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Old 09-02-2014, 02:43 PM   #1
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Why tag axle

I don't understand the reason for a tag axl. Can someone tell me?
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Old 09-02-2014, 02:48 PM   #2
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Why tag axle

Simplest answer is the tag axle allows much more weight to be carried on the chassis.


Additional Carrying Capacity

A motor home with a tag axle will provide greater carrying capacity than a single-axle, generally resulting in a 10,000 to 20,000 pound increase. A tag-axle motor home will have a greater cargo carrying capacity than a single-axle motor home of similar size and power. Additionally, the addition of a tag axle allows for the construction of larger motor homes than single-axle designs, providing more space for the occupants.

Increased Rear Chassis Support

The tag axle provides greater support for the rear chassis, adding an extra set of shock absorbers and spreading the load across a larger section of the chassis. In addition, the tag axle is generally located farther to the rear of the chassis than a single axle, decreasing the leverage of the chassis extending past the rear axle. This reduces the likelihood of the rear chassis coming into contact with the ground when navigating steep inclines or uneven terrain.

Reduced U-Joint Wear

The addition of a tag axle pushes the drive axle further forward on the chassis. The engine of most motor homes is located behind and above the rear axle. The greater distance between the motor and the drive axle results in a shallower angle for the drive shaft, allowing it to create a more nearly level connection between the drive shaft and the drive axle. This reduces the strain on the U-joint, thereby reducing wear.

Additional Braking Power

While the tag axle is not connected to the motor, modern tag axles are often equipped with brakes. An additional braking axle greatly increases the traction and stopping distance for a motor home of equivalent weight. The ability to make sudden decelerations and stop more quickly is both a convenience to the driver and an important safety consideration.



Read more : http://www.ehow.com/info_8583486_adv...otor-home.html
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Old 09-02-2014, 03:03 PM   #3
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For the weight and for the brakes. We're over 42,000 pounds for our biennial run to Alaska.
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Old 09-02-2014, 03:05 PM   #4
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That about covers it. Also they just look
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Old 09-02-2014, 03:49 PM   #5
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It's been a few years since I retired from the truck equipment industry and my answer may be outdated. You have to look at "bridge laws" and the amount of weight allowed for the vehicle. It used to be you were allowed a weight of 450lbs per inch of tire tread width, I don't know if that is still the case, but adding another axle be it a single wheel or dual wheel tag increases the GVW and GVWR. Again taxing my memory, a 6 wheel truck normally would have a maximum GVW rating of 28,500#. Tag axles on a MH probably cannot be lifted so it won't change your turning radius.

Bridge laws vary from state to state. The bridge laws can get a little complicated. You may see trucks with extra wide tires, in particular on the front axle. Back to my memory, 11,000# or12,000# was the normal max front axle capacity depending on the number of wheel lugs and by adding "super single" tires you could go as high as 18,000# most common on concrete trucks.

In a nutshell the tag axle is to increase the increase the GVWR and meet state GVW laws.
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Old 09-02-2014, 03:55 PM   #6
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Quote:
Originally Posted by KT4Wextra View Post
Tag axles on a MH probably cannot be lifted so it won't change your turning radius.
I believe that most tag axles on MHs can be lifted. At least I have never seen one that you couldn't lift the tag axle!

The tax axle provides greater stability to the MH as you have more tire tread on the ground. I really like our tag and do not plan on having an MH without one!
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Old 09-02-2014, 04:50 PM   #7
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I'll add that most tags have a bit shorter turning radius than non tags. The drive axle is set forward a bit more, and with the tag lifted, you have a shorter turning radius. (My 40' IFS Country Coach with Tag, can turn in a tighter radius then our T28 Bounder on the non IFS F53 Chassis.) But yes, you do need to account for the rear end swing in these tighter turning situations.

A few cons include: Loss of a full storage bay to accommodate the tag. Two more shocks and tires and air bags to buy/maintain. More weight to the coach.

To me, the Pro's nudged me to the tag. The added stability and a CCC of GT 11,000 pounds made it a slam dunk. And to quote Executive, more often found on RV.Net, "They just look sexy!"

