Ok, is this idea insane? Lay it on me, good and bad.

[G_Hage]

As I look at, and crawl around underneath our Mount Rushmore and look at the frame, axles, and think about all that beautiful [and extremely heavy] granite throughout, I truly question if two Mor/ryde IS axles with Goodyear tires is really adequate for this fiver. I'm not sure if the GVWR of 16,000 lbs and/or the UVM of 12,580 is truly correct (actual scaled weight) or simply a calculated weight. Does Heartland actually weigh each unit to determine an accurate dry weight? Does anyone know how much additional weight the granite added to the MR, as compared to the other counter tops (corian, composite,etc) Heartland uses?

I feel that rather than always running the current 2-axle configuration at or beyond their 8000 lbs capacity rating (if that's in fact the actual rating of the replacement axles that were put under this Fiver after the originals failed), I would be more comfortable pulling this MR with three Mor/ryde IS axles. I do not see need for the third axle to be a braking axle since the current two are equipped with hydraulic disc brakes providing the two are 8000 lbs rated.

Looking at the slides and frame it would appear adding the third axle behind the original two could be easily done, meaning ordering the triple axle fenders, cutting the aluminum sheeting under the fender, welding the axle mounting tubular steel etc to the frame, etc.

Has anyone seen this done to the Mount Rushmore? Does it sound feasible? Or does it sound insanely out there? Knowing the history of this unit, and wanting to tow it in peace and without worry of damage from overloaded tires, etc, I feel this would be a worthwhile improvement to a very nice unit. I'm also seriously considering beefing up the ten inch I-beam on the Lippert frame by having 2x2 tubular steel welded to the bottom of the I-beam with 2x2 cross pieces (spacing yet to be engineered) from I-beam to I-beam for additional lateral strength.

We plan on keeping this unit a long time and for what we purchased it for, there's monetary room for such improvements.

 

[danemayer]

When we first started researching RVs, one of the things I read about was "porpoising" where weight and balance from pinbox to axles is poorly designed. An RV with poor weight and balance design will not tow well, even on smooth roads. I'd guess that adding a 3rd axle would change the weight and balance significantly.

 

[scottyb]

I was talking to a trailer builder about axles. They make a 9000 lb axle and he showed me the brakes that come with them. They are 4 times the brakes on 6-7K axles. Might be an option for your two axle rig. I really never liked 3 axles, but sometimes they are a must. If I could get around it, i would.

 

[G_Hage]

When we first started researching RVs, one of the things I read about was "porpoising" where weight and balance from pinbox to axles is poorly designed. An RV with poor weight and balance design will not tow well, even on smooth roads. I'd guess that adding a 3rd axle would change the weight and balance significantly.

That is one concern I do have and plan to talk to Lippert and/or Heartland regarding this. My plan would be to place the third axle at equal spacing as the front two, but it obviously changes the footprint of the fiver which will change tracking, etc. I two believe the balance of the unit, but to what degree is yet to be determined.

 

[Speedy]

I really think you are over thinking this and not taking into consideration the entire design of the frame, suspension, axles, tires and such. Unless you are an engineer and understand the complete design making those kind of changes will in the end will cause more problems than you started with.

 

[TXBobcat]

If you have Mor/Ryde IS then I would have no problem. Mor/Ryde weighs each tire and installs the proper IS Springs for that trailer. This was not installed by Heartland. They do not install Mor/Ryde. It is a previous owners upgrade. The Disk Brakes should be more than you need to stop your trailer. I have 7K MR IS and 8k Disk Brakes and it is working great. Just be sure to grease the IS every 6k miles or so. When you do raise the tires off the ground when you grease it. Now some will say you don't have to, but trust me, it is better if you do. The bushings are fibre bushings and will wear out quickly if you don't grease it with high pressure and temperature grease.

Your trailer has been greatly improved and if you have a concern you might get with Mor/Ryde and let them help you. Lippert and Heartland has nothing to do with this suspension.

