The IndyCar Series rookie was in the Turn 3 braking zone when the right front corner of his car suddenly collapsed and sent him into the wall.
The suspension broke at 185 mph (300 km/h) before hitting the wall at 135 mph (217 km/h).
Unable to slow his car down, Foster ploughed into the back of Meyer Shank Racing driver Felix Rosenqvist at close to 120 mph (193 km/h).
Both drivers were taken to the trackside medical centre where they were cleared of any injuries.
Foster was left shaken up by the incident, which he said would be investigated by the team.
“Firstly, thank you to everyone for all of the messages, I am okay,” Foster wrote on social media.
“I’ve talked to Felix and I’m also very happy that he is okay.
“Massive thank you to the IndyCar medical team and IndyCar as a whole for continuing to put driver safety first.
“To explain what happened: on Lap 83, approaching T3 at 180 mph, my front right suspension failed.
“This was by far the biggest and scariest crash I’ve had in my career, I’m very thankful to be able to get out under my own power.
“We believe it was caused by a bolt failure on the mounting block, but more internal investigation is required to be sure.
“Biggest bummer is that we were on for our season best result, and we led multiple laps, up the front on our strategy. But this is racing, sometimes it doesn’t love you back.
“See you all in two weeks.”
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Foster sits 24th of the 27 full-time drivers in the standings and is just two places behind fellow rookie Robert Shwartzman.
Foster’s best finish to date this year is 11th at the Indianapolis Grand Prix.
IndyCar returns to Gateway on June 16 (AEST).
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