Class A with Tag axle

[Crasher]

Originally Posted by luvlabs

Gary,

Hate to disagree but tag axle tire pressures have minimal impact on TPs at other positions. Too high front axle weights and too low drive weights are caused by improper pressures in the air bag suspension for the tag axle.

Tire pressures for the tag axles should be the same has the drive axle tire pressures per the tire experts.

Agreed. Tire pressures have nothing to do with the weight on an axle. The weight balance or shift is determined by the pressure in the tag suspension bags which is determined by the proportioning valves.

[AE Wanderer]

We had our 2008 American Eagle 42F weighed at Escapees in Texas. They weigh each wheel position individually, and give a total rig weight. Our coach weighed 39,600# total. This is with fuel and fresh water tanks full. Based on the individual wheel weights, I run 120psi in front, 80psi in rear duals, and 85psi in tags. This has worked good for me over the last 3 years.

[Ivylog]

AE W^^^^, at only 40K lbs, how much over the actual table psi are you running or is the rig badly out of balance?

[benbom]

So if the axle corner weights for the rear drive axle suggest that a tire pressure of 90 psi is recommended, then the Tag pressure should be 90 psi, right? The 90 psi calculation from the table is based upon 2 drive tires not the 3 that are on the same side, right?

[AE Wanderer]

Originally Posted by Ivylog

AE W^^^^, at only 40K lbs, how much over the actual table psi are you running or is the rig badly out of balance?

The front is at its max weight. Nothing up there can be shifted back (driving equipment, generator, fuel tank). So yes, front to rear bad balance.

[RandDescape]

Originally Posted by benbom

So if the axle corner weights for the rear drive axle suggest that a tire pressure of 90 psi is recommended, then the Tag pressure should be 90 psi, right? The 90 psi calculation from the table is based upon 2 drive tires not the 3 that are on the same side, right?

Correct base the PSI for the weight carried on that axle using the chart for single / double based on on the number of wheels on one end of that axle.

So typically that means steer and tag are single and drive is double.

- Richard

[Crasher]

Originally Posted by benbom

So if the axle corner weights for the rear drive axle suggest that a tire pressure of 90 psi is recommended, then the Tag pressure should be 90 psi, right? The 90 psi calculation from the table is based upon 2 drive tires not the 3 that are on the same side, right?

I disagree. To determine the optimum pressure for the drive or the tag requires separate position weights. If the drive axle calls for 90 psi, the tag pressure should be whatever the load inflation table recommends for the weight it is carrying. My steer axle is at 120 psi, the drive is 85 and the tag is 75. All values are based on the weight each is supporting plus 5%. Been that way for 7 years and 65,000 miles.

Edit: FWIW, the placard on the coach calls for 110 psi for all positions. That would have me under inflated on the steer and way overinflated on the drive and tag.

[JohnBoyToo]

that's the way I read it crasher...

[NCC-1701A]

Based on DS Don's information on Newmar providing the "as manufactured" weights, I had them send my coach's information. It was interesting comparing it to my current axle weights (I don't have individual tire weights). The percentage on the front is basically the same. A tad higher percentage on the drives and a little less on the tag, but it's a couple percentage points. While I don't have actual side-to-side weights, the Newmar information showed a 50/50 weight ratio.

The most interesting thing I saw on the Newmar weights was that the side to side on my drives was 700# more on the driver side, and the side-to-side on my tag was 700# more on the passenger side. If there was going to be a weight imbalance side-to-side on the tag, I guess I would have bet on the driver's side with the big heavy radiator full of fluid over there, not the passenger side. Also, the 700# imbalance on the tag would exceed the 5% margin adder one might use if they don't have individual wheel weights...except that the load is still well within the 85# minimum pressure my Goodyear table shows. So not to worry, but it does highlight that having real individual wheel weights is definitely a positive.

[Ivylog]

My 04 Dynasty had a similar 700 lb ^^^^ side to side imbalance, drive to tag, which made no sense. Since the drive has 2 ride height valves I increased the height on low side by less than 1/4” which balanced them out almost perfectly. It did change the front too which actually helped it.

[Crasher]

The ride height adjustments are critical for keeping uniform weight distribution. Freightliner uses two in the rear and one in the front, whereas my Power Glide chassis has 4 valves, one at each corner. I was told that if the front side to side was less than 500# difference and the rear was less than 1,000#, it was acceptable. I've adjusted to be much closer than that. Since I converted the proportioning valves to manual regulator valves, I can adjust each tag side to be even. As it is, I carry 3 psi more on the passenger side.

[NCC-1701A]

Originally Posted by Crasher

The ride height adjustments are critical for keeping uniform weight distribution. Freightliner uses two in the rear and one in the front,

It may vary on Freightliner by year or model, etc. I say that because mine has two up front (just replaced them both), but only one in the rear. I have a copy of the book Freightliner gives in their class one pays for down in Gaffney (prior owner took the class and left the book) and that shows two in front, two in the rear. My SIL and I followed all the lines in the back and they only went to the one ride height valve.