FWIW
BC

On Edit:
I would not try to put an extra axle set on your trailer. Mor/Ryde has the proper suspension for your trailer. Adding another axle would make it harder to park and maneuver. You shouldn't need an extra axle.
Again... Contact Mor/Ryde not Heartland or Lippert...
Ben Wiginton - Service Mgr574-293-1581 X-219

 

[Wharton]

I agree Morryde weighs the rig and puts on the correct IS so I would not have any concerns there. Why don't you get your rig weighed so you have a better idea. Ideally a 4 tire weighing would be best but a truck scale would work for now.

 

[SouthernNights]

As I look at, and crawl around underneath our Mount Rushmore and look at the frame, axles, and think about all that beautiful [and extremely heavy] granite throughout, I truly question if two Mor/ryde IS axles with Goodyear tires is really adequate for this fiver. I'm not sure if the GVWR of 16,000 lbs and/or the UVM of 12,580 is truly correct (actual scaled weight) or simply a calculated weight. Does Heartland actually weigh each unit to determine an accurate dry weight? Does anyone know how much additional weight the granite added to the MR, as compared to the other counter tops (corian, composite,etc) Heartland uses?

1) Heartland DOES weigh each unit separately for a dry weight NOW. I do not know what they did back when your trailer was built but I suspect they did then also.

2) Granite vs. Corian / solid surface. Although most people call any solid surface Corian; Corian is a DUPONT name brand for the first solid surface on the market. They developed it and patented it. That is why using the word Corian has become generic for all solid surfaces but there is a huge difference. Corian outweighs; per sq ft.; most solid surfaces out there. It is a much denser product than say Hanex, Meridian, Avonite etc. Corian/ solid surface can also be ordered in different thickness's depending on application which can dramatically affect weight per sq ft. True Corian ALWAYS has the gold Corian coin embedded in it somewhere on the surface.

As with Corian/solidsurface, granite has a wide range of weight per sq. ft. also. Depending on the quarry (which determines it's name e.g. Santa Cecilia , Giallao Ornamental, Venetian Gold etc. ) and the thickenss will determine actually weight. There are typically two thickness of granite-2cm. and 3cm. 2cm is rarely used (or at least shouldn't be used) in any wet application because of the abuse that typically goes along with a wet application e.g. kitchen countertops are usually used for preparation whereas a Butlers Panty is for display and serving.

So before comparing weight of granite vs. solidsurface, you have to know exactly which product you have and would want to go to.


I feel that rather than always running the current 2-axle configuration at or beyond their 8000 lbs capacity rating (if that's in fact the actual rating of the replacement axles that were put under this Fiver after the originals failed), I would be more comfortable pulling this MR with three Mor/ryde IS axles. I do not see need for the third axle to be a braking axle since the current two are equipped with hydraulic disc brakes providing the two are 8000 lbs rated.

As several pointed out already, adding axles will change the dynamics of the trailer. It will effect pin weight, stress on the frame when turning, porpoising etc etc. Probably not a good idea unless you have an engineer design the set up for you.

Looking at the slides and frame it would appear adding the third axle behind the original two could be easily done, meaning ordering the triple axle fenders, cutting the aluminum sheeting under the fender, welding the axle mounting tubular steel etc to the frame, etc.

Has anyone seen this done to the Mount Rushmore? Does it sound feasible? Or does it sound insanely out there? Knowing the history of this unit, and wanting to tow it in peace and without worry of damage from overloaded tires, etc, I feel this would be a worthwhile improvement to a very nice unit. I'm also seriously considering beefing up the ten inch I-beam on the Lippert frame by having 2x2 tubular steel welded to the bottom of the I-beam with 2x2 cross pieces (spacing yet to be engineered) from I-beam to I-beam for additional lateral strength.

Before you beef up the frame, again you might want to get an engineer involved. I believe the older LMs used a tubular frame on the drop instead of I-Beam. With any type of frame, there is a certain amount of flexibilty built into it. If you build something to stiff it could cause lots of problems down the road(no pun intended). e.g. When I was a fleet manager, we used a Ford chassis on the LT9000 becuase of it's flexibilty. With the wheel base that we speced, the frame had 33" of flex at adjacent corners and still retained it's memory. We ran about 20% off road and the flex was important.

We plan on keeping this unit a long time and for what we purchased it for, there's monetary room for such improvements.

