Why Tesla Model X Electric SUV Is Late: Range, Towing, 'Falcon Doors'

Tesla Model X CES 2015 walkaround by TechVideo screencap

Electric-car fans and Tesla owners alike are eagerly awaiting the debut of the Tesla Model X electricSUV, now scheduled to go into production roughly six months from now.

Like every Tesla, the Model X has been delayed a number of times--but there's been little speculation about the reasons for the delays.

Green Car Reports asked Tesla Motors to spell out what had led to the delays, and whether the car was still on track for a Q3 launch.

"We continue to develop Model X and prepare for production," wrote Khobi Brooklyn, Tesla's global communications director.

"We are currently testing our Model X beta vehicles and on track for a Q3 launch."

Tesla Model X in camouflage being tested at former Alameda Naval Air Station [video: Juan del Real]

In other words: "Yes, it's going to launch in Q3, and we're not going to tell you anything about why it was late."

And yet, the final production version of the Model X hasn't been shown in public, even as the first pre-production prototypes would normally be rolling off the lines.

So we reached out to a number of sources, including those close to some of Tesla's parts suppliers, to ask why the Model X was delayed.

None of them would talk on the record--so what follows is thus largely speculation, though we'd suggest it's informed speculation.

For many, that will dilute its credibility. Still, we thought our various discussion would be worth summarizing.

Here are the three reasons we think the Model X schedule lagged significantly from its originally announced launch date of late 2013.

Tesla Model X

(1) RANGE RATINGS

EPA range ratings for the various Tesla Model S versions range from 208 miles (with the 60-kilowatt-hour battery pack) to 270 miles (the 85-kWh "D" all-wheel-drive variant).

The Model X crossover utility will have all-wheel drive as standard equipment--but it's larger and heavier, and has a greater cross-sectional area, than the lower, lighter, sleeker Model S.

A 60-kWh version could well be rated under 200 miles, likely making it a non-starter at a price of $70,000 or higher. The 85-kWh Model X would likely hit about 225 miles of range.

But we understand Tesla had really counted on replacing the door mirrors with video cameras to boost the range to around 250 miles.

Removing the door mirrors could add a significant boost to the range at highway speeds (where overcoming wind resistance consumes the majority of the energy).

But legal video mirrors aren't likely to happen soon, with the National Highway Traffic Safety Administration (NHTSA) having to study the issue, then issue proposed rules, wait for comments on them, and then put them into effect.

Tesla Model X at 2013 Detroit Auto Show

Even under the best of circumstances, that process almost surely will not happen by the third quarter of this year.

That means that Tesla is likely working furiously to get every single additional mile of rated range out of the Model X.

(2) STRUCTURAL IMPACT OF FALCON DOORS

One of the most striking features of the Model X is its falcon doors, which are hinged along the length of the center roof spine, and articulate as they rise to keep their width largely within the footprint of the car.

Tesla CEO Elon Musk said during an earnings call that the company "had learned a lot about door seals," and our sources tell us the sealing challenges are now solved.

Tesla Model X at 2013 Detroit Auto Show

Side impact ratings

There may remain two issues: Side-impact protection, and the effect of the complicated torsion springs on the aluminum roof structure.

Tesla buyers will likely expect the Model X to get the same top crash-safety ratings as the Model S in every category, including side impact.

That means the falcon doors themselves must contain strong beams that interlock into the rest of the body structure when the door is closed, to protect occupants in a side impact.

Tesla Model X

Such reinforcements can impinge on interior room, and significantly increase the weight of the doors.

Torsion springs for falcon doors

Which leads to the second challenge: anchoring the rotary door hinge mechanism for what is likely a fairly heavy door (since it contains a substantial chunk of roof too).

While aluminum is light and strong, its metallurgical characteristics differ from those of the heavier high-strength steel alloys now used in the latest vehicle structures.