Brake noise

[gmcbuffalo]

On my 91 XL chassis I get a loud bang if a hit them hard like in a panic stop. Only on the right side. I have had it checked by Prevost ML and by Southern Oregon Diesel and both told me no problems. But why the noise and the feeling something is breaking looose?
GregM

[Jon Wehrenberg]

Greg,

Did they check your bushings? When you are making a hard stop the steer and tag axles are trying to rotate and move rearward. The only thing that keeps them from doing that is the radius rods that position the axles. Unless bushings have been changed sometime during the life of the coach they may be allowing movement that would otherwise be snubbed.

I think the same could be true of the drive axle, but in that case the axle cradle is supported at each end with air bags.

[Joe Cannarozzi]

Greg is it on the steer axle? Do you have a 4 shock front end?

[dreamchasers]

I can equate to the loud bang noise when applying moderate breaking pressure. When I owned an American Eagle, built on a Spartan chassis, I had loud banging noise and a sharp pull to the right occur when I applied the brakes with moderate pressure. The banging was coming from the right front brake assembly. After many months of in and out of various shops, with all saying 'no problem', I took the coach to the
Spartan factory in Michigan. With a breif description of the problem, these guys went right to the problem and in quick order it was repaired.

The problem centered around the 'S' cam that extends into the brake housing and activates the brakes when twisted by the braking air chambers. The 'S' cam rides on two rollers attached to each brake shoe. When the brakes are applied, the shaft connected to the 'S' cam twists because of brake air chambers, thus twisting the 'S' cam and pushing out on the brake shoes. The brake shoes came in contact with the brake drum, thus slowing the vehicle. The issue was the rollers on the end of the brake shoes that rode on the 'S' cam were seized from non or low usage. When the brakes were applied the rollers would skip on the 'S' cam instead of rolling and applying smooth braking pressure.


To resolve the problem, Spartan removed the brake shoes, freed up the seizes rollers on the end of the brake shoes. They lubricated all with a light coating of 'never seize' and all was well. It took a half dozen attempted repairs at shops all over Fort Worth of failed repairs for me to drive to Michigan for factory repairs.

I hope someone that is familiar with the Prevost braking system jumps in to help, because the experience I am relating is with the Spartan chassis braking system.

Hope this helps.

Hector

[Joe Cannarozzi]

Good post Hector I too have been experiancing that and never tore that corner down to that point. It has been bugging the hell out of me.

It only happens when I stab the brake pedal, usually when jocking around.

I also noticed on our 40 my front air bags are much taller than those Prevo sent us for Warrens 40. I have been experiancing breaking eyelets off the shock ends. I am now thinking the front air bags will raise the front end in level-low further than the shocks will extend.

Again great post Hector

[dreamchasers]

Joe,

Thanks for the comment.

Hector

[gmcbuffalo]

Thanks guy for the input. I will check the bushing or should I say replace them because I am sure they are originals. Yes, the problem is on the steer axle and I only have one shock on each wheel. I notice that there is holes for a second. Should I be adding a second shock to each side. Hector I will check the rollers for free movement.
Thanks
Greg

[Jon Wehrenberg]

Greg,

At one time the second set of shocks were added. As I recall it was to deal with converted coaches that had excessive weight on the front end that were experiencing rebound when going over bumps. If you have not had any bottoming of the suspension when going over bumps or undulations in the road I suspect you will not need that second set.

I think Hector's opinion of the problem may be on target and the simplest and fastest way to confirm that is to lube up the rollers and the S cam and go try a hard stop. They are likely to be easily accessed just by turning the front wheels fully left or right and using a mirror to see them.

[dalej]

Greg, if you have a smooth ride while driving thru dips and crossing bridges you don't need to add the other two shocks. They are only needed if your bus has a front weight heavier then the two shocks can handle. It you can think of what a bus would ride like without shocks, you wouldn't stop moving after hitting a dip, the bus would be going up and down almost all the time.

Our bus has 4 shocks on the front and I'm going to remove two of them now after 10 years and see if I get a better ride. My front weighs in at 12,800, road ready, i.e. full of fuel and water.

[Joe Cannarozzi]

I am going to pull the brake drum remove the return springs on the shoes and back off the slack adjuster.

That way all tension on that s-cam is gone and I can grab it and see if I can shake it around.