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  #1  
Old 12-02-2004, 02:18 PM
MountainCamper
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Default TM Weighing Process

My better half and I are planning to upgrade from our pop-up to either a 2720SL or 3124KS early next year. Iíve been shadowing the forum for almost 2 years and finally became a site sponsor the middle of this year due to the wealth of info provided here. We live above Colorado Springs, CO, at about 6900í, and we depart from there to go camping UP into the Rockies. This is very similar to the posts from RockyMtnRay, ColoradoCop, CastleRockCamper, ColoradoAl and a few others here along the Front Range of the Rockies, so high altitude loss in the TV performance is just another part of everyday life. As can been seen by my signature, we currently have a 03í 4x4 Pathfinder w/ factory tow package, which would be the probable TV for the 2720SL, but I strongly feel we would need to secure a more substantial TV if we decide to go with the 3124KS. In either situation, TM weights play a part into the decision making, thus below, I have a few questions on realistic TV & TM weights.

Iíve researched many of the posts within discussing TM loaded weights in trying develop a matrix of reality: what a nominally optioned and outfitted TM weighs, either with or without fluids & gear loaded, supporting how many adults, for how long, etc, etc, but I still have a basic question regarding these posted TM weights. (Realize, I know Iím an Engineer, but we all have handicaps to overcomeÖÖ) Is there a consensus between the forumís weight-gurus as how the TM weights have consistently been determined: i.e.: which weighting process below (or some other) might have been used to calculate the TM weights published within the forums?

#1) the full TM alone on the truck scale, providing the combined axle + tongue weight, with no WDH attached from the TV, or

#2) the just the TMís axle alone, with the tongue statically supported off scale but not by the WDH to the TV, providing the TM gross axle weight only, or

#3) the just TMís axle with the WDH installed to the TV, which also includes the portion of the WDH-distributed tongue weight onto the TMís axle

Net, Iím unsure yet when I read about a recorded TM weight, say 3600#, which of the 3 above weighing processes derived that weight since the 3600# could imply differences of several hundred pounds with regard to the TM gross axle and tongue weights, as well as the TV gross vehicle, gross axle (front and rear) and gross combined vehicle weights.

Thanks in advance..
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  #2  
Old 12-02-2004, 02:54 PM
Windbreaker
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My #3600 weight was trailer (total) lightly loaded for one night out, full gas, no water, no tv, one change of clothing for two, three meals.

Having said that, I would suggest that what ever you come up with you add at least 1000# to your figures because your gear, WDH and other things you carry will amount to that much. I started with a Dakota 4x4 and moved to a full sized truck quick. I've been very pleased with the result, I'm in total control now and did not feel that to be the case with the smaller truck.
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  #3  
Old 12-02-2004, 02:59 PM
Windbreaker
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One more quick note. This last fall my trailer breaks failed and the full sized truck was still in control. In driving grades this is a big plus. The truck I now drive is a heavy duty and that means better breaks as well as more get up and go.
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  #4  
Old 12-03-2004, 08:22 AM
RockyMtnRay RockyMtnRay is offline
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Location: Colorado Springs, CO
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Thumbs up Greetings from across town!

Quote:
Originally Posted by MountainCamper
My better half and I are planning to upgrade from our pop-up to either a 2720SL or 3124KS early next year. Iíve been shadowing the forum for almost 2 years and finally became a site sponsor the middle of this year due to the wealth of info provided here. We live above Colorado Springs, CO, at about 6900í, and we depart from there to go camping UP into the Rockies. This is very similar to the posts from RockyMtnRay, ColoradoCop, CastleRockCamper, ColoradoAl and a few others here along the Front Range of the Rockies, so high altitude loss in the TV performance is just another part of everyday life. As can been seen by my signature, we currently have a 03í 4x4 Pathfinder w/ factory tow package, which would be the probable TV for the 2720SL, but I strongly feel we would need to secure a more substantial TV if we decide to go with the 3124KS. In either situation, TM weights play a part into the decision making, thus below, I have a few questions on realistic TV & TM weights.
Glad to have another Springs area member here! I'm an east-sider...Cimarron Hills...a mile east of Powers at Palmer Park; have lived there for about 24 years.

