The previous-generation Astra convertible weighed in at 1320kg, 140kg more than the three-door hatch. Now the 2.0T TwinTop tips the scales at a chunky 1645kg – 342kg more than the 2.0T SRi hatch.
As you would expect, the mass serves to blunt acceleration. As in other applications, the familiar 2.0-litre turbo petrol engine is smooth-spinning and with a nicely zingy soundtrack. But even with 197bhp the TwinTop has a power-to-weight ratio of 119bhp/tonne. (The gutless 1.6 version manages just 71bhp/tonne.)
This 2.0T struggles getting away from the line, as evidenced by an 8.3sec 0-60mph time, although the in-gear acceleration is considerably more respectable. The 50-70mph sprint takes only 4.3sec in third gear, and a still-decent 9.8sec in sixth. Slippery aerodynamics helped the Astra to a 143mph top speed in Millbrook’s high-speed bowl, which correlates closely to the official 146mph figure.
Lid lowered, the TwinTop suffers from noticeable scuttle shake, with vibration coming through the steering column and making the rear-view mirror unusable when the car is driven over rough roads. The optional 18-inch wheels on our test car probably didn’t help.
The car feels far sturdier with the roof in place, driving as you would expect a heavier version of the three-door hatchback to drive. The electro-hydraulic power steering is respectably quick but gives little feedback.
An optimistically titled Sport button sharpens up the throttle response, while holding the same switchgear down for three seconds de-energises the stability control. Grip levels are respectable, but the TwinTop feels less agile than the conventional Astra and far less keen to tighten its cornering line once you take your foot off the gas.
The middle pedal feels slightly inert but delivers strong response, the Astra pulling up square under maximum braking. The six-speed ’box doesn’t like to be rushed, but with time delivers slick changes.
