What is the difference between 275 55R20 and 275 65R20 Tire?

Both 275 55R20 and 275 65R20 are great tires. Either of them will offer a strong grip while driving on the road. 

Surprisingly, people try to know the difference between 275 55R20 and 275 65R20 yet most of them have little knowledge of the tire size index. However, we are not going to discuss that in this article. Rather, we will demonstrate on 275 55R20 vs 275 65R20 more.

If you are not aware of the tire size index, you will understand both the comparison and tire size index after reading this article. Because we have arranged everything in a convenient way. 


The Difference Between 275 55R20 and 275 65R20 Considering 4 Aspects

Before you go into the details of 275 55R20 vs 275 65R20, you should know the tire size index has 4 components, each indicating a different aspect. We break the tire size index 275 55R20, we find –      

  • 275 stands for – Tire width in meters
  • 55 stands for – The aspect ratio of height/width
  • R stands for – Construction type
  • 20 stands for – Rim diameter in inches

As a result, we have also broken down the difference between 275 55R20 and 275 65R20 in 4 sections.  


The very first digit of the tire size index represents the width. Generally, tire manufacturers are responsible for measuring tire widths. So, no matter what is written on the tire size index is 100% right in terms of width. The width is measured from one sidewall of the tire to the other and it is commonly expressed in millimeters.

Judging by both 275 55R20 and 275 65R20, the first digit is 275. So, there is no difference in the width of these tires. You can attach any one of these tires if the width is your only concern. 

Aspect Ratio

Usually, the second number of the tire size index indicates the aspect ratio of the tire. It is the ratio of the height and the cross-section of the tier. The aspect ratio is distributed in percent. So to calculate the aspect ratio, you can follow the equation – 

Aspect Ratio of Tire = Height/Width x 100%

Looking at both tire size indexes 275 55R20 and 275 65R20, we see a great difference in the aspect ratio. The first tire, which is 275 55R20 has an aspect ratio of 55. On the other hand, the tire 275 65R20 has an aspect ratio of 65. Hence, the difference in aspect ratio is 10. 

According to the aspect ratio, we can also tell the height of the first tire is 55% to its width. And the height of the second tire is 65% of its width.

Construction Type 

The construction type indicates the handling characteristics of the tire and how it was assembled. It is an important term in the tire size index and it is the third letter after the aspect ratio. Most of the time, we can see the letter ‘R’ and ‘B’ in the tire size index. Here, ‘R’ suggests the tire is a radial type tire whereas ‘B’ suggests it is a bias ply or cross ply type tire.

Both 275 55R20 and 275 65R20 have the letter ‘R’, which stands for “Radial Construction”. It also means both are radial type tires. Judging by the tire type, we can tell both tires have a sophisticated construction with square shaped footprints on them.  

Rim Diameter

The rim diameter is the blank space in the middle of the tire where the rim goes in. It is expressed in inches and you have to measure it from one opening pellet straight to another. There is also another term called “Effective Rim Diameter” or ERD used to find the right spoke length.

The rim diameter is represented by the last digit of the tire size index. Here, both 275 55R20 and 275 65R20 have the same last digit, which is 20. It means the rim diameter for both tires is 20 inches. Hence, there is no difference here.

Summing Up With An In-depth Comparison Table – Tire Size 275 55R20 vs 275 65R20

For those who are in a hurry, don’t worry. We have drawn a detailed comparison chart of 275 55R20 vs 275 65R20 to provide a quick overview.

Parameter275 55R20275 65R20 Difference
Section width10.8 inch10.8 inch0 inch (0%) 
Overall diameter31.9 inch34.1 inch+2.2 inch (+6.8%)
Circumference100.2 inch107 inch+6.8 inch (+6.8%)
Revs per km632591.9-40.2 (-6.4%)
Sidewall height6 inch7 inch+1.1 inch (+18.2%)
Aspect Ratio5565+10 (5.5%)

From the above comparison table, we see the diameter differs to 6.8%. This leads to a change in ground clearance to 1.1 inches. Since the change in diameter is greater than 3%; it would be risky to switch from 275 55R20 to 275 65R20 suddenly. Also, the aspect ratio shows a significant increase of 5.5%.

The following 2 pictures will show a comparison of 275 55R20 and 275 65R20 from front and side.


Great! You are fully aware of the difference between 275 55R20 and 275 65R20. And that’s not all, you know various aspects of the tire by knowing the tire size index. Now, choosing the right tire size for your vehicle will be a piece of cake.

In the end, we leave it up to you whether or not you are going to change your existing tires if you have either 275 55R20 or 275 65R20. In case you are determined to switch tires, we recommend changing all 4 of them.

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