It comes in handy if you know the difference between tire sizes. Unfortunately, very few vehicle owners can read tire size index. Consequently, they face difficulty switching tires from one size to another.
When you look at tire size, all you see is a bunch of numbers or combinations. These are not random numbers but tire size indexes. They tell you several factors about a tire. You will instantly have an idea about the compatibility of the tire with the vehicle just by looking at it.
Here in this article, we will discuss the difference between 275 70R17 and 285 70R17 in a way that you can understand the tire size just by looking at the numbers. To begin with, let’s learn the tire sizes right away.
If you know the exact size of a tire, you can decide if the tire is compatible with the vehicle or not. The tire size of 275 70R17 is 275 millimeters in width, which is 10.83 in inches.The Sidewall Height of the tire is 192.5 millimeters, which is 7.58 inches. This tire is designed to fit a 17-inch wheel rim.
The tire size of 285 70R17 is 285 millimeters in width, which is 11.22 in inches.The Sidewall Height of the tire is 199.5 millimeters, which is 7.85 inches. This tire is designed to fit a 17-inch wheel rim.
As we said, tire size index tells you about 4 factors of a tire. These factors will enable you to know the exact size of a tire instantly. The factors are Width, Aspect Ratio, Construction Type, and Rim Diameter.
Let’s say, the tire size index 275 70R17 is fragmented, then we get this 4 information –
- 275 stands for – Tire Width in Millimeters
- 70 stands for – The Aspect Ratio of Height/Width
- R stands for – Construction Type
- 17 stands for – Rim Diameter in Inches
Let’s elaborate these factors to know the tire sizes of 275 70R17 and 285 70R17 better.
If you look at the tire size index, you can see some numbers. The first three digits of a tire size index indicate the Width of that tire. As you can see, the first three digits of one of the tires are 275, and the other’s are 285. It means that the Width of the tire 275 70R17 is 275 millimeters. Likewise, the Width of the tire 285 70R17 is 285 millimeters. So the difference in their Widths is 285 – 275 = 10 millimeters.
To get the width, they measure from one sidewall to the other sidewall and it is expressed in millimeters. Now, only a 10-millimeter difference in Width shouldn’t affect your vehicle performance. But the suitability of a tire doesn’t only depend on its Width.
Tire manufacturers are very careful when measuring width, making it 100% accurate. So, there is no need to doubt the width of the tire by looking at the digit on the tire size index.
The next thing you can learn from the tire size index is the aspect ratio. After the width, the next two digits indicate the aspect ratio of a tire. So, the aspect ratio of 275 70R17 is 70 and the aspect ratio of 285 70R17 is 70. The aspect ratio is measured in percentage.
The most important thing about aspect ratio is that it tells the Sidewall Height of a tire. For instance, the aspect ratio of 275 70R17 is 70%. It means that the Sidewall Height of this tire is 70% of its Width.
To calculate, the Sidewall Height of 275 70R17 tire size is 275 × 70% = 192.5 millimeters. Likewise, the aspect ratio of the tire size 285 70R17 is 70%. So, the Sidewall Height of this tire is 285 × 70% = 199.5 millimeters.
So, the gap of the height on the sidewall between the tires is 199.5 – 192.5 = 7 millimeters. As you can see, there is a big difference between the two tires. Moral of the story is that you cannot interchange between tire sizes 275 70R17 and 285 70R17. Doing so would affect your riding experience and the reading on the speedometer. If you switch from one size to another, make sure to change them all.
The next thing you know by looking at the tire size index is its Construction Type. The letter in a tire size index is the construction type of that tire.
Both 275 70R17 and 285 70R17 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.
Another letter ‘B’ can be often seen in the tire size index. It indicates the tire is a bias ply type, having a different construction type than the radial type tires. The bias ply or cross ply tires are better for driving off roads.
By looking at a tire size index, you can learn instantly if that tire is suitable for your rim size. The last two digits of a tire size index tell the Rim Diameter of that tire. It is measured in inches.
As you can see, the Rim Diameter of 275 70R17 is 17 inches. Likewise, the Rim Diameter of 285 70R17 is 17 inches. It means that if your vehicle has a 17-inch wheel rim, you can use both the tire sizes. But make sure to use the same size tires for all the wheels.
Wrapping Up with a Comparison Table between 275 70R17 and 285 70R17:
|Aspects||285 70R17||275 70R17||Difference|
|Diameter inches||32.71||32.16||-0.55 (-1.7%)|
|Width inches||11.22||10.83||-0.39 (-3.5%)|
|Circumference inches||102.76||101.03||-1.73 (-1.7%)|
|Sidewall Height inches||7.85||7.58||-0.28 (-3.5%)|
|Revs per mile||616.6||627.17||10.57 (1.7%)|
|Aspect Ratio %||70||70||–|
Evidently, both the tire sizes are usable for a 17-inch wheel rim. But there’s a huge difference between the two tire sizes. So, if you decide to switch from one size to another, make sure to switch them all. Otherwise, it can affect your riding experience.
As you have read the whole article, we assume now you know a lot about tire size. Now you can calculate tire width, sidewall height, construction type, and rim diameter of a tire just by looking at the tire size index. Apply the same method for every tire size.
Finally, the 275 70R17 and 285 70R17 tires are not interchangeable. You cannot replace one tire with another size of these two. Check out our other comparisons to learn more about tire sizes.