While many car owners are familiar with tire brands, they are unfamiliar with tire sizes. As a result, people purchase the incorrect tire size for their automobiles. Understanding the tire size is essential for car owners.
For example, 285/70R17 and 285/75R17 are two names used to describe tire sizes. Here the aspect ratio of one has 70, and another has 75. You are wrong if you think you can interchange these because the aspect ratio difference is only 5!
Don’t be bothered. This article will compare 285/70R17 vs 285/75R17 tires and point out what’s the difference. If you want to understand whether they are interchangeable or not, go all the way to the conclusion.
- 285/70R17 vs 285/75R17 Tire: Comparison Table
- How to read the tire sizes 285/70r17 and 285/75r17?
- What’s The Difference Between 285/70r17 and 285/75r17 Tire?
- Can You Interchange Between 285/70R17 and 285/75R17 Tire?
- What you must consider Before Interchange or Replace Tire?
- What Size Tires Is 285/70r17 in Inches?
- What Size Tires Is 285/75r17 in Inches?
285/70R17 vs 285/75R17 Tire: Comparison Table
The size variation between 285/70R17 and 285/75R17 tires has been calculated in-depth in the tire comparison table. Their overall diameter, circumference, sidewall height, section width, and clearance are measured and compared.
|285/70R17 Tire||Type||285/75R17 Tire|
|32.71 Inches or 830.8 mm||Overall diameter difference 1.12 (28.5) 3.4%||33.83 Inches or 859.3 mm|
|11.22 Inches or 285 mm||Width difference 0 (0) 0% inches (mm)||11.22 Inches or 285 mm|
|102.76 Inches or 2610.04 mm||Circumference difference 3.53 (89.54) 3.4% (mm)||106.28 Inches or 2699.57 mm|
|7.85 Inches or 199.5 mm||Sidewall Height difference 0.56 (14.25) 7.1% (mm)||8.42 Inches or 213.75 mm|
|616.6 RPM or 383.14 KM||Revolutions per mile difference -20.45 (-12.71) -3.3% (km)||596.15 RPM or 370.43 KM|
These two tire sizes have identical widths. But do not purchase just based on this fact. Their diameter difference is more than 3%. It indicates that they are not interchangeable.
Overall diameter and sidewall height increase by 7.1% and 3.4%, which would be high. If the difference in diameter and sidewall height is more than 3%, specialists don’t recommend switching tires as it’s dangerous.
The 285/75R17 tire is also significantly more extensive than the 285/70R17 tire due to the increased percentage. It will result in less revolution per mile.
How to read the tire sizes 285/70r17 and 285/75r17?
There are four parts to the tire size 285/70r17, and each part bears a certain meaning. Before you decide to interchange or replace the Tire, you must learn about them. Here is the explanation of each part of the tire size 285/70r17.
- 285 indicates the width of the tires in millimeters
- 70 shows the percentage of height in relation to the width or the Aspect Ratio
- R indicates Radial Construction
- 17 indicates the Diameter of the Rim
Doing the Same for Tire Sizes 285/75r17
- 285 means the width of the tires in millimeters
- 75 shows the percentage of height in relation to the width or the Aspect Ratio
- R indicates Radial Construction
- 17 indicates the Diameter of the Rim
What’s The Difference Between 285/70r17 and 285/75r17 Tire?
By now you’ve learned the basics of using two tires interchangeably, now let’s see implementing the theory in a real example. Below, we have compared 285/70r17 and 285/75r17 tires in terms of width, aspect ratio, construction materials, and rim diameter.
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 285/70r17 are 285. It means the width of that tire is 285 millimeters.
Likewise, the three-digit number of 285/75r17 is 285. It means the Width of that tire is 285 millimeters. So the difference in the Width is 285 – 285 = 0 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.
As you can see, the only difference between the two Tire sizes is the Aspect Ratio. The aspect ratio of 285/70r17 is 70, whereas the aspect ratio of 285/75r17 is 75. On the other hand, the width and the Rim diameter of the two Tire sizes are identical.
So to check the interchangeability of these tires, our sole concern is to analyze how the differences in the aspect ratio impact the other measurements. Let’s start with the simple question first: what is the aspect ratio? And its relation with other measurements.
