Community Forums

dnhxx · 04-27-2018, 10:59 PM

Hello,

We recently had our rig weighed, a 2017 Newmar Bay star 3401, and we are slightly over on the rear axle. Thankfully, we did have the chassis upgraded from the 22K to the 24K chassis. The rear GAWR was about 400lbs over (rated 15,500 - only 500 lbs more than the 22K chassis) with less than 1/2 tank of fuel and empty tanks. The front is 1500 pounds under. Unfortunately almost all the storage inside is behind the rear wheels, and there are only 2 full basement bays in front of the rear axles. I have moved as much as possible. We do plan on removing another couple of hundred pounds, but since the fuel tank is behind the wheels, a full tank of gas (and some fresh water) will add 350-400 lbs on the rear, so we will still be over.

We are concerned because we were told if we were in an accident, we could be liable if they weighed the rig and we were over. I have checked into some suspension upgrades, (i.e. Sumo springs), but I haven't found anyone yet that will say they will increase GAWR, although I am sure they will help the ride and handling, which really isn't the issue.

The only thing I fairly certain will increase the GAWR is to swap in the springs for the 26K chassis, but I do not know if that is possible. Newmar has referred me to Ford, but I haven't got an answer from them yet.

Is it possible to put on an after market upgrade or a suspension modification to increase the GAWR? We only need 600 lbs more....

thank you

Don

kylemcmahon1 · 04-28-2018, 06:27 AM

Nothing you add on will increase the gawr. A bunch of stuff will like you said make it handle better, ride better. But nothing will increase the gawr.

Dale70 · 04-28-2018, 06:59 AM

I might put that a bit differently.

There might be things that will enable the axle to carry more weight,dependent upon what the limiting factor currently is -- and you do not know that.

However the GAWR is set by the manufacturer of the chassis (most likely)
and can therefore can only legally changed by the manufacturer.
Others may have things they think will help carry the load -- but my guess is they will not want to accept legal responsibility of changing the GAWR.

I would suggest you continue working to contact the manufacturer, and redistributing load, neither of which are probably easy.

thx Dale

kylemcmahon1 · 04-28-2018, 08:15 AM

Quote:

Originally Posted by Dale70

I might put that a bit differently.

There might be things that will enable the axle to carry more weight,dependent upon what the limiting factor currently is -- and you do not know that.

However the GAWR is set by the manufacturer of the chassis (most likely)

and can therefore can only legally changed by the manufacturer.

Others may have things they think will help carry the load -- but my guess is they will not want to accept legal responsibility of changing the GAWR.

I would suggest you continue working to contact the manufacturer, and redistributing load, neither of which are probably easy.

thx Dale

Gawr is set by the axle manufacturer. Gvwr is set by the chassis manufacturer. An axle is only rated to carry so much. The chassis manufacturer may put a lower gawr so it falls in line with the gvwr. The problem is unless you can get the axle manufacturer to tell you what the rating is which you will not. They will refer you most times to the chassis manufacturer. So the only way to legally raise a gawr or gvwr is by the chassis manufacturer. Which in most cases if you could find one to do it. It can be very expensive. Reason being they have to make sure in the event of a lawsuit they are covered. It all boils down to CAY. Cover your ass.
With all that said. I would move as much weight forward as you can. If for some odd reason if you got into a major accident. The only time you would get weighed is if someone was majorly injured or killed. Most cases an RV is way to destroyed to get a true before accident weight. Even if the box is still there everything will be thrown everywhere.
Do the best you can with moving weight around. Then enjoy you mh.
I do applaud the op for trying to do the right thing. I wish more people would do it.

Betr2Trvl · 04-28-2018, 08:52 AM

The Ford F53 24k GVWR / 30k GCWR chassis and the 26k/30k differ only on the rear spring ratings. That's it. They both ride on exactly the same 17.5k rated rear axle, but the 24k chassis has rear springs are rated at 15.5k, and the 26k chassis has rear springs rated at 17.5k. They both have the same 9k front axle.

So while the axle ratings total 24.5k, the GVWR is 24k so you have to keep that in mind as well.

The OPs coach sits on a 220 wheel base with a 419" overall coach length, giving it a 52.5% wheelbase to length ratio, which is maybe "fair to average" on a gasser, given 50% being minimum.

As a comparison, the similar Tiffin floor plans are the 31SA as I have that is 33' (57% WB/ L) and 32SA at 34' (55%). So while the OP's Newmar is almost 35', and proably has more rear storage volume than the Tiffins, given the same wheelbase and chassis ratings the Newmar with more coach struture aft of the rear axle probably has no more, if not less, actually weight capacity in the rear basement bays.

