How big is a 255 tire


What Do the Numbers on My Tires Mean?

Tires June 14, 2021

Being able to quickly glance at the sidewall of your tire and determine the tire size your specific vehicle needs can save you time, trouble and money. Even still, not many people know how to actually read a tire size even though it’s printed right there on the sidewall. As a mix of letters and numbers, it’s not as easy to read as finding a size 9 shoe. 

Why Tire Size Matters 

Other than the fact that tires need to physically fit on your vehicle, there are several reasons why having the correct tire size is necessary.  

Your tires support the entire weight of your vehicle and are the only parts of your car that actually make contact with the road. Making sure that you select the proper tire size when it’s time to shop for new tires is critical to the health of your tires and vehicle.

A tire’s job is to carry your vehicle and guide it where it needs to go, so when a tire is too large or too small, not only is performance hindered but your safety is also put at risk. Your tires need to be wide, strong and thick enough to carry the weight of your vehicle while still being able to turn and move. Scratching along the sides or getting caught while trying to turn could cause serious damage to your tires, forcing you to replace them much sooner than you’d otherwise need.  

What Do the Numbers on My Tires Mean?

Looking at tire size for the first time can feel like reading a foreign language, but once you learn how to break down what each section of the tire size means, you’ll find they’re not all that complicated.

Tire Type 

Tire type refers to the service or type of vehicle that the tire was designed for. “P” stands for “passenger” and is the most common type of tire. “LT” (light trucks that carry heavy loads) is another common tire type designation that you’ll likely run into. Other tire types include “T” (temporary), “ST” (trailer) and “C” (commercial). If there is no letter, that usually indicates that the tire was manufactured in Europe for European cars. These types of tires are called metric or Euro-metric tires and are similar in many ways to a passenger tire.

Tire Width 

Measured in millimeters, this is the distance from sidewall to sidewall across the width of your tire.

Aspect Ratio/Profile 

Aspect ratio refers to the relationship between the tire’s sidewall height and the tire’s width in the form of a percentage. Sidewall height can be determined by measuring the distance between the edge of the rim and the top of the tire at the edge of the tread. Aspect ratio translates to how well your vehicle can handle the tire. The higher the aspect ratio, the longer it takes for your tire to respond to a turning command, making lower aspect tires often easier to command.

Construction Type 

This refers to how the tire was constructed. Typically, you’ll only see “R” for “radial tire” since that is the most common type of tire produced nowadays. Radial tires are constructed by assembling piles perpendicular to the direction that they travel, allowing for a smoother ride, longer tread life and reduced fuel production.

Wheel Size/Rim Diameter 

Measured across the center of the tire from one end to the other, wheel size refers to the diameter of your wheel and is typically measured in inches. Overall wheel size is often indicated by the rim diameter as a shorthand for what size tire your vehicle needs.

Load Index 

Load index is a shorthand way of describing the total weight that the tire can handle when it is fully inflated. The higher the load index rating, the more weight the tire can carry. You need a tire load index rating chart to see how your load index rating correlates to the weight the tire can carry.  For example, a load index of 81 means that the tire can carry up to 1,019 pounds. Load index ratings for the average vehicle range from 75-100, but some tires can range all the way up to 150, which equates to 7,385 pounds.

Speed Rating 

Like load index, speed rating is another shorthand way to reference how fast the tire is designed to go. It is indicated by a letter that corresponds to the maximum speed of the tire. For example, a speed rating of “T” means that the tire is designed to go up to 118 miles per hour.

Read: A Guide to Tire Load Index & Speed Ratings

How to Read Tire Sizes

Breaking down a tire size measurement into its individual parts makes it easy to read once you’re in the know. Now that you know what each element of tire size means, we can walk through an example of how to read a tire size off of a sidewall.

Example: P255/45R18 103H

P (Tire Type): This tire is a passenger tire, one of the most common types of tires.

255 (Tire Width): The tire width is 255 millimeters from sidewall to sidewall (just over ten inches).  

45 (Aspect Ratio): The tire’s sidewall is 45% of the tire’s width, which means the sidewall is about 114 millimeters or just over 4 inches.

R (Construction Type): Radial tire, the most common type of tire produced today.

