Tesla Motors Inc (NASDAQ:TSLA) and Bayerische Motoren Werke AG (ETR:BMW) (FRA:BMW) have apparently been working together on electric vehicle technology for some time. As it turns out, BMW could have the answer to the weight problem that’s believed to be an issue for the falcon doors on the Model X.

BMW's Carbon Fiber Could Save Tesla Model X Doors

Tesla contradicts itself?

Today Tesla responded to suggestions posed by Morgan Stanley about why the Model X launch got delayed yet again. The automaker claims that the complexity of the falcon wing doors actually doesn’t have anything to do with the delay, which is contrary to what Morgan Stanley’s Adam Jonas suggested on Monday. However, a green car expert points out that Tesla has made comments about problems with the doors before.

“When it comes to the delay of the Model X, while Tesla claims that the falcon wing doors are not the main reason for it, and that they are ‘relatively easy to execute,’ the company officially admitted a while ago that the doors didn’t provide optimal insulation from wind and rain,” Jordan Perch of DMV.com told ValueWalk. “So they definitely have something to do with the delay.”

Tesla could use BMW’s carbon fiber material

One of the suggestions Jonas made about a challenge Tesla could be facing with the Model X doors is their weight. The falcon wing doors’ complex design would probably result in extremely heavy doors. So what could Tesla do to fix the problem? It’s simple, really. Just use lighter material—and BMW just happens to have the perfect thing.

Until recently, Tesla’s and BMW’s partnership was believed to have been focused on developing electric vehicle technology and speeding up adoption of EVs. It seems likely that the two automakers only started discussing BMW’s carbon fiber technology recently when executives from both companies met a few months ago to talk about sharing their technologies.

It’s believed that Tesla representatives were interested in BMW’s knowledge regarding the manufacturing of carbon fiber components, while BMW wanted to know more about Tesla’s batteries and electric vehicle charging system.

Tesla aims to reduce Model X’s weight

Of course one of the challenges Tesla faces in making the Model X have a range that’s similar to that of the Model S is overall weight. The crossover vehicle is expected to weigh approximately 10% more than the 4,600-pound Model S.

Perch said using BMW’s carbon fiber to make some of the Model X’s components can significantly reduce the vehicle’s weight, making it easier for it to have the desired range of around 250 miles per charge. Perch believes that Tesla is indeed considering using BMW’s material technology for the Model X.

“Elon Musk’s company is considering using carbon fiber to make certain parts of the Model X, especially for the falcon wing doors,” Perch told ValueWalk. “They are much heavier than conventional doors, and making them out of a lighter material – such as carbon fiber, would be the perfect solution for reducing the overall vehicle weight.”

How big of a difference would carbon fiber make?

So just how much lighter could Tesla make the Model X if it made some of the components out of carbon fiber instead of steel? Quite a bit, it turns out.

“A car component made out of carbon fiber can be anywhere between 30 and 60 percent lighter than a steel component,” Perch said. “So given that Tesla doesn’t intend on giving up on the falcon wing doors and replacing them with traditional doors, chances are that the company will go with carbon fiber doors, sticking with the original design.”

He suggests that a partnership between Tesla and BMW might mean that BMW supplies carbon fiber parts to Tesla, which would then provide its expertise in electric powertrains and EV charging infrastructure.