Vehicle Overview

The rear-wheel-drive BMW 1 Series enters its fifth year on the market with a few visual changes, as well as a new higher-performance version from BMW's M division, dubbed the 1 Series M. At the other end of the lineup is the 128i, which is the least-expensive entry point to BMW's entire lineup. Available as a coupe or convertible, the compact 1 Series occupies a space with few competitors. The Nissan 370Z, Infiniti G37 coupe and top-end versions of Detroit's muscle cars come closest to filling out the competitive slate.

Exterior

Visual updates for 2012 affect the 128i more than the 135i. The 128i carries revised circular fog lamps, replacing last year's horizontal lamps. Outboard of the fog lights, vertical slats improve air flow around the fenders, enhancing the car's aerodynamics. The headlights have new whitecaps up top, mirroring the headlight treatment across most other BMWs. These lights include a string of LEDs embedded in the caps; it's a visual cue used in the automaker's redesigned 6 Series.

On the 128i, an optional M Sport Package adds dark window frames and a more aggressive front bumper with three large air inlets. Rather than the 3 Series convertible's folding metal hardtop, the 128i convertible has a fabric soft-top that can open or close in 22 seconds, BMW says. It operates at speeds up to 25 mph.

The 1 Series remains a small car overall, about 2 inches shorter and narrower than a Scion tC. The BMW 3 Series coupe is about 10 inches longer.

Interior

The 128i's interior design is fairly traditional, with more upright shapes than sweeping contours. Dual-zone climate controls sit below the center air vents and optional navigation system, with BMW's latest-generation iDrive knob controller ahead of the center console. The system can read text messages aloud or stream songs off a paired Blackberry smartphone.

BMW says the cabin controls boast "a more refined look and feel" for 2012, though the layout is hard to distinguish from 2011's. In contrast to the seat belts that motor forward for easier reach in the 3 Series coupe, the 1 Series' belts are fixed onto the B-pillars.

On 128i coupes, the two-position backseat folds in a standard 60/40 split. The convertible offers only a center pass-through. Vinyl seats are standard, with leather optional. The M Sport Package adds unique headliner materials, an M-branded steering wheel and shifter, and sport seats with more aggressive side bolstering.

Under the Hood

BMW's inline-six-cylinder engine makes 230 horsepower and 200 pounds-feet of torque in the 128i. It works through a six-speed manual or a six-speed automatic. The automaker says a stick-shift 128i coupe can hit 60 mph in 6.1 seconds, with the automatic making the sprint in 6.7 seconds. The M Sport Package adds a sport-tuned suspension.

If that isn't enough, consider stepping up to the 300-hp, turbocharged 135i, which is covered separately in the Cars.com Research section. It trims the zero-to-60 mph sprint down to about 5 seconds, BMW says.

Safety

Active head restraints, two-row side curtain airbags, front airbags and side-impact airbags for the front seats are all standard. So is an electronic stability system, antilock brakes and traction control. Like most convertibles, the 128i convertible does not have the curtain airbags; it does have pop-up roll bars behind the rear seats that deploy in the event of a rollover.

1 Series M

Rather than the single-turbo setup from the 135i, the 1 Series M gets a twin-turbo six-cylinder that's good for 335 hp and 332 pounds-feet of torque. In extreme situations, the 1 Series M can enter an overboost mode to crank out 369 pounds-feet of torque (horsepower remains the same). A standard limited-slip differential can go all the way to lock, rendering maximum straight-line acceleration and better traction on slippery surfaces.

The 1 Series M comes only as a coupe, and only with a six-speed manual transmission. Citing a lower center of gravity and overall weight savings of 35 pounds, BMW will not offer the 1 Series' optional moonroof on the M car. That helps it tip the scales at just under 3,300 pounds, more than 400 pounds less than the 414-hp M3 coupe — the next rung up on BMW's M ladder. Indeed, the 1 Series M's zero-to-60 time — just 4.7 seconds, BMW says — ties a stick-shift M3's.

Visual changes include unique side mirrors that look similar to those on the M3, as well as a more aggressive front bumper and quad tailpipes. The 1 Series M's extended fenders house a track that's 2.8 inches wider up front and 1.8 inches wider in back versus the 135i. The suspension, which shares its aluminum components with the M3, supports lightweight 19-inch wheels. The car also gets cross-drilled 14.2-inch front and 13.8-inch rear brake discs.

Inside, the 1 Series M gets standard sport seats, plus gray gauges and leather-wrapped portions of the dashboard.