The 2013 BMW 1-Series remains available in two main versions: the 128i and the 135i. With the 1-Series M Coupe now out of the mix, 2013 brings a model that channels some--but not quite all--of that performance goodness: the 135is.
BMW 128i models are powered by a 3.0-liter normally-aspirated inline six-cylinder rated at 230 horsepower, while the 135is borrows the same engine that's found in the 335i, delivering 300 horsepower and 300 pound-feet of torque. 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 135is gets a stronger version of the engine, making 320 hp and 317 lb-ft. It includes special programming for the stability control system; and a new differential in the 135is offers cooler operating temperatures and, in theory, somewhat greater efficiency in power delivery. It does this by using new double-helical ball bearings, reducing friction and the amount of lubricant needed within the differential. The 135is still doesn't get a true mechanical limited-slip differential like that found in the 1-Series M Coupe, however, instead relying on the familiar brake-based simulated differential lock to improve acceleration and low-traction grip.
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.
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. Integrated stability and traction control systems are not overly invasive, allowing a fair amount of aggressive driving without stepping on the driver's inputs.
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.