Eli5: how is it so easy for cars to flip? Do certain types of cars flip easier than others?


Eli5: how is it so easy for cars to flip? Do certain types of cars flip easier than others?

In: Physics

It’s not that easy, but physics can’t be stopped when the car wants to go sideways for some reason but the tires are still gripping the road. That means everything *except* the wheels keeps going sideways and the car flips over.

Taller and narrower vehicles are more likely to roll over in an accident than lower and wider ones. In the early days of the SUV craze in the late 90s and early 2000s there was a lot of hand-wringing about how easily those tall-but-not-wide beasts rolled in accidents.

It’s a lot easier to flip an Escalade than it is to flip a Corvette.

Some are more too heavy than others and since the weight is up high and not really down low, you take a turn and all that weight up top has to go somewhere.

Try an experiment. Take you a pencil or something tall and skinny, and put like an apple on top… oh yeah perfect example! Take a pencil and shove it into a pencil but only at the top… now hold that pencil at the bottom and just move your hand across the table, feel how too heavy that pencil feels? Now flip it around where the Apple is on the table and that pencil is sticking up. Now move that Apple around with your hand. See how when you have the Apple up top how much it tries to lean to one side or the other? But it doesn’t do that when you have the Apple on the ground and the pencil up in the air? It’s KINDA the same thing for vehicles

Vehicles with tires wider than the fenders seem to have a bad time with other vehicles and roll themselves over on the other vehicle’s body, tires, bumpers. I watch a lot of accident videos, it is quite amazing.

Many rollovers are due to outside forces, not the vehicle’s own handling. Once a vehicle leaves the road, things like hills or drops, guardrails or other obstacles may cause it to flip. This is why high speed crashes so often end in rollovers, the vehicle’s own tires and suspension are not the only factor once it’s airborne or completely smashed up.

It’s only “easy” to roll large topheavy vehicles and even the Ford Explorers that were infamous for this turned out to have faulty tires, they were not THAT prone to rollovers just due to their design. Smaller cars are near impossible to roll on flat pavement with steering input alone… but once you drive it off a cliff or into a drainage ditch, anything can happen.

It’s about the center of gravity.

Take a tall bookshelf. Fill the bottom shelf with heavy books. Try to tip it over, kind of hard. It keeps wanting to go upright again because the center of gravity is right next to the ground. Now put the books on the top shelf, and it’s easy to tip over because of the high center of gravity.

Cars with a high center of gravity are also easier to tip, all else being equal. So jacked up pickups have a high center of gravity and are notorious for flipping. A Tesla has a very low center of gravity because the heavy battery pack and motors are about as low to the ground as they can possibly be.

There’s a common rollover test. Send the car sideways to hit a raised edge. The edge stops the tires, and the momentum of the car then tries to flip it. Cars normally do well, SUVs and trucks do not. The test repeatedly failed to flip the Tesla SUV because of the very low center of gravity. Even when it was thrown at the barrier at a high enough speed to tip completely on its side and even a bit over that, it just came back down on the wheels.