Bam Margera's taking more shots at Steve-O ... ripping his former friend for having some of the worst skateboarding style he's ever seen.

The former "Jackass" star tore into Steve-O's skateboarding mixtape with a video response, mainly taking issue with the way Steve-O completes his kickflips.

Bam says it's proof Steve-O's not as good a skater as him ... and he's also dissing his old buddy for not doing a rail slide in the video with Tony Hawk.

The back-and-forth began with Bam dissing his "Jackass" features on a song with rappers Cult Shotta and Tanboymiguel ... which drew a video response from Steve-O.

Bam linked back up with rappers this week in Los Angeles and watched Steve-O's skate tape together ... and Bam's anything but impressed.

While Bam's a pro skater and recently hit up this year's X-Games, it sounds like there is a strong bias behind his critique.

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