18 (Wheel Size/Rim Diameter): Going from edge to edge, the tire’s diameter is 18 inches across.

103 (Load Index): A load index of 103 means this tire can carry up to 1,929 lbs.

H (Speed Rating): A speed rating of “H” means that this tire is designed to withstand speeds up to 130 miles per hour.

In summary, a P255/45R18 103H tire would be a passenger tire with a width of 255 millimeters, a thickness or aspect ratio equal to 45% of the tire height which here is 114 millimeters. It is also a radially constructed tire with a diameter of 18 inches that can carry up to 1,929 pounds and can go up to 130 mph.

We’ll Help You Decode All Your Tire Needs

If reading tire sizes still seems like a mystery, drop by your local Virginia Tire & Auto and let our tire experts walk you through the process. We’ll help you find the exact tire your vehicle needs. Schedule an appointment online or call 855.425.3677 to talk to a tire expert.

Helpful Tire Info - BUDNIK

Our chart shows the overall section width, the outside diameter, the sidewall height and the recommended rim width range.

If your car requires something unique, start with picking the tire for the end of the car that is the most difficult.

If you’ve mini-tubbed the rear for example, and are going to run a big tire with less brand/tread/size choices, start by figuring out that size and what your options are. Then see if the those tire manufacturers also make a matching tire for your front.

We’ve included the sidewall height of the tire as a quick way to make sure your front tire doesn’t have a taller sidewall than your rear tire when doing staggered sizes. That’s usually not a good look.

There is a recommended rim width range for any given tire size with the ideal width usually around the middle of that spread. Some things to consider are how much sidewall bulge you want to see and most importantly, how wheel width affects the tires ride, handling and wear characteristics.

For grip and even wear the wheel width needs to allow for a good contact patch where the tread meets the pavement.

A wider wheel tends to make the tire more responsive to steering inputs but also taken to extremes can make the ride harsh because the sidewall doesn’t flex as easily.

A narrower wheel can give up some of that responsive handling and will tend to give a softer ride because the sidewall has more curve that flexes more easily.

Budnik Tire Chart     
      
      
SIZEOverall DiameterOverall (section) WidthSidewall HeightApprox Rim WidthsNitto Tires
205/40-1723.58.13.37.0-7.5NT01
205/45-1724.38.13.67 
205/50-1725. 18.147 
215/35-1722.98.537.0-8.5 
215/40-1723.88.53.47.0-8.5 
215/45-1724.78.53.87.0-8.0 
225/35-1723.28.93.17.5-9.0 
225/40-1724.18.93.57.5-9.0 
225/45-17258.947.0-8.5 
225/50-1725.98.94.46.0-8.0 
235/40-1724.49.33.78.0-9.5NT05,NT01
235/45-1725.39.34.27.5-9.0NT555, INVO
235/50-1726.39.34.66.5-8.5 
245/35-1723.89. 63.48.0-9.5 
245/40-1724.79.63.98.0-9.5INVO
245/45-1725.79.64.37.5-9.0INVO, NT01
245/50-1726.79.64.97.0-8.5 
255/40-17251048.5-10.0NT05,NT555,NT01
255/45-1726104.58.0-9.5 
265/40-1725.310.44.29.0-10.0 
275/40-1725.710.84.49.0-11.0 
275/50-1727.810.85.47.5-9.5 
285/40-172611.24.59.5-11.0NT555
315/35-1725.712.44.311.0-12.0NT05,NT555,NT01
      
18″Overall DiameterOverall (section) WidthSidewall HeightApprox Rim Widths 
205/40-1824. 58.13.27.0-8.0 
215/35-1823.98.537.0-8.5 
215/40-1824.88.53.47.0-8.5 
215/45-1825.68.53.87.0-8.0 
225/35-1824.28.93.17.5-9.0 
225/40-1825.18.93.67.5-9.0NT05,NT555,NT01
225/45-18268.947.0-8.5NT555, INVO
235/35-1824.59.33.29.0-9.5 
235/40-1825.49.33.78.0-9.5NT05, NT555, NT01
235/45-1826.39.34.27.5-9.0 
245/35-1824.89.63.48.0-9.5 
245/40-1825. 79.63.98.0-9.5NT05,NT555,INVO,NT01
245/45-1826.79.64.47.5-9.0NT555, INVO
245/50-1827.69.64.87.0-8.5 
255/35-1825103.58.5-10.0NT05, NT555
255/40-18261048.5-10.0 
255/45-1827104.58.0-9.5 
265/35-1825.310.43.79.0-10.0NT05, NT555, INVO
265/40-1826.310.44.29.0-10.0 
275/35-1826.710.83.89.0-11.0NT555, INVO,NT01
275/45-1826.710.84.98.5-10.5 
285/35-1825.911.23.99. 5-11.0NT05, NT555
295/35-1826.111.64.110.0-12.0NT05. INVO
315/30-1825.412.43.711.0-12.0NT05,NT01
335/30-1825.913.2412.0-13.0 
345/30-1826.113.64.112.0-14.0 
      
