Spies currently lives in Longview, Texas. He started racing on 125cc bikes in Texas as a teenager. In late 2000 he qualified on the front row for his debut in the AMA Supersport Championship series. For the next 2 years he primarily raced Superstock, although troubled by a knee injury . He then joined the Yoshimura Suzuki factory team in .
Again with Valvoline Suzuki in 2001, Spies won the Pikes Peak round of the AMA 750 SuperStock Championship, and took four additional series podium finishes.
For 2002 Spies joined the Attack Suzuki team, paired with Jason Pridmore. He earned three top-five finishes in AMA Supersport, and four top-five finishes in AMA Formula Xtreme.
Now with American Suzuki team, Spies won the 2003AMA Formula Xtreme Championship with five wins and two additional podium finishes. He also contested the AMA Supersport series, earning a win at Road Atlanta and taking two additional podium finishes. His best AMA Superbike result this year was seventh-place at Daytona Intl Speedway
Again with American Suzuki team in 2004, Spies raced in the AMA Supersport Championship, earning a win at Infineon Raceway and taking two additional series podium finishes. He earned wins in the AMA Superstock Championship races at California Speedway and Road Atlanta, and earned two additional podium finishes in the series.
In 2005 Spies won the AMA Superbike race at California Speedway and earned 13 additional podium finishes. He was runner-up for the AMA Superbike title, and raced in AMA Supersport, earning five top-five finishes.
Spies joined the Yoshimura Suzuki team as a teammate to Mat Mladin fo2 006. He won the AMA Superbike Championship title with 10 wins and seven additional podium finishes. Spies took six successive wins early in the 2006 season, and staved off a late season surge by team-mate Mladin to win the title by 649 points to 641. In total he took 7 poles and 17 podiums , and lead the most laps 10 times. Spies also raced in select AMA Supersport events, earning a podium finish at Mazda Raceway Laguna Seca. produced one of the tightest championship battles in the history of the series, Spies won a second AMA Superbike Championship in 2007, by a single point over Mladin, with seven wins and 12 additional podium finishes. He captured Superbike pole position at nine events, and also won the AMA Superstock title with seven wins and seven pole positions.
In 2008 Spies won his third straight AMA Superbike Championship to become only the fourth rider in the history of the series to win the title three consecutive times (after Reg Pridmore, Fred Merkel and Mat Mladin). This included an AMA Superbike record of seven successive wins
He also had wildcard outings at Laguna Seca and Indianapolis on 20 July and 14 September. He achieved 8th at Laguna Seca despite stomach pain, which ultimately led him to require appendix-surgery 2 days after the race. At the next AMA race at Mid-Ohio Sports Car Course he aggravated the injury in bizarre fashion, swerving to avoid 2 fallers in front of him (Mladin and Jamie Hacking) who had fallen on water spilled from a bridge by a spectator. Despite the pain he took the restart, and took a pair of 2nd places behind Mladin.
Spies finished 6th at the Indianapolis MotoGP round, beating both the full time factory Suzuki riders, Capirossi and Chris Vermeulen.
He has been rumored to have a full time ride with Rizla Suzuki in 2009 in MotoGP. However, with the recent upturn of Loris Capirossi and Chris Vermeulen, he was linked a satellite third Suzuki bike, or even another manufacturer.