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, 285/70r17 Tire size has a width of 285 with an aspect ratio of 70%. So the sidewall height will be 285 x 0.70 or 7.9 inches or 199.5 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 285/75r17 is 8.4 inches.
Though the Width of the two tire sizes is identical, there’s a gap between the sidewall heights because of the Aspect Ratio.
This change affects the value of diameter, circumference, and the total number of revolutions per mile.
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 285/70r17 and 285/75r17 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 great 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.
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 285/70r17 is 17 inches. Similarly, the Rim Diameter of 285/75r17 is 17 inches.
It means that if your vehicle has a 17-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 285/70R17 and 285/75R17 Tire?
It is evident from the variability in dimensions that exchanging 285/70R17 and 285/75R17 tires is not a good idea. Especially remarkable are the height and diameter changes.
You can have an inaccurate speedometer, variations in max speed, and other concerns with such a significant change in height. As a general guideline, keep the substitute tire and wheel combination inside 3% of your old tire.
Speedometer Difference: Using the current Tire Size 285/70r17 Instead Of the New Tire Size 285/75r17
Look at the Table. It shows differences in speedometer reading and the actual speed at any given time when the current Tire Size is 285/70r17 instead of 285/75r17.
|Speedo Reading||Actual Speed|
|20 mph (32.19 km/h)||20.69 mph (33.29 km/h)|
|25 mph (40.23 km/h)||25.86 mph (41.61 km/h)|
|30 mph (48.28 km/h)||31.03 mph (49.94 km/h)|
|35 mph (56.33 km/h)||36.2 mph (58.26 km/h)|
|40 mph (64.37 km/h)||41.37 mph (66.58 km/h)|
|45 mph (72.42 km/h)||46.54 mph (74.9 km/h)|
Speedometer Difference: Using current Tire Size 285/75r17 Instead Of New Tire Size 285/70r17
The table shows the differences in speedometer reading and the actual speed at any given time when the current Tire Size is 285/75r17 instead of 285/70r17.
|Speedo Reading||Actual Speed|
|20 mph (32.19 km/h)||19.34 mph (31.12 km/h)|
|25 mph (40.23 km/h)||24.17 mph (38.9 km/h)|
|30 mph (48.28 km/h)||29.01 mph (46.68 km/h)|
|35 mph (56.33 km/h)||33.84 mph (54.46 km/h)|
|40 mph (64.37 km/h)||38.67 mph (62.24 km/h)|
|45 mph (72.42 km/h)||43.51 mph (70.02 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 285/70r17 tire with the 285/75r17 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, to a certain extent, such as minor changes in the diameter or the sidewall, you can switch Tires. 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 285/70r17 and 285/75r17
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 right after 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: 285/70r17 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 Index||Kg||Speed Index||Speed Limit|
|65||290||Q||Up to 160 Km/h|
|66||300||R||Up to 170 Km/h|
|67||307||S||Up to 180 Km/h|
|68||315||T||Up to 190 Km/h|
|69||325||H||Up 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 285/70r17 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 285/70r17 in Inches?
285/70r17 tires have a 32.7″ diameter, 11.2″ section width, and 17″ wheel diameter.
The circumference is 102.7″ and they make 617 revolutions per mile. The Sidewall Height of this Tire is 7.9 inches.
What Size Tires Is 285/75r17 in Inches?
285/75r17 tires have a diameter of 33.8″, a section width of 11.2″, and a wheel diameter of 17″.
The circumference is 106.2″ and they have 596 revolutions per mile. The Sidewall Height of this Tire is 8.4 inches.
Both of these tires will provide exceptional grip and power. The 285/75r17 tire sets can offer your car a powerful, robust look and boast racetrack-level handling and grip. 285/70r17 tires are for individuals who desire a budget-friendly style and performance.
After reviewing the above comparison, we hope you understand the differences between 28570R17 and 28575R17 tires. You’ve taken the first step in selecting the best tire for your car.
Remember that there is a difference, no matter how small or great it is. Minor variations in tire size can have a significant impact on driving safety.