Tag Axle vs Single Axle

[dandandan]

Originally Posted by CampDaven

When I bought my 09 Monaco w/tag in 2014, in the mix of the available rigs the 36-38 ft were more expensive. The 43/tag rigs were cheaper and undesirable due to the market. Everyone wanted the State Park size!






I have “extra brakes” because I’m way under loaded. I bought it partially because of the tag! I love a great ride.

Mine has had proper weight distribution since it was built. The tag pressure adjustment was right on with Monaco manual. There was nothing to “correct”.

So much for the braking, pricing, and tag cost/complexity.


Now, please, what is the MCU that I don’t have nor need?

Happy Trails

You think you have "extra brakes" because you are under loaded. But the more your rear axles deviate from 2/3 & 1/3 load the sooner the brakes lock into a skid or the anti-lock feature kicks in early decreasing your stopping ability even though your axles are other wise under weight. Don't get me wrong the tag is much more capable of carrying a motorcycle on the rear due to tag extra weight rating. But the more the rear axles deviate from 2/3, 1/3 the less capable the stopping ability.


You state the weight distribution from Monaco "was right on" but give NO actual weights. Hard to believe the distribution was perfect when so many are down right poor.


Chassis manufacturer, even if in house, does not know the floor plan it will be used on. Further they do not know how the owner will load it. There is NO way the chassis builder can build an ideal 2/3, 1/3 load distribution on the rear wheels with these unknowns. So a tag has either some what less braking ability or a lot less braking ability depending on how the chassis is actually loaded.


Tag still has MORE load carrying ability as in a motorcycle and greater stability.


MCUs are a different issue. They reduce rate of change of air flow to the air bags increasing the stability of a DP in high winds.


Stability and braking are separate issues.


Poor loading of rear axles leads to poor braking of rear axles. Most tags just do not get close to ideal 2/3, 1/3 loading of axles so that all 6 tires see the same load.

[CampDaven]

Originally Posted by dandandan

You state the weight distribution from Monaco "was right on" but give NO actual weights. Hard to believe the distribution was perfect when so many are down right poor.

I’m very happy with my rig.

There are more folks like me that have tags and have weighed it and have made correct decisions. And Monaco did better builds and attention to detail back before they failed.
And less weight means more efficient braking.

[jcussen]

Originally Posted by dandandan

Tag is a nice to have, but a DP with motion control units (MCU) will provide significantly enhanced stability in cross winds.



Many tags are delivered with their weights not in proportion and excessive weight on the front axle.


A lot of complexity with not as much need now that 24k axles are available.

Can you provide some documentation that proves that most tag axle coaches are delivered with their weights not in proper proportion? Have had two tag axle coaches, one with air adjustment valve that you can set tag bag pressures. Easy to put on scale and adjust air pressure to load tag to it proper rating. Would think most better quality manufacturers would do this to each coach before it leaves the factory. The other coach had tag bags adjusted by same Height Control Valves as main axle so proportion remains the same regardless of weight.
If properly set up, pretty sure braking power of 6 rear wheels would be superior to 4 wheels. Kind of why Nascar cars have big tires, not because of weight issues, but because of more surface area which affects handling and braking.

[dandandan]

Originally Posted by CampDaven

I’m very happy with my rig.

There are more folks like me that have tags and have weighed it and have made correct decisions.
And less weight means more efficient braking.

"less weight means more efficient braking"


NO, NO, NO


You are not understanding. You want all 4 tires on a single axle or all 6 tires on a drive and tag axle to be the SAME weight. The tire or axle weight really does not matter. The more one tire DEVIATES below the average the less the braking force, as it starts skidding or kicks in the anti lock braking earlier than the other tires. The uniformity of the weight not the weight is what matters.


Mass is linear and drops out of f=ma, kinetic energy is 1/2mv**2, and friction is mu x weight. The weight does not matter if the brakes are adequate.


The variation of the tire weight with the LOW weight causing the skidding or anti lock brake to kick in early.


1) There are advantages to a tag but braking is NOT one of them as you can never get the weight distribution ideal.


2) The advantages of a tag have decreased now that 24k axles are legal. When max axle weights were 20K tags were more advantages as they were more necessary to carry additional loading.

[Gary RVRoamer]

The pros and cons are largely academic anyway. It's not an option. You are going to get a tag axle if the GVWR of the coach you choose requires an extra axle to carry its weight and not otherwise. That's simply because there isn't enough extra value in a tag to justify the extra cost except for increased GVWR.


