Contents: Passenger Tires | Light Truck, Jeeps & SUV | Tire Size | Large wheel - Low Profile Tires | Air Pressure | Miscellaneous/Tips | Ratings (Car , Truck)
Typical Passenger Tire

Labeling information at:
Handyman USA from Tire Guides, Inc., Boca Raton, FL
NHTSA: Cars, Light Trucks

Source: Tire Rack

Section Height = Width * Aspect Ratio
Diameter = wheel diameter + (Section height x 2) / 25.4 mm/in
e.g. for 235/75R15: Diameter = 15 + (235 * .75 * 2) / 25.4 = 28.9 in
Speed Index
Lode Index
P - Passenger
LT - Light Truck
AT - All Terrains
MT - Mud Terrains
SL - Standard Load
XL - Extra Load
HT - Highway Tread
AP - All Purpose
ST - Special Trailer
M+S or M/S-
  Mud & Snow
- Snow tire
Index MPH
G 56
H 130
K 68
L 75
M 81
N 87
P 93
Q 99
R 106
Index MPH
S 112
T 118
U 124
H 130
V >130
Z >149
W 168
Y 186
ZR >186
Index lbs.
71 761
75 853
80 992
81 1,019
82 1,047
83 1,074
84 1,102
85 1,135
86 1,168
87 1,201
88 1,235
Index lbs.
89 1,279
90 1,323
91 1,356
92 1,389
93 1,433
94 1,477
95 1,521
96 1,565
100 1,764
105 2,039
110 2,337
Source: Tire Rack Source: Tire Rack

A Mud & Snow (M+S or M/S) rating is a secondary designation and will appear in addition to other designations when a tire meets the RMA definition of a mud and snow tire.
This symbol designates a tire for severe snow conditions. (i.e. a snow tire)

For tires having a maximum speed capability above 240 km/h (149 mph), a "ZR" may appear in the size designation. For tires having a maximum speed capability above 300 km/h (186 mph), a "ZR" must appear in the size designation.

The Department of Transportation (DOT) requires each manufacturer to grade its tires under the Uniform Tire Quality Grade (UTQG) labeling system and establish ratings for treadwear, traction (The tire's ability to stop on wet pavement) and temperature resistance.

A tire graded 200 would wear twice as long as one graded 100.

Tread Wear:
A Best
B Intermediate
C Acceptable
A Best
B Intermediate
C Acceptable
Traction :
Standard SL 35  
Extra XL 41 
B LRB 354
C LRC 50 6
D LRD 658
E LRE 8010
F LRF 9512
Load Range (LR)
A term which is gradually replacing the term "Ply Rating" and which is indicated as Standard Load (SL) and Extra Load (XL) for auto tires and Load Range C, D etc. for light truck tires. It helps identify its strength and ability to contain air pressure. (The carrying capacity is increased with higher air inflation pressures.)
LR Can be designated after the description e.g. 31x10.50R-15C or after the LR on the sidewall e.g. LRC
Today's load range/ply ratings do not count the actual number of body ply layers found inside the tire, but indicate an equivalent strength based on early bias ply tires. Most cars now have 1-2 plys and light truck tires have 2-3 plys.
See: Tire Specs Explained at
Labeling Systems:
P & LT Metric and European Metric: P225/75R15

LT Flotation (Light truck "flotation" tire, designed to deliver better traction on sand and soft soil found in watery off-road situations):
29X9.50R15LT [29 - Tire Diameter, 9.5 -tire's section width in inches]

LT Numeric (older sizing system is still used on older commercial vehicles):
8.00R16.5LT [8.00 = tire's section width in inches, 16.5 - rim diameter]

all season performance<BR>all season ultra high performance winter all terrain
All-season Performanced All-season Ultra-High
Winter All-terrain
Some other examples:
BF Goodrich Mud-Terrain T/A

