kurtsue

Front Axle Weight Way Different Side To Side

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kurtsue   

Hi ya’ll Happy New Year to all.

 We are at Sumter Oaks in Bushnell Florida and got Smart weighed today. We have a 2012 Newmar Ventana LE. When weighed the front driver axle weighed 5700 LBS. The front passenger axle weighed 3770 LBS.

Has any one had this much difference in weight from one side to another? Could this be an air bag issue?

The coach rides and steers fine. I carry 110 LBS of air in the tires.

Any help will be appreciated. Thanks, Cheers to all.

 

 

 

 

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Seems like more of a difference than I'd expect. Was the measurement on the rear axle(s) as out of balance as the front? Without knowing the specifics of how things are laid out in your coach it would be hard to know what could cause this, that is if the measurements are accurate. Even a fully loaded water tank or fuel tank wouldn't account for this much of a difference left-to-right, so it would have to be something pretty big.

To my knowledge if the coach is sitting level when weighed the air bags would not account for this discrepancy.

When I get results which are skewed so much my first step would be to re-measure, and I'd do so on another set of scales (hopefully scales known to be accurate.)

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RayIN   

How long since ride height was checked/set? That is the first step towards even weights on the corners, and also for total wheel alignment.

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manholt   

That's the Escapees Park and they do a good job, I have used them before, but never camped there.  I just called and made an appointment.  Ray, you maybe right about the ride height, as the unit is portable and I have seen it in use at the camp site, drive onto scale then back up...think that would give a bad reading.

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wolfe10   

I agree with RayIN,

Very first thing to check with out of balance weights is  RIDE HEIGHT. Don't know whether your coach has two ride height valves in front or rear, but start on the axle with two and get it to spec.  Then "average" the measurements on the other axle.

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Wheel alignment and air bags nor ride height adjustment have absolutely no effect on actual weight on the weight on a single wheel. Inaccurate scales could be a culprit, but then again unless all four corners were not weighed on the same scale, the scale is probably ok.  Yes it needs to be reweighed to make sure the right front tire was not resting partially off the scale. Most holding tanks are set up to drain to the left side of a coach, but are usually crosswise of the coach to make sure that the weight is evenly distributed right to left. The fuel tank itself can weigh as much as 200# empty, and fuel weighs close to 7# per gallon, so 150 gallons of fuel could weigh 1150# plus the tank could be1350# then also the driver may outweigh the passenger. Of course I don't know where the fuel tank is located in your coach, just trying to point out some possibilities for the weight difference. Yes I would be a little concerned about the difference and try to correct if possible, but please don't panic, I would start by having the two fronts reweighed if possible as stated above.

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kurtsue   

Hi all thanks for all the great replies on this . Al,the smart weigh tech double checked the front weights, and when finished his thought was that the air bags were out of balance. Don’t know what that means as if the air bags inflate and don’t leak air how can they be out of kilter. Also the back axle weights are within 450 LBS of one another, 8550LBS. On back right and 8050 LBS on back left. The GAWR on front is 12,000LBS the rear being 19,000LBS. The weights are within these limits. If ya’ll have any other thoughts please don’t hesitate to reply. Also this proves not to just weigh the axles as one weight. Weigh them on the wheel points.  We are heading to Marco Island for the Christmas vacation so please all drive careful if driving today.

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wolfe10   

It is the RIDE HEIGHT VALVES that determine the amount of air to the air bags. Said another way, air bags "just do what they are told" by the ride height valves.

With very rare exception, coaches have three ride height valves-- two on one axle, one on the other.  Adjustment is started on the axle with two.

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Air bags only provide a cushion between the wheels and the chassis. It doesn't matter if the pressure in one bag is 30# and the other is 50#, that only means that the chassis on the 50# side will be higher in relationship with the axel than the 30# side, this is the reason for ride height, to proportionally raise the height of the chassis in order to make the chassis as level as possible. It actually compensates for the weight difference on each corner, without the ride height valves, the driver front side would be sagging compared to the passenger front side. In other words, what Brett said is true, I'm only trying to give an example for better understanding.

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3 hours ago, kurtsue said:

Also this proves not to just weigh the axles as one weight. Weigh them on the wheel points.  

Yes this is a very good reason to use four corner weighing, this is the only way to determine if you need to redistribute the weight inside the coach, or in the storage compartments, so that the tires are all doing their very best to carry their share of the load.

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I think it would be a good idea to set the ride height so the bags in front are at the exact same height. This is what I think is happening.B) When one bag is higher it is carrying more weight. They may be the same pressure but the taller bag will start lifting the weight on the front faster than the shorter bag. This is why the first thing they do when working on the front end is to adjust the ride hight. 

