Red Hot Chili Peppers, O2 Arena, London

California screamers' blasts from the past help set the stage on fire

Mr spice guy: Red Hot Chili Peppers frontman Anthony Kiedis (AP)

Maybe Anthony Kiedis was destined to sing in a classic rock band when as a boy he started hanging out with his dad in LA's Rainbow Bar, watching the imperial 1970s excesses of The Who and Led Zeppelin at close quarters. Red Hot Chili Peppers are the last group to carry that baton, developing their own funk and rap-nuanced version of rock, and delivering it with commitment to mass stadium audiences for the majority of a near-30-year career.

Their 10th album I'm With You, though, grapples with the least comfortable, inevitable part of that tradition: the record too far. It feels played out, unnecessary to any new convert. After the retirement of peers REM, the Chili Peppers' future too sounds at risk. Though a mix of standing and seating tickets makes it hard to be sure, this first night at the O2 before giant gigs next summer doesn't seem full. Still, this is a band who will always fight on.

Kiedis and his childhood friend, bassist Flea, are topless as always, and as muscular as the band's playing. Recent single "The Adventures of Rain Dance Maggie" is the only new track to make much impact. This portrait of the sort of LA wild girl Kiedis knows well has an attractive 1970s Faces sway, during which he goes on a head-banging dance between Flea and new guitarist John Klinghoffer. After Klinghoffer's weird, whipping feedback on "Throw Away Your Television", Flea gives a cartoon madman's yelp, as if he too means to get himself up for this. The volume is huge, pumped up for bigger jobs. "Under the Bridge", Kiedis's wonderful song of drug-haunted LA loneliness, is greeted by the crowd with shouts of exultation, and a sea of mobile phones in the dark. But even this has its subtlety trampled.

The Chili Peppers re-earn their right to carry on with "By the Way". The chorus of this song about rock show rites rises from its thrashing verses to meet the crowd in mutual confirmation. In such moments, and the weary certainty in Kiedis's voice during "Don't Forget Me" too, this is still a great band. But the glories they draw on may stay in the past.