similarly, the three-digit number of 285 75R16 is 285. It means the Width of that tire is 285 millimeters. So the difference of the Width is 305 – 285 = 20 millimeters.
Width is the measurement from one sidewall to the other sidewall of a tire. It is expressed in millimeters. Evidently, the 305 70R16 tire size is wider than the 285 75R16 tire size.
But from the Width alone, you cannot decide if two tire sizes are interchangeable. It depends on Aspect Ratio or Sidewall Height. If the tire sizes are interchangeable, you can switch to 305 70R16 from 285 75R16 for wider tire size or vice-versa for thinner tire size.
Now, let’s find out the Aspect Ratio and Sidewall Height and learn if the tire sizes are interchangeable.
The next thing you can learn from a tire size index is the Aspect Ratio of a tire. Aspect Ratio is actually a percentage. The Sidewall Height of a tire depends on its Aspect Ratio percentage.
After the Width, the next two digits indicate the Aspect Ratio of a tire. So, the Aspect Ratio of 305 70R16 is 70% and the Aspect Ratio of 285 75R16 is 75%.
Now, we can calculate the Sidewall Height of these tires in respect of their Aspect Ratio. The Sidewall Height of 305 70R16 will be 70% of its Width. Similarly, the Sidewall Height of 285 75R16 will be 75% of its Width.
To calculate, for 305 70R16, Sidewall Height = 305 × 70% = 213.5 millimeters, which is 8.41 in inches. And for 285 75R16, Sidewall Height = 285 × 75% = 213.75 millimeters, which is 8.42 in inches.
As you can see, the Sidewall Height of the two tires are almost similar. There is a difference of 0.25 millimeters or 0.01 inches only.
So, here is the green light. You can interchange the tire sizes 305 70R16 and 285 75R16. In simple words, if you decide to change one or two tires of your vehicle from size 285 75R16 to 305 70R16, or vice-versa, you can do it. You don’t necessarily need to change all the tires from one size to another.
You can learn the Construction Type of a tire from the tire index. The Letter in the tire index indicates the construction type of that tire.
As you can see, both 305 70R16 and 285 75R16 have the same letter ‘R’. So, both the tires have Radial Construction in terms of construction type.
Such tires have a sophisticated construction with square footprints on the top. The radial type tires are ideal for driving on-roads. They are heat and water resistant. Radial type tires are next-gen tires and can provide great fuel efficiency.
If you find the letter ‘B’ in the tire index, it means the tire is of Cross-ply construction type. It is also known as Bias Ply. This type is great for driving off-roads. So, you can decide which tire is suitable for you just by looking at the tire size index.
Last but not least, the tire size index informs you about the Rim Diameter of a tire. You must know the Rim Diameter of a tire to know which tire fits your vehicle. For instance, if your vehicle has a 16-inch wheel rim, you need a tire size which is 16-inch in Rim Diameter.
Now, the last digits of a tire size index express the Rim Diameter of a tire. Hence, the Rim Diameter of 305 70R16 is 16 inches, and the Rim Diameter of 285 75R16 is also 16 inches. It means that these two tire sizes are suitable for a 16-inch wheel rim. In other words, you can use both the tire sizes if you own a 16-inch rim wheeler.
Wrapping Up with a Comparison Table between 305/70R16 and 285/75R16:
|Diameter inches||32.81||32.83||0.02 (0.1%)|
|Width inches||12.01||11.22||-0.79 (-6.6%)|
|Circumference inches||103.08||103.14||0.06 (0.1%)|
|Sidewall Height inches||8.41||8.42||0.01 (0.1%)|
|Revs per mile||614.67||614.31||-0.37 (-0.1%)|
|Aspect Ratio %||70||75||5|
Evidently, the 305 70R16 and 285 75R16 are simillar in Sidewall Height. Thus, they are perfectly interchangable. The only difference between them is their Width.
Hence, if you prefer wider size tire, you can switch from 285 75R16 to 305 70R16, and the vice-versa if you prefer thinner size tires.
It is evident that the two tires are similar in size. In the same way, you can compare between other tires by interpreting the tire size index. By calculating and comparing these 4 aspects, you can decide which tires are suitable for your vehicle.