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Old 05-15-2013, 06:29 PM   #15
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Originally Posted by Sky_Boss View Post
While I agree with most of what you said, in the interest of total fairness...

Newmar de-rated my Spartan MM IFS front axle from 14600 to 14200 for...drum roll...tire size. Yes, if my rig is properly balanced from left to right I can put the full 14600 on the front axle without having to run the maximum 120 PSI in my 305/70Rs. If I was perfectly balanced I would never need more than 110 PSI. I don't want to run more than 110 PSI simply because of ride quality. Newmar took the conservative route and reduced the axle rating for situations where the balance was not as even.

I have to assume this was a (pardon the pun) a balancing act for cost control. Clearly the drive and tag axles have no need for a 315/80Rs. My current tires will NEVER be stressed at all in the rear. Only the front tires are being put to the test. So, instead of 8 really expensive tires, I need 8 almost, really expensive tires.

Anyway...this should give the OP some more background on factors that are out of his/her control.
And on our DSDP Newmar had Spartan replace the 12,000 OEM axle with a 14,600# unit and issued us a new "modified" weight sticker, however they used the OEM tires which limited us to 13,200#'s. Michelin even got in on the act and allowed the tires to be rated at full capacity with only 120 psi even though the tires required 125 psi.
Now we've replaced the tires and wheels, went up to 305/70's on the front so I can use the full 14,600# rating.
Another interesting thing is that while at Spartan the mechanics wondered why Newmar had derated the rear axle to 19,000#'s, they stated that there was no reason for that as it was a 20,000# rated axle. The only thing we can think of is a CYA since most people overload their rigs.
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Old 05-15-2013, 07:05 PM   #16
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Originally Posted by Maritimer View Post
Hi folks,
I'm wondering what the legitimate methods of increasing GVWR are? Tires and shocks seem to be the easy answer but I'm wondering what other things can be done.
Thanks!
Legally no, the only one that can change any of the weight ratings is the manufacturer of the completed vehicle. Only they are allowed to issue or change the ratings given to the vehicle.
Newmar did it on ours when the front axle was changed.
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Old 05-15-2013, 07:22 PM   #17
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So OEMs have some magical power that say a capable fabrication shop with mechanical engineers on staff wouldnt?

Certain components could be changed to increase load. Cost wise... well the benefit would have to be weighed against the cost.

I can't answer about "Magical Power", you can ask them.
You and also ask the Feds as they ONLY accept what the OEM puts on the sticker.

That makes it legal. Mystical or not.

Maybe you could go into business, be accepted by the FEDS as a builder, then rebuild everything and get them the accept your new ratings based on your engineering staff. Then they would be legal.

If you are illegal aka over weight you have major problems in a accident case.

As an individual your educated guesses as to what works does not go far with the Feds. in making something legal under their system and laws.
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Old 05-15-2013, 09:04 PM   #18
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Originally Posted by Oldme View Post
I can't answer about "Magical Power", you can ask them.
You and also ask the Feds as they ONLY accept what the OEM puts on the sticker.

That makes it legal. Mystical or not.

Maybe you could go into business, be accepted by the FEDS as a builder, then rebuild everything and get them the accept your new ratings based on your engineering staff. Then they would be legal.

If you are illegal aka over weight you have major problems in a accident case.

As an individual your educated guesses as to what works does not go far with the Feds. in making something legal under their system and laws.
you danced around but didnt answer the question. Might as well have saved the key strokes and typed "only OEMs and the infallible gov't can issue weight ratings...lol
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Old 05-15-2013, 10:39 PM   #19
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Did you ever watch Monster Garage? A bunch of shop mechanics decided to play engineers and construct monstrosities that for the most part failed miserably. If you want a higher carrying capability, look for a coach with the carrying capacity you want, instead of looking to some garage mechanic. If you want to do a proper way of upgrading a coach for added load capacity, you'll spend a lot less money buying the right coach in the first place!
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Old 05-16-2013, 07:29 AM   #20
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Originally Posted by WeatherTodd View Post
So OEMs have some magical power that say a capable fabrication shop with mechanical engineers on staff wouldnt?
It's been my experience that most fabrication shops don't have mechanical engineers. They have people who build things that call themselves "Engineers", without the education that title might infer. The Magic is math, it allows prediction of outcome based on scientifically verifiable testing.

OP, if you want carry weight focus on a Tag axle MH.
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Old 05-16-2013, 12:48 PM   #21
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you danced around but didnt answer the question. Might as well have saved the key strokes and typed "only OEMs and the infallible gov't can issue weight ratings...lol

NO Dancing.

Your questions WAS answered and YOU finally comprehended the answer; when you typed "only OEMs and the infallible gov't can issue weight ratings". That is the way the LAW is setup.

Maybe YOU can change the law.
Otherwise it is what it is.

Let us know how your discussion with the OEMs and the Feds go.
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Old 05-16-2013, 12:51 PM   #22
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Most likely there are no legitimate options as this capacity is typically determined by the frame nd then the other systems are built around the frame to support it's max load. The only way to increase capacity is to increase frame strength or replace the frame.
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Old 05-17-2013, 10:38 PM   #23
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NO Dancing.

Your questions WAS answered and YOU finally comprehended the answer; when you typed "only OEMs and the infallible gov't can issue weight ratings". That is the way the LAW is setup.

Maybe YOU can change the law.
Otherwise it is what it is.

Let us know how your discussion with the OEMs and the Feds go.
so who certifies who? Do the OEMs funnel money to the DOT or does the US Govt have a merry band of top level engineers backed by the full faith & credit of the United States?

Because from where I sit... everytime there is a recall it looks as though BOTH have failed miserably. But you keep following the law as its spoon fed to you. Surely your motorhome brakes or tires wont fail since those institutions have you covered!
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Old 05-17-2013, 10:46 PM   #24
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Most likely there are no legitimate options as this capacity is typically determined by the frame nd then the other systems are built around the frame to support it's max load. The only way to increase capacity is to increase frame strength or replace the frame.
Not really, the capacity is that of the LOWEST rated component of the unit. It could be the frame, the brakes, the bearings, the wheels, the tires, the suspension, the transmission, the engine.
That's what the engineers at that manufacturing plant go through when deciding on a weight rating
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