What you need to know - Convertibles

Today's market offers a similar choice. There are convertibles or cabriolets that are open roof conversions or a variation of an existing sedan or hatch. Or you can buy a purpose-built sports car that happens to have a fabric roof. These are some of the things you might need to consider before making a choice:

CONVERTIBLES/CABRIOLETS
The original Saab 900 cabriolet was a pioneer of this genre in Australia and had all the good and bad points typical of this type of vehicle. The upside was that it was almost as spacious and practical as a two door Saab 900 sedan with the bonus of a top down facility.

The downside is that you can't chop the roof off a modern sedan or hatch without weakening it. To restore its crash strength and rigidity, the body and windscreen pillars have to be reinforced with heavy box sections and other reinforcements that add weight.

Very few of these conversions are ever as rigid as the original sedan or hatch and display scuttle shake which is experienced as the dash and steering wheel moving separately from the rest of the car on rough surfaces. To disguise this, some manufacturers fit softer suspension which can affect the handling. It also follows that regular pounding over rough roads is going to do more damage to a convertible than a sedan.

If the weight increase is too high, a bigger engine and transmission may be required to restore performance adding further to the purchase price and running costs.

Because turning a production sedan or hatch into a convertible is fiddly and disruptive to production, most manufacturers sub-contract this work to specialist facilities which is why the Holden Astra Convertible wears the Bertone badge and the various Peugeot Cabriolets are linked to Pininfarina. German cabriolet specialist Karmann is associated with several European makers including Volkswagen.

SPORTS/ROADSTER
These models are designed from the outset as open cars so their structure is specifically engineered not to rely on the roof for strength. These sports models can be as tight in the body as a normal sedan hence suspension and tyre packages can be tuned for higher cornering speeds with a tighter ride. Because their platforms will stay rigid under high power outputs and extra cornering loads, performance and high speed handling are usually superior.

These models are more likely to be two seaters only with tight boot space as the integrated structure is usually located through the centre and sills. The BMW 3 Series convertible and the Z3 Roadster highlight these fundamental differences even though they share the same mechanical package. Similarly, the Mercedes-Benz SL sports range is very different from the CLK models and early cabriolets based on the E-class.

COUPE-CONVERTIBLE
An increasing number of European convertibles are offering folding steel roofs instead of a fabric roof. However, the body structure still requires reinforcement for when the roof is retracted. This design offers increased security and longevity but the extra weight of the roof and its complex folding mechanism can alter the handling of smaller cars with this feature and ruin performance.

Before you buy a soft top, consider this

STILL WANT A SOFT TOP? CONSIDER THESE UNDER $40,000 BARGAINS:

Alfa Romeo Spider 1998 onwards: Stylish open top version of coupe hence front drive and some body wobbles but a choice of entertaining engines and several limited editions. Classification: Convertible for smooth road cruising

Audi 80 1994-99 Cabriolet: More thorough conversion than most with major structural reinforcement hence standard V6 engine. Just starting to date but the quality is there. Classification: Convertible for most roads and usage.

BMW E36 328i Convertible 1995-2000: Based on the earlier E36 shape, this is still the prestige benchmark and its rear drive handling is best enjoyed with the later 2.8 engine. Classification: Convertible with sports edge for most roads.

BMW Z3 Roadster 1997-02: Early four-cylinder models are tame to look at and drive but cheap. Later sixes with mid-1999 styling upgrade look and drive much better. Classification: Purpose-designed open sports car.

Ford Capri Convertible 1989-94: Still the most depreciation-proof small car on the market especially later Series II twin-cam models in good shape. Cannot be a lemon when it's a Laser convertible and forerunner to today's small soft tops. Classification: Convertible for most roads and usage.

Holden Astra Convertible 2001-05: Comprehensive conversion included bigger 2.2-litre engine and slick interior. Even if $18,990 Classic has not helped the image, it is still the benchmark. Classification: Convertible for most roads and usage.

Jaguar XJS V12 Convertible 1989-95: Get your head and wallet around the big maintenance and fuel bills and this is one of the best ways to travel without a roof. Later cars had extra stiffening rails. Classification: Convertible to be used as you can afford it.

