Either way, this new three-door 1-series is eagerly, muscularly and excitingly quick with the potential, you may think, to become a flailing handful if you dare to meddle with the ESP button. But the first bold dive into a rain-sheened bend uncovers grip reserves far deeper than expected – deep enough that when that DSC button is prodded for partial disengagement, it takes some lead-foot ambition to get the rear axle’s wider 245/35 R18s to get a skate on, the slide part-managed by a brake-deploying virtual limited slip diff.
So it’s pretty neat, controllable and reassuring, the more so because this rear-driver is quite a finely balanced tool, as proved by a too-fast arrival into a tight, low speed turn that fails to bring on any plough-on understeer. That said, you can expect to see plenty of the orange light that confirms an active ESP system, which is no surprise given all this energy and rear-wheel drive.
Perversely, it’s best to experience all this in the Comfort setting of the £515 Adaptive M Sport suspension, an essential option. It softens off the electronic dampers and lightens the steering effort to produce a satisfyingly communicative, more absorbent chassis and best of all, usefully more feelsome steering. Of course, tripping the Comfort mode slows the shift times and the gearbox’s willingness to hold a gear, but that’s easily undone by sliding the gearlever to leftwards to Sport, which gets you a more eager gearbox.
The result is a an excitingly rapid drive that sits just the right side of hectic, the excitement of the six’s keen blare built on by the ‘box’s light thumps in sport, the ra-ta-tat of the exhaust’s over-run, the lightly clasping support of the seats and an excellent driving position. While some may desire the more uncompromising character of the 1M Coupé, the fact is that this M135i’s ride is less maskingly firm, its steering more delicate and its character easier to live with. And it’s also a whole lot cheaper, being almost £10k less.
Of course, you do without the some of the 1M’s alloy suspension hardware and massive brake rotors – although the 135i’s enlarged blue-calipered discs are entirely effective – but remember that the M135i rides on the latest 1-series platform besides benefiting from bespoke suspension geometry and its own springs, dampers, anti-roll bars and bushes.
More immediately noticeable M135i identifiers include a new front bumper unit with larger air intakes, a rear bumper with twin exhausts and 18in alloys, and tyres, that are wider at the rear. Inside you get leather sports seats (the UK won’t be getting the appealing Alcantara/hexagon cloth mix of the test car, which seems a pity), a black headlining, an M footrest, blue accent stitching to the seats, patterned aluminium trim inserts and modified instrument faces. Not a huge amount of differentiation then, but enough to mark this 1 out as something sportier. The cabin is robustly constructed too, although it’s not as finely, designed, finished or textured as the cabin of the latest Audi A3.
Much of the M135is’s considerable entertainment repertoire is provided by the straight six. This Twinpower motor features a twin-scroll variable geometry turbocharger, variable timing of both inlet and exhaust cams, variable valve lift and direct injection, these features managing to almost eliminate turbo lag. Indeed, you must actively search it out to find any, by shifting manually and having the revs build from 1000rpm to the 7500rom limit in second, say. Then you’ll uncover a slower-moving tacho needle to 1300rpm. From this point the six has already reached its 320lb ft torque peak, this figure impressively maintained through to 4500rpm, although the revs don’t rush at you until this peak has passed, the tacho needle performing a lightning flit to the limiter.
Throttle response is not as instant as you’ll find in a normally aspirated M3, but it’s sharp enough for most circumstances. Couple the six’s breadth of urge to that eight-speeder, and you have a car that powers near seamlessly from a dawdle to its easily struck – and restricted - 155mph maximum.
M division has tuned the 135i’s exhaust to provide a smoothly busy soundtrack that makes paddling your way through eight ratios an absorbing business, even if the noise can turn slightly wearing. Happily it quietens off at a motorway cruise. And we suspect the same may be true of the ride, which showed signs of choppiness on Germany’s mostly smooth roads.