I NEVER IMAGINED THAT my first taste of Porsche's legendary precision engineering was going to leave me so shattered. Sweat-stained and puffing, I wrenched through the gears but could barely muster enough speed to pass a tram. With tens of thousands of dollars of brand-new German technology under me, shouldn't I have a bit more zip? Not when the machine in question was a mountain bike and the only accelerator pedals were ones my increasingly tired legs were pumping. Sure, for small change short of $50,000 Porsche makes a really nice bike - full suspension, disc brakes, the works, right down to the firm's famous rearing black stallion logo. Here in Hong Kong, you can also pedal home with help from Mercedes or BMW if you don't have the cash for the coupe or you just want to accessorise. The trend for motor manufacturers to sell their own brand of bicycle, mostly mountain bikes, is on the rise. 'We are trying to promote a lifestyle,' says Lars Petersen, general manager of Porsche Hong Kong and China. Of the three car manufacturers that offer matching mountain bikes for sale here, Porsche is the only one not just to slap its own name on someone else's existing bike. The German company Votec was commissioned to design and build an entirely new machine, and I test-rode the middle bike of three models available - the aluminum-framed FS (full suspension) which retails for $31,470. With top-of-the-line Shimano components (the largest bike-component manufacturer in the world), and suspension more than 10cm deep, the Porsche bikes are designed to swallow bumps, rocks and muddy wilderness trails, leaving rose petals strewn in their wake. I couldn't wait. 'Don't take it off-road,' Petersen commanded after he agreed to lend me the bike. What? Well, I guess I should have known - he didn't want it to get muddy. 'I think most of them end up hanging on walls,' he said. So I pedalled the Porsche over to one of Hong Kong's two shops catering to mountain-bike racers and high-performance riders. Sin Tak-chiu of Bicycle World in Wan Chai pointed to comparable bikes selling for a third of the price of the Porsche. 'You're paying for the brand,' says Sin. This is nothing that Petersen doesn't admit - after all, no luxury car-maker has ever championed affordability. And Hong Kongers have always been very much at home seeking prestige through labels. None of the three companies have exact records of the number of bikes they have sold in Hong Kong, but all maintain - surprisingly - that the number is pretty low. Sin says he has tuned up a few car-brand bikes in his six years as manager of Bicycle World and that the owners are typically aged between about 30 and 40. In the US, where mountain-biking is much more popular, due in part to the fact that there are legal, rideable and fun trails, the car-makers all say they've sold thousands. BMW sells three high-performance mountain bikes, made by a US bike company called Montague. Although all three car-makers offer roof-racks to hold their bikes, BMW has decided that its potential bike owners should forgo the risk of scratching their cars and pop the two-wheeler into the boot. Just don't expect them to throw in the bike after you've plonked down $935,000 on a 740i saloon. 'Absolutely not,' says salesman Francis Lau. 'They're not getting a $10,000 souvenir,' he adds, speaking of the price for the cheapest model. Mercedes-Benz also offers three mountain bikes, built by American automotive component manufacturer AMP Research. In comparing each company's top machine, Porsche's model, the FS Evolution, is the heaviest and most expensive of the three, weighing 12.4kg and costing $45,000. BMW's top bike, the Supertech, weighs 12kg and weighs in at around $30,000, while the Mercedes FS Exclusive weighs 11.2kg and will set you back $40,000. The Porsche is made of carbon fibre and is the most eye-catching of the three thanks to its bright yellow 'mag' (triple-spoke) wheels. The other two are both aluminium-framed, the Mercedes chrome-coloured and the BMW black. Like the cars, all three have fully adjustable front and rear suspension, and both the Porsche and Mercedes have disc brakes. Mountain bike magazines around the world have generally given the bikes positive reviews. But when other riders outside the Wan Chai shop checked out my borrowed Porsche I felt uncomfortable with its exclusivity, and realised that I'm not cut out for the elite, preferring camaradarie over cliques. Then I saw this new bike, made by GT. It's based on the world downhill champ's bike, costs $50,000 and only 50 have been built . . .