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Old 12-08-2009, 11:22 AM   #85
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Originally Posted by kennethowens View Post
...I noticed that flyfisher in post #30 of this thread came to a conclusion(maybe temporary) about loading the rear of his trailer...
well THIS brings us back on topic, thanks for the reminder.

fly's scale report in post #32 ((for the truck)) is very similar situation to what airstream01 will have for his big move...

fly's trailer is longer/heavier but the truck axle ratings and loads are similar.

and his findings that the TONGUE is significantly heavier than the a/s estimates is a COMMON finding here.

shifting any heavy trailer payload to the axle region is a good thing, when space is available.

with rear door units (with front beds) there may be a tendency to take LOTs of stuff forward to the bed zone...

which can grow the tongue weight quickly.

sorting out the 'ideal' packing/loading for each floor plan takes effort, and feedback from the weight platforms.

cheers
2air'
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Old 12-15-2009, 02:22 PM   #86
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Just for kicks, I weighed my truck today. With a half tank of diesel (~15 gal) and me NOT in the truck, the front axle weighed 4340 and the rear was a 2920. My front bumper must weigh an un-godly amount. Anyone wanna trade for a stock bumper??
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Old 12-15-2009, 02:38 PM   #87
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so the front axle is 4340 UNhitched and 4140 hitched AND with the w/d bars tensioned.

it's not just he weight of the bumper, but the OVERHANG in front of the axle.

this magnifies the load at the axle.
_____________

not to hijack this thread but i would imagine a local salvage yard OR truck repair shop would have oem bumper for your truck.

or online'bay or other vendors.

they built a zillion of these truck, so parts are plentiful.

and a normal bumper might improve mpg slightly (shape/drag AND weight)

cheers
2air'
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Old 12-15-2009, 02:41 PM   #88
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its amazing what the options add...
that F250 has a 5900# curb weight

my suburban is somthing like 1500# over published numbers, on account of the 496ci option
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Old 12-17-2009, 11:22 PM   #89
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Input from the truck stop side of CAT scales

Let me pass this along from a message I received from Mr. Dave Kemp affiliated with the Iowa80Group of truck stops. He is not a member here and I will not suggest that an interplay of questions & responses will happen easily. I feel this adds to the knowledge base on this topic, so let's go...

Dave starts discussing errors noted by 87MH in post #3 and 2airishuman in post #8, and then adds some other useful perspectives. And then goes on to explain other details. It's a good read. From Dave Kemp:
Hi Administrator- an open message .... re the thread "visited CAT scales - the numbers are in..."

Amidst this thread, and others, there are references to errors of 20lb, and that they seem reasonable. Here's a little more depth on the subject:

The variation you see between weighs and reweighs is not a matter of error, it's a matter of NIST Handbook 44 rules for scales certified LEGAL FOR TRADE.

CAT Scales are rated for 200,000lbs of gross weight distributed over three platforms:
Scale 1 ('steer axle') is rated for 60,000lbs.
Scale 2 ('drive axle') is rated for 60,000lbs.
Scale 3 ('trailer axle') is rated for 80,000lbs.
This yields total capacity of 200,000lbs.

Per Handbook 44, a scale certified LEGAL FOR TRADE -MUST- be set up with 10,000 increments... that is... 0.0001 of it's total capacity... therefore, a 200,000lb truck scale is incremented in 20lb steps.

SINCE our scale has THREE individual segments, EACH SEGMENT must be incremented per that rule.

ALSO, per Handbook 44, the scale MUST ROUND to the nearest 20lb increment. At 11lbs, it rounds to 20. At 9lbs, it rounds to 0. Within the window of 9 to 11, the range is UNDEFINED, and as such, will toggle one increment (20lbs) based on a rather small change.

Furthermore, this rounding MUST occur ON EACH SCALE ELEMENT... SO...

If your actual weights are:

5650, 8709, and 7431, the scale could indicate:

5640 or 5660, 8700 or 8720, 7420 or 7440. Gross weight, therefore could be anywhere from 21760 to 21820, and be totally correct and accurate.

WHEN variation occurs, it's usually attributable to motion on the scale. Wind blowing, passengers moving, liquid loads, even rough-idling engines cause variation. Having brakes set induces a certain amount of binding between scales, and the more recent proliferation of air-ride suspension systems, particularly trailing arm suspensions, leveling valves 'jacking' the suspension with brakes applied causes some interesting antics with weight distribution between tow vehicles' steer and drive axles.

IN any event, the CAT Scale is a perfectly viable method for determining weight balance of road vehicle and trailer weights- just keep in mind that the scale is intended and incremented for weighing over-the-road tractor-trailers, so... even though it seems 'heavy' by average conception, weighing a light truck or passenger car with trailer on a CAT Scale is akin to measuring a Pinewood Derby car (or a quarter-cup of sugar) on a bathroom scale.

