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Old 03-07-2019, 04:18 PM   #1
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Model: A.C.E. 29.2
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THOR #10300
In need of suspension affirmation

The problem: When we top off water, propane and fuel tanks along with the usual stuff one carries in a 29' MH plus me and DW, we are significantly over the manufacturer's GVWR of 16,000# (although not over the individual front and rear GAWRs).

The details: MH is a 2014 Thor ACE 29.2 mounted on a 190 inch wheelbase Ford F53 chassis. I noted subsequent versions of the ACE 29.# are on the 18,000# GVWR chassis. Soooo, I compared the 190 in. wheelbase F53 16K specs with those of the 190 in. wheelbase 18K for the 2014 model year.

The findings: Both have the same Max GCVWR, and all specs related to the power-train, frame, brakes, steering, wheels, tires and suspension related parts (axles, stabilizer bars and shocks) are identical for the two versions. The only difference is the deflection rates of the springs, although both versions are single-stage, constant rate with the same number of leaves and the same dimensions. One is 550 lbs./in./spring and the other is 650 lbs/in./spring for the fronts, and 950 lbs./in./spring and 1120 lbs./in./spring for the rears. There are absolutely no other differences in the two chassis's I can find.

My solution: I realize no one can alter the GVWR a manufacturer assigns to a chassis. However, realistically, if the only difference is the deflection rate of the two sets of springs, I rationalized I can, in fact, increase my payload (by ~800 - 900#) by installing helper springs (SuperSprings in the rear and SumoSprings on the front to mitigate the deflection rate difference since that is what helper type springs are designed for (stabilizing and reducing squat).

The question: Are there any flaws in my thinking on this matter (besides any legalistic issue)?
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Old 03-07-2019, 04:29 PM   #2
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I don't think that it ever hurts to add some more spring...
But they might not be the limiting factor!
It could be the rear axle, axle ratio, strength of the frame. the wheels, the tires...
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Old 03-07-2019, 04:36 PM   #3
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Originally Posted by jwcorry View Post
The problem: When we top off water, propane and fuel tanks along with the usual stuff one carries in a 29' MH plus me and DW, we are significantly over the manufacturer's GVWR of 16,000# (although not over the individual front and rear GAWRs).

The details: MH is a 2014 Thor ACE 29.2 mounted on a 190 inch wheelbase Ford F53 chassis. I noted subsequent versions of the ACE 29.# are on the 18,000# GVWR chassis. Soooo, I compared the 190 in. wheelbase F53 16K specs with those of the 190 in. wheelbase 18K for the 2014 model year.

The findings: Both have the same Max GCVWR, and all specs related to the power-train, frame, brakes, steering, wheels, tires and suspension related parts (axles, stabilizer bars and shocks) are identical for the two versions. The only difference is the deflection rates of the springs, although both versions are single-stage, constant rate with the same number of leaves and the same dimensions. One is 550 lbs./in./spring and the other is 650 lbs/in./spring for the fronts, and 950 lbs./in./spring and 1120 lbs./in./spring for the rears. There are absolutely no other differences in the two chassis's I can find.

My solution: I realize no one can alter the GVWR a manufacturer assigns to a chassis. However, realistically, if the only difference is the deflection rate of the two sets of springs, I rationalized I can, in fact, increase my payload (by ~800 - 900#) by installing helper springs (SuperSprings in the rear and SumoSprings on the front to mitigate the deflection rate difference since that is what helper type springs are designed for (stabilizing and reducing squat).

The question: Are there any flaws in my thinking on this matter (besides any legalistic issue)?
ive own'd those with the 16k chassis and you are correct , the only difference is the springs,,,.. un less you are have'n problem with it I would do nothing,... but if I did it would be to just add sumo max to the rear,,, the fronts have too stiff of a spring to begin with and hardly ever go over weight...
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Old 03-07-2019, 04:37 PM   #4
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did you weight it on a scale, and what were the weights??
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Old 03-07-2019, 04:47 PM   #5
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Yep, I thought about that, but could find absolutely no differences in the other limiting factors between the 16K and 18K GVWR chassis's -- only the spring deflection rates were different. That's why I thought "helping" the springs would come close to or actually equalize the two platforms' payloads. Additionally, remaining within the 16K GVW is nearly impossible to attain and still be reasonably usable.
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Old 03-07-2019, 04:53 PM   #6
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I have the 29 hurricane right now, weighed it ready to travel...16,500... front 5960 and 10,600 rear... the 18 only has 500lb more springs in the front , and 1000 in the rear...that being 7000 on the front and 12000 on the rear...as yours is 6500 front and 11000 rear... the 6500 front springs ride better... so what I would look for is wear on the rear snubber and how close it is...doing the sumos on the rear net a better stable ride... helper springs or adding a leaf make it stiff.... do sumo's and put them to the rear of the axel and it'll ride and corner like a dream.... the sumo's are a progressive durometer , you'll probley have to use 7'' bags, but check first, and go with the 8'' if you can... use the yellow bags...try to set it up with about 3/4'' preload or close...
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Old 03-07-2019, 04:53 PM   #7
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Yes we weigh on CAT scales every time we go out. Going from memory (scale tickets are on MH at storage facility), we have been as much as 800+ lbs. over 16K GVWR; however we have not exceeded GAWRs (6,500 front and 11,000 rear).
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Old 03-07-2019, 05:00 PM   #8
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Quote:
Originally Posted by jwcorry View Post
Yep, I thought about that, but could find absolutely no differences in the other limiting factors between the 16K and 18K GVWR chassis's -- only the spring deflection rates were different. That's why I thought "helping" the springs would come close to or actually equalize the two platforms' payloads. Additionally, remaining within the 16K GVW is nearly impossible to attain and still be reasonably usable.
how far are you over weight...the gvwr is a factory fed number... they say that's what it will hold..people go way way over that with no problems...I remember back in the day, the first thing I would do was run over to skips spring shop in vegas and add a leaf, they all were under chassised…

