Under the bonnet: The long and the short of it

The plastic-panelled Smart Fortwo is, not surprisingly, quite cheap to fill. Photo / Supplied

It doesn't take a genius to figure out that the main advantage of a long wheelbase (LWB) vehicle is more space for occupants. That's why manufacturers sometimes offer limo-like models as their range-toppers.

But there's more than just acres of legroom for rear-seat passengers. Wheelbase, by the way, is the distance between the front and back wheels, measured at the centre of the axles.

Generally, vehicles fall into one of three wheelbase categories: short, medium or long. Trying to define which is which is a bit difficult; what American manufacturers see as medium is likely to be long to the rest of us, despite Detroit downsizing its thinking.

But clearly, a tiny Smart Fortwo falls into the short wheelbase class with its 1810mm spread. Something like a Toyota Camry is medium at 2775mm and a Holden Caprice is long at 3009mm.

It's common, though less than it once was, for manufacturers to add wheelbase to a basic design to add interior space. Ford and Holden have done it on Falcon and Commodore for years, although Ford has ended its Falcon-based LWB offerings and Holden has dropped the Statesman, leaving the Caprice.

It takes only a minute comparing, say, a Commodore with a Caprice to see the advantage of a longer wheelbase. Rear-seat space is significantly improved. No wonder LWB cars have been favourites of chauffeur and taxi companies.

LWB cars usually have better stability and handling at speed, plus a smoother ride, features that attract buyers who have no particular need for the added space. A longer wheelbase is also widely regarded as better for towing.

LWB SUVs may have an advantage off-road in rough conditions, able to straddle ruts and tackle some hills more easily than the shorties. However, LWB vehicles of all types are less agile and usually have a wider turning circle - a curse in narrow urban streets or in tight spaces off-road.

Longer vehicles are heavier than the vehicle on which they are based, leading to higher fuel consumption and lower performance. But these differences needn't be large. When Jaguar added 125mm to the X358 model XJ, weight went up by only 24kg, considerably less than most of its stretched rivals.

Going steady

Wheelbase debates aren't just a car thing. It's a topic of discussion for everyone from skateboarders to locomotive designers.

You'll hear it discussed by touring cyclists. Fans of long-wheelbase bikes also cite greater stability on, say, a fast, bumpy descent, along with quicker steering and better comfort. It also helps avoid pedal-to-luggage space problems.