Your Pathfinder will indeed be fine for a 2720SL...you've got enough torque and a low enough axle ratio...and enough wheelbase for this size trailer. However, I concur that you will need more wheelbase (and quite a bit more torque) if you want to tow a loaded 3124KS here in Colorado. I'm sure the Nissan dealers would be happy to arrange a tradeup to an Armada (or Titan)...either of these would be great with a 3124KS...and you still would have a Nissan.

Quote:
Iíve researched many of the posts within discussing TM loaded weights in trying develop a matrix of reality: what a nominally optioned and outfitted TM weighs, either with or without fluids & gear loaded, supporting how many adults, for how long, etc, etc, but I still have a basic question regarding these posted TM weights. (Realize, I know Iím an Engineer, but we all have handicaps to overcomeÖÖ) Is there a consensus between the forumís weight-gurus as how the TM weights have consistently been determined: i.e.: which weighting process below (or some other) might have been used to calculate the TM weights published within the forums?

#1) the full TM alone on the truck scale, providing the combined axle + tongue weight, with no WDH attached from the TV, or

#2) the just the TMís axle alone, with the tongue statically supported off scale but not by the WDH to the TV, providing the TM gross axle weight only, or

#3) the just TMís axle with the WDH installed to the TV, which also includes the portion of the WDH-distributed tongue weight onto the TMís axle

Net, Iím unsure yet when I read about a recorded TM weight, say 3600#, which of the 3 above weighing processes derived that weight since the 3600# could imply differences of several hundred pounds with regard to the TM gross axle and tongue weights, as well as the TV gross vehicle, gross axle (front and rear) and gross combined vehicle weights.

Thanks in advance..
Perhaps I should just explain how the experts from the RV Safety Education Foundation have weighed my rig at the 2 weighins I've gone to. Incidentally in checking their 2005 Weighin Schedule , I see the good folks at Pikes Peak Traveland (on the east side...Platte at Wooten) are again hosting a weighin on July 30th...I'll definitely be getting my rig weighed again due to mods I've done since the last one.

Anyhew, their process is simple and requires just two weighings:

1. With trailer hooked to tow vehicle they get the weight on all tow vehicle and trailer tires.

2. Then they unhook the trailer and get the weight on all the tow vehicle tires (the trailer is NOT reweighed).

From these numbers, they get the hitch weight by subtracting the weight of TV without trailer from the weight of the TV with trailer. To get the total trailer weight, they add the hitch weight to the weight that was on the trailer tires when hitched up. Badda bing, badda boom.

In my case, at the last weighin I had about 3300 lbs on the TM axle when hooked up (this includes some weight (150 lbs?) being transferred back from the WDH) and about 500 lbs being carried by the tow vehicle for a total trailer weight of around 3800 lbs. I'm guessing that I actually had somewhere around 650 lbs on the TM tongue (if that had been weighed while unhitched) and around a fourth of this was being transferred back to TM wheels by the WDH.

Some notes:

This method tells you exactly what each tire of the TV and the trailer is carrying when hitched up. No guessing, no estimation of the effect on any tire from the weight distributing hitch.

The differences in weight on the front tires of the TV with/without trailer are an excellent indication of whether or not the weight distributing hitch has been properly adjusted. In theory, half the hitch weight should be distributed to the front of the TV when hitched. What I've found both times I got weighed ( ) was my TV front tires were getting unweighted by the trailer indicating that I did not have my hitch properly adjusted.

The other thing that's great about these RVSEF weighins is that they measure the weights on each wheel and not just the axle in total. With the 2720SL TM where all the tanks and fridge ride on the driver's side, knowing the individual wheel weights is critical...the first time I had mine weighed I had several hundred pounds more on the driver side than on the passenger side.

