Steve-O is an expert on rehab and substance abuse ... and he's torn up over the recent troubles of his old friend and "Jackass" co-star Bam Margera.
We got Steve-O out in L.A.'s Franklin Village ... and he told us how he's broken up by news of Bam's relapse.
As we reported ... Bam was robbed at gunpoint during a super sketchy cab ride in Cartagena, Colombia ... and handled it by downing his first drink in more than 7 months.
Steve-O drops some insight into the struggles Bam and other alcoholics face on a daily basis -- with a spot-on metaphor for the whole situation. He also has an opinion on Bam's claim he had been sober since he went to rehab back in January following his DUI arrest.
If there's one person who can get through to Bam ... it's got to be Steve-O.