After the swim, athletes shed their wetsuits and go to the transition area, where their bikes and clothes are waiting. Then, they start the biking part. (Photo: Chloé Morrison)

Thousands of athletes and spectators will descend on downtown this weekend for the Ironman 70.3. 

The event is a 1.2-mile swim, a 56-mile bike ride and a 13.1-mile run. 

In 2014, officials announced that the Ironman 70.3 would come to Chattanooga, making the city one of 10 cities in the world to host both the full Ironman and the shorter competition. 

Additionally, the Ironman Expo will be open on Riverfront Parkway's green space near Ross's Landing from noon to 7 p.m. Friday and 9 a.m. to 5 p.m. Saturday and Sunday. 

On Saturday morning, there's an Ironkids race that starts at 9 on Riverfront Parkway. 

On Friday and Saturday, spectators can participate in free test drives for several Toyota vehicles. Drive opportunities will take place Friday from noon to 7 p.m. and Saturday from 9 a.m. to 5 p.m.

Ironman 70.3 starts early Sunday morning, with the swim portion beginning at 6:50.

Athletes will transition to the bike race from about 7:30 to 9:30 a.m.

Click here to read about and see photos of last year's event. 

Click here and here for details about road closures and delays.