I suppose there are a few buyers who would choose a larger/heavier and more expensive coach than they really wanted just so they could brag about having a tag axle. If that's your thing, go for it.

[chuckftboy]

I don't think there is 2/3,1/3 ratio that needs to be followed. I can dump the air in my rear axel and it still goes down the road just fine. Its just here to carry additional weight.

[Crasher]

Originally Posted by jcussen

Can you provide some documentation that proves that most tag axle coaches are delivered with their weights not in proper proportion? Have had two tag axle coaches, one with air adjustment valve that you can set tag bag pressures. Easy to put on scale and adjust air pressure to load tag to it proper rating. Would think most better quality manufacturers would do this to each coach before it leaves the factory. The other coach had tag bags adjusted by same Height Control Valves as main axle so proportion remains the same regardless of weight.
If properly set up, pretty sure braking power of 6 rear wheels would be superior to 4 wheels. Kind of why Nascar cars have big tires, not because of weight issues, but because of more surface area which affects handling and braking.

What dandandan said is true. Up until 2014, Tiffin with their powerglide chassis used a 60/40 proportioning valve. 60% on the drive and 40% on the tag. This made for a bad distribution of weight transferring too much weight to the steer and too little on the drive. I had them swap the prop valves for manual regulator valves. They did this for many owners. After several settings, I arrived at what I wanted which took 700# off of the steer axle and 4,000# off the tag which increased the drive weight to 19,500# on a 22,000# rated axle. Freightliner had the same problem for several years, but only the owners that checked knew about it. Freightliner used an adjustable prop valve and helped those who asked change it. Since I along with other owners sent our conclusions to Tiffin, they eliminated the prop valve which gave them a 70/30 distribution of the drive and tag due to the difference in air bag sizes. None of the axles or tires were overloaded with the OEM setup, but the weight distribution was just not what it should have been.

[jcussen]

Originally Posted by Crasher

What dandandan said is true. Up until 2014, Tiffin with their powerglide chassis used a 60/40 proportioning valve. 60% on the drive and 40% on the tag. This made for a bad distribution of weight transferring too much weight to the steer and too little on the drive. I had them swap the prop valves for manual regulator valves. They did this for many owners. After several settings, I arrived at what I wanted which took 700# off of the steer axle and 4,000# off the tag which increased the drive weight to 19,500# on a 22,000# rated axle. Freightliner had the same problem for several years, but only the owners that checked knew about it. Freightliner used an adjustable prop valve and helped those who asked change it. Since I along with other owners sent our conclusions to Tiffin, they eliminated the prop valve which gave them a 70/30 distribution of the drive and tag due to the difference in air bag sizes. None of the axles or tires were overloaded with the OEM setup, but the weight distribution was just not what it should have been.

So Tiffin powerglide and Tiffin freightliner? Any other makes or chassis's ?

[bucks2]

Wow, all these scientists explaining why more rubber against asphalt doesn't increase stopping ability. Next they'll explain why drag racers do just as well with narrow tires on the back as they do with wide ones because it doesn't matter how much rubber is on the asphalt, it depends if the car is balanced properly front to back.......

Of course distributing heat from 6 brake rotors inside 6 wheels isn't any better than 4 rotors and 4 wheels. Obviously, if they're "sized right" 50% more heat can escape from inside a wheel of any fixed diameter and width. I suppose if a semi truck would just size their brakes right, they wouldn't need them on each wheel/tire assembly because they only need a couple......... I wonder why those silly engineers do that?

[Crasher]

Originally Posted by jcussen

So Tiffin powerglide and Tiffin freightliner? Any other makes or chassis's ?

I don't know. Most of my info and knowledge came from a Tiffin forum or my own trial weighing till I got what I wanted. The same Freightliner chassis is used on several brands of DP. My coach has 15.6K front, 22K drive and 13K tag for a 51K GVWR. It weighs 41K loaded. Being 10K under GVWR, I was more concerned with keeping the steer axle 1,000# under the tire and axle ratings, so I dialed in a 75/25 ratio. Have never had a stopping problem or sliding tires. Newmar has had some issues with overweight steer axles that they corrected with heavier axles. I would be surprised if many manufacturers test and shoot for a perfect distribution. They just want to stay within the axle and tire ratings. Different options on the same wheelbase makes for different settings. My sons Newell weighs 60,000#. 19K the steer and 41K between the drive (28,600 rating) and tag (16,000 rating) Not sure of the ratio.

