The effort to preserve artifacts is not to alter them but to maintain them as much as possible in the state in which the Smithsonian acquired them. Also, when the aircraft was recently lowered to the floor of the museum's Milestone's gallery, the tires were removed and replaced with "forklift" style tires. This was done to preserve the Spirit's original tires which, due to age and lessening of vulcanization, are unable to sustain the aircraft's weight without disintegration (conservation was also likely undertaken on the wheel assembly itself).[18][19]