19″Overall DiameterOverall (section) WidthSidewall HeightApprox Rim Widths 
225/40-1926.18.93.57.0-9.0NT05, INVO
235/35-1925.59.33.28.0-9.5NT05, NT555,NT01
235/40-1926.49.33.78.0-9.5 
245/35-1925.89.63.48.0-9.5NT05, NT555, INVO
245/40-1926. 79.63.98.0-9.5NT05, INVO
245/45-1927.79.64.37.5-9.0 
255/30-19251038.5-9.5INVO
255/35-1926103.58.5-10.0INVO
255/40-19271048.5-10.0NT05, INVO
265/35-1926.310.43.79.0-10.5 
275/35-1926.610.83.89.0-11.0INVO
275/40-1927.710.84.39.0-11.0 
285/30-1925.711.23.49.5-10.5INVO
285/35-1926.911.23.99.5-11.0INVO
285/40-192811.24.59.5-11.0 
295/35-1927. 111.64.110.0-12.0INVO
305/30-1926.2123.610.5-11.5NT05,NT01
305/35-1927.4124.210.5-11.5 
315/40-1928.912.4511.0-12.0INVO
325/30-1926.712.83.812.0-13.0INVO
345/30-1927.113.64.112.0-14.0INVO
345/35-1928.513.64.811.0-13.5 
      
20″Overall DiameterOverall (section) WidthSidewall HeightApprox Rim Widths 
225/35-2026.28.93.17.5-9.0NT555
235/30-2025.69.32.88. 5INVO
235/35-2026.59.33.28.0-9.5 
235/45-2028.39.34.27.5-9.0 
235/55-2030.29.35.16.5-8.5 
245/30-2025.89.62.98.0-9.0NT555, INVO
245/35-2026.89.63.48.0-9.5NT555, INVO
245/40-2027.79.63.98.0-9.5NT555, INVO
245/45-2028.79.64.37.5-9.0INVO
245/50-2029.69.64.87.0-8.5 
255/30-20261038.5-9.5INVO
255/35-2027103.58.5-10NT05, NT555, INVO
255/40-20281048. 5-10NT01
255/45-2029104.58.0-9.5NT05, INVO
255/50-20301057.0-9.0 
255/55-2031105.57.0-9.0 
265/30-2026.310.43.19.0-10.0 
265/35-2027.310.43.79-10.5NT555
265/40-2028.310.44.29.0-10.5 
265/45-2029.410.44.78.5-10.0 
275/30-2026.510.83.29.0-10.0NT555, INVO
275/35-2027.610.83.99.0-11.0NT05, NT555, INVO
275/40-2028.710.84.39.0-11.0INVO
275/45-2029.710. 84.98.5-10.0 
285/30-2026.711.23.49.5-10.5NT555, INVO
285/35-2027.911.23.99.5-11.0NT01
285/40-202911.24.59.5-11.0 
285/45-2030.111.259.0-10.5 
295/30-202711.63.510.0-11.0 
295/35-2028.111.64.110.0-11.5INVO
295/40-2029.311.64.610.0-12.0 
295/45-2030.511.65.29.5-11.0 
295/50-2031.611.65.88.0-10.5 
305/35-2028.4124.210.0-12.0 
305/40-2029. 6124.810.0-12.0 
315/35-2028.712.44.310.5-12.5NT05, INVO
335/25-2026.613.2412.0-13.00 
335/30-2027.913.2411.5-12.5 
345/25-2026.813.63.412.0-13.0INVO
      