If you have your trailer by July, I strongly encourage you to call Pikes Peak Traveland (Parts Dept) and see if you can get on the weighin schedule...you have to have an appointment time. This has been a free weighin...Pikes Peak Traveland has been paying all the RVSEF expenses as a community service.
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Ray

I use my TM as a base camp for hiking, kayaking, mountain biking, and climbing Colorado's 14ers


The Trailer: 2002 TM Model 2720SL ( Mods: Solar Panels (170 Watts), Dual T-105 Batteries, Electric Tongue Jack, Side AC, Programmable Thermostat, Doran TP Monitor System)

The Tow Vehicle: 2003 Toyota Tundra V8 SR5 4X4 w/Tow Package (Towing & Performance Mods: JBA Headers, Gibson Muffler, 4.30 gears, Michelin LTX M/S Tires, Prodigy Brake Controller, Transmission Temperature Gauge)


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  #5  
Old 12-04-2004, 08:07 PM
MountainCamper
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Thanks for the replies so far. Ray: thanks also for the details on the RVSEF procedure and weigh schedule locally. Straight forward and provides the necessary weight items, especially the individual wheel weights. My goal is/was to try to simply the mistique around the delivered-to-the-dealer TM weights. To this, as Wind suggested, the owner-supplied goody (interior & exterior) weights can be added. This really isn't rocket science and shouldn't be viewed as such. Noone should be put into the position of buying a TM and then find out after the fact that their TV doesn't cut it, and then have go out and buy a new TV just to keep the new TM. For the owners that do end up buying a new TV also, from an enginerring perspective, that purchase just shouldn't be a suprise.
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  #6  
Old 12-06-2004, 12:41 AM
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Denny_A Denny_A is offline
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Join Date: Jul 2002
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Default TM Weights, etc.

Quote:
Originally Posted by MountainCamper
My goal is/was to try to simply the mistique around the delivered-to-the-dealer TM weights. To this, as Wind suggested, the owner-supplied goody (interior & exterior) weights can be added.
Delivered weight will be 300 -400 + lbs greater than the TM specs page lists. F'rinstance; a 2005 2720 SL - @ 2865 lbs (w/o options), will likely weigh between 3165 and 3265+ lbs delivered. The more options...etc. A 3124KB will likely be 3090 + 300-400 lbs; and so it goes.

Quote:
No one should be put into the position of buying a TM and then find out after the fact that their TV doesn't cut it, and then have go out and buy a new TV just to keep the new TM. For the owners that do end up buying a new TV also, from an enginerring perspective, that purchase just shouldn't be a suprise.
Regarding weighing, below is a quick and dirty summary.

A. Tongue and axle weight combined weighing is useful when getting aquainted with the vehicle. The 2005 2720 SL should not exceed 2865 + 1210 = 4075 lbs. fully loaded (per specs). It's good to have a reality check on how much stuff can ACTUALLY be carried.

B. However, the axle or tire limit should not be exceeded either. So measuring the force on the tires, with the tongue freely supported off the scale is also very useful. The axle limit for earlier models of the 2720 is 3500 lbs. Tire load limit is 1860 each, for a total of 3720 lbs. TM use fully loaded trailer tongue weight as 14.7% of trailer weight. So, if the trailer weighs 4075 lbs, the tongue will weigh 4075 x .147 = 600 lbs. Axle load will be 4075 - 600 lbs = 3475 lbs. Within limit for axle and 245 lbs under the tire load limit.

C. When the (a) WDH is connected properly, 1/3 of the tongue weight will be redristributed to each of the three axles. Obviously, using the 600 lb tongue weight example above, the trailer would see 200 lbs additional down force on the axle. Same trailer is then registering 3675 lbs (or so) at the tire to road contact. Tire limit is stiil ok, but the axle isn't - or is it?

This is where TM adds a bit of a "twist in the math". Since the axle supports the trailer, but NOT the wheel assemblies, then it follows (per TM) that the wheel assembly weight of 200 lbs (2 wheels) may be subtracted from the total weight of the trailer as seen BY the AXLE. That is if the scale reads 3700 lbs at tire contact, one may subtract 200 lbs. to arrive at axle load. The info, regarding "twist in math" came from corespondence and a conversation between the TM engineer and me.