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Old 09-02-2014, 05:49 PM   #8
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To clarify a couple of misleading points. You do not gain as much extra carrying capacity as you would think. My coach has a 15,600# front axle, a 22,000# drive axle and a 13,000# tag. That comes out to a 50,600# GVW. Looks nice on paper, but there is no way you can carry that much weight. The manufacturers want as much basement area as they can get, so the drive axle is back further than necessary to make full use of the axle capacities. I carry 14,700 on the front, 19,000 on the drive and about 5800# on the tag. If I increase the tag air bag psi, the weight will shift to the tag and front axle from the drive. In order to utilize all of the axle capacities, the drive and tag axles would have to be several inches forward from their current location. That would reduce the basement area, (which no one wants) but would allow more weight to be evenly distributed. However, you would have to carry gold bars underneath to get that much weight into the motorhome. A tag does allow more practical payload, but only 3-5000# at most. The biggest advantage is a much smoother ride and better control in windy conditions plus the ability to go longer without overloading the drive axle. The other big advantage for me is the ability to pull a 12,000# trailer and not overload the drive axle. I can carry the 1500# tongue weight mostly on the tag axle by increasing the air pressure in the air bags. I could not pull this trailer without a tag. The steer stays under 15,000# and the drive bumps up to 20,000# and the tag is between 6500 and 6800#.

Sorry to be so long winded, but some of the responses were not entirely accurate.

edit: 95% of all tag coaches do not lift the tags. You can "dump the tag" which drops the bag pressure from a normal 40-65 psi down to approx 20 psi. In my case, there is still 3000# on the tag. Any less than that and the tag wheels will slide on the pavement when braking below 10 mph where the ABS does not work. This helps prevent digging up the ground when backing or turning sharp. A dumped tag will not drag as much. Some of the high end coaches ($1,000,000 to $2000,0000) can raise the tag and they will also steer when turning.
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Old 09-02-2014, 06:10 PM   #9
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Monaco used a lifting tag axle on some of their 2008-2009 units, they don't steer however. Or at least that's what the owners manuals state. We've never owned one but have been looking at them closely right now.
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Old 09-02-2014, 07:42 PM   #10
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Most of what I know about tag axles relates to semi tractors and trailers. In my other life I sold piezo sensors that were imbedded in a road surface that could measure the weight of a vehicle within 5% of actual weight and it could be traveling 70mph. In many cases it was used to preweight a truck coming into a weight station so they could give it a green light if it wasn't close to the max weight, in particular box trailer as they couldn't tell if it was loaded or empty. It was also used for vehicle classification (number of axles). If you can lift the tag it would be nice but as Crasher said the best you can do is dump the air on the air bags but still slide the tires on a tight turn. Steerable tag and pusher axles are becoming more common for big trucks. By the way it is against the law in Georgia and a few other states to have the air bag pressure control inside the vehicle, it must be mounted on the outside. The biggest reason is for semi's. An experienced driver of a semi could manipulate the pressure on the air bags when going over a weight treadle to make it appear lighter to the weight police so putting it on the outside stops that. No need for that on a MH since it would be doubtful that they would approach the 80,000 limit. (well maybe a country western band coach like the ones Conway and MMMMMel had)
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Old 09-02-2014, 07:44 PM   #11
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Quote:
Originally Posted by Mr_D View Post
Monaco used a lifting tag axle on some of their 2008-2009 units, they don't steer however. Or at least that's what the owners manuals state. We've never owned one but have been looking at them closely right now.
I have seen a Monaco Dynasty maneuvering through a campground with the tag raised. I believe you are correct about some Monaco tag units being able to lift the tag axle.
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Old 09-02-2014, 08:36 PM   #12
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Quote:
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To clarify a couple of misleading points. You do not gain as much extra carrying capacity as you would think. My coach has a 15,600# front axle, a 22,000# drive axle and a 13,000# tag. That comes out to a 50,600# GVW. Looks nice on paper, but there is no way you can carry that much weight. The manufacturers want as much basement area as they can get, so the drive axle is back further than necessary to make full use of the axle capacities. I carry 14,700 on the front, 19,000 on the drive and about 5800# on the tag. If I increase the tag air bag psi, the weight will shift to the tag and front axle from the drive. In order to utilize all of the axle capacities, the drive and tag axles would have to be several inches forward from their current location. That would reduce the basement area, (which no one wants) but would allow more weight to be evenly distributed. However, you would have to carry gold bars underneath to get that much weight into the motorhome. A tag does allow more practical payload, but only 3-5000# at most. The biggest advantage is a much smoother ride and better control in windy conditions plus the ability to go longer without overloading the drive axle. The other big advantage for me is the ability to pull a 12,000# trailer and not overload the drive axle. I can carry the 1500# tongue weight mostly on the tag axle by increasing the air pressure in the air bags. I could not pull this trailer without a tag. The steer stays under 15,000# and the drive bumps up to 20,000# and the tag is between 6500 and 6800#.

