A pair of Chevy Volts riding on stylish chrome 20-inch wheels could very well be development mules for Cadillac's new Voltec luxury car.

Two Chevrolet Volts spotted in Michigan wearing stylish 20-inch alloy wheels could be more than just a pair of tricked-out versions of the bowtie brand's extended-range EV.

Our spy photographer found these two Volts prowling the streets of the Detroit area, where their 20-inch wheels wrapped in performance-oriented all-season Bridgestone rubber indicate that something rather unusual is going on. The presence of more than one Volt with the same set of wheels confirms that GM engineers aren't just having a little fun. Either a performance and style-oriented version of the Volt is just around the corner or these are powertrain mules that hint at Cadillac's upcoming Volt-based sports car.

Well before the Volt hit the market, General Motors stated that it planned to use a version of the car's so-called Voltec extended-range EV powertrain to motivate other cars, including a Cadillac-badged variant that initially took the form of the Cadillac Converj concept car. The on-again, off-again Converj was finally given the production green light and the ELR moniker last summer, and while little new is known about the ELR, it's assumed that the car will get a sportier and likely more advanced version of the Volt's plug-in extended-range electric powertrain.

The multi-spoke wheels on these Volts do seem to fit within the Cadillac mold in terms of their design, although their center caps seem a little more Discount Tire than Art and Science.

Similarly, a report last year suggested that a Buick-badged version of the Volt's Opel Ampera kissing cousin was headed to North America, but we haven't heard a peep about that project since last March.

On the other hand, the wheels might simply serve as development place holders, of sorts, for their weight and size if not their design. In this case, they might hint at an upcoming sport-oriented Volt variant. Despite its eco-friendly nature, the Volt is actually rather nimble thanks to quick steering and an ultra-low center of gravity created by its gigantic battery pack. Of course, larger wheels will dent EV range and overall fuel economy, which goes against the Volt's mission.

Just what is GM up to? Stay tuned.