Pressure on tag axle - Printable Version

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+--- Thread: Pressure on tag axle (/showthread.php?tid=257)

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RE: Pressure on tag axle - Fulltiming - 10-15-2012

Steve, now I am confused about Newell advising using the tag switch to shift weight to the drive axle "for scaling purposes". My 1992 only has a tag axle dump which the manual said was to improve traction. In later models (1994-about 1997), Newell installed a two way switch to either dump pressure for an increase in traction or increase tag pressure on the tag since it was the drive axle that was overweight and the idea was to transfer the weight off the drive axle to get through tollway scales.

Confused!!

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RE: Pressure on tag axle - RussWhite - 10-15-2012

Okay - for those interested in what Newell has to say - here it is and I quote from the owner's manual.

"Tag Axle Control Switch - When attempting to start the coach moving in poor traction conditions such as snow, ice, or mud, the drive axle tractions can be significantly improved by releasing air pressure in the tag axle suspension, thereby decreasing the weight carried by the tag axle. To use this feature, first, ensure that the coach suspension has achieved normal road height by idling the engine with the leveling system in travel mode. Then, release the air pressure in the tag axle by pushing on the top of the switch marked TAG located on the coach instrument panel. The coach should not be driven more than a short distance in this mode.

If it is necessary to decrease the weight carried by the drive axle to comply with axle weight limits, the TAG axle switch is pushed on the bottom, increasing tag axle suspension air pressure. This transfers weight from the drive axle to the tag axle. It is not recommended to operate the coach is this mode except on a temporary basis."

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RE: Pressure on tag axle - Fulltiming - 10-15-2012

Thank Russ, that was my understanding.

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RE: Pressure on tag axle - Richard - 10-15-2012

Ok, if I could point to the schematic this would be easier.

First, let's talk about the leveling valves. The travel solenoids isolate the HCV. Air supply pressure to the HCV does not come from the six pack. Air is supplied directly to the HCV and the HCV also exhausts directly. The six pack is BETWEEN the HCV and the air bags. You have to get that straight first.

Ok, on the single six pack setup, the tag bags see the same pressure as the drive bags as you can see from the schematic.

The solenoid valves for the tags are TWO way. Look at the schematic. When neither soleniod is activated the the air pressure goes straight through to the tags. When you flip the switch up to decrease pressure on the tag, the second solenoid valve in line changes position which isolates the tag pressure from the drive pressure, and the second solenoid in line changes position and exhausts pressure from the tag bag.

When the switch is pressed downward the first solenoid changes position and isolates the tag from the drive pressure, but it connects the tag pressure to line pressure. That way tag pressure is increased.


The three keys to understanding the schematic are:the HCV is between the six pack and the air bags, only two lines out of the six pack connect to the air bags (one for each side) and the other two lines connect to the HCV, and the solenoid valves for the tag are TWO way, not open and closed.

Clear as mud, right?

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RE: Pressure on tag axle - Gordon - 10-15-2012

Thanks Steve & Richard,
I forgot there was a 3 position switch on the single 6pack rear w/tag.
That explains the line pressure question I had.

Makes total sense now

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RE: Pressure on tag axle - folivier - 10-15-2012

Glad I don't have a tag....my head hurts following this discussion.

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