Wimmer grew up in Wausau, Wisconsin, and showed early athletic versatility — he competed in the United States National Junior Olympics in downhill and slalom skiing at age fourteen, finishing 13th among 150 competitors. Racing was in his family too: his father was the owner of his uncle Larry Detjens' race team, and Detjens was a champion late model driver at Slinger Speedway and Wisconsin International Raceway before his death in 1981, an event now commemorated by a race named in his honor.
Wimmer began racing at State Park Speedway in 1991 at age fifteen. He moved through the Midwest ranks, then headed south to earn Rookie of the Year honors in the Hooters Cup late model series in 1997. In 2000, he was Rookie of the Year runner-up in the American Speed Association series, beginning the season without a sponsor for his family-owned team but winning the first two races to secure funding for the full year.
Wimmer's NASCAR career began in 2000 when he was signed to drive the No. 20 AT&T Pontiac for Bill Davis Racing in the Busch Series. After failing to qualify for his first race at Rockingham, he finished 18th in his series debut at Memphis. He was named Davis' permanent driver of the No. 23 car in 2001, posting two top-fives and eight top-tens while finishing 11th in points — second to Greg Biffle for Rookie of the Year.
Wimmer's best Busch Series season came in 2002, when he won four races in the fall — at Dover, Memphis, Phoenix, and Homestead — and finished third in the championship standings. A switch to Chevrolet and loss of crew chief Bootie Barker hampered his 2003 season; he managed one win at Pikes Peak with four top-fives and twelve top-tens for a ninth-place points finish.
His final Busch Series victory came in 2008, driving the No. 29 Holiday Inn Chevrolet for Richard Childress Racing at Nashville — his first win since 2003 and his sixth career win in the series. Wimmer continued to race part-time in the Nationwide Series through 2011, picking up occasional top-ten finishes in limited schedules.
Wimmer got his first sustained Cup opportunity when he was named full-time driver of Bill Davis Racing's No. 22 Caterpillar Dodge for the 2004 season. He opened the year impressively at the Daytona 500, running near the front after the final pit cycle before being overtaken by Dale Earnhardt Jr. and Tony Stewart to finish third. That run raised expectations that the season never quite fulfilled — he recorded only one other top-ten at Dover and finished 27th in points.
The 2005 season was worse: no finish better than 11th in any race, 32nd in points. He was released from Bill Davis Racing by mail at the end of that season, which subsequently led to a lawsuit against the team.
Wimmer joined Morgan-McClure Motorsports for 2006 but left mid-season after the team lost its primary sponsorship due to non-payment. He drove the season finale at Homestead for Morgan-McClure in the No. 33 Holiday Inn Chevrolet, finishing 12th. He ran additional Cup races in 2007, 2008, 2009, and 2011 in various limited arrangements, never returning to the consistent top-ten results of his early career.
In 2012, Wimmer stepped away from full-time racing. He and his father had purchased State Park Speedway in Wausau in 2009, making significant improvements to the facility. Wimmer also took on a driver coach and spotter role for young talent Cody Coughlin, who ran through late model series, ARCA, and eventually Camping World Truck Series starts under Wimmer's guidance. Coughlin won multiple championships in the ARCA/CRA Super Series and JEGS/CRA All-Star Tour during those years, reflecting Wimmer's effectiveness in a mentoring capacity.
Their association ended in January 2017 when Coughlin joined ThorSport Racing. Wimmer continued to run State Park Speedway, maintaining a connection to the Wisconsin short-track scene where his racing life began.