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Old 04-30-2014, 09:43 PM   #1
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2014 31' Classic
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Talking The scales story 2013

I took our Classic loaded with all personal gear and water in the fresh tank and the truck loaded with nearly all gear we would take boon docking to the local Love's CAT scales. I crossed the scales with the trailer attached, then dropped the trailer at the back of their lot (leaving the ProPride stinger in place in the truck receiver) and crossed with the trailer only.

The results are in the top half of the spread sheet below.

The next day, I took my two sets of four wheel scales to the storage unit and jacked the unit up on each side to slide a scale under each wheel and the jack stand. The results are in the bottom half of the spread sheet.

Adding to the original empty weight is the 800 watt solar installation with four 92 pound lifeline batteries on the front in a stainless steel enclosure and a Magnum converter/inverter and the disc brake conversion.

My 2013 25FB International Serenity was heavy by several hundred pounds on the curb side rear wheel and so is the Classic. A friend stated today he has replaced the curb side rear tire several more times on his 2005 25' Airstream than the other three due to more loading. I wonder if many Airstream rear curb side wheels seem to have a heaver loading?

The numbers show I still have lots of weight capacity in both the truck and the Airstream. The truck has a 5,500 pound rated front axle and a 6,010 pound rated rear axle so legally can have a 11,510 gross vehicle weight. The trailer has another 900 pounds or so load capacity. The gross combination vehicle weight is 20,000 pounds.
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File Type: pdf Classic scale results 29APR2014.pdf (32.8 KB, 434 views)
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Old 05-07-2014, 05:05 PM   #2
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A thread I've been looking forward to for some time. Our rigs are similar in TT type except for suspension differences in both vehicles, and overall length. I expect my GCW to be quite close. We've touched on all of this in other threads.

Did we miss the TV & TT HITCHED, (but WD inactivated) CAT Scale Reading? Load transfer by WD activation; per axle, overall, and per wheel, indvidually, since you have the portable scales. (I was pulled off the road by TX DOT on Monday for a Level One inspection, and we talked about the new scales carried in back of those lowered Tahoes).

Frame twist on both vehicles is likely -- WD activation can put a few thousand pounds torque across the rig -- so static measurements tell a story about weight distribution. It may not be an even application across any given axle.


Hard to beat this handy analysis, the Ron Gratz Chart as a starter.

Weighing #1 -- TT attached and Weight Distribution Activated
Let Front Axle Load be "FA1" 4640
Let Rear Axle Load be "RA1" 5460
Let TT Axles Load be "TT1" 7960

Then, while in same position on scales, take
Weighing #2 -- TT attached and Weight Distribution Not Activated (WD bars unloaded, but hanging in place)
Let Front Axle Load be "FA2"
Let Rear Axle Load be "RA2"
Let TT Axles Load be "TT2"

Then, drive off scales and drop TT. Return to scales and take
Weighing #3 -- TV only -- TT Not Attached
Let Front Axle Load be "FA3" 4980
Let Rear Axle Load be "RA3" 3960

From the above values, you can calculate:

TV weight = FA3 + RA3 8940

Gross Combined Weight = (FA1 + RA1 + TT1) 18060
{should also be equal to (FA2 + RA2 + TT2) if scale weights are correct}

TT Weight = Gross Combined Weight - TV Weight 9120

Tongue Weight = (FA2 + RA2) - (FA3 + RA3)

Load Transferred to TT Axles
when WD System is Activated = TT1 - TT2



For the rest of us, this .pdf form on how to weigh tire loads individually should suffice.

HOW TO WEIGH RV: Bridgestone & RVSEF [.pdf]

" . . My 2013 25FB International Serenity was heavy by several hundred pounds on the curb side rear wheel and so is the Classic. A friend stated today he has replaced the curb side rear tire several more times on his 2005 25' Airstream than the other three due to more loading. I wonder if many Airstream rear curb side wheels seem to have a heaver loading?"

If nothing else, the starboard tires are the ones to hit curbs, more potholes and get off the paved surface more often in normal driving. If weight is higher, then it just adds to the problem. Higher loadings on the starboard side will drag the TT in that direction more easily. I have more than once been surprised by not centering a several thousand pound single pallet (out of a dozen otherwise in rows of two) on a flatbed and been able to tell the difference at the wheel . . she is gonna move that way faster.

And a trailer that does that sets us up for a loss-of-control accident. A few pounds may not matter, but why not get things as good as can be if all it is is moving some packed things around in the interior? A few inch drop-off at road edge is enough to upend the rig if the driver tries to fight it. I see this all the time both as it happens in traffic ahead of me, or in reading the aftermath. I want the the least exposure to this potential problem.

The second question would be what tire pressure is now set for baseline purposes on the TV (as TT tire pressure is always to be to sidewall maximum)? What are the ranges for Steer and Drive on your truck as given by DODGE (door placard) and where are you starting within those manufacturer guidelines (Tire engineer CapriRacer notes that 2008 revisons are best for those of us with older vehicles where comparisons can be made).

Tire life, fuel economy, wind-handling and best braking are all related. Fewest steering corrections per 100-miles is part of it. Best mechanical baseline of the rig, individually and combined, is truly where the rubber meets the road.

.
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Old 05-07-2014, 09:29 PM   #3
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And here's a fill in the excel version of Ron's calcs. Has the results for my new Sierra 2500HD Duramax, FC25 Rear Bed, Propride. Trailer full water and other stuff. Truck with me, wife, dog, misc stuff and full fuel.
Attached Files
File Type: xlsx Cat Calc Sierra 2500 5-3-14.xlsx (37.4 KB, 56 views)
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Old 05-07-2014, 09:36 PM   #4
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Switz, based on what I have learned here you may want to make adjustments to get more weight back on the front axle. Combo of higher jacks on the tension bars or change in the height of the stinger. With my truck change I got lucky on the setup. Needed to change the install height of the stinger, 2500 has a higher hitch than the 1500. Tried the same 6.5 inch lift I had with the old truck and the axle weight with hitched with WD engaged and the truck by itself were the same. Wheel well method was within 1/2 inch.
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Old 05-07-2014, 10:02 PM   #5
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More Data

Quote:
Originally Posted by slowmover View Post
A thread I've been looking forward to for some time. ...
.
There is some additional data at http://www.airforums.com/forums/f438...ml#post1436272


I wonder if there is some way for the Moderators to pull this information together under a new thread heading?
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