Bill

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RayIN   

Anyone who thinks ride height is not related to corner weight has never been involved with auto racing. I can post a page of links but most articles are so technical they would not bother to read them. Ride height is perhaps the single most important starting point when designing a race car.

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Cantilevers on a race car work quiet differently from air bags on a truck or motorhome. Yes you do need to set the ride height on a truck or motorhome in order to achieve four wheel alignment on a T or M, but not for purpose of altering weight. Altering weight through of the use cantilevers in order to change the air flow around the vehicle is why the importance of ride height in a race car, also weight distribution is very important in a race car because the aerodynamics are very important when one is traveling at 190+ mph in very light racecar, if you don't add weight through aerodynamics to your race car, then you will leave the ground at tremendous speeds.

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manholt   

Race boats react in the same manner (no wheels) thru aerodynamics, speed, choppy water and wind...get wings and you can do cartwheels!  You got to compensate for the weight off all those horses behind you! :o:)

Back to coach.  Couple of hundred pounds on one side=load, 2,000+ you got a ride height problem!

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1 hour ago, manholt said:

Race boats react in the same manner (no wheels) thru aerodynamics, speed, choppy water and wind...get wings and you can do cartwheels!  You got to compensate for the weight off all those horses behind you! :o:)

Back to coach.  Couple of hundred pounds on one side=load, 2,000+ you got a ride height problem!

Are you saying weight imbalance affects ride height or that ride height affects weight imbalance?

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manholt   

Richard.

I believe that not having correct ride height of coach, will give a skewed weight reading!  What else would explain a 2,070 pound difference between R & L, on front axel ?

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Not disputing the ride height difference but I am having a hard time seeing how a 1 inch difference over an 8 foot span could shift 2,000 pounds from one side to the other.  One of the first things I would do would be to unload the coach and have the coach re weighted. If there is still a 2,000 lb difference then it has to be how the coach was laid out. What items are on each side that may effect the weight. i am trying to visualize what could make that much of a difference. :o:wacko:

Herman

Edited by hermanmullins
Changed Now to NOT. Sorry it didn't look right to me either.

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wolfe10   
33 minutes ago, BillAdams said:

  What is the front axle weight rating?  3770 sounds really light.

From the original post: " When weighed the front driver axle weighed 5700 LBS. The front passenger axle weighed 3770 LBS. "

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wolfe10   
2 hours ago, richard5933 said:

Are you saying weight imbalance affects ride height or that ride height affects weight imbalance?

Indeed, even small "out of spec" on ride height can have material impact on weight distribution.

How many of your really strong friends would you have to line up to lift, say, the right rear corner or your coach up an additional one inch?  Yes, thousands of pounds can be shifted using ride height adjustments/out of adjustment.

In fact, I have used ride height spec tolerances to help balance weights.  So, if ride height spec, is say 8" +/- 1/8"  to help equalize weight side to side, you could set the heavier wheel position ride height valve at 7 7/8" and the lighter wheel position ride height valve at 8 1/8". Yes, these adjustments also affect weight distribution on the other axle.  Four individual wheel scales make fine tuning ride height a LOT easier. 

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RayIN   
14 hours ago, manholt said:

Richard.

I believe that not having correct ride height of coach, will give a skewed weight reading!  What else would explain a 2,070 pound difference between R & L, on front axel ?

 

OOPS! Just noted I quoted your post instead of richard, sorry.

Right!

Looking into this further, curtsue and I have exactly the same axle GVW's, 19K rear, 12K front. Rear weighs more than front, agreed? Now raise RF corner 1" or  more, what happens to weight on LF corner?  The rear axle weight will prevent the RF corner from dropping to equalize front corner weights-UNLESS anyone thinks the frame will flex enough to equalize front corner weights. Thus my race care analogy.

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FIVE   

As far as side to side weight differential is concerned, one of my manuals, don't recall if it was Spartan or Freightliner, said the maximum difference should be no more than 5%.

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wolfe10   

There are some floor plans that are absolutely out of balance left to right and the designers knew this before the coach even left the drawing boards.  But, interior designers often trump engineers in coach design.  The "poster child" for this is galley slides.  Weight of slide, galley cabinets, and appliances are on one side, with perhaps a recliner and maybe a table on the other side.

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jleamont   
2 hours ago, wolfe10 said:

The "poster child" for this is galley slides.

That's us! Two slides on one side, both heavy as the galley is the largest. They used the bathroom, aquahot unit, Nocold 1200 and washer dryer to offset. I have ruined some of their counter weights with the washer/dryer and residential refrigerator removed. When my slides are deployed the coach readjusts to re-level the coach as it leans to the drivers side (air leveling).

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