LT TRUCKOverall DiameterOverall (section) WidthSidewall HeightApprox Rim Widths 
265/60-2032.510.46.37.5-9.5TERRA
275/60-203310.86.57.5-9.5TERRA
285/55-6032.311.26.28.0-10.0TERRA
285/60-2033.511.26.78. 0-10.0 
305/55-2033.2126.68.5-11.0TERRA
      
22″Overall DiameterOverall (section) WidthSidewall HeightApprox Rim Widths 
235/30-2227.69.32.88.5 
245/30-2227.89.62.98.0-9.0NT555, INVO
255/30-22281038.0-8.5NT555, INVO
255/35-2229103.58.5-10INVO
265/30-2228.310.43.19.0-10.0INVO
265/35-2229.310.43.79.0-10.5420S
265/40-2230.310.44.29.0-10.5420S, NT555
265/45-2231. 410.44.78.5-10.0 
275/30-2228.510.83.29.0-10.0INVO
275/40-2230.710.84.39.0-11.0420S
275/45-2231.710.84.98.5-10.0420S
285/30-2228.711.23.49.5-10.5INVO
285/35-2229.911.23.99.5-11.0420S, NT555
285/40-223111.24.59.5-11.0420S
285/45-2232.111.259.0-11.0 
295/30-222911.63.510.0-11.0 
295/45-2232.511.65.29.5-11.0 
305/35-2230.4124.210.5-11.5 
305/40-2231. 6124.810.0-12.0 
305/45-2232.8125.49.0-1.0 
315/25-2228.212.43.111.0-12.0 
335/25-2228.510.83.211.5-12.5 
335/30-2228.713.73.312.0-13.0 

Tire size replacement table

Every motorist eventually comes to the moment when he wants to make a certain upgrade of the car. But any modification entails not only design changes, but also the improvement or deterioration of running gear. But is it possible to change tire sizes? Undoubtedly, this also applies to car tires with disks. Replacing tires and wheels is one of the most popular tuning manipulations. Everyone knows that wider and higher tires give the car solidity and attractiveness, even if the modified vehicle belongs to the budget category. But is increasing tire size really a good idea? Let's look at three options for replacing rubber with a factory dimension of full profile, low profile or extra low profile tire replacement options.

To begin with, it should be understood that the native size is chosen by designers for a reason. It is formed based on the technical capabilities of the car, its traction and acceleration characteristics. Also, the initial size is affected by the shape of the car body, weight, and its purpose.

Tire size is determined by three values, for example, in a tire with a size of 185 65 R14 they will be interpreted as follows:

  • 185 - profile width (not the tread!) in mm;
  • 65 - profile height in % of the profile width;
  • R14 - internal diameter in inches.

Changes to certain parameters have consequences in terms of clutch quality. Moreover, each case is private, there is no specific rule on how this or that modernization will affect the ride. In case of a planned change, it is necessary to consult with a specialist. Below is a table of replacement tire sizes.

Replacing R12 tires

Size 80 60 55 50 45 40
165/70 R12 145/80 R12 175/60 ​​R13 185/55 R13 205/50 R14 195/45 R14 ---------------
175/65 R12 (145 R12) 165/55 R14

Replacing R13 tires

Size 80 60 55 50 45 40
155/70 R13 155/80 R12 185/60 R13 195/55 R13 185/50 R14 195/45 R15
165/65 R13 (155 R12) 165/60 R14 185/55 R14
165/70 R13 145/80 R13 195/60 R13 195/55 R14 205/50 R14 215/45 R15 205/40 R16
175/65 R13 (145 R13) 175/60 ​​R15 175/55 R15 175/50 R15
175/70 R13 155/80 R13 205/60 R13 205/55 R14 195/50 R15 195/45 R16 225/40 R16
185/65 R13 (155 R13) 185/60 R14 185/55 R15 205/50 R15
185/70 R13 165/80 R13 215/60 R13 195/55 R15 215/50 R15 235/45 R15 205/40 R17
195/65 R13 (165 R13) 195/60 R14 205/55 R15 195/50 R16 205/45 R16 215/40 R17
195/70 R13 175/80 R13 205/60 R14 205/55 R15 225/50 R15 255/45 R15 255/40 R16

