The 2nd row seats only move forward and backwards a little bit. I'm guessing 6" at most. If you don't collapse the seat, there's no way to get back there from the back doors.

If the 3rd row seats are up, you'll have better luck getting in through the trunk by climbing over the seats.

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2008 X5 4.8
White w/ Black Interior w/ Bamboo Trim | Premium | Sports + 214" | Tech | Cold Weather | Rear Climate | Premium Sound | Active Vent Seats | Heads-Up | Comfort Access | 3rd Row | Aero Kit | Huper Optik Tint | Clear Reflectors