How to read your tire (most of us Know this but some dont)

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How to read your tire (most of us Know this but some dont) Empty How to read your tire (most of us Know this but some dont)

Post by Limey SE on Mon Dec 13, 2010 4:17 am

I am just putting this for general tire size help and basic info for some people have never learned that much about there codes for the tire

How to read your tire (most of us Know this but some dont) Tire_diagramThe DOT safety standard code is the date of manufacture of tire

Here's the breakdown on the US DOT tire date code. Tires made in the 90's use 3 numbers and tires made since 2000 have 4 numbers. If your tire does not have this style of code it is either non-DOT approved or too old in which case it is unsafe to use.

Quote from our TIA training guide: "According to experts, tires older than 6 years get increasingly more dangerous regardless of how long they've actually been on the road."

The tire size shown here is a Michelin Pilot Sport. DOT FH4Y HUEX 1505

DOT=Tire meets DOT safety standard.
FH=DOT's tire plant code
4Y=Tire size code
HUEX=Manufacturer symbol identifying tire brand
1505=Week and year tire was made-15th week of the year 2005

Prior to year 2000 three numbers are used for the Date of manufacture, first two numbers identify the week and the last number identifies the year of manufacture. To identify tires manufactured in the 90's a decade symbol (a triangle on its side) is located at the end of the DOT serial number.

Tire Math

Lets take the example picture from above. The tire size is 225/65/15. The first number 225 is the width of the tire in Millimeters. The second number 65 represents the sidewall and is a percentage of the first number 225. The last number 15 is the inner diameter measured in inches.

How do I find out how tall the side wall is?

225 (frist number) * .65 (second number) / 2 gives you the sidewall height from the outside of the wheel to the outside of the tire. To convert inches you need to divide answer by 25.4.

Speed Ratings

M 81 mph
Q 99 mph
R 106 mph
S 112 mph
T 118 mph
U 124 mph
H 130 mph
V 149 mph
W 168 mph
Y 186 mph+

*Z Rating Breakdown*

P295/35ZR19 max speed > 149 mph
*consult tire manufacturer for exact speed.*
P295/35ZR19 93W max mph = 168 mph
P295/35ZR19 93Y max mph 186 mph
P295/35ZR19 (93Y) max mph 186 +
*consult tire manufacture for exact speed.*
How to read your tire (most of us Know this but some dont) Tire_speed_ratings

Load Ratings

Load index is a number ranging from 0 to 270 that references with the load carrying capacity of a tire. Most passenger car tire load index range from 75 to 105. The higher the load index number the more load carrying capacity they have.

Using the example picture above, tire size 225/65R16 89H, the load index of 89 corresponds to a load carrying capacity of 1279 lbs. The H is a reference to the speed rating. As you can see in the above speed rating chart H is speed rated up to 130mph.

1977 Chevelle SE x2
One Mild original
one Wild NON original
Limey SE
Limey SE

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