When pop-punk outfit Unwritten Law jump on the Vans Warped Tour in Pontiac, Mich., on Sunday, look for them to unveil some new material at the daylong music-and-sports festival.

The group recently finished recording its fourth album, due early next year. Guitarist Rob Brewer said this time around the band didn't stick to the three-chord punk tunes they've built their career on.

"It's definitely a little different," Brewer said from home while taking a break from mixing the album. "I can't really explain how; it's just more of a rock record and there's more material. We're stoked on it."

The album will have more complex instrumentation and a more mature vibe than the group's past work, said Brewer, who insisted that the commercial success of their single "Cailin" (RealAudio excerpt), an uncharacteristically poppy ditty off their self-titled 1998 album, didn't have anything to do with the new sound.

"We do what we want. We didn't go into the recording studio thinking we need to write another 'Cailin,' " he said. "We believe we have songs that are radio-friendly — we just play what we like and hope everyone else likes it, too."

Singer John Pebsworth of ska-punk group Buck-O-Nine, who have played a number of shows with Unwritten Law, has heard parts of the record and said there was a noticeable change in the new material.

"It seemed more harder-edged, more aggressive. I really like what I've heard so far," Pebsworth said. "I've seen Unwritten Law over the years when they started off as more of a Southern California pop-punk band, but I think, especially with the new stuff, they're establishing more of their own sound."

Contributing to the group's harder sound was producer John Shanks, who has played guitar for Melissa Etheridge and Beth Hart and who has produced songs for boy band BBMak.

"We talked with a bunch of other guys who had done much bigger albums," Brewer said. "But they didn't really take the time to listen to the demos and had no solid input on what they liked or didn't like. John was totally different; he really listened to the songs and had some solid ideas."

Brewer said Unwritten Law plan to showcase one or two new songs during their half-hour Warped Tour sets. They also plan to play a number of more intimate, longer shows before the record is released.

"Being on Warped will let us cover some new area and reach new audiences — like, we've never been to Tennessee," Brewer said. "And I think it's important for us to tour as much as possible, get out there and stay in the loop."

Staying fresh on the minds of young punk rockers hasn't been easy for the quintet, which also features singer Scott Russo, drummer Wade Youman, guitarist Steve Morris and bassist Pat Kim.

Unwritten Law hail from Poway, an upper-middle-class San Diego suburb that's best known for being the home turf of close friends Blink-182 (in Blink-182's single "Josie," when Mark Hoppus sings "My girlfriend likes UL," he's referring to Unwritten Law). And though Unwritten Law's most recent album was released a year before Blink-182's Enema of the State, Unwritten Law have yet to land a video on MTV. (Sonicnet.com's parent company, Viacom, also owns MTV.)

"I think we come from a more musical point of view and Blink are more showmen," Brewer said. "I don't want to compare them to *NSync, but it's almost the same thing — if you're a good entertainer you're successful. Blink have an extra advantage because they're also good musicians and can play things beyond that three-chord pop element."

But for now, Brewer isn't dreaming about climbing the pop charts. He just wants to go out and play his band's new material.

"We may be limited as far as commercial success," he said. "But playing live is what it really boils down to. To me, that's what makes it worthwhile."