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Topic: Coach weight by axle, unbalanced?? (Read 946 times) previous topic - next topic

Coach weight by axle, unbalanced??

I had the coach weighed by a company using individual scales for each wheel/axle and the results were puzzling,  to me, anyway  The coach weighed 1100lbs more on the right side than the left with 850lbs of that at the drive axle, 200lbs at the tag. and 50lbs at the front( the total for the coach was 35,900#) This would seem to point to a very heavy point load on the right side/center of the coach. There doesn't seem to be enough stored on the right in the center section (kitchen and closets) to contribute to such a large imbalance.  I assume that all the water tanks are centered to keep things balanced and the coach is built to compensate for a "normal" load in the interior storage areas.  I'm assuming, also, that it isn't in the basement storage  as it is to far forward.  Does anyone have any ideas/ experience? 
Thanks


Larry Boyd, Alice and Fritz the Cat
'03 U320 40 "Brutus" / '08 Jeep Cherokee

Re: Coach weight by axle, unbalanced??

Reply #1 –
Post your wheel position weights and we can comment with more authority.

I just went through this with 53 coaches at an FMCA pre-rally and am conducting the Suspension Seminar here at the FMCA Convention in Madison. For those here at the Convention, the suspension seminar will be repeated tomorrow (Friday) at 11:30 am Seminar 6.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Coach weight by axle, unbalanced??

Reply #2 –
Here we go!

     
              Front            Drive          Tag                Total

Right        6,250            8,500          3750              18,500

Left          6,200            7,650          3,550              17,400

total        12,450          16,150          7,300              35,900

Thanks,
Larry Boyd, Alice and Fritz the Cat
'03 U320 40 "Brutus" / '08 Jeep Cherokee

Re: Coach weight by axle, unbalanced??

Reply #3 –
Do you have slides. If they are on one side that might account for it. I know we weighed all the coaches at one rally and the none slide coaches were within a couple hundred pounds on the front and the rear and tag were within about 100 pounds. The slide coaches were all pretty close too on front they were within 500 or so on the rear and the tags were within 50 pounds or so.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Coach weight by axle, unbalanced??

Reply #4 –
One slide-on the left.
Larry Boyd, Alice and Fritz the Cat
'03 U320 40 "Brutus" / '08 Jeep Cherokee

Re: Coach weight by axle, unbalanced??

Reply #5 –
Quote from: LBoyd –
I had the coach weighed by a company using individual scales for each wheel/axle and the results were puzzling,  to me, anyway  The coach weighed 1100lbs more on the right side than the left with 850lbs of that at the drive axle, 200lbs at the tag.

Larry,

Which floorplan do you have?  Washer/dryer (~150 lbs) (and where is it)?  Which side is the fridge (~300 lbs) on? 

We've been meaning to make a trip for a weighing session at Escapees' headquarters http://www.escapees.com/smartweigh/ to get the same info on our coach. 

-M
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320

Re: Coach weight by axle, unbalanced??

Reply #6 –
We are WTFS. No washer/dryer, the fridge is on the right.
Larry Boyd, Alice and Fritz the Cat
'03 U320 40 "Brutus" / '08 Jeep Cherokee

Re: Coach weight by axle, unbalanced??

Reply #7 –
Ideal is to have the same percent of capacity on each axle. So, for example, all your axles are close to 85% of the GAWR (Gross Axle Weight Rating) from the plate by the driver's area. That can be achieved by moving your personal gear and with the tag axle by taking more/less weight on the tag.  Increasing the weight on the tag removes weight from the drive axle and shifts some weight to the front axle.

And with your heavy right side, as much of your personal gear, particularly in the basement that you can put on the driver's side, the better.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Coach weight by axle, unbalanced??

Reply #8 –
Question: Isn't the engine/drive train off center? Just enough to account for the difference? I don't know myself as I am not familiar with newer coaches. I do know our '89 Gv sits a 1/2" lower on the passenger rear. This I found out when I tried to put a landing pad under the leveling jack on that side. The axle housing/differential seems positioned toward the pass side also. So the entire engine and drive train weight is also shifted over.
Nitehawk,  Demolition Lady, & our NEW master, Zippy the speeding BB cat.
1989 Grand Villa 36' ORED
Oshkosh chassis, 8.2 DD V8
2006 Saturn Vue AWD

Re: Coach weight by axle, unbalanced??

Reply #9 –
Were you full of fuel?  What about your black and grey tanks, full or empty, both?  And fresh water tank?

180 gallons of fuel            =  1,314.0 lb
17 gallons of LP                =      71.9 lb
112 gallons of fresh water  =    933.0 lb
115 gallons grey water        =    958.0 lb
56 gallons black water        =    466.5 lb

so often we forget this stuff when considering weight.  This can throw weight all different directions depending on coach layout of tanks.  I normally go down the highway starting out with a full tank of fuel, 1/2 to 3/4 tank of fresh water and nothing in either of the waste tanks.  This is also how my coach was weighted (and with full LP).  I get LP as I need it.  Both my fuel and LP are on the right side of coach.  My fresh water is centered in the front.  I don't know if my waste tanks are centered or not.