Regardless of what the truckstop personnel say, dropping of landing gear or disconnecting a trailer while on a CAT Scale is not allowed, and for many reasons. IF a soveriegn wieght for the trailer is necessary, weigh the entire assembly, then pull off, park, block, and unhitch the trailer, and weigh the tow vehicle independant of the trailer, and subtract the differences.
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Old 12-17-2009, 11:51 PM   #90
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interesting info bob

and this reinforces the notion of weighing the whole rig then coming back on to get the truck solo.

i was aware that wind, and driver motion and fluid sloshing could affect the measurements...

but didn't know about the round up/down issue.

HOW exactly did he happen on to this thread out in cyberspace, did he relay that info?

what a nice thing to take the time and offer useful stuff for the rest of us!

THANKS dave!

cheers
2air'
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Old 01-24-2010, 03:58 PM   #91
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My cat

I finally got hitched up and had some free time so it's off to the Flyin J scales this morning.
2006 Dodge 3/4 SB 2X4 quad cab Diesel, 10 gallons of diesel, empty bed
1991 34' classic Airstream, no water, 60 lbs of LPG 1 battery, Hensley Hitch 1,400 lb bars and a 4" drop stinger

I cranked the WD jacks to 3" of exposed tube, recorded the trucks ride HT and headed for a flat parking lot. Drives great!
Stopping at a flat area, I adjusted the WD jacks until the Airstream was level. This took dropping the WD down until 5" of WD jack was exposed. Recorded the truck ride ht and hit the road toward Flyin J. The truck wanders a bit at 5" of exposed WD Jack.
4 passes at the scale. 5" of WD jack, 3" of WD jack, WD jacks sloppy loose and finally, just the truck.

My concerns were 1) did the 4" stinger have enough drop and 2) what happens when I really load up...soooo
I created a spreadsheet to calculate the changes in axle loading, ride height and ball height based on todays numbers...
It looks like I will be ok when the water tank is full, batteries are added, the misses and campin stuff join me in the truck...3" of exposed tube or slightly tighter on the WD jacks.
3800 lbs on the front of the truck, 4700 on the rear, 1130 tongue wt and a ball height of 18.5". Total weight of 16,454 lbs
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Old 01-24-2010, 07:40 PM   #92
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good info vernon...

so the truck Unhitched was....3920 front/2920 rear

and hitched but LOOSE was...3420 front/4400 rear

that's a 2000lb SHIFT with the rear axle going UP 1500lbs and the front down 500 lbs...

all from the 1130 tongue, wow.
____________

with "3 in" showing this was...3740 front/4060 rear

which is within 200 lbs of UNhitched at the front axle, pretty good.

and similar to my 34 experience almost NOTHING was added to the trailer axles (20 lbs)

and the 'drives like crap' feedback was with only 300 lbs LESS than baseline on the front/steering axle...

proving a little bit makes a big difference for steering/control.
____________

the rest are calculated values based on predicted loading?

so after the 2nd battery is added up front the 1130 tongue will go UP some...

but with a FULL load of fresh water it should go down slightly.

still at 11-1200 lbs the tongue has plenty of weight.
_____________

look closely (unless u mounted them backwards) at the LOWER screw jack extension tubes...

there are marks/divots/impressions it those tubes to help gauge adjustment...

time to go camping!

cheers
2air'
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Old 01-24-2010, 08:35 PM   #93
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Quote:
Originally Posted by 2airishuman View Post
good info vernon...

so the truck Unhitched was....3920 front/2920 rear

and hitched but LOOSE was...3420 front/4400 rear

that's a 2000lb SHIFT with the rear axle going UP 1500lbs and the front down 500 lbs...

all from the 1130 tongue, wow.
____________

with "3 in" showing this was...3740 front/4060 rear

which is within 200 lbs of UNhitched at the front axle, pretty good.

and similar to my 34 experience almost NOTHING was added to the trailer axles (20 lbs)

and the 'drives like crap' feedback was with only 300 lbs LESS than baseline on the front/steering axle...

proving a little bit makes a big difference for steering/control.
____________

the rest are calculated values based on predicted loading?

so after the 2nd battery is added up front the 1130 tongue will go UP some...

but with a FULL load of fresh water it should go down slightly.

still at 11-1200 lbs the tongue has plenty of weight.
_____________

look closely (unless u mounted them backwards) at the LOWER screw jack extension tubes...

there are marks/divots/impressions it those tubes to help gauge adjustment...

time to go camping!

cheers
2air'
You nailed it in the above summary. I'm looking at the scale sheets.
The calculated stuff is based on where the loads are in relation to the centerline of axles/truck/trailer and the ball pivot. I can verify the numbers when I really get her loaded up.

As far as the 20 lbs added to the trailer...keep in mind, thats the scale resolution, it might have been 5 -35 lbs added that flipped the number...still, that ain't crap for crankin on 1,400 lb bars.

Full fresh tank droppin the Hitch weight? I do have to assume you've seen it...I wonder if our tanks are in the same spot. Visually, mine seems to be centered between axles 1 and 2...even at that, I guessed full vs empty wouldn't have much difference on the tongue. Am I off base?

