Your car will fail a Missouri safety inspection primarily for issues with critical safety components like brakes, lights, steering, and tires. The inspection focuses on ensuring your vehicle is safe to operate on public roads, not its overall mechanical condition. Emissions testing is not required in Missouri.
The most common reasons for failure involve faulty lighting. Every light on your car must be operational. This includes headlights (both low and high beams), tail lights, brake lights, and turn signals. A cracked lens that allows moisture in or alters the beam color can also cause a failure.
Brake system integrity is non-negotiable. Inspectors check brake pad thickness, rotor condition, and fluid leaks. If your brake pedal feels soft, travels too far to the floor, or the vehicle pulls to one side when braking, it will likely not pass. The parking brake must also hold the vehicle securely on an incline.
Problems with steering and suspension are major red flags. Excessive play in the steering (where you can turn the wheel significantly before the wheels respond) indicates worn components. Worn ball joints or tie rod ends that create looseness will result in a rejection.
Your tires must have adequate tread depth. The legal minimum is 2/32 of an inch, but inspectors often recommend replacement before reaching that point for safety. Any tire showing cords, bubbles, or deep cracks is an automatic failure. All four tires should also be of the same type and size.
Other critical fail points include a malfunctioning horn, a cracked windshield that obstructs the driver's view, missing or illegally tinted mirrors, and a faulty exhaust system with leaks that could allow fumes into the passenger cabin.
| Common Failure Item | Specific Requirement / Failure Threshold |
|---|
| Brake Pad Thickness | Less than 2/32 of an inch |
| Tire Tread Depth | Less than 2/32 of an inch |
| Windshield Damage | Crack longer than 6 inches directly in driver's sightline |
| Headlight Aim | Beam too high, blinding oncoming traffic |
| Tail Light/Brake Light | Any light not functioning |
| Steering System Play | More than 10-15 degrees of free movement |
| Exhaust System Leak | Leak before the catalytic converter |
| Windshield Wipers | Wipers that smear or fail to clear the windshield |
To avoid a failed inspection, it's wise to do a pre-check of these items yourself or have your regular mechanic look them over before your official appointment.
