PDA

View Full Version : Tag Brakes



gmcbuffalo
05-02-2013, 01:17 AM
Anyone have a clue why my tag brakes don't work? Hear air but no movement of the canister rod. Last work on the brakes was when Prevost replaced the brake air lines from a old recall. I replaced all the Norgren valves and air bags last year.

Joe Camper
05-02-2013, 07:58 AM
Well initally U SHOULD hear air movement but after the brake has been applied and held for a few seconds that air movement noise should STOP.

If not seek out the source. IF the tag axle air bags are not aired up the brakes for them will be diabled so be sure to start the bus air it up and make sure the tags not in the up position and nothing would make me happier that to find out U were incorrectly checking them with the tag up.

When we step on the brakes the air coming from the pedal is not what is actually being fed into the brake diaphrams at the hubs. The signal from the pedal goes to a relay valve if older stuff its r(relay)12 if newerantilock U have r-14s.

These relay valves are put as close to the brake tank and corrisponding axle as possible. When the brake pedal signal air is sent the relays open a path (a short path) directly from the air tank for that axle and very close to that axle and to the hub. If those pnewmatic relays were not there we would get difering delays in the opperation of the brakes on the axles farther away. Braking would be late or slow or delayed.

Greg see if your pnewmatic schematic shows if U have additional r-12s disabling tag brakes withtag up or if U have an inversion valve doing it.

U gotta have service air back there if the drive axle service brakes are working. We should be able to get U straight without too much trouble

gmcbuffalo
05-02-2013, 09:08 PM
Got them working the key was the Key has to be on to have the norgren working.

Joe Camper
05-02-2013, 10:20 PM
How far out of adjustment were they?

gmcbuffalo
05-03-2013, 01:15 AM
The fronts were out about 2" and the tags and drive OK ~1/2"

Joe Camper
05-03-2013, 07:52 AM
Well thats good news Greg that tells me someone has been adjusting those brakes without U aking for it.

Good news U have auto adjusters on the drive axle as well. Just dont ignore the drive because of that . When U are in doing periodic manual adjustment on the steer and tag be sure to at least check slack on the drives to be sure eveything continues to work correctly even tho they are adjusting themselves there.