Any idea what could cause this???? 86 k5 vibrating

[michael bustamante]

when I tore apart my front brakes and rotors I noticed the washer with all the holes in it was broken in pieces. I was tearing apart the front end to turn the rotors for vibratrion. I also noticed the pin that goes in that waser was sheared. after I replaced those two pieces and turned the rotors, the vibration was gone. It could also be real simple though, like the wheel weights came off one of the tires and now theres a vibration after 30 mph like you said. (unbalanced tire)