Tag axle brakes

[Jeff Horton]

I have the tag axle tires off of my 1991 Newell Coach and it is up on jack stands. Both tag axles drums turn free even thought the brake is set. Is this correct? I will have someone apply brakes tomorrow to see if they stop turning. If it is not correct that they turn I assume the brakes need to be adjusted.

[fulltiming]

Jeff, there is no spring brake on the tag axle so the wheels will turn freely unless the service brake is applied. Since you have the wheels off, I would recommend setting the slack adjusters. As I recall, there should be about 5/8" free travel.

[Richard and Rhonda]

Jeff,

Only the rear drive brakes are locked with the E brake on. The way it works is this. On all axles there is an air diaphragm that pushes on the actuation rod for the brakes. You can see a large round canister at each brake that contains the diaphragm.

On the drive axle, you will notice TWO cannisters stacked in tandem. The second cannister contains a diaphragm and a very strong spring. The diaphragm works backwards in this cannister. When you set the E brake or you lose air pressure the spring applies the brake or if you lose air pressure the spring applies the brake. When you deactivate the E brake, you send air pressure to the second cannister that actually compresses the spring to release the brake.

Michael may be right on the stroke adjustment for the tags. If you want to fiddle with it, you can set it a little closer if you have the axles off the ground by setting it to drag, and then backing off about a turn. A word of caution on adjusting the tag brakes too tight though. If you set them too tight they will lock up. Those axles have the least weight on them of all the tires.

A bit of counter intuitive trivia is that on a coach the primary brakes are the drive axle not the front like an automobile.

[Jeff Horton]

Thanks guys, I did not know there was not a spring brake on the tag axle. I finished up in the dark and did not take time to look under the coach. Sometimes it's easier to ask the question. I had the brakes looked at and adjusted last summer by a local shop and we really haven't done that many miles since. I will look at the slack adjusters but hopefully I got what I paid for and they are good.

Thanks again