With the long(er) rear overhang, and with the heavy rear weight bias it is also affecting / creating the light front end, which isn't good for handling any more than a heavy rear end with a long overhang is (think pendulum effect both fore / aft weight transfer and push / pull). I'd actually be more concerned about the effects on handling more than anything else.........

As you noted, a full tank of gas will make it a bit worse, but as you burn off gas, you'll get better.

Back to the original question...... Can you upgrade the rear springs to those on a 26k? A Tiffin owner recently looked into this as well, and found that once the chassis is built, and the house structure on, it's simply not within any reasonable manner to change out the rear springs. So, you can probably cross that off. I don't remember what, if anything that owner decided to do......

Probably just time to relook at load distribution, proably focusing more on just getting rid of stuff, with due consideration on gas and fresh / waste water load impacts.

Good luck.

Finance · 04-28-2018, 07:25 PM

Weigh it again. I have seen scales significantly in error. I weighed at a Cat scale with a rig before that I knew well and the error was in the thousands of pounds. Told the scale operator it was inaccurate and they reset the scale and did it again. Next weigh was as expected .

dnhxx · 04-28-2018, 10:23 PM

Thank you everyone. That all makes sense. It is a shame the manufacturers build the coaches with storage you cannot use. When we upgraded to the 24K chassis, I thought we would be safe and never have to worry about weight, I didn't realize how heavy the rear would be and that I was really only gaining 500 lbs capacity in the rear (although we are still almost 1000 lbs under GVWR). Next coach, I will check the storage location vs the wheelbase.

Finance, First weighing was with the portable scales on each wheel. Second time just the axles on a CAT scale, we had a full tank of gas so it was about 300 lbs heavier on rear.

I agree best solution is get rid of stuff, and possibly transfer some items to TOAD while traveling. The two back basement bays are empty now, I'll start moving things from the next two up to the front, and move anything light to the back. I weighed almost everything in the coach and where it is from the rear axle and then made a spreadsheet. I can get a good idea of what will happen.

Betr2Trvl - do you think Sumo spring are worth it, and will they make any difference in ride and handling if we just install in the back or should both axles be done?

Don

Betr2Trvl · 04-29-2018, 06:09 AM

Don,

I found the thread the other forum about the guy wanting to see about upgrading his rear axle on his 24k/30k Tiffin. In short, and the details from that are a bit sketchy, it sounds like he found a shop to add a leaf spring to the rear packs. Not sure how, how much, etc., and he is fully aware that it does nothing for the posted ratings. But for him, thought it was a viable path.

As for the Sumos, Tiffin has them as an option, so as this is our first RV, I've never driven one without them, so no before / after for me. I've never felt like we had any sway or push / pull type issues though.

After 26,000 miles in 3 years, I did just get the aftermarket Bilsteins installed last week, but have only driven 20 miles from the shop to storage. Initial feelings are positive (wife says the placebo must be pretty good

), as my primary objective with them was to try to address the lack of damping on smaller abrupt road imperfections (lack of what can be referred to as fast compression dampening which the OEM Bilsteins are lacking; nothing to do with speed, but with the action on the shock). I did drive a short way on a concrete road with the normal section seams which seemed better, also better dive control under braking, and it also seemed a better transition on slow turns. We'll get a better idea on our next long trip, and it will be interesting to see what my wife thinks from both the passenger and driver's seat...... In any case, I'm not a fan of just doing one end of any sort of suspension modification, as the F/R need to work in unison.

So going back to your weight issue, just curious as to how you have so much rear weight and related to that's, what is your posted UVW as that may be a key indicator of how much more weight is put on the rear axle to start with.....

My posted UVW is 19,086#, with a CCC of 3,544 (OCCC of 4,822) which is obviously pretty exceptional for a gasser, and better than a lot of DPs.

Using round numbers, 8,400#s F / 14,200#s R, so ~22,600#s fully loaded for our travels (most recently 4 corner weighed in Perry in March, and that weight was within 100#s of our previous CAT scale weight). So, that means we are 3,500#s over the UVW as posted for our coach.

That includes almost full fuel, full fresh water (81 gal / 672#s) and both of us (~325#s), so that means we carry ~2,500# of "stuff" with us, in our 31SA. I think that's kinda ridiculous, even though are gernerally loaded for trips that are usually from 1-3 months.

Regards

dnhxx · 05-02-2018, 01:10 PM

here are the dry weights from Newmar, weighed at the factory, with empty tanks, I presume.

front 6605, rear 13580.
UVW is stated for our coach as 20525

With full tank of fuel and 20 gallons of fresh water CAT scale showed, front: 7320, rear: 16360, 23680 total. which is 320 under GVWR.