Light Trucks, Jeeps and SUVs

all season all-terrain mud-terrain
Maximum Traction
See also: Off-road tires
Size Type Diam Diam
P205/75R15 AT 27   8      
P215/75R15 AT 27.5   8.5   755 X, S(-2002)
P225/75R15 AT 28.5   8.9   733 S, X(O)
LT235/75R15 AT 29 29/29.1 9.25 7.5
30x9.5xR15 LT AT 29.5 29.7/29.8 9.5   719 S(O), U
LT245/75R16 on/off road 30.5 30.7/30.7 9.6  677 R, U(O)
P265/75R15 AT 30.5   10.4    
33+ off-road tires.
More on Tire Sizes for Light Trucks at
* Jeep - X-X, S-Sport, R-Rubicon, U-Unlimited, (O)-Optional
† BF Godrich and Goodyear Diameters are for Mud-Terrain tires

See larger sizes at off-road tires.
Tire ratings below.

All Terrains (ATs) and Mud Terrains (MTs). All Terrains are far superior on wet or icy roads, and they also do well on many types of off-road terrain (except for mud, where the narrow channels quickly get clogged). On the other hand, MT's are great in all types of off-road terrain, from plowing through mud to climbing over rocks. The great majority of trail riders that I know use Mud Terrains. MTs are dangerous in icy conditions.

Tire Size:

Tire Sizes for Light Trucks at

  • Changing to a larger diameter tire will have the following effects:
    • Raised center of gravity for better clearance at the cost of being more top heavy and prone to rolling over.
    • Like having a lower axle ratio for less power but better mileage.
    • Speedometer reading will be low. (ay be speeding ticket time!).
  • Larger tires will be more prone to hydroplaning and have less traction in snow, however the large gap between treads will compensate for some of this in all terrain tires. According to a Jan. 2004 ConsumerReports article, a 245/40ZR18 tire (with 9% more contact area) will be 25% more likley to hydroplane and have 20% less traction in snow than a 225/55ZR16 tire, but will have a 4% advantage in wet/dry cornering and a 5% advantage in ice braking.
  • Extreme plus-size truck tires put an even greater strain on brakes, wheel bearings, and suspension parts.
  • Larger, grippier tires could also make some SUVs and trucks tippier by sticking rather than sliding under hard cornering forces and also during emergency road maneuvers.
  • A March, 2004 ConsumerReports article describes a test comparing All Wheel Drive (AWD) cars with Front Wheel Drive using factor all-season and "winter" tires.
    Ice braking was virtually the same for all configurations.
    AWD cars accelerated to 20 MPH in 1/2 the distance of a FWD car with factory tires.
    Winter tires accelerated to 20 MPH in 2/3 the distance of all-season tires on a FWD car.

Low Profile Tires and large wheels:

Low profile tires with larger wheels look cool, so have become popular, but there are pros and cons.

Larger wheels (rim to rim) are usually paired with lower profile tires (shorter sidewall) to get the same total diameter to avoid a total larger tire diameter (tread to tread) which will require that you change your speedometer and possibly gearing. The three combinations to the right all result in a 25 inch tread to tread measurement. See above for how it is measured.

  Low profile tires give better performance because there is less sidewall distortion on corners, so more tread stays on the road and they respond quicker.
  On the other hand, a low profile tire usually has a stiffer ride than a standard tire because there is less sidewall flex on bumps.
  Larger tires may decrease mileage because of they are heavier. A Car and Driver magazine tests showed mpg going from 22.8 to 21.9 with 18 vs 17" wheels.
  Because there is less flex in the sidewall on a low profile tire, a bump against a curb may distort the bead where the tire connects to the wheel rim, causing a loss of pressure.

Can and Driver says,
"Subjectively, both the 17-inch and 18-inch wheels and tires were in the sweet spot of grip, braking performance, ride comfort, and steering feel. Moving from 17-inchers to 18s barely degrades ride quality, and the additional grip is welcome."

