Revised GVWR after axle upgrade??

[TundraTower]

We have a 2014 TT that came with two 3,500 lb axles/springs and very little payload capacity. By the scales the axle/springs run at 96% of capacity at trip weight and within the GVWR. The springs were always flat, it had developed a lean on the kitchen side, and we bent one axle on a long trip out west last summer.

This winter I had the 3,500 lb axles replaced with 5,200 lb axles and springs. This is much better suited for even the original GVWR and I can tow with more confidence.

I know several folks here have done this modification. I'm just wondering if anyone has found a way to rationalize a higher GVWR for the upgraded trailer system? Not from the OEM of course, but a new higher guideline for your own situation.

The new axles, springs, tires, and wheels weigh 200 lbs more than the stock components. I think I can increase the GVWR number by that 200 lbs because that is all below the frame and limited only by trailer brake capacity which now far exceeds what I need.

The next limiting factor on GVWR seems to be the frame/tongue assembly, and that is very difficult if not impossible to evaluate. I tried to decipher how far up the model line the OEM used that frame versus those respective GVWR's, but that is far from exact and only adds a couple of hundred pounds at most.

For those of you that have done this modification, are you just staying around the original GVWR and towing with more confidence and better handling, or have any of you increased the payload limit with the new suspension by some calculation or rationalization?

I would like to have more payload but I know that frame was built to a price point just like the axle sizing. I've tried to explain to DW that the cast iron stove and hot tub are probably not going to make it on the load manifest either way.

Thanks

[JIMNLIN]

5200 lb axles replacing 3500lb axles is a net gain of 1700 lbs or 3400 lbs gross axle capacity.......if the tires and wheels meets or exceeds the 5200 lb per axle numbers.
A gross axle or a gross vehicle weight is measured at the tire/ground interface.

I've inquired about raising a triaxle 18k flatdeck or equipment trailers GVWR with two different trailer mfg after I had higher rated 7k axles installed.
No go....neither mfg would re-sticker the trailer at a higher 21k GVWR than their original registered GVWR......even though their 21k triaxle trailers had the same frame specs.

I wouldn't worry abut a gvwr number for your trailer for no more xtra weight than your looking to carry.

[Huntindog]

I think that most manufacturers use the same frames for several models... If this is true in your case, look to see what was the heaviest one they made with your frame.... I would be surprised if Lippert said anything at this point.. The way things work, it could expose them to problems.

[westend]

That is just a 700 lb increase over what the original GVWR was. I would have no problem rationalizing that.

FWIW, when I did my restoration, I increased my hauling weight by about 500->600 lbs over the GVWR. I checked similar trailers in the same Starcraft product line and found they all use the same 8" tubular beam frame. My rationalization took about 5 seconds. If I had a deck of 2x6, my trailer would be built about the same as some I've used to haul equipment. My axles and tires aren't up to the task but I'm not going to load a skid-steer in there, either.:B

[TundraTower]

I really appreciate your thoughts and comments. For clarification, here are the exact modifications:

Replaced the two 3,500 lb lippert axles with 5,200 lb Dexters. Brakes went from 1.5"x10" to 2"x12". Old brakes were self adjusting which over tightened, so I went with manual adjustment on the new axles.

Replaced the 1,750 lb each springs (3,500 per axle) with 3,500 lb each springs (7,000 lbs per axle). No reasoning for this mismatch other than this is what this shop "usually puts" on travel trailers. The Lippert equalizer between the 2 springs was re-used, as were the hangers.

Wheels were previously 15" and I stayed with 15", but the new axles had 6 lugs so got 5 new wheels.

Previously had 205/75-15 tires and could have kept those, but was due for tires now anyway. The 5,200 lb axle calls for 225/75-15 tires and that is what I went to, in a 10 ply Maxxis. I had steel valve stems installed to enable higher pressures and running now at 65 PSI (still playing with that).

Height increased exactly 3" so I had to re-adjust the EQ hitch. Also a work-in-progress but almost there.

I researched the weight of each component before and after, and know that the new suspension added 200 lbs of weight (axles, springs, tires). This added weight is all "unsprung weight" and should only be relevant to brake capacity but not GVWR, therefore at this point I have only increased my old GVWR by this 200# addition.

EVERYTHING below the spring hangers is new, and of significantly higher capacity. The limiting factor below the spring hangers is the new axles at 10,400 lbs capacity.

WHAT DO I WANT? Before the change and trip ready we typically weighed 7,600 lbs against a 7,698 GVWR (we were 7660 as we left for Utah, trip of a lifetime). We want to replace two rocker chairs with recliners + haul 4-5 gallons of water in the tank + transfer 50-100 lbs of stuff from the truck to the trailer. With extra unsprung weight of the new suspension I figure new limit is now 7,898, but that just covers what I was already hauling. So with the extra weight listed above I'm looking to rationalize my way to a limit in the ballpark of 8300-8400 lbs.

AND, I want to carry what I have with much more confidence, which I have accomplished anyway.

[goducks10]

westend wrote:

goducks10 wrote:

westend wrote:
The weight ratings are calculated from the weakest link in the chain. In your case, that would be the frame and the weight it was designed to carry. Since you haven't upgraded the frame, the "official" GVWR remains the same. The practical limit of carrying is not going to be that much greater.

You don't know that for sure. How do you know that it's not his springs and tires? Thats why a call to Lippert is the real answer. No one really knows. It'a all speculation at this point.

Assuming a mfg builds to a certain engineering design, i.e. doesn't put a very heavy frame on a weak suspension but designs for all parts to meet a criteria.

