We follow plug-in cars pretty closely here, and occasionally we manage to break stories.

One was the production green light for the Cadillac Converj electric car concept, confirmed by GM as the Cadillac ELR coupe just six days later. 

So when we see an article that's ... let's say implausible ... it's hard not to write a rebuttal.

Yesterday, in the widely followed trade journal Automotive News, product editor Rick Kranz penned a piece suggesting that the Cadillac ELR would have rear-wheel drive, which he calls a "game changer" for the electric Caddy coupe. (It's subscription only, so you may not be able to read the linked piece--sorry.)

The Cadillac ELR is essentially a higher-margin vehicle using the Voltec extended-range electric vehicle platform that sits under the Chevrolet Volt. The front wheels of the Volt are powered by its 111-kilowatt (149-horsepower) electric traction motor. Always have been.

Kranz believes that to be distinctive and to resonate with the Cadillac brand, the ELR electric coupe should have rear-wheel drive.

He notes that the upcoming Cadillac ATS compact sport sedan will ride on an all-new rear-wheel drive platform, code-named "Alpha." That architecture is designed to be used underneath future Cadillac CTS and Chevrolet Camaro models too.

2012 Chevrolet Volt

2012 Chevrolet Volt

Now, we're all in favor of rear-wheel drive plug-in and electric vehicles--and they certainly exist. Consider the Tesla Roadster, the 2012 Fisker Karma, and next year's Tesla Model S all-electric sedan, for instance.

But the idea that GM would create an entirely new, rear-wheel drive compact electric-drive platform is highly, highly unlikely. Right now, it has exactly one platform--its "global compact," or Delta architecture--that's been designed to accommodate the 400-pound T-shaped lithium-ion battery pack that stores energy in the Volt.

The crossbar of that T sits essentially between the rear wheels of the Volt--right where a differential and axle shafts would have to be located.

Kranz nods to the packaging issues, but suggests the pack could be raised over the rear axle. And he highlights a Cadillac description of the car as a "2 + 2" rather than a four-seat coupe.

Volt Battery Pack

Volt Battery Pack

He suggests that's "a signal that the battery pack will be eating up some of the rear-passenger space so the ELR can be offered as a rear-drive coupe."

We were sufficiently startled by this notion that we contacted our inside source at GM, who laughed out loud at the notion that the company plans to create a variation of the Alpha platform to accommodate a Voltec extended-range electric powertrain.

Then we got into the reasons why that won't happen:

  • A rear-wheel drive extended-range electric platform would require far more engineering resources than GM has available right now
  • GM wants to keep the pack as low and as central in the car as possible to achieve NHTSA five-star crash ratings for its plug-in vehicles
  • Mounting the battery pack above the axle would raise the center of gravity so high that any rear-drive handling advantages would disappear
  • The Voltec unit (including drive motor, generator, clutches, planetary gear set, and final drive) would need to be heavily reworked to allow a power takeoff for a driveshaft

All of these hurdles mean you can rest assured that the production version of the 2014 Cadillac ELR will remain a front-wheel drive plug-in coupe. Its mission is simply to boost the sale price on a few of the very pricey Voltec vehicles, to push that project closer to profitability.

We're still eager to drive it ....


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