Power Hungry Performance Forum  

Go Back   Power Hungry Performance Forum > FAQ > Tips, Tricks, Troubleshooting and Technical Documents

Search FAQ Search FAQ
Search Word(s):
Matching Options:
Search in:

How to Read Tire Ratings

I occasionally have people ask me, "How do I interpret the speed ratings on my tires?" This is important to understand in this business because we make a living out of helping people go fast. So after poking around a bit, I found a useful breakdown of tire speed and load ratings. I hope this is useful.


Using a P195/60R15 87S tire size as our example, the 87S at the end of the size represents the tire's service description. A service description identifies the tire's load index and speed rating. Service Descriptions are required on all speed rated (except for Z-speed rated) tires manufactured since 1991.

The first two digits (87S) represent the tire's load index and are followed by a single letter (87S) identifying the tire's speed rating.

Load Index

P195/60R15 87S - The load index (87) is the tire size's assigned numerical value used to compare relative load carrying capabilities. In the case of our example the 87 identifies the tires ability to carry approximately 1,201 pounds.

The higher the tire's load index number, the greater its load carrying capacity.

89 = 1,279 pounds
88 = 1,235 pounds
87 = 1,201 pounds
86 = 1,168 pounds
85 = 1,135 pounds

A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original.

Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110.

Load Index Pounds Kilograms
Load Index Pounds Kilograms
71 761 345 91 1356 615
72 783 355 92 1389 630
73 805 365 93 1433 650
74 827 375 94 1477 670
75 853 387 95 1521 690
76 882 400 96 1565 710
77 908 412 97 1609 730
78 937 425 98 1653 750
79 963 437 99 1709 775
80 992 450 100 1764 800
81 1019 462 101 1819 825
82 1047 475 102 1874 850
83 1074 487 103 1929 875
84 1102 500 104 1984 900
85 1135 515 105 2039 925
86 1168 530 106 2094 950
87 1201 545 107 2149 975
88 1235 560 108 2205 1000
89 1279 580 109 2271 1030
90 1323 600 110 2337 1060

Speed Rating

In Germany some highways do not have speed limits and high speed driving is permitted. Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments). Despite the tire manufacturer's ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.

Speed ratings are based on laboratory tests where the tire is pressed against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds (in 6.2 mph steps in 10 minute increments) until the tire's required speed has been met.

It is important to note that speed ratings only apply to tires that have not been damaged, altered, under-inflated or overloaded. Additionally, most tire manufacturers maintain that a tire that has been cut or punctured no longer retains the tire manufacturer's original speed rating, even after being repaired because the tire manufacturer can't control the quality of the repair.

Over the years, tire speed rating symbols have been marked on tires in any of three ways shown in the following examples:

225/50SR16 225/50SR16 89S or 225/50R16 89S

Each of these was an acceptable method of identifying speed ratings.

Early tires had their speed rating symbol shown "within" the tire size, such as 225/50SR16. Tires using this type of branding were not to have been produced after 1991.

225/50SR16 112 mph, 180 km/h
225/50HR16 130, 210 km/h
225/50VR16 in excess of 130 mph, 210 km/h

Beginning in 1991, the speed symbol denoting a fixed maximum speed capability of new tires must be shown only in the speed rating portion of the tire's service description, such as 225/50R16 89S. The most common tire speed rating symbols, maximum speeds and typical applications are shown below:

L 75 mph 120 km/h Off-Road & Light Truck Tires
M 81 mph 130 km/h
N 87 mph 140km/h Temporary Spare Tires
P 93 mph 150 km/h
Q 99 mph 160 km/h Studless & Studdable Winter Tires
R 106 mph 170 km/h H.D. Light Truck Tires
S 112 mph 180 km/h Family Sedans & Vans
T 118 mph 190 km/h Family Sedans & Vans
U 124 mph 200 km/h
H 130 mph 210 km/h Sport Sedans & Coupes
V 149 mph 240 km/h Sport Sedans, Coupes & Sports Cars

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.

W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars

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.

225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h

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:

285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h

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.





Submitted 12/05/2009

Bill Cohron
Power Hungry Performance

Data provided by Tirerack.com


Ford VIN Breakdown

Manufacturer Code

Positions one through three of the vehicle identification number (VIN) indicate the world manufacturer code.

1FD - Ford Motor Company, USA, incomplete vehicle
1FM - Ford Motor Company, USA, multi-purpose vehicle
1FT - Ford Motor Company, USA, truck, completed vehicle
2FM - Ford Motor Company, Canada, multi-purpose vehicle
3FD - Ford Motor Company, Mexico, incomplete vehicle

Brake and Gross Vehicle Weight Rating (GVWR)

Position four of the VIN indicates the vehicle brake type and GVWR code (all vehicles use hydraulic brakes).

N - 8,501-9,000 pounds GVWR with driver and front passenger air bags
S - 9,001-10,000 pounds GVWR with driver and front passenger air bags
W - 10,001-14,000 pounds GVWR with driver and front passenger air bags
X - 14,001-16,000 pounds GVWR with driver and front passenger air bags
A - 16,001-19,500 pounds GVWR with driver and front passenger air bags
H - 8,501-9,000 pounds GVWR, without air bags (Mexico)
J - 9,000-10,000 pounds GVWR, without air bags (Mexico)
K - 10,001-14,000 pounds GVWR, without air bags (Mexico)
L - 14,001-16,000 pounds GVWR, without air bags (Mexico)
M - 16,001-19,500 pounds GVWR, without air bags (Mexico)

Vehicle Line, Series and Body Type

Position five through seven of the VIN indicate the vehicle line, series and body type.