Lotus Elan S2 Convertible 1994-97: Rare but they can be found. The benchmark front drive open sports car with reliable Isuzu mechanicals. Classification: Purpose-designed open sports car.

Lotus Elise Roadster 1997-2001: Wild four wheeled motor cycle with mid-engined rear drive layout that demands youthful agility to access especially when roof is up. You don't sit in it, you wear it. Classification: Specialist open sports car.

MGF/TF120 Roadster 1997-2002: Relatively refined mid-engined rear drive sports car with extra heritage and running costs over MX-5. Classification: Purpose-designed open sports car.

Mazda MX-5 Roadster 1989-2005: Definitive open sports car with rear drive and rigid structure with a model to suit every budget. Early 1.6 limited editions in top order are already collector's items. First 1.8 models were dullards but later 113kW and 121kW turbo models are a good drive despite cheap cabin feel. Classification: Purpose-designed open sports car.

Mazda RX-7 Series IV Convertible 1987-90: Heavy Series IV body was designed to have its roof removed hence it's better than most open top coupes. Smooth rotary struggled with extra weight but handling balance and refinement were outstanding. Some big repair bills and watch for private imports as Turbo convertible was never sold here. Classification: Sports convertible.

Mercedes-Benz 320CE/E220CA/E320CA Cabriolet 1993-97: Biggest convertible sold in Australia from this era hence most suitable as prestige open air family cruiser. Entry level 2.2-litre four works hard with the heavier convertible body which is almost as big as a Commodore but the sixes are sweet. Classification: Convertible for most roads and usage.

Mercedes-Benz SLK200 Cabriolet 1997-2000: Sharp baby Mercedes sports didn't do much with the unsupercharged 2-litre four and 100kW hence much lower used price but it looked the goods and was a civilized two seater runabout. Classification: Purpose-designed open sports car minus the sports at base level.

Peugeot 306 Cabriolet 2.0-litre 1997-2003: One of the sweetest of its type with upgraded engine to handle extra structure and weight. Comfortable and well-equipped, it also looks better than most of its type with the roof cut off. July 1997 upgrade boosted power to 100kW. Classification: Convertible for most roads and usage.

Porsche 944 S2/968 Cabriolet 1989-95: Low volume conversion not quite as integrated as equivalent RX-7. Outstanding 944 chassis means it is sportier than most but the hewn from granite Porsche feel is compromised. Classification: Sports convertible.

Renault Megane Cabriolet 2001-05: Although this model only reached Australia towards the end of its model life and was replaced late in 2004, it is outstanding value. Its 1.6-litre four delivers reasonable performance as a manual with exceptional economy and is fun to drive. Classification: Convertible for most roads and usage.

Saab 9-3 S/SE/Aero Convertible 1998-2003: Major facelift introduced 9-3 badge, stiffer structure and more compliant suspension in 1998 despite similar appearance to previous 900 model. Last examples would still be out of reach except desirable new model is prompting Saab's loyal owner base to update leaving a wide used choice. Classification: Convertible for most roads and usage.

Toyota MR2 Spyder Convertible 2002-2005: Toyota's generic looking mid-engined sports car has fallen off the radar screen lately hence some great used buys. Main obstacle seems to be the sequential six-speed when a simple manual gearbox and clutch would do. Classification: Purpose-designed open sports car.

Volkswagen Golf GL Cabriolet 1998-2003: VW's second Golf convertible was based on the Golf III which was then tweaked to look like the Golf IV late in 1998. It remained a generation behind until it was withdrawn. Older lolly-basket cabriolet looks don't have the presence of some rivals yet it's still a good compromise. It's now under attack from the keenly priced New Beetle convertible so look for some great used buys. Classification: Convertible for most roads and usage.

Volvo C70 2.4T Convertible 1999-2000: Expensive and exclusive Volvo convertible offers the usual Volvo virtues with unprecedented elegance although body structure could be stiffer. Appointments and five cylinder turbo performance in both 2.4T and high performance T5 spec are first class. Classification: Convertible for most roads and usage.