Quick Reference
Tire Rotation
Pattern depends on drive type
Tire rotation diagram
Tap to expand
When to rotate Every 5,000–7,500 miles. At Les Schwab, usually done with every oil change interval.
AWD note AWD follows the same pattern as RWD — rears go straight forward, fronts cross to the rear.
Tire Size
What each part of the code means
P215/55R17
P
Vehicle type — P=Passenger, LT=Light Truck, T=Spare, ST=Trailer
215
Tread width in millimeters (sidewall to sidewall)
55
Aspect ratio — sidewall height is 55% of the width
R
Construction — R = Radial (almost always R)
17
Rim diameter in inches — must match your wheel exactly
How to calculate sidewall height
Width × (Aspect ÷ 100) = sidewall in mm
The aspect ratio number is stamped on the tire already — you don't calculate it, you read it. What you calculate from it is how tall the sidewall actually is.
215/55 — sidewall
215 × 0.55 = 118mm
235/45 — sidewall
235 × 0.45 = 106mm
265/70 — sidewall
265 × 0.70 = 186mm
205/40 — sidewall
205 × 0.40 = 82mm
Does rim diameter affect this? No. The rim diameter has nothing to do with sidewall height — it just has to match your wheel. Sidewall height is only ever Width × Aspect%.
Tread Depth
Measured in 32nds of an inch
New
10–11
Good
7
Watch
5
Replace
3
Done
2
numbers = 32nds of an inch
New tire (most)
10–11/32"
Good shape
6–9/32"
Start watching
4–5/32"
Replace soon
3/32"
Legal minimum
2/32"
Quarter test Quarter in tread, Washington's head first. If you see the top of his head, you're at or below 4/32" — talk replacement.
Penny test Penny in tread, Lincoln's head first. See all of his head = 2/32" or less — legally worn out.
Fractions
How to say them out loud
tread depth — 32nds
2/32
"two thirty-seconds"
= 0.063"
3/32
"three thirty-seconds"
= 0.094"
4/32
"four thirty-seconds"
= 0.125"
5/32
"five thirty-seconds"
= 0.156"
6/32
"six thirty-seconds"
= 0.188"
7/32
"seven thirty-seconds"
= 0.219"
8/32
"eight thirty-seconds"
= 0.25"
9/32
"nine thirty-seconds"
= 0.281"
10/32
"ten thirty-seconds"
= 0.313"
11/32
"eleven thirty-seconds"
= 0.344"
socket & wrench sizes (imperial)
3/16
"three sixteenths"
= 0.188"
1/4
"quarter inch"
= 0.25"
5/16
"five sixteenths"
= 0.313"
3/8
"three eighths"
= 0.375"
7/16
"seven sixteenths"
= 0.438"
1/2
"half inch"
= 0.5"
9/16
"nine sixteenths"
= 0.563"
5/8
"five eighths"
= 0.625"
11/16
"eleven sixteenths"
= 0.688"
3/4
"three quarter inch"
= 0.75"
13/16
"thirteen sixteenths"
= 0.813"
7/8
"seven eighths"
= 0.875"
15/16
"fifteen sixteenths"
= 0.938"
Pattern to remember Say the top number, then the unit. Bottom number tells you the unit: 32 = thirty-seconds, 16 = sixteenths, 8 = eighths, 4 = quarters, 2 = halves.
Load Index
Number on sidewall = max load per tire
Stamped right after the tire size on the sidewall (e.g. 215/55R17 95H). Never go lower than what's on the door placard. Going higher is always fine.
IndexlbskgTypical
70739335Compact
71761345Compact
72783355Compact
73805365Compact
74827375Compact
75853387Small car
76882400Small car
77908412Small car
78937425Small car
79963437Small car
80992450Small car
811019462Small car
821047475Small car
831074487Sedan
841102500Sedan
851135515Sedan
861168530Sedan
871201545Sedan
881235560Sedan
891279580Sedan
901323600Sedan
911356615Sedan / CUV
921389630CUV
931433650CUV
941477670CUV
951521690Very common
961565710CUV / SUV
971609730CUV / SUV
981653750CUV / SUV
991709775CUV / SUV
1001764800Very common
1011819825SUV
1021874850SUV
1031929875SUV
1041984900SUV
1052039925Very common
1062094950SUV / Truck
1072149975SUV / Truck
10822051000SUV / Truck
10922711030SUV / Truck
11023371060SUV / Truck
11124031090Truck
11224691120Truck
11325351150Truck
11426011180Truck
11526791215Truck
11627561250Truck
11728331285Heavy truck
11829101320Heavy truck
11929981360Heavy truck
12030861400Heavy truck
12131971450Heavy truck
12233071500Heavy truck
12334171550Heavy truck
12435271600Heavy truck
12536381650Heavy truck
12637481700Commercial
12738581750Commercial
12839681800Commercial
12940791850Commercial
13041891900Commercial
Speed Rating
Letter after load index = max sustained speed
On the sidewall right after the load index (e.g. 95H). Never go below the original rating. H and V are the most common at Les Schwab — highlighted below.
L
75 mph / 120 km/h
Off-road / light truck
M
81 mph / 130 km/h
Spare / off-road
N
87 mph / 140 km/h
Spare
P
93 mph / 150 km/h
Spare
Q
99 mph / 160 km/h
Winter / studded snow
R
106 mph / 170 km/h
Light truck — common
S
112 mph / 180 km/h
Family sedan / minivan
T
118 mph / 190 km/h
Family sedan / CUV
H
130 mph / 210 km/h
Sport sedan — very common ★
V
149 mph / 240 km/h
Performance — very common ★
W
168 mph / 270 km/h
Sport car
Y
186 mph / 300 km/h
Super car
(Y)
186+ mph / 300+ km/h
Exotic / unlimited
Z
149+ mph / 240+ km/h
Older high-perf rating
Key rule Match or exceed the original. Car came with H? Don't put S or T on it. H and V cover probably 80% of what you'll see.
Notes
Notes for specific cars & jobs
Photos