F20 - F-250, Regular Cab, 4x2, single rear wheels
X20 - F-250, SuperCab, 4x2, single rear wheels
W20 - F-250, Crew Cab, 4x2, single rear wheels
F21 - F-250, Regular Cab, 4x4, single rear wheels
X21 - F-250, SuperCab, 4x4, single rear wheels
W21 - F-250, Crew Cab, 4x4, single rear wheels
F30 - F-350, Regular Cab, 4x2, single rear wheels
X30 - F-350, SuperCab, 4x2, single rear wheels
W30 - F-350, Crew Cab, 4x2, single rear wheels
F31 - F-350, Regular Cab, 4x4, single rear wheels
X31 - F-350, SuperCab, 4x4, single rear wheels
W31 - F-350, Crew Cab, 4x4, single rear wheels
F32 - F-350, Regular Cab, 4x2, dual rear wheels
X32 - F-350, SuperCab, 4x2, dual rear wheels
W32 - F-350, Crew Cab, 4x2, dual rear wheels
F33 - F-350, Regular Cab, 4x4, dual rear wheels
X33 - F-350, SuperCab, 4x4, dual rear wheels
W33 - F-350, Crew Cab, 4x4, dual rear wheels
F34 - F-350, Regular Cab (Chassis Cab), 4x2, single rear wheels
X34 - F-350, SuperCab (Chassis Cab), 4x2, single rear wheels
W34 - F-350, Crew Cab (Chassis Cab), 4x2, single rear wheels
F35 - F-350, Regular Cab (Chassis Cab), 4x4, single rear wheels
X35 - F-350, SuperCab (Chassis Cab), 4x4, single rear wheels
W35 - F-350, Crew Cab (Chassis Cab), 4x4, single rear wheels
F36 - F-350, Regular Cab (Chassis Cab), 4x2, dual rear wheels
X36 - F-350, SuperCab (Chassis Cab), 4x2, dual rear wheels
W36 - F-350, Crew Cab (Chassis Cab), 4x2, dual rear wheels
F37 - F-350, Regular Cab (Chassis Cab), 4x4, dual rear wheels
X37 - F-350, SuperCab (Chassis Cab), 4x4, dual rear wheels
W37 - F-350, Crew Cab (Chassis Cab), 4x4, dual rear wheels
F46 - F-450, Regular Cab (Chassis Cab), 4x2
W46 - F-450, Crew Cab (Chassis Cab), 4x2
W42 - F-450, Crew Cab (with box), 4x2, dual rear wheels
W43 - F-450, Crew Cab (with box), 4x4, dual rear wheels
F47 - F-450, Regular Cab (Chassis Cab), 4x4
W47 - F-450, Crew Cab (Chassis Cab), 4x4
F56 - F-550, Regular Cab (Chassis Cab), 4x2
W56 - F-550, Crew Cab (Chassis Cab), 4x2
F57 - F-550, Regular Cab (Chassis Cab), 4x4
X46 - F-450, SuperCab (Chassis Cab), 4x2
X47 - F-450, SuperCab (Chassis Cab), 4x4
X56 - F-550, SuperCab (Chassis Cab), 4x2
X57 - F-550, SuperCab (Chassis Cab), 4x4
W57 - F-550, Crew Cab, (Chassis Cab), 4x4
U40 - Excursion, 4x2, XLT
U41 - Excursion, four-door, 4x4, XLT
U42 - Excursion, four-door, 4x2, Limited
U43 - Excursion, four-door, 4x4, Limited

Engine Type

Position eight of the VIN indicates the engine displacement and number of cylinders.

L - 5.4L, Modular, SOHC, EFI, V8, Gas
S - 6.8L, SOHC, EFI, V10, Gas
F - 7.3L, OHV, DI Turbo, V8, Diesel
Z - 6.8L, gaseous fuel prep (F-Series)
D - 6.8L, propane only (F-Series)
B - 5.4L, propane only (F-Series)

Check Digit

Position nine of the VIN is a government assigned, computer-generated check digit.

Model Year

Position ten of the VIN indicates the model year code.

A - 1980
B - 1981
C - 1982
D - 1983
E - 1984
F - 1985
G - 1986
H - 1987
J - 1988
K - 1989
L - 1990
M - 1991
N - 1992
P - 1993
R - 1994
S - 1995
T - 1996
V - 1997
W - 1998
X - 1999
Y - 2000
1 - 2001
2 - 2002
3 - 2003
4 - 2004
5 - 2005
6 - 2006
7 - 2007
8 - 2008
9 - 2009

Assembly Plant Code

Position eleven of the VIN indicates the assembly plant code.

S - Allen Park (Allen Park, Michigan)
E - Kentucky Truck (Jefferson County, Kentucky)
M - Cuautitlan (Cuautitlan, Mexico)

Vehicle Build Sequence Code

Positions twelve through seventeen of the VIN are an alphanumeric code for the vehicle build sequence. This is also the vehicle serial and warranty number.





Submitted 12/05/2009

Bill Cohron
Power Hungry Performance



All times are GMT -4. The time now is 04:56 PM.


All Contents Copyright 2008-2024, Power Hungry Performance