It is a mass of people that causes massive problems and San Francisco Police Chief George Gascon is questioning its existence.
"We definitely are looking at the process, evaluating it, looking at where we can improve," said Police spokesperson Lyn Tomioka.
The idea that this could be one of the last Critical Masses in San Francisco, delights some of the officers who have to protect it.
"I think that if we have our chief behind it and he wants to do it, I'm sure there's going to be an end in sight," said Sgt. Neil Swendsen.
But the bikers, who take over the city streets on the last Friday of the month, do not think the chief stands a chance against this movement.
"Good luck, hee, hee, hee. I don't see it happening," said "Roller Girl" from San Francisco.
Critical Mass also got attention in New York City. A judge there ruled that the bikers do need a parade permit and requiring one is not a violation of their freedom of speech.
"I think it's a poor decision. I'm obviously against it, but I don't think that means there's going to be bad things that will happen for Critical Mass. It will find a way to exist," said biker Elijah Post.
The San Francisco police chief says he is taking a critical look at this protest because residents complain bitterly about it.
"I think that's a bunch of people breaking the law in the city and they should be prosecuted for it. They're making people's life miserable," said driver Vad Shamis.
"Yes, if you're driving, I can see that it wouldn't be that fun, but maybe you can jump out of your car and jump on a bike," said San Francisco resident Marci Bravo.
The bicyclists block traffic and run red lights to raise awareness about the benefits of biking. Critical Mass started in San Francisco in 1992.
"The message is out. We're trying to be greener. The message is out. What we don't need to continue is to punish the public with tying up traffic. It's the wrong thing to do," said Swendsen.
"I think it's here to stay and it's something that makes San Francisco really special," said "Roller Girl."
It also makes for a special kind of problem for the San Francisco police chief.