Replacing R14 tires

0036 80 60 55 50 45 40
195/65 R14 (175 R13) 185/60 R15 215/55 R15 205/50 R16 225/45 R16 225/40 R17
205/65 R14 (185 R13) 205/60 R15 205/55 R16 205/50 R17 205/50 R17 225/40 R18
165/70 R14 145/80 R14 215/60 R13 205/55 R14 205/50 R15 235/45 R15 225/40 R16
175/65 R14 (145 R14) 195/60 R14 185/55 R15 215/50 R15 205/45 R16 205/40 R17
175/70 R14 155/80 R14 205/60 R14 225/55 R14 225/50 R15 255/45 R15 255/40 R16
185/65 R14 (155 R14) 185/60 R15 205/55 R15 205/50 R16 215/45 R16 215/40 R17
185/70 R14 165/80 R14 215/60 R14 215/55 R15 215/50 R16 245/45 R16 235/40 R17
195/65 R14 (165 R14) 195/60 R15 205/55 R16 225/50 R16 205/45 R17 245/40 R17
195/70 R14 175/80 R14 235/60 R14 225/55 R15 235/50 R16 215/45 R17 255/40 R17
205/65 R14 (175 R14) 215/60 R15 215/55 R16 205/50 R17 225/45 R17 225/40 R18
205/70 R14 185/80 R14 245/60 R14 235/55 R15 245/50 R16 245/45 R17 275/40 R17
215/70 R14 195/80 R14 235/60 R15 225/55 R16 265/50 R16 255/45 R17 295/40 R17

Replacing R15 tires

Size 80 60 55 50 45 40
205/65 R15 (185 R14) 225/60 R15 225/55 R16 215/50 R17 255/45 R17 235/40 R18
215/65 R15 (195 R14) 215/60 R16 245/55 R16 225/50 R17 245/45 R18 255/40 R18
165/70 R15 145/80 R15 215/60 R14 215/55 R14 225/50 R14 225/45 R16 255/40 R16
175/65 R15 (205 R14) 195/60 R15 205/55 R15 215/50 R16 215/45 R17 235/40 R17
175/70 R15 155/80 R15 205/60 R15 225/55 R15 225/50 R16 245/45 R16 245/40 R17
185/65 R15 (155 R15) 195/60 R16 205/55 R16 205/50 R17 225/45 R17 225/40 R18
185/70 R15 165/80 R15 215/60 R15 235/55 R15 245/50 R16 235/45 R17 265/40 R17
195/65 R15 (165 R15) 205/60 R16 215/55 R16 215/50 R17 245/45 R17 235/40 R18
195/70 R15 175/80 R15 225/60 R15 225/55 R16 255/50 R16 245/45 R17 285/40 R17
215/65 R15 (175 R15) 215/60 R16 225/50 R17 255/45 R17 255/40 R18
205/70 R15 185/80 R15 235/60 R15 245/55 R16 265/50 R16 245/45 R18 265/40 R18
225/65 R15 (185 R15) 225/60 R16 225/55 R17 225/55 R17 255/40 R19
215/70 R15 195/80 R15 235/60 R16 235/55 R17 255/50 R17 255/45 R18 295/40 R18

Replacing R16 tires

Size 80 60 55 50 45 40
215/65 R16 (195 R15) 205/55 R18 235/50 R18 245/40 R20
205/70 R16 195/80 R15 235/60 R16 235/55 R17 255/50 R17 255/45 R18 285/40 R18
215/65 R16 (195 R15) 205/55 R18 235/50 R18 255/40 R19

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255/65 R17 vs 265/65 R17 Tire size comparison with graphic visualization

00

Your machine size

/ 25303540455055606570758085
R 121314151617181920212222. 52324

Calculate

00
135145155165175185195205215225235245255265275285295305315325335345355365375385395 / 25303540455055606570758085
R 121314151617181920212222.52324

New tire size

CM INCHES


Index Old New difference
Diameter - - -
Width - - -
Circumference - - -
Profile height - - -
RPM - - -
Clearance change -
Result: -

With speedometer:

Real speed will be:

Comparison of tire sizes 255/65 R17 and 265/65 R17.


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