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Det_Riot

How to Read Sidewall Writing

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This is a very simple process for those trying to decipher the numbers and letters on your tires. Most importantly, your overall tire height. This is helpful if you want to upgrade your rim size and keep the same overall dimensions or for calculation of gear needs.

For this example, we're going to use the sample tire size P215/50R17 91V

The first character, usually P, LT, or T stand for the type of vehicle this tire has been engineered for.

P for passenger car

LT for light truck

T for temporary

etc, etc

If there is no indication of a character, then the tire has been manufacturer in accordance with European Standards

Common tire sizes are broken down into three parts

First Number: Tread Width, usually in millimeters (215)

Second Number: Sidewall Ratio of tread width to sidewall height (50)

In this example, the side wall is 50% of the tread width

Sidewall height = Tread width * Sidewall Ratio

Sidewall height = 215mm * 50%

(when multiplying a percentage, use a decimal to signify the percent of the value we are multiplying. In our case, use
.50
)

Sidewall height = 107.5mm

To convert this number to inches, multiply the Sidewall height by .03937

107.5mm * .03937 = 4.23in

Third Number: Wheel Diameter (R17) The R in the third number stands for a Radial Tire.

Now, In order to determine total tire height, Multiple the sidewall height by 2 (to account for the top and bottom sidewall) and then add the rim diameter

4.23in + 4.23in + 17in = 25.46in

The next part I copied from another site as it explains it best

"The second part of the number is the service description. Written here as 91V, this tells us two things.

First, 91 indicates the tire's load index. This is an assigned numerical value used to compare the relative load-carrying capabilities of any given tire. In general, higher numbers indicate greater load carrying capacities.

A standard conversion table is used to decode the maximum load for any given tire. The scale starts at 50 (418.8 pounds) and goes up in single increments to 124 (3,527.5 pounds) though most modern passenger cars and light trucks fall somewhere between 70 and 110. In our example, this tire can be loaded with up to 1,356 pounds.

Second, and just as important, is the speed rating for this tire. This is also an assigned value system. In this case, V indicates this tire is approved for speeds up to 149 mph."

[TABLE=width: 600, align: center]

[TR=bgcolor: transparent]

[TD=bgcolor: transparent]Rating[/TD]

[TD=bgcolor: transparent]

M

[/TD]

[TD=bgcolor: transparent]

N

[/TD]

[TD=bgcolor: transparent]

P

[/TD]

[TD=bgcolor: transparent]

Q

[/TD]

[TD=bgcolor: transparent]

R

[/TD]

[TD=bgcolor: transparent]

S

[/TD]

[TD=bgcolor: transparent]

T

[/TD]

[TD=bgcolor: transparent]

U

[/TD]

[TD=bgcolor: transparent]

H

[/TD]

[TD=bgcolor: transparent]

V

[/TD]

[TD=bgcolor: transparent]

W

[/TD]

[TD=bgcolor: transparent]

Y

[/TD]

[TD=bgcolor: transparent]

Z

[/TD]

[/TR]

[TR=bgcolor: transparent]

[TD=bgcolor: transparent]Max. MPH[/TD]

[TD=bgcolor: transparent]

81

[/TD]

[TD=bgcolor: transparent]

87

[/TD]

[TD=bgcolor: transparent]

93

[/TD]

[TD=bgcolor: transparent]

99

[/TD]

[TD=bgcolor: transparent]

106

[/TD]

[TD=bgcolor: transparent]

112

[/TD]

[TD=bgcolor: transparent]

118

[/TD]

[TD=bgcolor: transparent]

124

[/TD]

[TD=bgcolor: transparent]

130

[/TD]

[TD=bgcolor: transparent]

149

[/TD]

[TD=bgcolor: transparent]

168

[/TD]

[TD=bgcolor: transparent]

186

[/TD]

[TD=bgcolor: transparent]

>149

[/TD]

[/TR]

[TR=bgcolor: transparent]

[TD=bgcolor: transparent]Max. KM/H[/TD]

[TD=bgcolor: transparent]

130

[/TD]

