255/75R17 vs 265/70R17 Tire: What’s the Difference?

Nowadays, trying out different-sized tires on a vehicle is trendy. It is exciting to swap the stock tires of a vehicle with bigger or smaller-sized tires. It is known as upsizing and downsizing tires.

But using mismatched tires causes trouble in the long run of driving. It is because, with a small change in the tire parameter, many changes take place in the execution of the vehicle on the road.

Considering you want to swap your 255/75R17 tire with a 265/70R17 one. Then you would need to know all about the comparison between 255/75R17 vs 265/70R17 to make a wise decision and check if these are interchangeable.

255/75R17 vs 265/70R17 Tire: Comparison Table

We can see two major differences in the tire type 255/75R17 and 265/70R17. These are the section width and aspect ratio (in %).

An increment of 10mm width with a decrement of a 5% aspect ratio also causes the major parameters to change, responsible for a good performance of a vehicle.

255/75R17 TireType265/70R17 Tire
35.06 inches or (890.5)mmDiameter difference: -0.45 (-11.5) -1.3% inches (mm)34.61 inches or (879)mm
10.04 inches or (255)mmWidth difference 0.39 (10) 3.9% inches (mm)10.43 inches or (265)mm
110.14 inches or (2797.59)mmCircumference difference: -1.42 (-36.13) -1.3% inches (mm)108.72inches or (2761.46)mm
7.53 inches or (191.25)mmSidewall Height difference: -0.23 (-5.75) -3% inches (mm)7.3 inches or (185.5)mm
575.26RPM (357.45)KmRevolutions per mile difference: 7.53 (4.68) 1.3% (km)582.79 RPM (362.13)Km

From the comparison chart we can see there has been a very low decrease in diameter and circumference. Both of these parameters are steady at 1.3% lower than the previous. It resides within the standard accepted limit of 3%.

The width difference is observed to be 3.9% due to 10mm of increment. This increases the tire’s width and improves stability, cornering at high speed, and balance in different types of climates.

It is seen that the sidewall height reduces by 3.3%, which is manageable and under the limit. Finally, the RPM increment is observed, which improves fuel efficiency in long drives.

How to read the tire sizes 255/75r17 265/70r17?

There are four parts to the tire size 255/75r17, 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 255/75r17.

  • 255 means the width of the tires in millimeters
  • 75 shows the percentage of height to the width or the Aspect Ratio
  • R indicates Radial Construction
  • 17 indicates the Diameter of the Rim

Doing the Same for Tire Sizes 265/70r17

  • 265 means the width of the tires in millimeters
  • 70 shows the percentage of height to the width or the Aspect Ratio
  • R indicates Radial Construction
  • 17 indicates the Diameter of the Rim

What’s The Difference Between 255/75r17 and 265/70r17 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 255/75r17 and 265/70r17 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 255/75r17 are 255. It means the width of that tire is 255 millimeters.

Likewise, the three-digit number of 265/70r17 tire is 265. It means the Width of that tire is 265 millimeters. So the difference in the Width is 265 – 255 = 10 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 tire sizes. The aspect ratio of 255/75r17 is 75, whereas the aspect ratio of 265/70r17 is 70.

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, 255/75r17 Tire size has a width of 255 with an aspect ratio of 75%. So the sidewall height will be 255 x 0.75 or 7.5 inches or 191.25 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 265/70r17 is 7.3 inches. Though the Aspect Ratio of the two tire sizes is different, they have almost a similar sidewall height.

Hence 265/70 is wider but interchangeable with 255/75.

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 255/75r17 and 265/70r17 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 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.

Rim Diameter

To know which tire size fits for 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 255/75r17 is 17 inches. Similarly, the Rim Diameter of 265/70r17 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 255/75R17 vs 265/70R17 Tire

Yes. You can interchange the 255/75R17 tire with the 265/70R17 tire. Swapping from the 255/75R17 to  265/70R17 tire does not violate many issues because. The diameter difference and circumference remain under the limit of 3%.

Due to this, the RPM value increases by 1.3% which reduces the actual speed to the speedometer speed by a negligible margin. Therefore it won’t cause any trouble against the traffic rules.

Speedometer Difference: Using the current Tire Size 255/75r17 Instead Of the New Tire Size 265/70r17

Look at the Table. It shows differences in speedometer reading and the actual speed at any given time when the current Tire Size is 255/75r17 instead of 265/70r17. 

Speedo ReadingActual Speed
20 mph (32.19 km/h)19.72 mph (31.73 km/h)
25 mph (40.23 km/h)24.65 mph (39.67 km/h)
30 mph (48.28 km/h)29.58 mph (47.6 km/h)
35 mph (56.33 km/h)34.51 mph (55.53 km/h)
40 mph (64.37 km/h)39.44 mph (63.46 km/h)
45 mph (72.42 km/h)44.36 mph (71.4 km/h)

Speedometer Difference: Using current Tire Size 265/70r17 Instead Of New Tire Size 255/75r17

The table shows the differences in speedometer reading and the actual speed at any given time when the current Tire Size is 265/70r17 instead of 255/75r17.

Speedo ReadingActual Speed
20 mph (32.19 km/h)20.29 mph (32.65 km/h)
25 mph (40.23 km/h)25.36 mph (40.81 km/h)
30 mph (48.28 km/h)30.43 mph (48.97 km/h)
35 mph (56.33 km/h)35.5 mph (57.13 km/h)
40 mph (64.37 km/h)40.57 mph (65.3 km/h)
45 mph (72.42 km/h)45.64 mph (73.46 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 255/75r17 tire with the 265/70r17 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 255/75r17 and 265/70r17

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: 255/75r17 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 255/75r17 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 255/75r17 in Inches?

255/75r17 tires have a 32.1″ diameter, 10.0″ section width, and 17″ wheel diameter.

The circumference is 100.7″ and they make 629 revolutions per mile. The Sidewall Height of this Tire is 7.5 inches.

What Size Tires Is 265/70r17 in Inches?

265/70r17 tires have a diameter of 31.6″, a section width of 10.4″, and a wheel diameter of 17″. 

The circumference is 99.2″ and they have 638 revolutions per mile. The Sidewall Height of this Tire is 7.3 inches.

Conclusion

Going through this entire article would have enlightened you about the pros and cons of swapping 255/75R17 with 265/70R17.

You can swap the existing tire with the new one for getting more stability while driving. But if you want more top speed in your vehicle then staying with the previous one would do it.

You can interchange the tires as most data favors it without causing much trouble. But you can further study the tire sizes by going through the comparison charts.

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