Loose ends: I am not sure of axle limits on 2005 models, especially the 3023 and on up to the 3124KS, since they have 15", D rated Goodyear tires. I think others have said 5000 lb axle limit and 2050 lb tire limit. If so, the tires are (would be) the primary limiting condition.

Most owners who have towed their TM for awhile would recommend enough excess towing cpacity to handle any towing situation w/out breaking into a nervous sweat whilst towing (like a minimum of 25-35% excess towing capacity for the MVW of the trailer you own).

Don't know if this was a proper response to your original question, but I hope it is useful.

Denny_A
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  #7  
Old 12-08-2004, 02:57 PM
MountainCamper
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Denny:

Good additional clarification on the importance of axle / wheel weights also, as a follow-on to suggestions from Ray. I remember reading something similar to this, I believe it was a post from you, back in late 02 or there abouts.

This calculation process seems to lend itself to a fill-in-the-blank calculator for a TM base model, with options ordered, and supplies & expected personal accessories to be carried, being towed by xxxx vehicle with it's specific GCWR, GVWR, GAWR, etc. Sounds like a straight forward exercise in Excel spreadsheet engineering with a few imbedded formulas. Anyone know if this has been tried before, specifc to TMs, either for current year models or past years? I found one such spreadsheet for a weight / tow calculator online (I'll find the link somewhere) but I don't believe it took into account the WDH weight transfer, axle loading, and I think it assumed sea-level altitude and a full-sized trailer box (wind resistance, etc), but also left out a few other items I think.

Would there be any interest on from the general TM forum members to try to create a tailored TM weight / capability calculator (maybe in MS/Excel format) in trying to answer the question that most folks have: "What TM model can I safely tow with my xxxxxxx TV?"
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  #8  
Old 12-08-2004, 04:04 PM
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Denny_A Denny_A is offline
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Default Re: TM Towing Spreadsheet

Quote:
Originally Posted by MountainCamper
Denny:

Good additional clarification on the importance of axle / wheel weights also, as a follow-on to suggestions from Ray. I remember reading something similar to this, I believe it was a post from you, back in late 02 or there abouts.
Yup, that was me. I worked with the TM engineer for several weeks trying to understand why the GVW was such that the axle would be overlaoded when using a WDH. That's where the "unsprung" wheel weight (not being included) surfaced. Their position is at odds w/Dexter and the official definition of Gross Axle Weight Rating(GAWR). Dexter do not dispute TM specifically (I asked), yet only support the official def'n of GAWR. I.e., GAWR is referenced to the load at the tire/road interface! A TM - Dexter GAWR application dichotomy.

Quote:
This calculation process seems to lend itself to a fill-in-the-blank calculator for a TM base model, with options ordered, and supplies & expected personal accessories to be carried, being towed by xxxx vehicle with it's specific GCWR, GVWR, GAWR, etc. Sounds like a straight forward exercise in Excel spreadsheet engineering with a few imbedded formulas. Anyone know if this has been tried before, specifc to TMs, either for current year models or past years? I found one such spreadsheet for a weight / tow calculator online (I'll find the link somewhere) but I don't believe it took into account the WDH weight transfer, axle loading, and I think it assumed sea-level altitude and a full-sized trailer box (wind resistance, etc), but also left out a few other items I think.
A spreadsheet "tow calculator" might be a bit of a challange, if one were to include all models and the last 2 to 5 yrs production. Different GVW and different axle GAWR's and changes in tire size, load rating of some models would have to be accounted for. Also, the issue of parasite drag (wind resistance) would be difficult to consider, since there may not be any established baseline for the TM box (all have nearly the same drag coeff.). Due to the low profile, I don't believe the effect of wind resistance has even been considered by TM.

However, there are enough geeks in here that would love to have a new toy (spreadsheet) with which to fool around. I developed my own customized tongue weight load graph awhile ago. By loading my hitch with weights, up to 500 lbs, and plotting hitch receiver deflection vs. load, was able to determine tongue weight by measuring pre/post load heights at the hitch receiver. Why - just for grins!