[TD=bgcolor: transparent]

140

[/TD]

[TD=bgcolor: transparent]

150

[/TD]

[TD=bgcolor: transparent]

160

[/TD]

[TD=bgcolor: transparent]

170

[/TD]

[TD=bgcolor: transparent]

180

[/TD]

[TD=bgcolor: transparent]

190

[/TD]

[TD=bgcolor: transparent]

200

[/TD]

[TD=bgcolor: transparent]

210

[/TD]

[TD=bgcolor: transparent]

240

[/TD]

[TD=bgcolor: transparent]

270

[/TD]

[TD=bgcolor: transparent]

300

[/TD]

[TD=bgcolor: transparent]

>240

[/TD]

[/TR]

[/TABLE]

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When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

[TABLE=width: 90%, align: center]

[TR]

[TD=width: 15%, bgcolor: #e0e0e0]W[/TD]

[TD=width: 20%, bgcolor: #e0e0e0]168 mph[/TD]

[TD=width: 20%, bgcolor: #e0e0e0]270 km/h[/TD]

[TD=width: 45%, bgcolor: #e0e0e0]Exotic Sports Cars[/TD]

[/TR]

[TR]

[TD=width: 15%]Y[/TD]

[TD=width: 20%]186 mph[/TD]

[TD=width: 20%]300 km/h[/TD]

[TD=width: 45%]Exotic Sports Cars[/TD]

[/TR]

[/TABLE]

While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

[TABLE=width: 90%, align: center]

[TR]

[TD=width: 50%, bgcolor: #e0e0e0]225/50ZR16[/TD]

[TD=width: 50%, bgcolor: #e0e0e0]in excess of 149 mph, 240 km/h[/TD]

[/TR]

[TR]

[TD=width: 50%]205/45ZR17 88W[/TD]

[TD=width: 50%]168 mph, 270 km/h[/TD]

[/TR]

[TR]

[TD=width: 50%, bgcolor: #e0e0e0]285/35ZR19 99Y[/TD]

[TD=width: 50%, bgcolor: #e0e0e0]186 mph, 300 km/h[/TD]

[/TR]

[/TABLE]

Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

[TABLE=width: 90%, align: center]

[TR]

[TD=width: 50%, bgcolor: #e0e0e0]285/35ZR19 99Y[/TD]

[TD=width: 50%, bgcolor: #e0e0e0]186 mph, 300 km/h[/TD]

[/TR]

[TR]

[TD=width: 50%]285/35ZR19 (99Y)[/TD]

[TD=width: 50%]in excess of 186 mph, 300 km/h[/TD]

[/TR]

[/TABLE]

As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------

In the tire industry, there are certain abbreviations that are used frequently and often those of us in the business forget that not everyone we talk to knows what all of the jargon means.

For example O.E. stands for Original Equipment and Ser. Des. means service description.

Other abbreviations associated with tires include:

The list can go on on from here, but these are some of the more common abbreviations used in the tire industry.

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Great bit of info here, Is there anything about D.O.T Numbers in there somewere that i missed?

Its good to know how to read the DOT to tell what the tires age is, Atleast with buying used tires so your not buying anything thats typically 6+ Years old..

For example your DOT Number might read " WYX4 HJY (2712) " The only part that matters is the end of the DOT that tells you that the tire was made on the 27th week of 2012. So if you come across a tire with a DOT number of (2405) That tire is no longer any good and shouldn't even been on the road.

If this help at all let me know, if not i can find a better explination of what im trying to say here :)

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Ah good call as well..I almost responded with that same info. then saw you posted the answer.. lol

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Most people don't know, and working with tires every day it was the first thing that came to mind.

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Who do you work for? I work for a Goodyear shop lol. I hate it

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Gonna keep this here for reference:

Sumitumos 275/40/17 = 25.6"

Kumho Xs 275/35/17 = 25.1"

M/T Radias 295/50/17 = 27.5"

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I work for pepboys, I make no money here and I hate it. But sadly where I live jobs are hard to come by unless you wana work for Disney :(

Heads up and ass kickin! Using Tapatalk 2

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