And to assist in calculating RV liquids:  RV Calculators - Liquid Weight Calculator
1994 U225
build #4514

Re: Coach weight by axle, unbalanced??

Reply #10 –
Oh, another thing.  Is your coach battery setup original?  Or do you have extra batteries?
1994 U225
build #4514

Re: Coach weight by axle, unbalanced??

Reply #11 –
Larry, Here are my weights from May 2010 at a Highway Dept. scale in Nevada (I think).

     
              Front            Drive          Tag                Total

Right        6,100          8,650          3,200              17,950

Left          6,150          9,150          3,550              18,850

Total        12,250        17,800        6,750              36,800

Interesting, you are 1,100 heavy on the right and I'm 900 heavy on the left.
  Tankage:  1/2 fuel, 1/2 fresh water, 1/4 waste, and full LP.

I am totally unaware of this while driving; no noticeable handling issues. Left slide in living room and smaller right slide for closet in bedroom.

Dick
Dick, '03 U320 40' Tag, 2 slides, Coach #6075
Full Timers
2009 Honda CR-V

Re: Coach weight by axle, unbalanced??

Reply #12 –
I was away from the computer for a few days.

Brett,
The biggest problem I have with moving personal grear around is that there isn't any place to put it in the interior of the left side of the coach in my floor plan.  I can shift stuff in the basements but the only place you can put it on the left is in the front compartment which I think is so far forward it won't make much difference , and may put the front axle out of balance, which could be a worse problem.
Dick,
It's interesting that you are heavier on left as I assume you have a rear slide on the right.  Your "liquid" load was very close to mine.  I haven't noticed any problems with driving.
 
 
Larry Boyd, Alice and Fritz the Cat
'03 U320 40 "Brutus" / '08 Jeep Cherokee

Re: Coach weight by axle, unbalanced??

Reply #13 –
LBoyd,

OK, thinking out loud.  I have not worked with Foretravel tag axles, but spent a lot of time this summer working on balancing Monaco product tag axle coaches (Late model Beaver tag axle coaches at a Caterpillar RV Engine Owners Club Rally).

Ideal world for most tags(verify this with those familiar with setting up Foretravels) would be for each axle to be loaded to the same percent of capacity.

On your coach, assuming GAWR of 13880 front, 21,000 drive and 9,000 tag, you are loaded to:
90% on front axle
77% on drive axle
81% on tag axle

My first though would be to reduce PSI on tag to lighten front axle, load drive and lighten tag.

Also,  you might look at your ride heights.  Spec allows for a little variance-- +/- 1/4". I would sure not hesitate to try lowering the drive axle heavier side 1/8" and raising the light side 1/8".  That will shift weight to the light side.  That would be even more advantageous if it was the right that was light as you could raise the right and correct for some of the road camber.

Would like to see some feedback from James Triana or some of the real suspension/alignment gurus at Foretravel.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Coach weight by axle, unbalanced??

Reply #14 –
In keeping this simple, Also remember this applies to the solid front axle, not the independent suspension, that is a whole different game.

Remember the front axle only has a height valve in  the center of the axle to keep the height at a predetermined height = simple. Meaning both front wheels will have nearly the same weight

Next, each side of the drive axle has a height valve to keep the height at a predetermined height Left and Right. Here is where you can get lopsided weights.

Last the Tag Axle must (I am guessing here) have a pressure regulator for a predetermined  amount of weight on the tag axle.  (This is how it is done on the MCI Bus setup.) I do not think the tag has a height valve, just a pressure regulator set about 35 psi. (Again MCI setup), one can adjust the tag regulator to put as much weight on the tag as you like.

AS most issues, there is more to this story, but to keep from driving everyone nuts and me, I surrender.
As usual FWIW

Re: Coach weight by axle, unbalanced??

Reply #15 –
Quote from: Dave M –
Remember the front axle only has a height valve in  the center of the axle to keep the height at a predetermined height = simple. Meaning both front wheels will have nearly the same weight

Next, each side of the drive axle has a height valve to keep the height at a predetermined height Left and Right. Here is where you can get lopsided weights.

Last the Tag Axle must (I am guessing here) have a pressure regulator for a predetermined  amount of weight on the tag axle.  (This is how it is done on the MCI Bus setup.) I do not think the tag has a height valve, just a pressure regulator

Good points from both Dave and Brett on ride height.  Here's what should be the air leveling schematic for Larry's '03 with tag.

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Michelle
Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

2000 U320 36' non-slide / WildEBeest Rescue
2003 U320