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How do the Different Tire Sizes Work?

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  • Last Modified Date: 30 September 2014
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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.

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 tire 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.

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The next number is the aspect ratio. Tire 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. Tire sizes with a “B” are belted and nearly obsolete.

The final number in the tire size 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 carry tire sizes that express rim diameter in millimeters, or that include different dimensions for the inside and outside edges of the tire. These tire 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 have tire sizes with a “Z” following the aspect ratio.

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Discuss this Article

anon971895
Post 70

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

anon947826
Post 69

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

mgalarza
Post 68

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

anon354593
Post 67

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.

anon346658
Post 66

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?

anon346229
Post 65

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

anon339740
Post 64

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

anon337606
Post 63

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

anon321405
Post 62

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

anon320852
Post 61

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

anon308434
Post 60

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

anon307355
Post 59

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?

anon303548
Post 58

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

anon302368
Post 57

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

anon269672
Post 56

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

anon266405
Post 55

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

ycarrillo
Post 54

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.

anon263330
Post 52

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

anon247434
Post 50

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

anon242560
Post 49

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?

anon231991
Post 48

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.

anon231405
Post 47

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

anon221155
Post 46

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

anon210551
Post 45

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

Moderator's reply: Thank you for visiting wiseGEEK and participating in our discussions! Unfortunately, we are not equipped to respond to specific questions, which is why we created this discussion section on each article page. In this section, a reader may discuss article topics with other readers. Whether and when questions will be answered, however, depends on fellow readers and posters.

Thanks!

The wiseGEEK Team

anon207006
Post 44

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.

anon187281
Post 43

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)?

anon179292
Post 42

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

anon158913
Post 40

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?

anon142980
Post 38

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?

anon142914
Post 37

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

liondaniel
Post 36

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.

anon133460
Post 34

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).

anon130905
Post 33

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

anon123816
Post 32

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

anon122817
Post 31

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

anon114516
Post 30

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

anon110941
Post 29

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

anon109063
Post 28

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.

anon99673
Post 27

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?

anon86753
Post 26

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

anon86496
Post 25

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

anon84069
Post 24

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

anon64136
Post 23

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

anon64047
Post 22

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

anon54696
Post 20

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?

anon54019
Post 19

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

anon53342
Post 18

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

anon47103
Post 17

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

anon42111
Post 16

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

hyndia san fe

anon32619
Post 15

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

anon28622
Post 14

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

brucejayne
Post 13

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?

anon25412
Post 12

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.

wpsantan
Post 10

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.

anon9872
Post 8

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

anon8823
Post 7

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

anon6806
Post 6

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.

anon6193
Post 5

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.

Thanks

Mr. Worried

anon4215
Post 4

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

anon4104
Post 3

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?

Thanks

anon3952
Post 2

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.

anon1867
Post 1

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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