The 2015 BMW 4-Series might have a lot in common with the 3-Series sedan, in terms of engineering and what's underneath, but it doesn't use its identical wheelbase or overall length to allow as much interior space. It's a half-inch wider than the sedans, but the roofline is some 2 inches lower.
With those numbers in mind, the back seat of the 4-Series isn't comfortable at all for most adults. Anyone over five feet tall will feel cramped, so it's best not to plan on using the two-door as an everyday car for four. Gran Coupes are better, but still don't have the head room of a traditional 3-Series sedan.
As for the front, it's a different story completely. Seating is low in the 4-Series, and you grip an SUV-sized steering wheel. You'll learn to love the seatbelt presenter because reaching for the belt every time would lead to rotator-cuff problems. No matter which model you're considering, you'll get firm, comfortable front seats, of the sort we'd choose as desk chairs; although to be fair they don't have the same level of adjustment and side bolstering of the sport seats (which can have heating and ventilation) offered with the M Sport package.
Cargo space is great, which makes the 4-Series an ideal weekend machine for two. Its trunk is carried over almost intact from the sedan, and finally, BMW has fitted enough storage space inside the car, from useful cupholders to its glovebox.
The interior gives us some minor fits. On base cars, the black-on-black plastic scheme looks drab and depressing; it's amazing how a few stylish add-ons like contrast-stitched leather can liven it up. The display screen for iDrive sits on top of the dash like an unmounted LCD TV, but the display itself has pretty high-resolution graphics.
As for convertibles, the hardtop mechanism can stow or restore the roof in 20 seconds, even if the 4-Series is puttering along at less than 11 mph. Trunk space of 13 cubic feet only slims down to 7.8 cubes when the top is put away. BMW has added warm-air vents at neck level and a standard windblocker to lengthen the convertible's useful driving season.