Mysterious cracking noise?
 

Hi all. My 2013 FR-S has developed a strange cracking noise under acceleration. It ranges from a tap like a stone hitting the undercarriage to a loud crack. Hard to tell which direction it comes form but majority opinion leans toward the front. It is unpredictable but seems to usually happen when weight shifts back under acceleration. prior turning and braking may set it up for the crack but it is really unpredictable. Seems to happen more after the car has been driven for a while. Inspection by several mechanics found nothing.

The car is driven on the track (maybe 15 days so far) and the problem first happened immediately after a track session. Couldn't find anything in this forum on this but it is hard to search this subject and I am not even sure this is a suspension issue but it seems more likely than anything else.

Any ideas?

Check your strut tower support bars. Make sure they are tight and the nuts haven't come loose

I checked them with my fingers but will recheck with a wrench. Certainly seemed tight. Some further research may be pointing at the rear axel nuts or axels.