Some Examples of tire options on popular cars:
Standard Optional Total size
Subaru Outback P225/60HR17 P225/55HR18 25"
Toyota Camray P205/65R16 P215/55R17
Honda Accord LX-S P215/55R17 235/45R18
Honda Civic EX-L 215/45R17 225/40R18
Honda CR-V 225/65R17 225/60R18
Honda HR-V 215/55R17

Off-road vehicles like jeeps may use a 15 inch wheel with a high sidewall to result in a 33-35 inch total diameter giving maximum grip at low pressures used for rock crawling. Links:
Effects of Upsized Wheels and Tires Tested - Tech Dept. - Car and Driver
What We Should Know About Tires: |
Are Low Profile Tires Worth It? - Straight Dope Message Board

Rolling Resistance and Tread life effect on cost:

Consumer Reports rates tires on Rolling Resistance and Tread life.
The don't say what the difference is from a poor and excellent tread life, but a difference of 40,000 to 60,000 miles can increase the cost of tires by 50% (e.g. 3 sets to get 120,000 miles vs 2 sets).

They say the difference between the mileage from the worst to the best rolling resistance is 3 MPG (miles per gallon). So a one rank change in rolling resistance rating from good to fair could be 0.6 MPG at a gas price of $3/gal. and av. 20 MPG with a 60,000 mile tire that could be $65 in gas per tire over the life of the life of the tire, increasing the cost from 50-66% for a change of one rating or more than doubling the price of the tire for a two rank (very good to fair) change.

Tire Rack will ship tires to local dealers you can lookup on their web site where they will mount and balance the tires and dispose of the old tires for about $25 per tire. I found the price to be about the same as buying locally.

All Season passenger car ratings with average or better snow and ice traction.
Consumer Reports rating: (5-Excellent, 1-poor)
Tire Rating score
Tire Rack Consumer Reports
Hankook Optimo H727 $96 4 4 4 4 4 3 3 3 99 82
Toyo Versado LX $91 4 3 4 3 4 3 5 3 76
Cooper CS4 Touring $86 4 3 5 3 3 3 3 2 72
Cooper Lifeliner GLS $78 4 3 4 3 3 3 2 4 68
Toyo Extensa A/S $99 3 4 4 3 3 3 3 3 76
Goodyear Assurance TripleTred * $121 3 3 4 3 4 3 3 3 96 80
Cooper GFE $83 3 3 4 3 3 3 2 4 76
BFGoodrich Traction T/A T $90 3 3 4 4 4 4 3 2 95 74
Dayton Quadra LE $86 3 3 4 3 3 3 3 3 74
Uniroyal-Tiger Paw Tour SR $77 3 3 4 2 4 2 2 5 73 72
Michelin HydroEdge $116 2 3 5 4 4 4 5 3 84 84
Light Truck and SUV Tire ratings: (5-Excellent, 1-poor)
Arranged in order to weight wet & ice braking and snow traction.
See also Ratings at the Off Road Tires page
Tire max 15"
diam Rating score
All Season
Firestone Destination LE 31x10.5 31 $115 4 3 3 4 4 3 1 2 66 86
Bridgestone Dueler H/L Alenza 265/70R15 29.5 $154 4 3 3 4 4 4 2 3 66 91
Dayton Timberline HT I P235/70R15 28 $99 3 3 3 4 4 4 1 2 66  
General Grabber HTS     $105 3 2 5 4 5 5 2 3 80 94
Michelin LTX M/S     $165 5 4 2 5 3 3 4 3 67 100
Goodyear Wrangler SR-A     $133 5 3 2 4 4 3 3 4 64 67
BFGoodrich Rugged Trail T/A     $127 3 2 2 3 3 3 5 3 53 71
All Terrain Tire
Pirelli Scorpion ATR     $163 3 2 4 4 5 3 3 1 79 98
Bridgestone Dueler A/T Revo     $143 4 2 3 5 4 3 2 2 71 99
Firestone Destination A/T     $112 3 3 2 4 4 3 3 3 66 100
Michelin LTX A/T 2     $158 3 2 2 5 3 4 5 3 68 99
Source: ConsumerReports See CR for more factors
(Rolling resistance, emergency handling, cornering, noise, ...) rated

See ratings at off-road tire page. (e.g. Hydroplaining, Handling, ...)