Again, as someone else pointed out-you can get an individual wheel weight, call Mor Ryde and talk with Ben or Gary. Tell them your concerns. They may recommend changing the sheer spring to a higher GVW. The rubber sheer spring is designed to be replaced at given intervals anyway depending on the usage.

Tire size. You could go up in tire size to a 17.5 which as you know considering what you guys do for a living is also called a lowboy tire. This is a very common modification that quite a few people on this forum have done. The 17.5 will carry a higher payload and run cooler than the 16s. Not cheap but one good way to justify it is look at the DOT date on your current tires. If they are approaching 4-5 years, time to change tires any way.

Hope this helps. Good luck on whatever you do, maybe we will run into each other in FL.


ON EDIT: When we were at Mor Ryde last October, I remember one of the Mor Ryde reps talking with another customer. They were discussing what size sheer spring to put under his trailer. Although the customer thought he wanted they heaviest spring possible, Mor Ryde pointed out that too stiff a ride is just as bad as not enough spring. Good advice and something to consider.

 

[hoefler]

Another thing to remember, up to 25% of the trailer gross is to be carried on the pin. That would leave approximately 12,000 pounds of 16,000 pounds gross weight on the axles. As said above, adding an additional axle will grossly affect the dynamics of how it carries the load. A third axle tacked on behind the existing 2 will cause the pin weight to go up dramatically. Most 16k tandem axle trailers have 7k axles. Most triple axle 16k trailers have 4k-6k axles. It is all about foot print and balance.

 

[jnbhobe]

Larry has pretty much spelled it out, Mor-ryde has allready added 3 cross pieces to the frame when the IS was installed. If your really worried you can change out the rubber springs to 8K if I'm not mistaken.

 

[Ray LeTourneau]

As a few others have mentioned, call Mor Ryde. Talk to them about your concerns. I really feel a 3rd axle is not needed. Going to 17.5 wheels and Goodyear G114 tires will really be your best option. The after market suspension you have, may already have the 8K "springs" but MorRyde can also inspect and align your suspension to address your concerns.

Another option is an air suspension.

 

[wehavefun]

If you have Mor Ryde IS you are set!!
Now I just got mine done in December, but with about 3, 000 miles on the rig and I am more than satified!!!! I shot the wad, IS , disk brakes and Goodyear 17.5's. The ride, stability and peace of mind knowing I am set is priceless! ! I pull a a Big Horn and cross the scales at 26 k with my CC DRW Dodge consistently.

As stated before you change the dynamics by placing a third behind your current axles you will increase the pin weight as well as place additional twisting to your frame when turning and maneuvering.

I am sure after speaking with Mor Ryde you will be more than confident with your suspension and reliability .

 

[kakampers]

Agree with Larry completely, in fact, after discussions with More Ryde we too decided on 7K "axles" to insure a softer ride....and it works, especially considering we run very heavy. Had it weighed and every weight is within limits and with disc brakes and 17.5 tires and rims we are extremely confident in our set up...relax!!

One other thing...noticed you said it had a ten inch I beam...if I'm not mistaken, Landmark has always had a 12 inch I beam.

 

[porthole]

The MOR/ryde IS is a superior suspension to what came from the factory. It is used on several high end trailers as standard equipment.

The MR IS has roughly 5" of travel, about 3" more then stock suspension. And because of that, if you have the where with all you can check your own springs.
When the springs are new, and are the proper durometer, you well have about 2" of travel from unloaded. Once they settle in the correct height should be 2.5"

Too much or too little and you can easily change the springs, which BTW are warranted for 5 years.
I have the 7K set on my "heavy" 2 axle Cyclone. After a year of use MOR/ryde switched out my 7K springs for 8K and we have been good ever since.

Call Ben at MOR/ryde as Bob mentioned. Along with with Bob, I ditto his method of raising the trailer off the ground to grease the axles tubes.
Although, MOR/ryde says you don't have to do this. That might be about liability.

BTW, to go along with your IS, I bought a 20 ton low profile bottle jack. Fits perfect under the 1/2" steel plate to lift the tires off the ground.
20 ton is not overkill. Makes for an easy jacking when you are laying on the ground. Tractor Supply was the source.

