It's amazing, when you think about it. The same five guys who played on Aerosmith's 1973 debut album—and the ensuing four discs that made them the best American rock act of the '70s—are still performing in the band today. Singer Steven Tyler, guitarists Joe Perry and Brad Whitford, bassist Tom Hamilton, and drummer Joey Kramer are raging against the sands of time and touring under the sassy tag line “Cocked, Locked, Ready to Rock!”

There have been cracks in the classic lineup within the last year, though, some threatening to break it up for good. After Tyler injured himself falling off a stage in South Dakota in August of 2009—causing a tour cancellation and leading to a multi-million-dollar lawsuit—he talked of taking considerable time off to pursue a solo career. A pissed-off Perry countered that Aerosmith wouldn't sit around and wait for his return, and was seeking a replacement. Then rumours started flying that Tyler was signing on as a judge for TV's American Idol and that he hadn't even informed his bandmates of his plans. As a resigned-sounding Perry explains from the Aerosmith tour bus en route to his Boston home after a show in Cincinnati, his long-time cohort is full of surprises.

“One thing you know about Steven is you never know what he's gonna do next,” says the gangly guitar hero, who turns 60 on September 10. “And it could very well leave you high and dry with a handful of gigs to do and him not being there. I know he's not gonna change, so that's how it is.”

A prime example of the ongoing power struggle between the former Toxic Twins occurred last month during a show at Toronto's Air Canada Centre, when Perry gave Tyler a reciprocative nudge that sent him tumbling off the stage yet again.

“He apparently got this idea in his head that if band members bump into each other without the other guy knowing it, it looks cool,” he explains. “So I was standin' on the edge of the stage looking down at a pile of monitors and teleprompters—just a lotta hardware—and he came up behind me and rammed into me. I was tryin' to play a solo, and it was all I could do to keep my balance. Then he went over to the side of the stage, and as I was walking back I brushed him. He could have kept his balance or he could have jumped into the arms of 20 sweaty girls who were standin' right there, so he just kinda fell over into their arms.”

While the brotherly animosity between Tyler and Perry makes for plenty of headlines and YouTube hits, there's always the chance that a little on-stage tension might actually inspire the performances. But Perry's not so sure.

“I don't like to live like that,” he asserts. “I like to go out and concentrate on playin', and put everything that I've learnt working with this band to good use. I certainly don't need anger or frustration to get me charged; what I need is an audience that's excited about seein' the band play.”

Aerosmith plays Rogers Arena on Thursday (September 16).