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How do the Different Tire Sizes Work?

Tire sizes may seem cryptic, but they're a blend of width, aspect ratio, and wheel diameter, crucial for vehicle performance and safety. Each dimension affects your ride's handling, fuel efficiency, and comfort. Understanding this code ensures a perfect match for your car's needs. Curious about how to decode these numbers for a smoother ride? Let's dive deeper.
J. Dellaporta
J. Dellaporta

Tire sizes express the tire’s various measurements in a standardized format written on the side of the tire, also called the sidewall. The three measurements included in all tire sizes are section width, aspect ratio, and diameter. Depending on their intended use, some tire sizes also include information such as speed rating.

Tire sizes are expressed in the format WWW/AAXDD. WWW is the tire’s section width, measured in millimeters. AA is the aspect ratio or profile of the tire, which expresses the tire’s height as a percentage of its width. X is a letter indicating the tire’s internal construction. DD is the diameter in inches of the wheel that the tire is intended to be mounted on. An example of a tire size written in this format is 225/50R16.

Tires for sale.
Tires for sale.

This particular tire has a section width of 225 millimeters (8.86 inches). Section width is measured from the widest point of the outer sidewall - the side with the sizes and brand name that faces out from the vehicle - to the widest point of the inner sidewall when the tire is mounted on a specified width wheel. Narrower tires have lower section width numbers.

A woman filling her tires up with air.
A woman filling her tires up with air.

The next number is the aspect ratio. The sizes separate the section width from the aspect ratio with a slash. This tire has an aspect ratio of 50, meaning that the profile, or sidewall height measured from wheel to tread, is 50% of the section width. This number is also called section height; the higher the number, the taller the sidewall.

Tire sizes include a letter following the section height that is not a measurement, but an identification of the tire’s internal construction. This “R” indicates radial construction, in which the tire’s body plies “radiate” outward from the wheel’s center. A “D” indicates plies that crisscross diagonally, used for light truck or spare tires. Sizes with a “B” are belted and nearly obsolete.

The final number indicates the tire and wheel diameter to be used together - in this case, 16 inches. These inch rim sizes are used on most passenger vehicles, while some tires used on heavy-duty trucks or trailers use “half inch” sizes, e.g. 14.5. Some manufacturers' sizes express rim diameter in millimeters, or include different dimensions for the inside and outside edges of the tire. These sizes are intended for use with specific vehicles and should not be combined with traditional tire sizes.

Tire sizes follow the rim diameter with a service description, a code indicating load capacity and speed rating. This service description is required on all tires manufactured since 1991, except for Z-speed rated tires, which express sizes with a “Z” following the aspect ratio.

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Discussion Comments


ANS: 33x12.50 is typically used for Light Truck tires sizing and is know as the LTN system. Theses measurements are in inches (1 in = 25.4 mm), but are not exact. I found a converter online. Using that converter, the diameter if that tire is "33.03 inches or 838.96 mm" and the width is "12.52 inches or 318.01 mm."


I have a 2001 Buick Lesabre. Can I replace my 215/70r15 tires and rims with 225/60r16 tires and rims?


My suv calls for 265/70R15. What would be a good alternative that would also give good gas mileage?


Will p225/55r17 work on my car that had factory p205/60r15??


Can I fit a 215/70R15 tire on a rim that correctly has a 275/60R15 tire?


I have a 2007 Mazda 3 2L. My tire profile is original 195/60R15 and I was wondering if I could use a 205/55r16 winter tire.


I have a 2007 Edge with 235/65/17 tires and was told to go to 265/70 17 tires for better ride and control. Is this true?


Can I put four R15 tires on my 2007 Toyota Camry?


Will 265/70/17 tires already on rims fit on my 98 dodge ram 1500 that has 245/75/16 tires?


I drive a 2003 Dodge Durango SLT, was wondering if I could use size p225/75r16 instead of p245/70r16 tires?


Will a set of 255/70r15 tires fit on my 98' dodge durango?


Can I change from a 245/65r17 to 225/45r17


will a 245/60r19 fit a Saturn Outlook that has 255/60r19 tires on it now/?


I am using 33X12.50 R 16.5 on all four. I want a lower but same wide tire. What size is there for a light truck. Do they make a 30X12.50 R16.5 LT?


If I have 215/60/16.950 tires, can I use 205/55/16?


Would my winter studded 225/60r16s fit my 205/55r16s?


can I change my trailer tires from 205/75r15 to 205/75r14?


Will a 275 /70r 18 fit onto p255/65 r18 rim?


I have a question. The rims I have are u2 35s and they are 20 x 7.5. It has 225/30/20 tires but I want them a little bigger. What size should I get? I want to try 225/35/20. Is that good? Please help.


I have p16580r13 tires on a single axle trailer. Can I put p17570r13? or what other size 13 can I put on?


My car runs on 225-65-17 tires. Can I change them to 255-60-17?


I just bought a set of winter tires, P215/65R17 and now it turns out that we need to get another vehicle because ours is just not compatible for work etc. Do you know what other vehicles might take the same size of tire so I can get my new tires put on my new vehicle?


I have bought used mercedes s320 (2001), catalog (manual book) says the tires should be 225x60 r16 100v with original wheels, however the car had 235x60 r16 100w tires, and I have been using for more than 18 months. I made a thousand miles with 235x60 r16 100w no problem. Now the treads are worn out and I'm looking for new 235x60 r16 100w.


