There are many different kinds of rumbles, ranging from skin, to chain, to knife. Skin fights were the mildest rumbles, in which the only weapon allowed was one's skin, so punches, kicks, bites etc. are allowed. Tim Shepard and his gang are used to fighting with guns or pool sticks.
After Johnny had killed Bob, socs and greasers agreed to a rumble without weapons. The Gang was supported by Shepard's Gang, and Darrel's old friend Paul was fighting on the side of the socs. The rumble was won by the greasers.