Sorry to be so long winded, but some of the responses were not entirely accurate.

edit: 95% of all tag coaches do not lift the tags. You can "dump the tag" which drops the bag pressure from a normal 40-65 psi down to approx 20 psi. In my case, there is still 3000# on the tag. Any less than that and the tag wheels will slide on the pavement when braking below 10 mph where the ABS does not work. This helps prevent digging up the ground when backing or turning sharp. A dumped tag will not drag as much. Some of the high end coaches ($1,000,000 to $2000,0000) can raise the tag and they will also steer when turning.

mine lifts as a result of the spring loaded arms which is common and included on all Monaco tag coachs, Monaco likely accounts for more that 5% of the tag axle coaches, in addition several of the Monaco coach tag axle coaches were available with the significantly larger engines and transmission combinations that could not have been carried by non tag axle coaches the ISM and Allison 4000 with associated additional cooling easily accounted for several 1000 lbs in additional equipment
weight and a higher towing capacity which in turn allowed for a higher tongue weight, when you add up the additional weight of the tag assembly it self, the bigger engine/tranny combo and increased towing ability, increasing tag axle pressure to compensate for load only increase front axle weight if you exceed what is required to maintain ride height if and when drive axle capacity if surpassed, you add 2000lbs aft of the drive axles, you increase tag pressure to accommodate the 2000lbs plus the increase force created by the mechanical advantage the distance between the load and the pivot point this should not increase front axle weight if done correctly, if done incorrectly you could easily lightened up the front axle. weight added between axles front and drive will increase front axle weight no matter what you do to the tag pressure other than lowering the pressure which would likely exceed drive axle limits, Tax axle wheel bases are actually shorter than no tag coachs of same length, so while I have a fair amount of front axle capacity when I see 40 non tag coaches running rear axles over weight by several thousand pounds and consider how much more equipment I carry, how much more I tow, what the assembly weights, I cant imagine not having a tag axle on a 40 foot coach to safely carry me and my family down the road.

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Old 09-02-2014, 09:44 PM   #13
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Wow thanks you guys great information I had no idea that I tag was so important my coaches only 24,000 pounds so it's not a big deal for me but if I ever get a newer bigger one I'll definitely look into it thank you again
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Old 09-02-2014, 09:48 PM   #14
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You are correct Moxy. When I am towing our Avalanche or not towing anything I carry 40 psi in the tag bags. The front axle then weighs 14,700#. When I pull the trailer with a 1500# tongue weight I increase the tag bag pressure to 50 psi to get the front axle back up to 14,700. It took a lot of weighing to find the settings I wanted to allow me to keep the axle/tire weights well below their max capacity. Too little in the tag gets the steer axle light and too much can overload it. I finally got the state patrol to bring six individual scales to my home to help get it right. Unfortunately, many tag coach owners just run them as they are delivered to them. Mine was delivered with the steer axle carrying the same weight as the drive axle. Neither axle was over it's rated capacity, but had very poor weight distribution.
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