Why Do License Plates Easily Fall Off in Flooded Areas?
4 Answers
License plates are prone to falling off in flooded areas for the following reasons: When a vehicle is driving through water, the front of the license plate is subjected to the impact force of the water. The gap between the top two screws securing the plate and the front bumper is relatively large, allowing water to squeeze into these gaps. The license plate is then subjected to the combined impact forces from the water flow in both directions. The faster the vehicle speed, the greater the shaking amplitude of the license plate, making the screws more likely to loosen. Here are some effective methods to prevent license plates from falling into water: 1. Develop the habit of regularly checking the screws of the license plate. If they are loose, tighten or replace them immediately. 2. When driving through water, try to keep the speed as slow as possible to reduce the impact force of water on the license plate, thereby lowering the probability of the plate falling off.
I've been repairing cars for over a decade and have seen too many owners lose their license plates after water immersion. The main issue lies in the screw hole design. The original license plate frame only has two screw holes at the corners, causing uneven force distribution on the plastic plate when impacted by accumulated water. The fragile thin plastic plate is prone to cracking. The plastic material of the license plate can't withstand soaking—it expands, deforms, and loosens its grip on the screws. Especially when driving through floodwater during heavy rain, the water's impact can rip the entire plate off. I recommend using stainless steel screws to install a reinforced license plate frame before the rainy season, securing all four corners for better stability. By the way, last time a car owner found three license plates under an overpass, all washed away by floodwater.
Last year, my brand-new car lost its front license plate just three months after purchase when driving through a flooded area during a heavy rain. When I went to the DMV specifically to get a replacement, the staff said it’s quite common for plates to fall off in water. Standard license plates are just thin pieces of plastic, which become heavier when soaked, and the mounting screws can easily give way under water pressure. Some car models have lower bumper positions, so driving through water is like a boat pushing waves—the flow hits the plate directly. I’ve since learned my lesson and bought a metal license plate frame from Taobao, secured with four screws and reinforced with 3M adhesive. This year, even driving through deep puddles during a typhoon didn’t cause any issues. By the way, the replacement fee for a license plate costs over 100 yuan, enough to buy two sets of reinforcement accessories.
A classmate who works in vehicle design once discussed this detail with me. Most license plates are installed right below the bumper. When driving through waterlogged sections, the water flow impacts the license plate surface at speeds of 10-20 km/h. A standard license plate can withstand water pressure equivalent to 5-10 kgf, yet the plate frame is secured with only two self-tapping screws. After soaking in water, the plastic becomes brittle, and stress concentrates around the screw holes upon impact, making it prone to cracking. It's advisable to reduce speed to a minimum when wading to minimize water resistance. For modified off-road vehicles, installing a high-mounted license plate bracket is highly recommended.
