Tag Axles

[BOOKWORM]

Been looking at used Gas Class A's lately.
I want bigger/older 1997>2000.

Lots of the coaches that have tag axles have tires that are almost bald or at least in worse shape than the main axle with the four tires on it.

TELL ME ALL ABOUT TAG AXLES, Please.

Are they added by the House Builder, not the Chassis Builder?

I looked at a 1997 National Tropical 35'. The tag axle had airbag "springs" and a note near the dash said "not under 20 pounds, not over 100 pounds".
That's an awful large variance, so how do you set them?
How do you figure to divide the weight on the tag axle compared to the weight on the rear main axle?

Other coaches just looked like they had regular shock absorbers and springs on them.
What's the difference???

[BOOKWORM]

Been looking at used Gas Class A's lately.
I want bigger/older 1997>2000.

Lots of the coaches that have tag axles have tires that are almost bald or at least in worse shape than the main axle with the four tires on it.

TELL ME ALL ABOUT TAG AXLES, Please.

Are they added by the House Builder, not the Chassis Builder?

I looked at a 1997 National Tropical 35'. The tag axle had airbag "springs" and a note near the dash said "not under 20 pounds, not over 100 pounds".
That's an awful large variance, so how do you set them?
How do you figure to divide the weight on the tag axle compared to the weight on the rear main axle?

Other coaches just looked like they had regular shock absorbers and springs on them.
What's the difference???

[Argosy]

The tag axle and frame extension are added by the house builder. They give a better ride, better handling, more load capacity.

Tag tires do wear faster. They scuff on every corner, the distance the tag axle rear axle isn't very long. But, given rv tires generally are replaced because of age rather than wear it isn't something that I am super concerned about.

Can't help with the air bags, mine has coil springs. I can see where it would be a benefit for different loads, especially way past the tag.

[LVJ58]

BOOKWORM, Argosy provided a good answer to your question. Regarding the air bag tag suspension, do the bags have separate valves to fill them, or is there an on board air compressor that keeps them inflated?

If separate valves, I would start by inflating them to between 40 & 60psi.

We have Henschen tag axles on our coach with horizontal torison bar springs encased in rubber within a tubular frame and they work great. They do not use shock absorbers and so far the tag tires haven't shown any excessive wear from scrubbing.

Jim

[Les Stallings]

One way to set the tag pressure is to measure tire temperatures. I have an inexpensive Radio Shack IR temperature gauge. When I stop for fuel, I immediately walk around the coach and shoot the tire temperatures. A tire with low air pressure will be running higher temperatures than properly inflated tires, due to sidewall flex. On the tag axle, assuming properly inflated tires, the temperatures will be lower than the adjacent drive axle tires if the tag is not carrying equal weight. Conversely, the tag tires will be a little hotter if they are carrying too much of the weight.

On our Dynasty, there is a pressure regulator and gauge for the tag axle that is fairly easily adjusted. I can also lift the tag via a switch when taking 90? turns, to reduce scuffing.

Note: tires in the sun will also run higher temperatures than those on the shady side. Tire temperatures can tell you a lot about the health of your tires and can save you from a blowout if monitored regularly.

[Gary RVRoamer]

Not all tags are added by the body builder, but they were on the National you are asking about and on all gas chassis that I know of. On larger diesel chassis the tag often comes with the chassis. They may also be equipped with a mechanism that can raise the tag for sharper turns and a few other cases where a tag can be a problem rather than a help.

[Mac and Chris]

We have a tag on an old gasser. Since it carries only about 3500 lbs our worst tires always go on the tag.

Most gassers have a wheelbase that's shorter than I'd prefer. The tag cheats this a little and allows the RV to be 35-40 feet.

I dislike our tag for these reasons:
1. Another 2 tires to buy & maintain
2. Another set of brakes to maintain

Of course, #2 goes both ways, probably get better braking

Mac