If he has upgraded the suspension, what is then the limiting part of the puzzle?

I hear ya, just thinking that maybe it's his axles and tires. An 8" frame is pretty robust. I have an 8" frame on my 5th wheel with 11,400 for GVWR. Running 5200 lb axles and 15" 225 tires. On my previous Tt I had an 8" frame, 4400 lb axles and 15" 225 tires. It had an 8400lb GVWR. Both GVWR were tied into the axle rating.
If the OP did nothing more than upgrade his axles and tires then he could comfortably haul at the TT's GVWR with out concern. I'm not sure if he's looking to carry way more or carry the OEM weight with a cushion.

[dodge_guy]

westend wrote:

goducks10 wrote:

westend wrote:
The weight ratings are calculated from the weakest link in the chain. In your case, that would be the frame and the weight it was designed to carry. Since you haven't upgraded the frame, the "official" GVWR remains the same. The practical limit of carrying is not going to be that much greater.

You don't know that for sure. How do you know that it's not his springs and tires? Thats why a call to Lippert is the real answer. No one really knows. It'a all speculation at this point.

Assuming a mfg builds to a certain engineering design, i.e. doesn't put a very heavy frame on a weak suspension but designs for all parts to meet a criteria.

If he has upgraded the suspension, what is then the limiting part of the puzzle?

There more than likely isn't! Especially considering he has an 8"Ibeam frame, just like my 11k lb trailer.

[westend]

goducks10 wrote:

westend wrote:
The weight ratings are calculated from the weakest link in the chain. In your case, that would be the frame and the weight it was designed to carry. Since you haven't upgraded the frame, the "official" GVWR remains the same. The practical limit of carrying is not going to be that much greater.

You don't know that for sure. How do you know that it's not his springs and tires? Thats why a call to Lippert is the real answer. No one really knows. It'a all speculation at this point.

Assuming a mfg builds to a certain engineering design, i.e. doesn't put a very heavy frame on a weak suspension but designs for all parts to meet a criteria.

If he has upgraded the suspension, what is then the limiting part of the puzzle?

[goducks10]

westend wrote:
The weight ratings are calculated from the weakest link in the chain. In your case, that would be the frame and the weight it was designed to carry. Since you haven't upgraded the frame, the "official" GVWR remains the same. The practical limit of carrying is not going to be that much greater.

You don't know that for sure. How do you know that it's not his springs and tires? Thats why a call to Lippert is the real answer. No one really knows. It'a all speculation at this point.

[westend]

The weight ratings are calculated from the weakest link in the chain. In your case, that would be the frame and the weight it was designed to carry. Since you haven't upgraded the frame, the "official" GVWR remains the same. The practical limit of carrying is not going to be that much greater.

[boosTT]

goducks10 wrote:

TundraTower wrote:
bossTT: My frame is made by Lippert and the tag from them is very readable with SN, PO#, etc. It also says it is specifically for the 264L with rear cargo rack (which I have removed).

How would I research the basic load rating of the frame itself as you suggest?

Call Lippert with your frame number. I've had to call them before and they were decent enough to work with.

Customer Service
Email: customerservice@lci1.com
Phone: 574-537-8900

That is what I would do.

[goducks10]

TundraTower wrote:
bossTT: My frame is made by Lippert and the tag from them is very readable with SN, PO#, etc. It also says it is specifically for the 264L with rear cargo rack (which I have removed).

How would I research the basic load rating of the frame itself as you suggest?

Call Lippert with your frame number. I've had to call them before and they were decent enough to work with.

Customer Service
Email: customerservice@lci1.com
Phone: 574-537-8900

[TundraTower]

bossTT: My frame is made by Lippert and the tag from them is very readable with SN, PO#, etc. It also says it is specifically for the 264L with rear cargo rack (which I have removed).

How would I research the basic load rating of the frame itself as you suggest?

[TundraTower]

thanks for the replies so far.

One of the early replies indicated that the axles, springs, and frame had come as a "matched set" from the factory and that perhaps I had screwed that up. I submit that a 30'x8'x12' box weighing almost 4 tons that is matched to a suspension system running at 96% capacity as it sits in the parking lot is not a match made in Heaven. I cringe when I think about the dynamic forces as I drag that around the mountain curves in the Smokeys at any speed.

DODGE GUY, thanks for the research you did. My frame is indeed an 8" I-beam, and the tongue is mounted to the bottom of that I-beam frame. The tongue is a 6" x 2" box beam (formed not extruded), and surprisingly they have added flat plates between the tongue structure and square frame to weld to and minimize those stress concentrations. Now you have me intrigued. Next time you are under there, see what the height is of your frame I-beam??? I would suspect at your length it is 10 or 12". And at 10 years old, I wonder if yours is made fundamentally stronger than mine, back before greed just over-whelmed all other motives for manufacturing?

The suggestion of putting extra weight in the center over the axles is also intriguing, and an angle I had not considered. ON the passenger side of the middle we have the kitchen and most of the cabinets, and on the drivers side we have an extra long/deep slide, maybe 30" x 15' (couch + dinette). Plenty of places under the couch and dinette seats to pack stuff, but is there a weight/load consideration for what goes onto that big slide???

[dodge_guy]

I wouldn't put much faith in what the manuf says. After seeing the poor excuse for welds and the fact my TT with an 11k lb GVWR that came with cheap LR "D" tires, not to mention plastic bushings in the springs and hangers.......... they have little value to me. I would do my own research on the frame.