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Unloading front axel?

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1 hour ago, runaway parents said:

So when running with tandem axels  how much unloading the front axel is considered to much?

Are you asking about the steer axle, or the front drive axle?

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31 minutes ago, runaway parents said:

Steer axle.

 

I can't think of a circumstance where the unloading of a steer axle would be recommended.  Under-loaded front axles (caused by shifting weight too far to the rear) could make the steering axle weight too light to steer safely.

Edited by spindrift

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I've unloaded the steer axle on my work truck by shifting the commercial hitch too far rearward.  It made for an exciting moment when I was trying to turn into the elevator on a wet road, over RR tracks.

That said, in our applications, I doubt unloading to the point of being unsafe is possible with a tandem, unless you bed overhang is REALLY long.  I don't think I'd want less than about 9k on the steer,because that tandem is going to want to go straight.  The longer your wheelbase, the less steer weight you'll need to to overcome the drivers in a turn.

How's that for a long winded way of saying, "Just depends?"

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If you are asking how to determine if you’ve unloaded your front axle too much, go to this link where Mark Shelley gave an excellent seminar on the formulas to calculate axle weights.  If you’re asking what is unsafe not sure anyone is going to have a real good answer.  Rick’s estimate of about 9k is probably as low as you would want to go.

http://www.hdtrally.com/Presentations/2008_bedbuild.ppt

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Lot more fun when you unload rear axle. Back in 50"s a 53 Ford my dad borrows my grampa's shuffleboard hauling trailer. It was long and narrow made for delivering shuffleboards. We go to feed store for seed and vertilizer for spring planting. Dad puts everything in back of trailer. First rise in road back end does a little wiggle. Next one the back comes up and we go from pointing north to south and in ditch. Not a pretty site. Whats that saying more fun than Cedar Point.

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I ment for my first answer to be longer but got interrupted by work. If you are carrying a vehicle length wise it should put some weight back on the front. It would take a very long overhang to make much difference on the front axle with a tandom truck. My Volvo was just under 10k when I got it, if it was 80k loaded then that means 35k on the tandems. So less than 1/3 on the steers. After singling it's about 40 percent on the front and 60 on the rear almost 50 50 empty. 

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I certainly respect everyone's opinion who clearly have more experience than me.  However, I still think it's important for the OP to know his axle weights before and after any modifications.  Also, exactly what changes is the OP making that first generated his question?

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After several decades of almost getting killed by out-of-balance-thingy-ma-jigs of various flavors (Cranes, Boats, Barges, Aircraft, Trailers, Etc, Etc...) and HAVING to ACTUALLY calculate ACTUAL Weight & BALANCE ......I......have simply given up being amazed at the "urbin-Leg-inz" that abound when a bunch of folks start .........using the "Thumb-in-the-air" method to arrive at ........"Truck / Trailer-out-of-balance-wild-A$$-Guesstimatez".........

Take this to the bank..........It is WAY, WAY, easier to hit TEN holes-in-one's at Pebble Beach than arrive at accurate with the “thumb-in-tha-air-method"Truck / Trailer Weight & Balance........BUT.......how much does it matter?  ?

How much does it really matter with a HDT / RV combo? ?

 

Most of the time it …...Likely…..HDT Balance matters not much history seems to say.

 

I the real world commercial heavy trucks wonder around with infinate load AND balance conditions and a LOT of scales abound on the sides of roads to check the ……...Balance……. of commercial trucks. Oh ya once in a while some trucks wonder onto the scale over-weight but far more often the out-of-balance is the problem that bites the trucker in the butt.

 

I used to cobble up more than a few RV weight & Balance calculations for mostly Truck and Trailer RV combos from LGT's, MDT's, and HDT's but for the last year or so my Wt & Bal Calc gig has dropped off to a nothingburger…….obviously I have …….solved RV Weight & Balance “problems” …….so…...next time you meet a F-150 rocketing by you at 77 MPH hooked to a 38 ft 5er with a Hog clamped to the back bumper…….smile…..rest easy…...maybe the chap has his WEIGHT and b a l a n c e calculated to the finely-tuned- edge to assure safe operations…….oh ya…..

 

Just scatching my head I looked over a couple hundred HDT weight and Balance calcs and threw a dart to find a example of front axle …...load / unloading….so….

