But the 135i has a not-so-secret weapon that those lighter, earlier BMWs didn't have: a twin-turbocharged, direct-injected straight-6 engine that not only produces 300 hp but also packs a 300 pound-feet wallop of torque from 1,400 through 5,000 rpm.
On the road, the power delivery of the turbo six is so smooth and relentless that it makes the 1 Series fast — very fast — but never furious. This engine simply grunts it out and pulls hard from the bottom of the tach to its redline at 7,000 rpm. And the thrill quotient goes up because all this is happening in a car that's almost 200 pounds lighter than the engine's customary 3 Series package.
So the 1 Series coupe doesn't share the "too fat" problem of the 3 Series.
At the track, the twin-turbo big hammer drove our 135i down the quarter-mile in 13.3 seconds at 104 mph. The 2008 Subaru WRX STI with 5 more hp and 48 fewer pounds does the same time in the quarter-mile, but with a slower 102.4-mph trap speed.
While the STI edges the 135i's 5.0-second acceleration to 60 mph by a fraction thanks to the launch traction afforded by the Subie's all-wheel drive, the BMW ultimately has the legs at the top end and catches the STI at the finish line.
This performance does nothing to dispel our continuing suspicion that the 300-hp rating of the twin-turbo inline-6 is conservative at best.
Sometimes the Small Numbers Are Best
A shorter wheelbase gives the 1 Series a dimension of agility that the 3 Series lacks, and it measures 104.7 inches, some 4 inches less.
The suspension layout of the E82 is similar to that of the larger 3 Series. It still carries front struts with split lower arms and dual lower ball joints, while the rear retains the latest multilink layout. But both ends have been recalibrated for the 1 Series application.
Our 135i coupe came with standard 18-inch Bridgestone Potenza RE-050A run-flat summer tires: 215/40R18s up front and 245/35R18s in the back. We're still deeply skeptical about the performance of run-flats, even after the latest improvements. The mega-stiff sidewalls of the 050As disrupted an otherwise tame ride whenever we encountered abrupt, sharp-edged breaks in the pavement or even pronounced ripples.
We wish BMW would offer us the option of conventional tires or space for a spare. But since the battery resides in the trunk to help achieve a weight distribution of 52 percent front/48 percent rear, a spare has no place to live.
Ultimately, We Drive the Machine
Spirited back-road driving proves the 2008 BMW 135i Coupe can deliver the goods, as it dispatched corners with crisp turn-in, an eager willingness to change direction and impeccable grip, without sacrificing the road-worthy poise of the 335i that we love. On our test track, this translates to a blistering 72.4-mph run in the slalom, easily outpacing the last 335i we tested (69.5 mph) and edging the 2008 STI (72.0 mph). Skid pad figures are a wash, as both BMWs generate 0.89g and the STI makes 0.90g.
Understeer has been rumored to lurk within the 135i, but it didn't rear its head until we hit the road-racing track, where high-speed sweepers at the limit work the outside front Bridgestone mighty hard. Track-day junkies might want to make changes, but we think most everyone else will have no complaints.
Our 135i came with six-piston fixed-caliper brakes and 13.3-inch rotors. These calipers (something we'll see more of, our BMW sources tell us) seem like overkill when the heavier 335i and faster M3 do quite well with rather pedestrian single-piston sliding calipers. But the advantage might come in the form of consistently firm pedal feel over several days of determined street driving and extended track testing. This 1 Series comes to a stop from 60 mph in 109 feet.
It's Nice in Here
Inside the cabin, our 135i includes the Sport package, a $1,000 option consisting of an M-sport steering wheel and Shadowline trim, plus an elevated limiter for top speed. The package also includes terrific eight-way manually adjustable seats that adjust quickly, hold on tight in corners and look great. Why spend the money for optional power seats?
Handsome textured aluminum accents are applied with strategic restraint in the interior. BMW is one of a few carmakers that have figured out that accents that have the dull sheen of hand-worn metal look more upscale than any sort of chrome. And no sunlight gets reflected back into the eyes of the driver, either.
The Bottom Line
The base price for the 2008 BMW 135i is $35,675. After adding the options (including the $1,450 Boston leather upholstery) plus a $400 iPod and USB adapter and the $600 Cold Weather Package, our car's as-tested price is $39,125. And beware, because many high-cost options lurking on the options sheet can drive the price much, much higher.
It's hard to pin down the competition for the 2008 BMW 135i. On price and track performance, this test car matches up quite well with the 2008 Subaru WRX STI we tested, which costs $39,440. It matches up on performance, too. That's not bad company to be in, but at the end of the day, the Subie is no BMW.
Is the 2008 BMW 135i Coupe worth it? It depends. It's easy to go overboard with the options and jack up the price of the 135i so it no longer makes sense.
If you value a high level of steering and handling refinement and outright twin-turbo nirvana in a package that's small enough to toss around, and you can live with limited backseat space, the 2008 BMW 135i is like nothing else.
And it doesn't matter that the pot-bellied BMW 135i isn't the most beautiful car in the world. If you're doing it right, you'll be on the inside, working the steering, pedals and shifter with a huge grin on your face, happier than a pig in, well, you know.