Tesla’s newest Cybertrucks have been shipping with a redesigned underbody panel that owners and reviewers spent weeks describing as a carbon fiber upgrade — until the truck’s own lead engineer said otherwise. In a September 7 post on his personal account, Cybertruck Lead Engineer Wes Morrill confirmed the panel is actually made of self-reinforcing polypropylene, a molded plastic composite, not carbon fiber.

Key Points

• The part in question is an aero shield mounted underneath the truck near the front and rear motors, which replaced an earlier stamped-aluminum underbody piece
• New Cybertrucks began arriving with the darker, woven-look panel over the summer, and its appearance led much of the ownership community to describe it as a carbon fiber addition
• Morrill’s post explains the material is polypropylene “stretched into fibers, then laminated” into its final shape — a manufacturing process distinct from how genuine carbon fiber composite is produced
• Per Morrill, the switch was driven by cost and weight rather than styling: the new panel is lighter and significantly cheaper than the aluminum piece it replaced
• Carbon fiber composite typically costs several times more per pound than reinforced polypropylene, one of the most common and least expensive plastics used in vehicle manufacturing

What Changed, and Why It Matters

Tesla did not introduce the new panel through a formal marketing push or an updated spec sheet — it appeared quietly on the production line, and outside observers filled the information gap themselves. That gap is what let a “carbon fiber” description spread across delivery videos and owner discussions well before Tesla’s own engineering team weighed in with the actual material breakdown.

Morrill’s account is the most direct answer available on the part, since it comes from the engineer responsible for it rather than a third party identifying the material from a photo. He said the change also delivers better impact resistance, improved aerodynamics, and reduced wind noise near the front wheel wells, on top of the cost and weight savings — trade-offs that make sense from a manufacturing standpoint even though they undercut the premium “carbon fiber” reputation the part had picked up.

What Owners Should Know

Cybertruck owners who assumed their trucks carry genuine carbon fiber underbody protection are not getting the material they may have believed they had, though the panel’s actual function — shielding components underneath the truck and smoothing airflow around the motor housings — does not appear to have changed with the material swap. Tesla has not published documentation clarifying which build dates received the polypropylene version versus the earlier aluminum piece, and the company has not commented on the confusion beyond Morrill’s post.