Power and acceleration numbers show the N55 single-turbo inline-6 is nearly identical to the twin-turbo N54. Thrust is abundant until it runs out of steam at 6,000 rpm, 1,000 rpm shy of redline. The 6-speed manual is smooth and precise.
A short wheelbase and moderately stiff suspension add up to a sport coupe with high limits and amazing precision at carving corners. Steering is well-weighted and communicative; a little bit of understeer keeps the chassis user-friendly.
Can be a bit harsh; highway ride should be cushy enough for most, but bumpy roads reveal the 135i's stiffer-than-average suspension settings. The sturdy sidewalls of the standard run-flat performance tires transmit harsh impacts.
Wind noise is noticeable only at elevated highway speeds. The 135i's run-flat performance tires can thump a bit over harsh bumps. Turbo inline-6 is reasonably quiet other than at wide-open throttle, when it becomes pleasantly sporty.
The manually operated sport seat is height adjustable and fits snugly aided by electrically operated seatback bolsters. Comfort is good, although butt cushioning could be softer. Controls are well located and generally easy to understand.
The 135i is surprisingly easy to see out of, with thin A- and C-pillars; no backup camera required. The 135i comes standard with BMW's adaptive xenon cornering headlights which greatly aid night visibility by pivoting through turns.
Seat Access & Space
The confines of the front seats are tighter than many cars, but you still shouldn't be bumping elbows. Accessing the rear seats requires more of a squeeze, and there's only room for two; rear headroom is below average.
Cargo & Storage
Just a 10.0 cu-ft trunk, but the 1 Series scores for its 60/40-split folding rear seat. Cupholders are on the shallow side, and the center armrest interferes with the rearmost holder. Smallish door pockets, minimal center armrest space.
Excellent build quality inside and out, especially when you consider this is BMW's entry-level model. Paint is glossy and resistant to chips; interior materials are of a high grade, offer a tactile feel and are screwed together well.