Jeep's controversial high-performance high-rider

All-new 6.4-litre V8 engine and unconventional run-flat tyres for Jeep's range-topping Grand Cherokee.

America's quintessential off-road brand has taken the wraps off its new high-performance model - the Grand Cherokee SRT8 - but this is one Jeep the brand doesn't expect people to take off the beaten track.

In a controversial move, Jeep will fit the flagship Grand Cherokee model with city-friendly run-flat tyres - rendering the usually "go anywhere SUV" virtually unusable for off-road work, while also making Jeep only the second brand (aside from BMW and sub-brand Mini) to fit its cars with the new-technology tyres.

Run-flat tyres allow a vehicle to drive to the nearest town for help rather than have to stop and change a tyre on a roadside, which can potentially be dangerous.

However, early generations of the tyres fitted to BMW and Mini cars soon earned a reputation for producing a rough low-speed ride that didn't fit with the luxury image the cars were trying to project.

The US brand's chief executive Mike Manley told Drive at the New York motor show the brand would eventually start to use Pirelli run-flat tyres across all its Cherokee models.

"There is the potential for us to roll out [run-flat tyres] across the range in the future," Manley says.

"It's all about space and packaging," Manley says, referring to the space required by a full-size spare which can be liberated if no spare is needed. "If we need the space, [run-flat tyres] is now an option that we will use."
 
The brutal new SRT8's aggressive new look is backed by a more potent V8 powerplant - a new 6.4-litre unit replaces the existing 6.1-litre V8, stepping up power from 313kW to 352kW and torque from 569Nm to a chunky 630Nm.

The SRT8 - which has been confirmed for an Australian debut around May 2012 - sends its power to all four wheels - or if it comes to it, 100 per cent of its torque to the one wheel with the most grip - via a five-speed automatic gearbox.

Even though it is capable of blasting from 0-100km/h in less than 5.0 seconds (the official 0-60mph figure is a slim 4.8 seconds) it is still more fuel-efficient than the model it replaces, saving 15 per cent on the fuel bill thanks to cylinder deactivation technology once only available on the smaller 5.7-litre Hemi.

Style-wise the SRT8 gets a revised front-end design with a new front bumper that makes the Grand Cherokee look as though it has a fat lip, while it sits on standard 20-inch wheels with run-flat performance tyres - more on that below.

However, one endearing touch - the double barrel chrome exhaust pipes that once poked out from the middle of the rear diffuser - is now gone, replaced with a set of side pipes that look just as lairy, but with much less drama.

Inside, the Cherokee now uses a Land Rover-style selection knob to switch the dynamic suspension settings between track, road, snow and off-road settings. There's even a towing setting that optimises the SRT8 for pulling big loads - the new-generation high-peroformance high-rider is rated at about 2.2 tonnes, an improvement on the former model's mediocre 1585kg limit.