Which statement best describes when slippage marks are required, ignoring any other factors?

Which statement best describes when slippage marks are required, ignoring any other factors?

• A. Only when the tire has tubes
• B. Only when the tire pressure is exactly 150 psi
• C. Either the tire has tubes or the pressure is 150 psi or less
• D. Only when the tire pressure is less than 100 psi

Answer: (C)

Slippage marks are used to detect whether a tire has slipped on the bead or shifted relative to the wheel during mounting or inflation. They’re important when there’s an inner tube because the tube can move independently of the tire, concealing misalignment or bead slippage. They’re also required when tire pressure is at or below 150 psi because lower pressure reduces the clamping force on the bead, increasing the chance of slippage. If neither condition exists—no tube and pressure higher than 150 psi—the risk of slippage is lower, so marking isn’t required. Therefore, slippage marks are needed if the tire has a tube or the pressure is 150 psi or less.

Slippage marks are used to detect whether a tire has slipped on the bead or shifted relative to the wheel during mounting or inflation. They’re important when there’s an inner tube because the tube can move independently of the tire, concealing misalignment or bead slippage. They’re also required when tire pressure is at or below 150 psi because lower pressure reduces the clamping force on the bead, increasing the chance of slippage. If neither condition exists—no tube and pressure higher than 150 psi—the risk of slippage is lower, so marking isn’t required. Therefore, slippage marks are needed if the tire has a tube or the pressure is 150 psi or less.