Crash your carbon-fiber i3 EV? Here's how BMW will fix it

The use of carbon fiber in the frame of the BMW i3 has many worried about high repair costs. BMW gives us an inside look at why it won't be so bad.

Tim Stevens Former editor at large for CNET Cars
Tim Stevens got his start writing professionally while still in school in the mid '90s, and since then has covered topics ranging from business process management to video game development to automotive technology.
Tim Stevens
3 min read

BMW i3
BMW Technical Training Manager Walter Malec shows the inner door structure of the BMW i3 Tim Stevens/CNET

NEW YORK -- The auto industry is a somewhat traditional one. Change tends to come slowly, and so whenever a major revolution comes along it's often met with skepticism at the least, or at worst, fear. That has definitely been the case with the carbon-fiber frame of the upcoming BMW i3, made entirely of a material that's stronger and lighter than steel but is generally considered unrepairable. In the world of top-level motorsports, where carbon fiber is de rigueur, the repair procedure is quite simple: throw away the broken part and bolt on a new one.

That's not an option when it comes to something like the frame of a $40,000 mass-produced car. This has raised many concerns about the viability of the material for use "regular" cars, with people fearing that the machines will be impossibly expensive to insure and maintain. This, in turn, has spurred BMW to be a little more open than usual about its repair techniques.

Repairing the carbon-fiber BMW i3 (pictures)

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When it comes to replacing body panels and the front or rear bumpers, the procedure is actually much the same as before. Body panels are some combination of plastic, aluminum, and carbon fiber and are mounted to the carbon frame using screws and clips that allow for quick removal and precise adjustment. This actually makes them quite easy to pull off and swap, in some cases more straightforward than a more traditionally constructed machine.

The new glass removal tool for the BMW i3. Tim Stevens/CNET

Replacing the glass, however, is a bit more complicated. BMW typically relies on a machine that uses piano wire to cut the adhesive bonding glass to frame. That wire could potentially damage the carbon, so BMW developed a system that works in the same way but uses a softer filament. "It's like a high-test fishing line," BMW Technical Training Manager Walter Malec told us. This works every bit as well as the wire option but is a fair bit gentler to the surrounding frame.

Every BMW dealer will be equipped to provide basic body work and replace glass on the i3. However, those cars requiring more attention, cars that have been more extensively damaged, will also require access to specialized expertise that not all dealers will offer -- at least, not at first.

The internal structure of the i3 is a carbon frame, called the Life Module, that makes up the majority of the shape of the car. That's bonded to the so-called Drive Module, a mostly flat aluminum structure that forms the base, where the suspension and the motor attach. The aluminum Drive Module can be mostly repaired just like any of BMW's other aluminum cars, which are many. It's the carbon Life Module that needs special treatment.

An illustration showing the various sectioning points. BMW

BMW has segmented the Life Module into five "sectioning points," basically telling technicians where to cut. A special carbon milling tool has been developed. It attaches to a vacuum to collect the carbon dust, giving a clean cut with no mess. If, for example, the A pillar is damaged (the forward structure that holds the windshield), that section of the composite shell will be cut starting at the front of the roof and again down at the footwell. That entire portion will be removed from the damaged car and a replacement section glued into place. (Yes, BMW techs will use glue, but don't worry: much of the car is held together with the stuff in the first place.)

That all sounds simple enough, but there's one major catch: you can't buy just a small portion of the carbon frame. BMW will offer only the entire left or right side of the Life Cell, which will then be sliced and diced as needed. It remains to be seen whether insurance companies will be required to pay for the entire portion, or if dealers will cut them up and sell the individual segments. It also isn't known what those components will cost.

The left and right portions of the Life Module, which will be cut into segments. Tim Stevens/CNET

That said, Malec, BMW's Technical Training Manager, estimated that overall repair cost of the i3 should be "comparable" to that of a traditional car. That's largely because, he reckons, the transition to carbon repair is actually a smaller shift than that from steel frames to aluminum, which BMW made over a decade ago. Training, Malec says, should be straightforward, and the specialty tools required are few -- basically just that new milling machine and a special vacuum to connect to it. That's good news for those considering buying -- and insuring -- an i3.