[jcussen]

Originally Posted by Crasher

I don't know. Most of my info and knowledge came from a Tiffin forum or my own trial weighing till I got what I wanted. The same Freightliner chassis is used on several brands of DP. My coach has 15.6K front, 22K drive and 13K tag for a 51K GVWR. It weighs 41K loaded. Being 10K under GVWR, I was more concerned with keeping the steer axle 1,000# under the tire and axle ratings, so I dialed in a 75/25 ratio. Have never had a stopping problem or sliding tires. Newmar has had some issues with overweight steer axles that they corrected with heavier axles. I would be surprised if many manufacturers test and shoot for a perfect distribution. They just want to stay within the axle and tire ratings. Different options on the same wheelbase makes for different settings. My sons Newell weighs 60,000#. 19K the steer and 41K between the drive (28,600 rating) and tag (16,000 rating) Not sure of the ratio.

Am sure not all Newell's the same, but on mine could adjust tag pressure with a regulator. When I got mine, went to cat scale and did a 3 axle reading and had to add 5 psi to tag to bring it to the proper ratio. Some Newells had overloaded front ends because there were no tires at the time that would handle the weight. Axles were okay. Think in the beginning they paid for the upgrade to bigger tires/wheels when they came out. But I had to pay for mine.

[Crasher]

Originally Posted by jcussen

Am sure not all Newell's the same, but on mine could adjust tag pressure with a regulator. When I got mine, went to cat scale and did a 3 axle reading and had to add 5 psi to tag to bring it to the proper ratio. Some Newells had overloaded front ends because there were no tires at the time that would handle the weight. Axles were okay. Think in the beginning they paid for the upgrade to bigger tires/wheels when they came out. But I had to pay for mine.

Unfortunately, what might be the correct ratio for braking at maximum weight, might not be the best for steering axle weight. Manufacturers shoot for a happy medium to accommodate the many different options on the chassis available to them. It is more important to me to have a safety buffer on the steer axle which I can dial in with the manual regulator valves and don't feel I am losing any braking ability being 10K under GVWR. When I hook up to a heavy trailer with 1200# of tongue weight, I have to increase the tag pressure by 12 psi to remain at the 75/25 ratio and the steer axle stays @ 1,000# under rating. It's working well for me with excellent ride and handling.

[jcussen]

While the general rule that more support the tag axle provides, the more weight is transferred to the front axle, may be true in some poorly designed coaches. On mine, tag basically supports the engine, transmission, radiator etc, and the rest of the coach is between the front and rear axles. I know Foretravel and Newell would move fuel, fw, tanks, aqua-hot, batteries etc to different bays, according to the number of slides and coach weight. Don't know how easy that is on a freightliner.
I know increasing the bag pressure and load on my tag to support the recommended 8000 lbs, did nothing to my front axle weight. The notion of building a 4 slide, 40+ foot coach on a single rear axle is possible, just wonder on the capacities and construction.
Engine size is important too, the ISL/3000 is quite a bit lighter than an ISX/4000.

[dandandan]

Originally Posted by Crasher

What dandandan said is true. Up until 2014, Tiffin with their powerglide chassis used a 60/40 proportioning valve. 60% on the drive and 40% on the tag. This made for a bad distribution of weight transferring too much weight to the steer and too little on the drive. I had them swap the prop valves for manual regulator valves. They did this for many owners. After several settings, I arrived at what I wanted which took 700# off of the steer axle and 4,000# off the tag which increased the drive weight to 19,500# on a 22,000# rated axle. Freightliner had the same problem for several years, but only the owners that checked knew about it. Freightliner used an adjustable prop valve and helped those who asked change it. Since I along with other owners sent our conclusions to Tiffin, they eliminated the prop valve which gave them a 70/30 distribution of the drive and tag due to the difference in air bag sizes. None of the axles or tires were overloaded with the OEM setup, but the weight distribution was just not what it should have been.

I am not saying a properly weight adjusted tag axle MH can not be manufactured. It just is not typically done and is difficult to optimize the weight distribution.


Very few owners learn about proportioning valves or go thru the effort of getting the valves changed like Crasher did.


MOST would be better off with a nontag axle 40-42ft coach that is less complex and essentially more idiot proof. Many tag axle MHs going down the road are very poorly distributed for weight and the owners don't understand this.


It is just not worth the added cost and complexity for most for a few extra feet imo.