Giebler was considered a top American prospect with an opportunity to race in Formula 1 early in his career. Following years in various Formula 3 ranks, Giebler ran in Formula 3000 in 2003 half the season putting up a number of good results. He returned stateside in '04 running in the Infiniti Pro Series and Toyota Atlantic, capturing a win in his IPS debut at Homestead-Miami Speedway, before being named as one of A1 Grand Prix A1 Team USA's drivers. He competed in the 2005-2006 season, and the early part of the 2006-2007 season before being replaced by Jonathan Summerton.
Driving for Playa Del Racing, he qualified for the last starting position and was one of two rookie drivers to race in the 2007 Indianapolis 500, but crashed and finished 29th. He was the recipient of the Indianapolis 500 Rookie of the Year award for 2007. For 2008, he unsuccessfully attempted to qualify for the Indianapolis 500 with the same team, now known as American Dream Motorsports.
| Year | Entrant | Chassis | Engine | Tyres | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | DC | Points |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2003 | Den Blå Avis | Lola B02/50 | Zytek-Judd KV | SMR | ESP Ret | AUT 8 | MON Ret | EUR 9 | FRA DNS | GBR | GER | HUN | ITA | 17th | 1 |
| Year | Chassis | Engine | Start | Finish |
|---|---|---|---|---|
| 2007 | Panoz | Honda | 33rd | 29th |
| 2008 | Panoz | Honda | Failed to Qualify | |