From Wikipedia:

> Wheels and tires retracted into housings where they were heated by engine exhaust gases. This was to prevent low-temperature cracking of the natural rubber compound. Long front and rear overhangs on the body were to assist with crossing crevasses up to 15 feet (4.6 m) wide. The front wheels were to be retracted so the front could be pushed across the crevasse. The front wheels were then to be extended (and the rear wheels retracted) to pull the vehicle the rest of the way across. This process required a complicated, 20-step procedure.

continuous tracks can be retracted too though, and they can be made without rubber.

But this process requires even more traction than simply moving, which the vehicle had problems to begin with.

My guess in answering the initial question would be bad engineering.

More research seems to indicate that continuous tracks do have significant maintenance drawbacks compared to tires (a tire can be expected to last significantly more miles than a track between repairs/replacement).

However, it definitely was a design defect as the cruiser was unable to travel reliably on the snow, and Byrd had previous success in Antarctica with tracked vehicles...