Elon Musk says "Use wheels . . limit the number of miracles in series"
At the the 2016 Pod Competition, Elon Musk was asked if he preferred maglev or air ski bearings. He said wheels were the better option for sub-sonic speeds. He stressed the importance of starting with the minimum achievable technology, leaving higher performance for future development.
This is very satisfying, the Cheetah project has been promoting wheels since 2013, but wheels have been unpopular, being 'boring' and low-tech.
Only 1 or 2 teams at the Pod Competition chose wheels, the rest of the 120 teams all proposed air bearing skis or maglev.
Elon Musk has elegantly described the priciples of achieveable development. The vacuum tube is unknown technology, the first miracle is to build the first full-size test track, about $100 million, and overcome the unknown problems.
As Musk says, we should not take more risks, and require further miracles with the development of new and untested levitation technology, when the humble wheel has shown to be capable of doing the job.
Wheels - the options and technical issues
Wheels have been proved at higher speeds than any other levitation
Pneumatic tires are the preferred option if achievable
Steel rim wheels on a resilient surface are a good alternative
Continuous traction is a great advantage
Wheel forces are analysed here