Series 1

The BMW 1 Series (E81/E87 and E82/E88 models) is a compact car produced by the German carmaker BMW since 2004. The BMW 1 Series is the only vehicle in its class featuring rear-wheel drive, 50:50 weight balance, a longitudinally-mounted engine and an advanced aluminum multilink suspension. It is currently BMW's second best-selling automobile, accounting for nearly one-fifth of the total sales in 2008.

It was launched globally in autumn 2004 and shares many structural, chassis, powertrain, hardware and electronic elements with the larger BMW 3 Series. The model was started to provide a lower point of entry into the BMW range as the 3 Series moved gradually up-market. Initially launched as a 5-door hatchback, a 3-door version was also launched in July 2007. The 1 Series is priced between the MINI and the current E90 3 Series. Because the coupe is the only rear wheel drive vehicle in its class, it is sometimes considered the successor to the BMW 2002.

The BMW 1 Series coupe (E82) and convertible (E88) went on sale in the United States in model year 2008 (30 June 2007) as the 128i and the 135i. Other countries received the 120i and 125i in both models. The convertible, unlike the 3 Series convertible, uses a soft-top instead of a folding hardtop. This is lighter, cheaper to manufacture and preserves more boot space than the folding hardtop would allow.

The North American introduction of the coupe and cabriolet was during the second quarter of 2008, which was credited for helping BMW overtake Lexus as the top luxury brand.

Hatchback (E81/E87)

The BMW 1 Series was originally sold as a 5-door hatchback, with the 3-door hatchback available in 2007. It replaced the BMW 3 Series Compact range as the smallest and most affordable vehicle (depending on the engine model) in the BMW range.

Coupe/Convertible (E82/E88)

Like the three- and five-door BMW 1 Series models, the E82 also features various BMW Efficient Dynamics components to reduce fuel consumption (see below). The Coupe is 133 mm (5.2 in) longer than the hatch, creating 20 litres of extra boot space. It is 220 mm (8.7 in) shorter than 3-series Coupe. 120d, 123d and 135i Coupe announced unladen weights (EU) are 1,450 kg (3,200 lb), 1,495 kg (3,300 lb), and 1,560 kg (3,400 lb), respectively (corresponding to approx. 3,285 lb (1,490 kg) curb weight for the 135i, 90 lb (41 kg) lighter than 335i Coupe).

Apart from slight modifications, it uses the same nose design as the rest of the 1 Series so as to ensure some visual consistency within the range.

The BMW 1 Series Coupe (E82) was unveiled in Internationale Automobil-Ausstellung (IAA) 2007, which went on sale on November 24, 2007.

Unlike its predecessor, the new vehicle is built on its own platform (E87) however, it shares many components with the E90 3 Series. Shared parts include MacPherson struts in the front of the car and a trapezoidal-link rear axle. BMW has stated that it shares over 60% of components with the current E90 BMW 3 Series.

The BMW 135i includes M sports package as standard. The 135i comes with the world's first differential with double-helical ball bearings which have the advantage of running at an even lower operating temperature reached more quickly than before thanks to the reduction of fluid required in the differential. The 123d (150 kW (204 PS; 201 hp)) heads up the range of diesels and is the first ever 4-cylinder diesel engine to come with sequential twin-turbo technology.

In terms of fuel consumption, the 123d and 120d rate between 4.8 L/100 km (59 mpg-imp; 49 mpg-US) and 5.2 L/100 km (54 mpg-imp; 45 mpg-US) (according to the ECE-driving cycle).

In 2007, coupe and cabriolet bodies were added to the 1 series. Exterior changes to the model were minor headlight and taillight revisions, new front/rear bumpers and minor revisions to the interior. The dashboard has been updated, and a recommended gear indicator is now present on models with manual transmissions.

New technologies include auto Start-stop system, Brake Energy Regeneration, Electric Power Steering, an electric water pump, and a host of drivetrain modifications designed for fuel economy, increased performance, and lower emissions. BMW marketing has named this combination of technologies Efficient Dynamics, which will also be implemented in other BMW models.