Four cylinders and just 115bhp were the best that the 5-series could offer on its debut in 1972, but that staid 520 was the start of something big. It was the start of a dynasty of top-notch mid-range saloons that have been everywhere and done everything -- from Munich taxi-cab to autobahn-burner.
That E12 5-series quietly earned itself a reputation for quality, reliability and refinement, and it was respectably quick once BMW inserted the 'big six' engine to produce the 528i and (for some markets) 530i. Though BMW’s works teams (and the works-supported Alpina and Schnitzer teams) concentrated on the 3.0CSL coupe as a racing machine, some 5s did find their way onto the track - notably in Britain, in the hands of Tom Walkinshaw, and in South Africa. There, the race regulations allowed much more scope for modifications than was the case in Europe. To take advantage of that, BMW Motorsport put together a 530i Motorsport Limited Edition for sale in South Africa, which had a big front spoiler and wheel arch extensions added to a lightweight bodyshell. Eddie Keizan raced the track version with considerable success.
Some of those modifications found their way onto occasional bespoke 5-series cars built for special customers by BMW Motorsport. Then in 1980 BMW built a ‘production’ hot 5-series, and called it the M535i.
The big six had been expanded to 3.5-litres for the racing CSLs, and a production version (with a slightly less extreme bore size) had gone into the 635CSi coupe and 735i saloon. Now Motorsport installed the 3.5-litre, 218bhp motor into the 5-series, mating it to a Getrag five-speed gearbox with a ‘dog-leg’ first gear. The chassis was uprated with stiffer suspension and bigger brakes (from the 635CSi), plus multi-spoke 6.5x14in Mahle alloy wheels, and there was a deep body-coloured air dam and a black spoiler on the boot lid. Recaro front seats and the steering wheel from the M1 supercar completed the package.
And what a package it was. The broad-shouldered performance of the torquey engine made the M535i effortlessly quick, and if the semi-trailing arm rear suspension struggled to deal with the big six’s maximum torque output of 224lbft then at least the well-balanced chassis made the oversteer controllable. Around 400 of these charismatic cars made it to the UK, of which perhaps 50 still survive.
Good though the M535i was, its production run was soon ended -- by the introduction of the new E28 5-series range in 1981. In 1984, BMW added 535i and M535i versions of the new 5, the only difference between the two being a Motorsport bodykit on the latter. But before long, the E28 5-series shell would get much more exciting motive power.
BMW Motorsport had developed a 24-valve version of the familiar straight-six engine, originally for the racing CSLs in 1973. Essentially the same engine had then powered the M1 supercar, and more recently had gone into the M635CSi. In fact in this latest version, the engine had a slightly higher compression ratio, so it produced 286bhp to the M1’s 277. Now this motor went into the 5-series shell to produce the awesome M5, which proved even quicker than the 6-series because the four-door body was lighter. Despite its towering performance, the M5 was as docile as you could wish in traffic, and it had unparalleled practicality.
The E28 5-series was replaced by the E34 in 1988, and an M5 variant wasn’t far behind. Only the ‘M’ badges and different wheels announced that this was no 518i. Again the power came from that race-derived 24-valve straight-six, now with a longer stroke to give it a slightly greater capacity of 3535cc. Maximum power rose to 315bhp. Munich toyed with the idea of producing a two-door M5 cabriolet, but decided against it, though there was an M5 version of the 5-series Touring estate. Meanwhile the Motorsport engineers at Preussentrasse bored and stroked the engine to 3.8-litres: the biggest six-cylinder engine BMW had ever produced, generating 340bhp.
The next M5’s engine was even bigger, but the big saloon was no longer powered by a straight-six. 5-Series customers had to wait until 1999 for sight of an E39 M5, but it was worth the wait. As before there was little to tell the casual onlooker that this was anything special, but look under the skin and there was no doubt: under the bonnet sat the 4.9-litre S62 V8 engine, with 400bhp, 114bhp more than the 4.4-litre V8 in the 540i, in part due to bi-VANOS variable valve timing. In common with the rest of the 5-series range, the M5 now had sophisticated, multi-link rear suspension, replacing the semi-trailing arms which had been Munich’s staple fare since the late 1950s. And as if that didn’t provide enough security in corners, BMW added Dynamic Stability Control to automatically reduce engine output and apply brakes on individual wheels if the car strayed off-line.
The latest car in the M5 line jumps from eight to 10 cylinders, the 5.0-litre V10 engine revving to 8250rpm and generating up to 507bhp. Also new is the seven-speed sequential manual gearbox and a ‘launch control’ function which ensures the big M5 can hit 62mph from rest in just 4.7 seconds and 124mph in 15 seconds. It’s electronically limited to 155mph, as ever - but BMW can’t help pointing out that, given its all, the latest M5 would max out at 205mph.
This comfortable, luxurious saloon with space for four can also lap the Nürburgring in eight minutes. And that would have been a respectable time for a Formula 1 car just a generation ago - back when the first 5-series was new.