When I weighed everything, I got 1000 lbs in the basement,and 1200 lbs inside. Us and the dogs are 400 lbs. 6605+13580+2600=22785. Add 680 fuel, 160 water and you get 23625 very close to actual weight.

One thing that we have is a dual hitch and carry a bike rack and two bikes. This is probably adding 150 lbs to the back. DW won't let me move them to the TOAD.

WorldCat25 · 05-02-2018, 02:39 PM

We were close to buying a Class A when I started looking at the GVW. It was 22k. Figured we couldn't put all our gear, passengers and fluids and be legal. Talked to another manufacturer. They would upgrade to the 24k chassis but not the 26k. Once you go up from 22k you get the different gearing and it's the same in bth 24k and 26k.

I have no ideal why all Class As in the larger sizes are not on the 26k chassis.

aether_one · 05-02-2018, 02:47 PM

Quote:

Originally Posted by dnhxx

Hello,

We recently had our rig weighed, a 2017 Newmar Bay star 3401, and we are slightly over on the rear axle. Thankfully, we did have the chassis upgraded from the 22K to the 24K chassis. The rear GAWR was about 400lbs over (rated 15,500 - only 500 lbs more than the 22K chassis) with less than 1/2 tank of fuel and empty tanks. The front is 1500 pounds under. Unfortunately almost all the storage inside is behind the rear wheels, and there are only 2 full basement bays in front of the rear axles. I have moved as much as possible. We do plan on removing another couple of hundred pounds, but since the fuel tank is behind the wheels, a full tank of gas (and some fresh water) will add 350-400 lbs on the rear, so we will still be over.

We are concerned because we were told if we were in an accident, we could be liable if they weighed the rig and we were over. I have checked into some suspension upgrades, (i.e. Sumo springs), but I haven't found anyone yet that will say they will increase GAWR, although I am sure they will help the ride and handling, which really isn't the issue.

The only thing I fairly certain will increase the GAWR is to swap in the springs for the 26K chassis, but I do not know if that is possible. Newmar has referred me to Ford, but I haven't got an answer from them yet.

Is it possible to put on an after market upgrade or a suspension modification to increase the GAWR? We only need 600 lbs more....

thank you

Don

What sea lawyer told you that? That could only apply if they could prove the extra weight was a contributing factor to the accident. Chances are if you are in an accident the house is going to explode anyway so the chassis will weigh much less.

Kiawah · 05-02-2018, 07:25 PM

I'll give a slightly different opinion, based on my personal situation with the rear axle on a diesel coach.

In my situation, the rear GAWR was increased 1K. In order to do that, all of the were checked for their individual ratings, and as long as they were equal to or higher than the desired new GAWR they were fine. If they were below, they had to get replaced/increased. In other words, the GAWR is the minimum of all of the rear suspension components.

Checked were: tires/rims/shocks/brakes/axle/air bags (ie springs)/frame attachments/etc.

I had to have my shocks upgraded, and my rear brake air canisters (brake pads and drums were already fine). All of the other individual components were already high enough. When those two items were upgraded, Freightliner put a new GAWR tag on the axle, and Tiffin issued a new door jam sticker reflecting the new GAWR.

Net/net....it may be more than just upgrading the weight carrying springs, and it can be pieces that you don't normally think about when 'carrying' the load.

Betr2Trvl · 05-03-2018, 06:26 AM

Quote:

Originally Posted by dnhxx

here are the dry weights from Newmar, weighed at the factory, with empty tanks, I presume.

front 6605, rear 13580.
UVW is stated for our coach as 20525

With full tank of fuel and 20 gallons of fresh water CAT scale showed, front: 7320, rear: 16360, 23680 total. which is 320 under GVWR.

When I weighed everything, I got 1000 lbs in the basement,and 1200 lbs inside. Us and the dogs are 400 lbs. 6605+13580+2600=22785. Add 680 fuel, 160 water and you get 23625 very close to actual weight.

One thing that we have is a dual hitch and carry a bike rack and two bikes. This is probably adding 150 lbs to the back. DW won't let me move them to the TOAD.

Don, still trying to reconcile your weights / distribution with mine, just out of curiosity since we have similar floor plans (I like to see someone with a Bounder 33C jump in too) but check your UVW if you can - my posted UVW clearly states that it includes full fuel.

Interesting that in either case, your UVW is 1,400#s more that my slightly shorter coach with the similar floor plan. With the longer coach on the shorter wheelbase, makes you think a lot of that is behind the rear axle......

Regards

Crasher · 05-03-2018, 08:04 AM

If the OP is not overloading the tires, I wouldn't be concerned about 500# over the 15,500# RAWR. That is only 3% over when most likely all components have a 10-15% reserve safety factor built into them. As long as the coach handles safely and the tires are inflated to safely carry the load, there is very little reason for concern.