what is causing brake shudder on a bus?

Question

they are brake drums and when you put your foot on the brake they make a patterned clunking noise which gets slower as you slow down. ive changed the drums and lining had a set of drums skimed. ive torn down everything cleaned it made sure everything was working properly but the noise is still there its only my second day at the job and the other mehanic left me with it and its been troubling him for 3 weeks any help would be good

ive checked the bearing and theyre fine along with the housing thre is no axel misalignment because it just had a lazer alignment 5 days ago the bus is a UD nissan im not sure what year but ive isolated the problem to the right hand front the only thing i can think of is the drums are dodgey because the previous set had a violent wheel wobble at 70 kph so i had them skimed but that made no difference when i put the new drums on with the pads thenoise started

Answer 1

Did you check that the wheel bearings aren't cracked giving you a rhythmic chatter .
Did you check that the half shaft isn't bent or broken and the noise is transferring along the inside of the axle.
Did you check that the problem isn't on the other side and noise transference is making you look in the wrong place.
Can you put the bus on a rolling road and spin one wheel at a time , this will tell you if the noise is there before the brake is applied and also if you move one wheel at a time it will tell you what side.Maybe a mobile wheel balancer can be used for this if a rolling road isn't available
Hope this helps , I love a good outcome. Especially on day 2 . Good luck

Answer 2

What kind of bus are you talking about? Did you check the drive line? Sometimes the drive line will make noises that sound like there is a problem in the brakes.Check the brake shoe clearance. I usually adjust the shoes while spinning the wheel until you can't spin it anymore and then back it off just enough to free up the wheel. If can can tell me exactly what kind of bus your working on I might be able to help you a little better.

Answer 3

Have You check
the wheels rollers(bearing) and racers( bearing's seats)
be sure,the end play of the spindle nut-bearing is right.
check. king pin( that also, make that sound)

in case of air brakes ,
also ,You have to check the "s" cam shaft's bushings, if they have play they will produce that sound too.
slack adjuster pivot for damage and play.
brake chamber: return spring (internaly broken.)

go under the vehicle meanwhile someone push and relief the brake pedal in the fast way