What is the bulge in the middle of the rear seat of a car?
2 Answers
The bulge in the middle of the rear seat of a car is part of the vehicle's floor, designed for the smoothness of the chassis. Since the underside of the car's chassis accommodates the exhaust pipe or drive shaft, rear-wheel-drive vehicles typically require a drive shaft to transmit the engine's power to the rear wheels, necessitating such a structural bulge. The reasons for the bulge in the middle of the rear seat are as follows: 1. Rear-wheel-drive vehicles need to accommodate the drive shaft: Cars with front-engine, rear-wheel-drive layouts require space for the drive shaft in the middle. The front-mounted engine transmits power to the rear wheels via the drive shaft. If the drive shaft is too low, it can easily scrape the ground, affecting the car's ground clearance. Raising the vehicle height would impact the car's center of gravity, hence the need for a locally raised floor to protect the drive shaft and enhance the car's stability, ground clearance, and handling. 2. Front-wheel-drive vehicles need to route the exhaust pipe: If the car's chassis is designed low and the vehicle is front-wheel-drive, the middle bulge is designed to provide space for the exhaust pipe. 3. Increasing chassis resilience: Generally, the raised floor can significantly increase the body's strength several times over. This design enhances the chassis's resilience. Many cars without such a bulge have been observed to break upon impact. The semi-circular bulge in the floor acts like a raised steel beam, reinforcing the structure.
The raised hump in the back seat of a car is commonly referred to as the center tunnel or driveshaft tunnel, and it's particularly prevalent in rear-wheel-drive or all-wheel-drive models. Its primary purpose is to house the drivetrain components running from the engine to the rear axle, preventing the floor from being completely flat and occupying too much underbody space. Through my experience in driving and car maintenance, I've learned that this raised design actually enhances structural rigidity and safety, as it helps distribute impact forces and reduces the risk of deformation during collisions. Of course, it can be quite annoying for passengers—those sitting in the middle rear seat have to awkwardly straddle it, making long trips especially uncomfortable. In electric vehicles, this hump sometimes conceals battery packs or charging cables to ensure safe power transmission. My advice when car shopping is to check reviews carefully and opt for models with a completely flat floor for greater comfort.