Air Pressure:

Use the inflation specified by the sticker on the door jam or the owners manual, not the maximum indicated on the tire.
A larger tire can have lower pressures, for example the Jeep Wrangler owners manual recommends 33 psi for P205 - P225/75R15 (27-29" tires) and 29 psi for 30x9.5 R15 LTs a 30" tire.
See Tire Air pressure at Off Road Tips for more.

  • Underinflation, by as little as 6 p.s.i., can cut gas mileage by 3%.
  • OR EVERY 10 DEGREE FAHRENHEIT CHANGE In ambient temperature, your tire's inflation pressure will change by about 1 psi (up with higher temperatures and down with lower.)
  • Use higher pressures for sustained high speed driving.
  • THE TIRE PRESSURE RECOMMENDED in your vehicle's owner's manual or tire information sticker is a "cold" pressure, so it should be checked in the morning before you drive more than a few miles.
  • Tires lose roughly 1 pound per square inch of pressure for every 10° F drop in outside temperature. You should check your pressures in Spring and Fall.
  • A standard load tire with a normal inflation pressure of 35 psi may be branded with a maximum inflation of 44 or 51 psi, indicating the tire's ability to meet special vehicle performance requirements. It does NOT increase the tire's load capacity.
  • If you have 1/2" in the description of your wheel (i.e. 16.5x8 -- found on many newer SUVs), DO NOT reduce your tire pressure when offroad! The bead found on the 1/2" variety wheels is not deep enough to keep the tire on during 4-wheeling excursions if the pressure is lowered.


  • Tread is considered worn out when it reaches the industry norm of 2/32 inches deep (i.e. when you can see all of lincoln's head on a penny in the groove). CR tests have shown that tires typically lose much of their wet-weather and snow grip long before that. Recommendations are:
    In wet conditions 4/32 inch or more
    In snow 6/32 or more (recommended by TireRack).
  • The Ultra High Performance tire that grips the track with tread temperatures of 200° is incompetent as its tread compound becomes like "hard plastic" at below 32°.
  • Siping - Cutting small slits perpendicular to the face of the tire, which in turn creates thousands of tiny edges that help with grip to improve traction and braking. Along with those two benefits, it improves tire life by 15 to 20 % and helps the tire run cooler. The National Safety Council performed tests on tires that have been siped, and found that there was a 22% increase in traction on snow and ice.

    Consumer Reports tested two performance all-season tires, with and without siping.
    The siped version of both models showed modest but measurable improvements in snow-traction and ice-braking performance. But braking distances on wet and dry pavement were a few feet longer. Besides costing $60 or so for a set of four, having your tires siped potentially voids any tread-wear warranty. We donŐt think the modest gains are worth the extra costs.
    See: article af 4X4 review
    Article at Consumer Reports .

Less Schwab
Tire rack

DOT - Department of Transportation

LR - Load Rating

NHSTA - National Highway Traffic Saafety Administration

PR - Ply Rating

RMA - Rubber Manufacturers Association.

Sidewall Types:
  BLK - Black, RWL - Raised White Letter
  WSW - White, OWL - Outlined White Letter

UTQGS - Uniform Tire Quality Grading System - A government-mandated tire rating system based on a tire's performance in treadwear durability, traction, and temperature resistance. UTQG ratings are branded on the tire's sidewall.

Tire Terms

Air Pressure at:
Tire Rack
Tire Wear and Pressure

See specific type links at the off-road tire page.

See Also:
Off-road tires and ratings at off-road tire page in recreation. formulas at
Recommended rim width
Substitute Sizes for tires
Tire labeling proposal at the DOT
Winter Tire Tech at TireRack
Tires at the National Highway Traffic Safety Administration (NHTSA) at the DOT

last updated 25 July 2010