 

Bit more than a year or so ago a fellow was in the process of buying a NEW HDT to RV with and the classic ……..”what will my axle weights be with 29 different hitch-smartcar-Hog-Drom-toolbox-Etc-42Ft fiver-hitched…..AND…..unhitched…..question was pondered.

 

So…….Scrap being…..Scrap, sent me THREE brand-spanking-NEW-Kenworths to cobble some weight a balance calculations with…..

 

Here is just one, of too many weight and balance calcs of one of the KW's

 

Example:

2017 KW 205” wheelbase with hitch at 241 inches aft of steer axle.

 

Empty:

steer axle= 9,460 Lbs (64.27 %) Avg Drive Axle (Center of tandems) 5,260 Lb (35.73%) total WT= 14,720 Lbs

 

Empty WT , With trailer hitched with 3,620 Lb hitch pin loading:

Steer= 8,286 Lbs (45.18%) Avg Drive Axle = 10,054 Lbs (54.82%) Total WT= 18,340 Lbs.

 

Sota a nothingburger…… so…...as I recall from a few hundred RV calculations my comment is that…. few IF ANY steer axles were unloaded very much…..BUT more that a few were pretty darn heavy at times when bobtale…..

 

Being a geezer and having seen a LOT of tire rubber flung-off-in-the-ditch I have a personal rule that I try to not exceed by 80% that the sidewall tire load rating of ANY tire on the RV…..

 

I have seen several RV combos that were +100% of steer tire load rating…...grim…..

 

Drive on…….(steer with…..care)

 

 

 

 

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After a good nights sleep, but before my coffee,  I'll suggest that the actual weight isn't nearly as important as the ratio of front/rear weight.  If you're still tandem, as the original poster asked about, the balance, or ratio combined with the distance from center of drives to steer axle, is far more important than the simple weight of said steer.   A 7k front weight might be plenty if you have a very long wheelbase and/or light weights on the drives.

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Just out of curiosity, is it even possible to unload the front to much in our configurations? Granted mine is singled so it is not a concern on mine. I carry a smart car but I also have a 14.6K front axle so I don't have concerns either way.

Brad

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The numbers are in . With trailer hooked up. Took it to scales found out we are running 8440 lbs on the front steer axel. That is with two half tanks of fuel . Seems to pull just fine sure can tell the difference in the ride not as bouncy. From what you guys are telling me I am right  in the safe zone with this. Truck seems to handle great.

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3 minutes ago, DesertMiner said:

What do the numbers say without the trailer hooked up?

DM ......that IS  the rattlesnake in the room........

Over many, many HDT RV Wt & Bal Calcs.......I have observed that it IS the BOBTAIL numbers that sometimes point to a NOSE-OUT-OF-BALANCE rigs......few are dangerous, but some would likely not be much fun with hard braking on a corner or slick road. 

HDT's often encounter less than ideal loadings........the nut behind the wheel is supposed to consider the loading and take care to not operate past the edge of the truck limits of handling......

 

Drive on..........(don't fall on your......nose)

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Ok here comes more numbers . Before bed installed steering11120lb drivers7880 total19000 lbs. After bed install steering 9540lbs drivers  14120 total 23660 lbs with out trailer hooked to it. Now with trailer hooked to it  steering 8440lbs drivers16840 lbs trailer 6960lbs total l32240lbs. all waights where taken with about 150 gallons of diesel on board. pin weight on trailer is 1400 lbs

 

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9 hours ago, Brad & Jacolyn said:

Just out of curiosity, is it even possible to unload the front to much in our configurations? Granted mine is singled so it is not a concern on mine. I carry a smart car but I also have a 14.6K front axle so I don't have concerns either way.

Brad

Why would it not matter if you are singled?  If you have a tail behind the rear axle you can  still unload the front axle to where it may cause issues.

My grandfather used to haul a D2 Cat on a KB5? International.  He would drive the dozer up to the back of the body and push down on it with the blade. The front of the truck would go up, and the back of the body would hit the ground. Drive the dozer up on, just had to be gentle when the teeter totter rocked down. I’m sure that dozer had to be parked in the right spot for it to be balanced right.

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Smoke, I wonder if he meant that his is singled "long" so that with his current length/load/configuration it isn't an issue, compared to the same length/load/configuration singled short, or mid.

Edited by Big5er

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