Link unit of brake assembly for bicycles

A brake system for bicycles, comprising:

• an arm unit including a first arm 11 and a second arm 12, said first arm 11 includes a first pivot point 15 located between a first extension end 111 and a link pivot end 112, said second arm 12 includes a connector portion 123 located between a second extension end 121 and a pivot end 122, the first and second arms pivotably connected to each other at said pivot end 122 of said second arm 12, two brake pads respectively connected to the first and second arms and located on two sides of a wheel rim, wherein said first arm includes a link pivot end;
• a cable unit connected to the second arm at connection portion 123 of said second arm 12 and including a brake cable, and
• a link unit connected between the first and second arms and located at one of the two sides of the wheel rim, the link unit including a first link which has a first end pivotably connected to the second arm and a second end of the first link connected with the brake cable, a second link having a first end thereof pivotally connected to the link pivot end of said first arm and a second end of the second link pivotably connected to a mediate portion of the first link.