After Lance Armstrong's fall from grace cost him millions of dollars in lost endorsements and lawsuit settlements, one thing kept him on his feet: his investment in Uber.

"It's saved our family," Armstrong told CNBC's Andrew Sorkin in an interview aired on Thursday. In 2009, the former pro cyclist invested $100,000 in Chris Sacca's nascent venture capital firm, Lowercase Capital. Armstrong said the bulk of the money went to Uber, which at the time was valued at just $3.7 million. Today, as the company prepares for its IPO, banks have valued Uber at as much as $120 billion.

At the time he invested in Sacca's firm, Armstrong said, "I didn't even know that he did Uber. I thought he was buying up a bunch of Twitter shares from employees or former employees, and the biggest investment in [the] Lowercase fund one was Uber."