sumos will be an up grade and give you great results for your situation..

you could pm the weight to me if you feel better and also feel free to contact me..I've done a lot of R&D work on sumos for and with them... great product when installed proper
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Old 03-07-2019, 05:08 PM   #9
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We went with SuperSprings on the rear (same folks that make the Sumos). They claim the SuperSpring is a progressive type (just like Sumos), which only engages when the OEM springs approach full deflection. So, from what I understand, they only come into play when springs are at or nearly maxed and only progressively then. Same principal as the Sumo???
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Old 03-07-2019, 05:14 PM   #10
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Quote:
Originally Posted by jwcorry View Post
Yes we weigh on CAT scales every time we go out. Going from memory (scale tickets are on MH at storage facility), we have been as much as 800+ lbs. over 16K GVWR; however we have not exceeded GAWRs (6,500 front and 11,000 rear).
Quote:
Originally Posted by vegasruv24.1 View Post
how far are you over weight...the gvwr is a factory fed number... they say that's what it will hold..people go way way over that with no problems...I remember back in the day, the first thing I would do was run over to skips spring shop in vegas and add a leaf, they all were under chassised…

sumos will be an up grade and give you great results for your situation..

you could pm the weight to me if you feel better and also feel free to contact me..I've done a lot of R&D work on sumos for and with them... great product when installed proper
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Old 03-07-2019, 07:39 PM   #11
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Originally Posted by jwcorry View Post
We went with SuperSprings on the rear (same folks that make the Sumos). They claim the SuperSpring is a progressive type (just like Sumos), which only engages when the OEM springs approach full deflection. So, from what I understand, they only come into play when springs are at or nearly maxed and only progressively then. Same principal as the Sumo???
kinda sorta,..they do the same as far as compression, but the sumo's give roll resistance to stop the teetering side to side
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Old 03-07-2019, 07:40 PM   #12
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:whist ling:
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Old 03-07-2019, 07:42 PM   #13
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Originally Posted by jwcorry View Post
Yes we weigh on CAT scales every time we go out. Going from memory (scale tickets are on MH at storage facility), we have been as much as 800+ lbs. over 16K GVWR; however we have not exceeded GAWRs (6,500 front and 11,000 rear).
that's not enough to worry about at all figuring you have the same motor and trans a 26k chassis
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Old 03-07-2019, 08:21 PM   #14
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For sure no power-train issues -- I pass trucks, other MHs & RVs going up Indian Mountain (I-75 in Jellico, TN) all the time even when towing a 5,000# Grand Cherokee.
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Old 03-07-2019, 08:46 PM   #15
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For sure no power-train issues -- I pass trucks, other MHs & RVs going up Indian Mountain (I-75 in Jellico, TN) all the time even when towing a 5,000# Grand Cherokee.

Sounds like you may be near me (Townsend)! We've just bought a Nissan Xterra that we'll be pulling with our ACE 29.3. Good to hear your Grand Cherokee pulls well, as it weighs a bit more than the Xterra.
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Old 03-11-2019, 01:19 PM   #16
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Sounds like you may be near me (Townsend)! We've just bought a Nissan Xterra that we'll be pulling with our ACE 29.3. Good to hear your Grand Cherokee pulls well, as it weighs a bit more than the Xterra.
Is the XTerra going to be flat towed? Stick or Auto?
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Old 03-11-2019, 03:42 PM   #17
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Is the XTerra going to be flat towed? Stick or Auto?

Flat towed. Discussion on another thread: Flat Tow an Xterra?
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Old 03-11-2019, 04:44 PM   #18
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While I don’t condone being overweight I suspect many RVs are over their max allowable on the road. I find it interesting that manufacturers seem to always build on the lowest possible rated chassis. Why not use an E450 instead of the 350 for goodness sake, or an 18,000 lb F53 instead of the 16,000? Lots of coaches leave the factory with less than 2,000lbs of CCC. One thing you can do is travel with your fresh water tank only half full. It’ll save a couple of hundred pounds.
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