With Goodyear G-114's (17.5") you should have no worries.

 

[lwmcguir]

We have a lot of Torsion axles on lighter trailers, 8K axles and down. The key to any suspension like this is the trailer has to be towed nearly level or you will overload one of the axles. Otherwise they are a lot less maintenance an if you are going tow a lot of miles then that is the way to go. The typical leaf/hanger suspension is the cheapest and highest maintenance that you can purchase.

 

[G_Hage]

Agree with Larry completely, in fact, after discussions with More Ryde we too decided on 7K "axles" to insure a softer ride....and it works, especially considering we run very heavy.

That makes sense. I'm hoping Mor/ryde will still have the information regarding the Mor/ryde axle assembly they shipped to Las Cruces to replace the ones that failed. They should be very familiar with this unit and hopefully can tell me which rating axles and IS springs I actually have. As you can see in the attached photos, we currently have the 16" rims with Goodyear tires. I need to look up the weight rating of the tires,as they may or may not be more than rated for the weight of our MR.

Had it weighed and every weight is within limits and with disc brakes and 17.5 tires and rims we are extremely confident in our set up...relax!!

I'm going to call Mor/ryde to also ask if there will be enough safe clearance between the tires if I replace the 16" rims with 17.5" as the axles already appear to be close as shown in the attached photo.

One other thing...noticed you said it had a ten inch I beam...if I'm not mistaken, Landmark has always had a 12 inch I beam.

That is what I was once told by a landmark dealer regarding a comparable model year Landmark we had looked at online. As you can see in the attached photos, Our MR is built on an 8" I-Beam frame in the drop Z below the basement, and 10" I-Beam on the rest of the lower frame area. It has box tubing for framing in the bedroom/ pinbox area. I don't know if that was the norm for MR's built as 2008 models in the last quarter of 2006 as this was. Maybe this will validate or bring understanding to my concerns and ideas. My technical engineering background was spent as a residential and multi-family dwelling designer, plus designing and inspection of the construction for municipal water distribution and wastewater collection systems. I am stepping into an area of engineering I've not had a lot of experience in the past, yet I have my concerns, as all other brands we previously considered in this weight class (16K GVWR plus) were built on 12" I-Beam frames or double stacked box beam frames.

All, please then understand my questioning the choice or reason for our MR being built on the frame it was and the axle configuration it was originally designed and built with.

 

[danemayer]

You should check, but I think the outside diameter of the G614 and G114 is almost exactly the same.


Sent from my iPad using Tapatalk HD

 

[TXBobcat]

This information should be helpful. A link to the mfgr specs and description from that link.
G114 215/75R17.5 H Diameter 30.5" Weight @ 125psi 4,805# & Weight @ 100psi 4020# Speed Rating 75mph
G614 LT235/85R16 G Diameter 30.7" Weight @ 110psi 3,750#
XPS Rib LT235/85R16 E Diameter 32.0" Weight @ 80psi 3042#

Goodyear Tire inflation Chart (PDF)

A photo to give you an idea.
XPS Ribs on the outside. G114 in the middle.



Hope this helps...

BC

 

[kakampers]

First, unless I am mistaken the original owner had new axles shipped to Las Cruces and then went to Mor Ryde later for the IS upgrade. Second...really surprised at the size of your frame members?? Really thought they always used the 12" frame...

Lastly...strangely the diameter of a 17.5 tire is actually just slightly smaller than the 16"...

 

[Dave49]

I just spoke with Mor/Ryde the other day about my 3670RL Bighorn and having them equip my trailer with the IS suspension. I have built race cars from the ground up, have a pretty good understanding of suspensions. But, it's always been my belief the ones that build the units are the experts and I will let them decide what I need. I will also weigh my trailer so that they know exactly what they have to work with. I want the best possible ride for the trailer and they are experienced and know what to do.

I am doing this as I have the problem of frame flex and Heartland has come up to the plate and willing to fix this when I get there in May at no cost to me. So it just seems like it would be a good upgrade to maybe help eliminate from this happening again. Along with helping the contents of the trailer a lot also.

Dave