I figure I'm gonna catch some flak over the heavy rear weight that is predicted when loaded. Before postin, take a look at the GAWR F/R and do some math...at 3,700 Front/4,700 Rear both axles are 79% of their max rating...Isn't there an Airforums song about 80% rule of thumb...

And yup...I do have the WD jacks on the wrong sides, notches inboard...

These 34'rs with a Hensley tow freaky good. the mass is there but it doesn't move the TV AT ALL!
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Old 01-24-2010, 08:58 PM   #94
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good info vernon...

i think the the tanks are pretty close to the same location on our trailers...

maybe it's the black tank FULL that lightens the tongue.

i confuse this tank thing, regularly...

looks like u are within specs for the axles and i'll assume the new truck tires are E rated...?

gotta love the long long traylas!

cheers
2air'
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Old 01-25-2010, 08:20 AM   #95
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Quote:
Originally Posted by 2airishuman View Post
...i'll assume the new truck tires are E rated...?

cheers
2air'
Michelin LTX A/S LRE LT 265/70R17 and since we now have scale values...
The Michelin site has inflation charts for this tire...
45 psi for 4510 lbs, 40 psi for 4150, 35 psi for 3780
My heavest scale reading was 4,400 lbs on the rear

I'm currently at 45 psi and I do see a small bulge on the rears...

AND the Goodyear Marathon site...
I've got 7400 lbs of trailer weight on the axles SO 7400/3 = 2,466 lbs per axle. The chart shows...60-65 PSI
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Old 01-25-2010, 06:51 PM   #96
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Quote:
Originally Posted by HiHoAgRV View Post
...AND the Goodyear Marathon site...
I've got 7400 lbs of trailer weight on the axles SO 7400/3 = 2,466 lbs per axle. The chart shows...60-65 PSI
I tossed this out hoping someone would bite...

I don't the above info is correct...
but ...
what I think is correct...don't look correct...

The Michelin chart is weight per axle, the Goodyear is weight per tire...

Right?

If that's correct, my trailer should be running 35 +-psi?
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Old 01-26-2010, 06:45 AM   #97
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Michelin LTX A/S LRE LT 265/70R17 and since we now have scale values... The Michelin site has inflation charts for this tire...
45 psi for 4510 lbs, 40 psi for 4150, 35 psi for 3780
My heavest scale reading was 4,400 lbs on the rear


I have a 2WD 2004 Cummins. Door sticker on mine indicates 50-psi FF, 70-psi RR for max loading (FF 4750-GAWR/RR 6010-GAWR/9000-GVWR) for same tires. I run the recommended 50-psi all around when solo. Wear has been minimal. I know the RV t-pressure .pdf, where was the one for the LTX A/S in this size?

I have an email somewhere from a tire consultant recommending that, after 1.5 hours steady state driving one is looking for a 3-psi rise. 5-psi is acceptable, but 3 is considered ideal. That recommendation would seem to accommodate road, load and other conditions per vehicle.

I have searched for, and been unable to find, any recommendations about tire temps (pressure monitors, in particular; at what temp to set alarm; default on one brand was 157F); my measurements on a hot Texas day, at shutdown (mildest braking) was 127F exterior/sidewall/tread on TV tires at 50/70 FF/RR on my rig with a bit less weight overall, but different W-D numbers/percentages.

EDIT: I see that I was at 4,560 on Drive Axle [Post #47].

I experimented with higher psi FF/RR and saw no "benefit". I was reluctant to go below factory numbers.
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Old 01-28-2010, 12:04 PM   #98
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Back to the Cat Scale measurements. My rig is a 2003 Suburban 1500 pulling a 2008 25' Safari Read Bedroom. A week before our trip in December I took the Suburban by itself to a Cat Scale near us and weighed it. I wanted to see where the scales were and what the process was like. Those results were:
Steer Axle 2960 Drive Axle 2900 Total Weight 5860

Then on the way to Florida I weighed the whole rig. My wife was terrified of all the big trucks around so we only did one weighing. The truck was loaded about the same as before, except for 2 sets of golf clubs in the back seat. Those results were
Steer Axle 2980 Drive Axle 3580 Trailer Axles 5320 Total 11880

From this I conclude that the trailer weighs about the difference between the two totals,
6,020. The Tongue Weight is about the difference between the two drive axle weights
because the Steer Axle was the same both times (680 lbs). The Airstream brochure for 2008 says the tongue weight is 860 for my model, 720 for the front bedroom, and 750 for the Sleep Six model. The tongue weight seems a little low. One of our propane tanks was nearly empty, and we had all the wardrobes full of clothes.

I have a Reese Dual Cam hitch, and I had it adjusted to 5 links under stress. The trailer tows the best that way, and it's the fewest links I've been able to get. The trailer level on the side shows that it is about one lynx leveler low in front when it is hitched up. I have 800 lb trunion bars.

So I guess this reinforces the fact that weight distributing hitches can get your steering axle back to it's non-towing weight, but not increase it.
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