285/55r20 vs 35×12.50r20 Tire: What’s the Difference?

There is nothing as hard as finding the right set of interchangeable tires that fit the prerequisite settings of your wheel. There are countless variables involved and several factors that determine compatibility. 

If you are looking for information on how to get the right pair of interchangeable tires, you are in the right place. In this article, we will be covering a comparison between 285/55r20 Vs 35×12.50r20 (315/60r20) tires.

So scroll down below and keep reading. Who knows how much this analytic article will enrich you with its information?

285/55r20 vs 35×12.50r20 Tire Comparison Table

There are several data you will first need to consider when analyzing this set of tires. We have drawn the required statistical data into a table and displayed it below. 

285/55r20 TireType35×12.50r20 Tire
32.34 Inches or 821.5 mmPercentage Difference In Diameter 8.3 percent35.02  inches or 889.6 mm
11.22 inches or 12.52 mmPercentage Difference In Width 11.6 percent12.52 Inches or 318 mm
101.61 inches or 25680.82 mmPercentage Difference In Circumference 8.3 percent110.03 Inches or 2794.76 mm
6.17  inches or 156.75 mmPercentage Difference In Sidewall Length 21.7 percent7.51 inches or 190.8 mm
623.58 RPM or 387.47 KMPercentage Difference In Revolutions Per Mile -7.7 percent616.6 RPM or 383.14 KM

Typically, we measure the compatibility based on the percentage difference of the factor against the compatibility margin which is set at 3 percent. Anything below 3 percent is good while; anything above isn’t. 

In the case of these two tires, all of the variables we have considered are above the 3 percent margin. For instance, the percentage difference for both diameter and circumference is about 8.3 percent. 

On the other hand, width and sidewall length have a percentage difference of 11.6 percent and 21.7 percent, respectively. 

Finally, when it comes to the revolutions per mile, this factor isn’t in the safe zone as well. The percentage difference is set at 7.7 percent, with the figure being negative. 

The negative represents the fact that the first tire will have greater revolutions per mile than the second one.

How to read the tire sizes 285/55r20 and 315/60r20?

There are four parts to the tire size 285/55r20, and each part bears a certain meaning. Before you decide to interchange or replace the tires, you must learn about them. Here is the explanation of each part of the tire size 285/55r20.

  • 285 means the width of the tires in millimeters
  • 55 shows the percentage of height to the width or the Aspect Ratio
  • R indicates Radial Construction
  • 20 indicates the Diameter of the Rim

Doing the Same for Tire Sizes 315/60r20

  • 315 means the width of the tires in millimeters
  • 60 shows the percentage of height to the width or the Aspect Ratio
  • R indicates Radial Construction
  • 20 indicates the Diameter of the Rim

What’s The Difference Between 285/55r20 and 315/60r20 Tire?

By now you’ve learned the basics of using two tires interchangeably, now let’s see the theory implemented in a real example. Below, we have compared 285/55r20 and 35×12.50r20 tires in terms of width, aspect ratio, construction materials, and rim diameter.

Width

If you measure from one sidewall to the other sidewall of a tire, you will get the width. It is expressed in millimeters. You can instantly learn the Width of a tire just by looking at the tire size index.

The first three digits of a tire size index indicate the Width of that tire. As you can see, the first three digits of 285/55r20 are 285. It means the width of that tire is 285 millimeters. 

Likewise, the three-digit number of 315/60r20 tire is 315. It means the Width of that tire is 315 millimeters. So the difference in the Width is 315 – 285 = 30 millimeters.

Now, if you switch to the tire size which is 0 millimeters more or less in Width, it shouldn’t be a problem. 

But you cannot switch tire size depending on Width only. You must consider the Sidewall Height as well. The Sidewall Height depends on Width and Aspect Ratio.

Aspect Ratio

As you can see, there’s a difference between the Aspect Ratio of the two tires. This change also affects Sidewall Heights and makes the tires incompatible with interchange.

The Aspect Ratio of 285/55r20 is 55, whereas the Aspect Ratio of 315/60r20 is 60.

Aspect Ratio is the ratio of the sidewall from wheel to tread and the width. This measurement is usually represented in a percentage.

In our example, 285/55r20 Tire size has a width of 285 with an aspect ratio of 55%. So the sidewall height will be 285 x 0.55 or 6.2 inches or 156.75 mm. You can get the number by simply putting the value on the equation.

Equation: Height of a Sidewall = Aspect Ratio of Tire x Width.

On the other hand, the Sidewall Height of 315/60r20 is 7.5 inches.

Hence, there’s a huge gap between the Sidewall Heights of the two tires, and this fact simply makes them incompatible to interchange.

Construction Type

The tire size index informs you about the Construction Type of a tire. It is expressed by a letter in the tire size index. 

Both 285/55r20 and 315/60r20 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 tires are ideal for driving on-road. 

They are resistant to heat and water. They are next-gen tires and can provide excellent fuel efficiency.  

Another famous construction type is Bias Ply. They are also known as Cross-ply. It is expressed by the letter ‘B’ in a tire size index. This type is great for driving off-road.

Rim Diameter

To know which tire size fits your vehicle, you must know the wheel rim size of your vehicle as well as the Rim Diameter of a tire. 

For instance, if your vehicle has a 16-inch wheel rim, you can use the tire which has a 16-inch Rim Diameter.

