ASVAB CampTires and Wheels flashcards
8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.
Term · 1/8
Decode the tire size P215/65R15.
P = passenger car; 215 = section width in mm; 65 = aspect ratio (sidewall height is 65 percent of width); R = radial construction; 15 = rim diameter in inches.
Formula · 2/8
How do you find sidewall height and overall tire diameter from a size like 195/55R16?
and , with rim inches times 25.4 mm. For 195/55R16: mm, rim 406.4 mm, mm.
Common trap · 3/8
Should you inflate a tire to the pressure on its sidewall?
No. The sidewall shows the maximum pressure the tire can hold. Use the vehicle maker's recommended cold pressure on the Tire and Loading Information label (driver's door jamb) or in the owner's manual.
Rule · 4/8
When should tire pressure be checked, and what about a hot tire that reads high?
Check cold, before driving or after sitting a few hours out of the sun. Driving warms the air and normally raises pressure a few psi; never let air out of a hot tire to match the cold figure.
Fact · 5/8
Load index and speed symbol in a code like 91H: what do they mean?
The number is a load index looked up in a table (91 = 615 kg per tire). The letter is the maximum rated speed under proper conditions (H = 130 mph). Neither is a target.
Fact · 6/8
TPMS: steady lamp versus flashing-then-steady lamp?
Steady: at least one tire is significantly low (US rule: 25 percent or more below recommended cold pressure). Flashing about a minute then steady: a system malfunction, so low pressure may go unwarned; check tires with a gauge.
Fact · 7/8
Tread wear limit: what do wear bars show, and how do you read the DOT date code?
Tread worn flush with the wear bars is 2/32 inch (about 1.6 mm): replace the tire. The DOT number ends in four digits, week then year, so 1822 means week 18 of 2022.
Formula · 8/8
How does wheel imbalance force change with speed?
(m in kg, r in m, in rad/s, ). Force grows with speed squared: doubling wheel speed gives 4 times the force, which is why a small imbalance shakes on the highway.