Aerosmith frontman Steven Tyler has checked into a California rehab facility, E! Online reports. The singer is being treated for undisclosed substance abuse at the center where Dr. Drew's Celebrity Rehab was filmed. The dad of actress Liv Tyler had been clean for over 20 years since his wild '70s and '80s heyday, but he reportedly fell off the wagon during a rocky stretch in his relationship with gal pal Erin Bradley. (More rehab stories.)