By looking at a tire size index, you can learn instantly the Rim Diameter of a tire. The last two digits of a tire size index indicate the Rim Diameter. It is measured in inches. 

As you can see, the Rim Diameter of 285/55r20 is 20 inches. Similarly, the Rim Diameter of 315/60r20 is 20 inches.

It means that if your vehicle has a 20-inch wheel rim, you can use both tire sizes. But make sure to use the same size tires for all the wheels.

Can You Interchange between 285/55r20 vs 35×12.50r20 Tire?

It is impossible to use these pairs as interchangeable tires. This is because, unlike most other tires, which show some degree of compatibility in most of their factors, this one doesn’t have any compatibility.

All of its factors have a percentage difference that is way above the 3 percent compatibility margin. Even after all of this, if you are still thinking about using this pair for interchange, you are incredibly naive.

Speedometer Difference: Using the current Tire Size 285/55r20 Instead Of the New Tire Size 35×12.50r20

Look at the Table. It shows differences in speedometer reading and the actual speed at any given time when the current Tire Size is 285/55r20 instead of 35×12.50r20. 

Speedo ReadingActual Speed
20 mph (32.19 km/h)21.66 mph (34.86 km/h)
25 mph (40.23 km/h)27.07 mph (43.57 km/h)
30 mph (48.28 km/h)32.49 mph (52.28 km/h)
35 mph (56.33 km/h)37.9 mph (61 km/h)
40 mph (64.37 km/h)43.32 mph (69.71 km/h)
45 mph (72.42 km/h)48.73 mph (78.42 km/h)

Speedometer Difference: Using current Tire Size 35×12.50r20 Instead Of New Tire Size 285/55r20

The table shows the differences in speedometer reading and the actual speed at any given time when the current Tire Size is 35×12.50r20 instead of 285/55r20.

Speedo ReadingActual Speed
20 mph (32.19 km/h)18.47 mph (29.72 km/h)
25 mph (40.23 km/h)23.09 mph (37.15 km/h)
30 mph (48.28 km/h)27.7 mph (44.58 km/h)
35 mph (56.33 km/h)32.32 mph (52.02 km/h)
40 mph (64.37 km/h)36.94 mph (59.45 km/h)
45 mph (72.42 km/h)41.56 mph (66.88 km/h)

What you must consider Before Interchange or Replace Tire? 

There are important things to consider before replacing or swiping the Tires. You cannot simply replace the 285/55r20 tire with the 315/60r20 tire that is in a different shape.

For example, if the aspect ratio of the existing tire is 40%, replacing it with a tire that has an aspect ratio of  45% might not be a good option.

Doing so will have various consequences on the car’s overall performance, such as variations in top speed and speedometer.

However, you can switch Tires to a certain extent, such as minor changes in the diameter or the sidewall. However, this can only be done in compliance with the manufacturers’ recommendations.

Anyway, when replacing the Tire, the simple guideline to follow is that the current tire’s size, load index, and speed rating should all match with the replacement Tire.

Load Index and Speed Index of a Tire 285/55r20 and 315/60r20

The load index refers to the maximum load-bearing capacity, whereas the speed index refers to the Tire’s maximum allowable speed at a full load. These are very crucial stats to know before you decide to interchange tires.

Index information can be found on the sidewall next to the Tire size number. It is a combination of numbers and letters that bear a particular meaning. 

Here is an example of how the index information is usually written on the sidewall: 285/55r20 90A. The 90A stands for load and speed index, with 90 indicating a maximum load-bearing capacity of 600 kg, whereas ‘A’ denotes an allowed speed of up to 170 km/h.

Check the load and speed index. They must be as close as possible to fit precisely. These values change depending on the vehicle’s weight and wheel size. Here is a table that shows various load and speed indexes, so you get the idea.

Load IndexKgSpeed IndexSpeed Limit
65290QUp to 160 Km/h
66300RUp to 170 Km/h
67307SUp to 180 Km/h
68315TUp to 190 Km/h
69325HUp to 210 Km/h

Size of the Tire 

The size of the Tire is another vital piece of information to know to exchange the tires properly. The large number on the sidewall shows the tire size.

For example, the marking 285/55r20 on the sidewall represents the size of the Tire. You can also find it in the user manual, on the sidewall, and in other places such as inside the fuel flap or glove compartment.

What Size Tires Is 285/55r20 in Inches?

285/55r20 tires have a 32.3″ diameter, 11.2″ section width, and 20″ wheel diameter.

The circumference is 101.6,” and they make 624 revolutions per mile. The Sidewall Height of this Tire is 6.2 inches.

What Size Tires Is 35×12.50r20 (315/60r20) in Inches?

35×12.50r20 tires have a diameter of 35″, a section width of 12.5″, and a wheel diameter of 20″. 

The circumference is 109.9,” and they have 577 revolutions per mile. The Sidewall Height of this Tire is 7.5 inches.

Conclusion

A significant issue with finding the right tire is that there are countless options that you can choose from depending on the size and spec of your car. 

So if you are confused about the right set of interchangeable tires to get from the store, consult a professional. He will be able to advise you on the best of what to get and what not to get. 

Additionally, there is the existence of Google to keep your back as well. Search in Google about your car, and the answers will flash instantly.

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