There are 2 versions of the 2nd row of the X5’s back seat. One is the “regular” version – which only folds flat, but does not recline. The other version is the one that comes in the X5 that has the 3rd row, or is available as the “comfort rear seats” (approximately $1K extra) in the X5 that does not have a 3rd row. While both versions have seat belt overlap between 2D & 2C that can affect car seat installation, there are two key differences between the standard and comfort rear seats that make it such that the comfort is much more favorable for car seats than the regular.
Center width: 2C in the “comfort” is 11 inches wide, while 2C in the “regular” is only 8.5 inches wide. These 2.5 inches make a huge difference – in that the footprint of most car seats (and all boosters) is wider than 8.5 inches, which means that most car seats and all boosters when placed in the standard center sit on top of at least one of the seat belt buckles for the driver’s side seat, which is not safe or acceptable. For those who are curious, the Chicco Fit2 is one of the few car seats we have found that is narrow enough to fit in the “regular” 2C.
Flexible vs. Rigid buckles: The “comfort” has flexible buckles that stand several inches above the seat cushion for all 3 seats in back. The “regular” has rigid buckles for 2D & 2P that are flush with the seat cushion – and 2C’s buckle, while technically flexible, has very little flexibility due to the rigid 2P buckle that is right next to it. Flexible buckles give you a little more leeway when trying to put multiple car seats, or car seats + adults, in back as when the buckle can move a little side to side you can often get the buckle out from under a car seat, instead of the car seat sitting on the buckle as happens in the “regular” back seat with its rigid buckles.
Therefore, if getting an X5 we recommend getting the comfort rear seats to get a center that is usable (we don’t recommend getting the X5 with the 3rd row as the 3rd row is so tight that we don’t recommend anyone sit back there).
In whatever X5 you get, we strongly advise NOT getting the optional TV screens that are affixed to the back of the front seats. First, they stick out 2 inches – meaning that you’ll have 2 inches less room in the back seat for a rear-facing car seat before it starts to push the front seat forward. Second, they are a risk for major head injury – as if your head hits these you are likely to suffer a severe head injury (they are not padded like the back of the vehicle seat is required to be).