This Friday is the first Critical Mass bike ride since August's road rage altercation, but this month's riders have even more to deal with than increasingly negative public perception of their event: Legions upon legions of aging hard rock fans headed to a concert at AT&T Park.

You know how Critical Mass works, of course! On the last Friday of every month, cyclists meet at Justin Herman Plaza at 6 p.m., then take off on an ever-changing, undisclosed course across city streets. Traffic is typically slowed or stopped as the riders pass through, and on rare occasions, the shit can totally hit the fan.

The ride can sometimes get rough on months when it passes through the masses of fans headed into AT&T Park for an SF Giants game, but this week's mix has the potential to be far more incendiary, as the ride will be kicking off at the same moment that AT&T Park's gates will open to 50,000 (according to the San Francisco Municipal Transportation Agency) fans of Australian rock legends AC/DC, whose Rock or Bust tour hits San Francisco that night.

The SFMTA isn't taking the crowds expected for the show lightly, saying that "motorists are advised to avoid the increased congestion in downtown San Francisco and to avoid using the Bay Bridge in the two hours before and after the event." So it seems that the area is expected to be hell, even though AC/DC claims that's not a bad place to be.

Fans of the 42-year-old band will be served by extra Muni trains "departing AT&T Park just like after a Giants game," the MTA says, which is fine if we assume that the band's fans live in San Francisco. (I dunno, you tell me?)

Our advice: avoid the area at all costs, because between bikes and the folks who still love AC/DC enough to go to one of their shows, it's going to be a tough time in SoMa that night.

Then again, as mentioned earlier, Critical Mass' route is kept under wraps, so we don't even know if they'll be heading past AT&T Park that night! And given that their most notorious rider appears to prefer the sweet sounds of Billy Joel, perhaps our worries are all for naught.