I now have 275/60/18s. Can I put a 275/65/18 on my car without worrying?


Can I put 245 65 17 tires on when the manufacturer used 235 65 17?


Why does everyone keep asking questions and no one is answering? I suppose this one won't get answered either.


I have three tires on my dodge durango that are 265 60 R18 and the spare they had under my truck is a 265 65 R17. How bad is this on my truck? I have called every tire company in my area to try to find a used tire to match the three I already have because they still have about 50-60 percent good tread.


My Car is P205/60 R16. I want to replace them with a P215/45 R17.

The aspect ratio is not well-understood and that's why I would like to ask, what difference would it make if I put them on my car. How does the aspect ration difference cause an effect (in what way)?


I have a Pontiac Trans Sport van. Original tires are 215/70R15. Can I change them to 215/65R15 without much to worry about?


I have a Santa Fe with 235/60R18 tires on them. Can I put 225 or 245 60/18 on it instead? Will it make a difference?


I currently have 225's on my truck but the owners manual says they should be 265. I've have these tires for over 40,000 miles. What kind of risk am I running by buying another set of 225's?


i have 225/55/18 now can i replace them with 235/50/18? thanks.


I have a question about tire size. I have a Dodge Caliber which has 215 55 R18's fitted. I need to replace a tire but am having trouble finding the 215 55 R18's. Can i use a different tire and would there be any problems. Cheers.


is the middle number(225/((60))R16) is higher your speedometer will read slightly lower and vice versa. is you have different middle numbers on front and back it can screw up your abs (anti lock brakes).


Jeep Patriot original tires 205/70R16 hard to find I was recommended to change to P215/65R17. Would this work?


Can I replace a tire ST205/75D14 with a ST205/75R14?


Can I use 245/65 R17 in place of 235/85 R17 on a Chrysler Pacific Touring AWD or is this a no no?


Can I interchange 205/65R15 with 205/70R15. Is there any danger?


i have size 385/65-R22.5 can i use 315/80-R22.5


I think a metric tire is calculated as follows:- 265 x 75 x 15 tires: 265mm (10.43 inches) wide x 75% of 265 (aspect ratio) = 7.82 inches high (rim to tread surface) x 15 inch (wheel).

A USA size would be calculated as follows:- 32 x 11,5 x 15.

32 inches tall (from the ground to the top of the tire) x 11.5 inches (291.98mm) wide x 15 wheel.

The height from rim to tread surface (termed aspect ratio in the 75) is actually 8.5 inches. (Tallness 32 inches – 15 inch rims = 17 divided by 2 = 8.5 inches. (8.5 inches rim to tread on ground and 8.5 inches rim to top of tire.


What are the pros and cons of the different rim sizes sold on trucks, such as 15, vs 18, etc.? Is there any mileage, or performance difference?


Can i use p275 70r16 on rims that currently use p 245 70r16 ?


I have a Buick Lesabre 205/70R15. can I use 205/65R15 on it?


can you replace a 165/70r13 with a 155/70r13?


I want to buy a new set of tires. I cannot choose but heard select Dunlap. I live in Iran please help me.


i recently bought a saturn outlook with tires of size p255/65r18. can they be replaced with p265/60r18?


Hi my question is that can you put two wheels the same tire size and put two different wheels on the other side of the truck?


what is the difference between radial tires and a normal tire. Please let us know about advantages and disandvantages.


can 195/55-15 replace 205/50-15? i drive a VW passat


original tire is 175/70-13. The car is Lancer 1300CC. is there any problem to place 205/50-13?


can 225 70 16 be replaced by 215 65 16? --

hyndia san fe


Was there any question posted here that has been answered, if at all?


My 2000 Cavalier has 195/65r15 tires. Can I use 215/65r15 on it instead?


My son has a 1998 Subaru Legacy Outback. Original tire size is 205/70/15. It now has 215/65/15 tires on it. Would there be any problem putting 215/60/15 tires on it?


for anon 1867. 33x12.50. you have an american sized tire. where say 175/70 is a metric size. your tire size 33x12.50 is 33 inches tall and 12 and a half inches wide tread. radial with 17 inch rim.


I had a set of 4 P255/65r17 on my SUV. I had an irreparable puncture to one of them and have replaced it with my full sized spare which is a P245/65r17. Can I go 10k miles like this or am I damaging my car? Thanks.


I have original size 195/65 R15 tires on my Mercedes. Would it be okay to put on 205/65 R15's? --Pete


I have 39 x 18 x 16.5 can i put 39 x 15 x 16.5 on my wheels?


Can I use 2 225/75R15 Long Trails with 2 215/75R15 Long Trails on the same car? The 225/75R15 on the front and the 215 on the rear.


I have a Honda Civic. Tire is 205 55R16. Somebody is giving me a set of winter tires size 205 65R16. Is it okay to use for my civic? Please let me know.


Mr. Worried


What is the new tire size to compare to 760/15 in old size?


If that is the case, my old tire is 205/65R15, which matches the car manual. However, can I use 195/65R15 tires on my car?



33 is the tire height while the 12.50 is the width of the tire...measurements can be throw off if the tire has new (presumably knobby) tread or it is mounted on an incorrect sized rim.


Here is a question about tire sizes. I have found plenty of information about the WWW/AAXDD tire sizes. However, I can not find what the following means, 33x12.50R-17. The R means radial, and the 17 is the rim size. What does "33X12.50" mean?

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