Quote:
Would there be any interest .......: "What TM model can I safely tow with my xxxxxxx TV?"
Maybe. TM has published a comprehesive Towing Guide (from Trailer Life) on their website - here.

Denny_A
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New (old) 2002 Silverado 2500 Duramax Diesel (7/13/07) 2008 Copper Canyon 32' Fifth Wheel TT
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  #9  
Old 01-03-2005, 12:26 PM
BobRederick
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Default WDH & TV loading

Mountaincamper

I would like to have this spreadsheet to help understand the loading on my '04 3326KS as well as on my GMC Envoy. Is there any possibility of making it generic for all TMs? We could type in our ratings off the plackard.

I have the additional problem that no one has been able to tell me how to set up the WDH on my Envoy which is equipped with load leveling airbag rear suspension. Talk about a mystery... everytime you change something the compressor kicks in and re-levels the truck. The original dealer had so much weight on my front tires that he ruined a 17 inch Michlin towing it home (2000 miles). For instructions on WDH setup, GMC points to trailer dealers, dealers point to hitch makers and hitch makers say to -- didn't even bother to ask. So best I can think of would be to measure weights on each tire as described above. A spreadsheet would be beneficial in the meantime. I didn't even consider additional weight on the TM due to the WDH.

My fix was to loosen the hitch chain 1 link (now hooked at the 3rd link). Everything seems a lot better now, but I am still really not sure if it is set up correctly. With this setup, attaching the TM lowers the front 3/8 inch and the rear is unchanged. It is also quite easy to load the chains. I lower the TM onto the ball to just touch it. Then close the hitch and load the chains. I don't have to lift the TV as before. Works great.

I talked to Ed Lytl at TM Cust Support and he told me the axles on my 3326 were good for 3500# each. That makes 7000# total axle capacity. Trailer ratings on the plackard are GVWR=4916, GAWR=3500, UVW=3870#. Tires are 14 inch Marithon 75R14.

I'm very puzzled.

Bob
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  #10  
Old 01-03-2005, 09:25 PM
RockyMtnRay RockyMtnRay is offline
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Default Pull the fuse for the leveling system

Quote:
Originally Posted by BobRederick

I have the additional problem that no one has been able to tell me how to set up the WDH on my Envoy which is equipped with load leveling airbag rear suspension. Talk about a mystery... everytime you change something the compressor kicks in and re-levels the truck. The original dealer had so much weight on my front tires that he ruined a 17 inch Michlin towing it home (2000 miles). For instructions on WDH setup, GMC points to trailer dealers, dealers point to hitch makers and hitch makers say to -- didn't even bother to ask. So best I can think of would be to measure weights on each tire as described above. A spreadsheet would be beneficial in the meantime. I didn't even consider additional weight on the TM due to the WDH.
Doncha hate trucks that "think" they're smarter than you are?

One workaround might be to disable the load leveling system while you're trying to get the WDH adjusted to provide equal squat on front and back axles.

I'd first load the Envoy for a trip and let the load leveler do its thing. Then I'd pull the appropriate fuse and disable it. Then do the WDH adjustments by measuring wheel well arch to ground distance at front and rear.

If the load leveler simply tries to maintain a level vehicle, it shouldn't do much if any "leveling" after you re-enable it with the trailer hooked up. OTOH, if it works by attempting to get a specific height on the rear suspension, you may wind up front end low, rear high...but at least you could be confident that you've equally distributed the tongue weight between front and rear axles of the Envoy

Since pulling a fuse is a pretty easy thing to do methinks it's worth a try.
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Ray

I use my TM as a base camp for hiking, kayaking, mountain biking, and climbing Colorado's 14ers


The Trailer: 2002 TM Model 2720SL ( Mods: Solar Panels (170 Watts), Dual T-105 Batteries, Electric Tongue Jack, Side AC, Programmable Thermostat, Doran TP Monitor System)

The Tow Vehicle: 2003 Toyota Tundra V8 SR5 4X4 w/Tow Package (Towing & Performance Mods: JBA Headers, Gibson Muffler, 4.30 gears, Michelin LTX M/S Tires, Prodigy Brake Controller, Transmission Temperature Gauge)


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