The 128i is powered by a 3.0-liter normally-aspirated inline six-cylinder rated at 230 horsepower. All 1-Series models are rear-wheel drive, available with a choice of six-speed manual or six-speed Steptronic automatic transmission (128i) or seven-speed dual-clutch transmission (135i).
The 135i is powered by a turbocharged 3.0-liter inline six-cylinder rated at 300 horsepower and 300 pound-feet of torque. Acceleration with the 135i is brisk, hitting 60 mph in just 5.3 seconds with the dual-clutch transmission. An available M Sport package further enhances performance with improved suspension calibration, aerodynamics, and larger wheels and tires, plus a host of comfort and aesthetic upgrades.
The M Sport package is available on either the 128i or 135i, while the Sport package offers a sportier-than-stock but less-aggressive than M Sport suspension calibration for the 128i. The Sport package's suspension calibration is standard on 135i models.
On the street, the 1-Series is impressive, handling with balance and poise, a noticeable but not excessive amount of body roll, high overall grip, and ready acceleration. The 135i sharpens all of these, particularly the acceleration. Braking is also a strong suit, stable and straight, though without upgraded brakes, track duty will quickly cause heat soak and fade--a standard trait of most road cars.
Integrated stability and traction control systems are not overly invasive, allowing a fair amount of aggressive driving without stepping on the driver's inputs.