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Old 04-28-2013, 07:50 AM   #43
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Thumbs up Lift the tongue...

Steve,

You can use your tongue jack to take the strain off the bars, makes adjusting the bars easier.

Bob
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Old 04-28-2013, 08:37 AM   #44
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Quote:
Originally Posted by ROBERT CROSS
Steve,

You can use your tongue jack to take the strain off the bars, makes adjusting the bars easier.

Bob
Thanks Robert. I do but I'm always afraid of just how far I can lift it before all hell breaks loose!!

I've redone the numbers (see pic below) so I have (from left to right) max capacity, TV alone (me in the seat), TV+TT w/6" WD, delta that created against TV alone, TV+TT w/7" WD and last the delta that created.

I included Ron's TW calculations too.

If the goal is to return the steer axle to unloaded weight, I'm thinking of trying 7.5" and re-weighing.

Very much appreciate the help on this forum!!

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Old 04-28-2013, 08:44 AM   #45
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Quote:
Originally Posted by SteveSueMac View Post
I have zero washers behind the rivet on the hitch - long story, but that's something I worked out with Sean. It's level at zero washers but a washer or two would push it on a bit of a downward angle toward the trailer and I can see how that might improve the WD.---
Your data indicate that, at 7", the steer axle still is 4680-4420 = 260# lighter than when unhitched.
So, if you want to restore the steer axle to the unhitched value, you need to transfer another 260#.

The 7" data and the adjusted 6" values indicate that 1" of jack travel caused an additional 80# to be transferred to the steer axle.
That suggests you'd need to raise the jacks approximately an additional three inches to return the front to the unhitched load.

I assume the jacks don't have an additional 3" of travel remaining,
so it appears that having zero washers behind the rivet will not allow full steer axle load restoration.

Ron
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Old 04-28-2013, 08:58 AM   #46
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ron, if my thinking was correct, that is one of the reasons i thought the stinger might need to be lowered one hole. i'm guessing but Sean would know the cause/effect of the adjustments.
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Old 04-28-2013, 09:44 AM   #47
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Setting the WDH is tedious, no question. But the point is rather to eliminate questions so far as we can in re combined rig performance. A numerical baseline against which to chart any changes. To investigate any perceived problems in the future from best practice. (What changes we might make from there, if any, are outside of what is good to begin with).

To that end -- best practice -- is tire pressure.

Rubber Manufacturers Association: Weighing RVs

Posts by current and retired tire professionals on this forum (and others) recommend weighing individual tire positions. While one always wants maximum sidewall pressure on TT tires, there is also the question of having a load reserve. One recommendation [CapriRacer] is 15% above scale weight, or, a tire that is rated for 115% of what the scale reveals (on a TT ostensibly loaded about as heavy as it will ever be).

So, while moving the rig numerous times at a scale is even more tedious, the numerical values obtained with weight distribution applied will show any close-to-the-bone concerns about weight, and may provide for adjusting the loads in either vehicle FF-RR or side/side to balance things out. They won't ever be perfect, but it's a level of familiarity (let's call it) which goes hand-in-hand with knowing how the particular rig responds over thousands of miles when the numbers have all been worked.

Optimized loading (the end of WD and best tire pressure) is then also applicable to questions of braking differences, bearing adjustments, steering anomalies, etc.

.
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Old 04-28-2013, 10:03 AM   #48
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Thanks Ron - I can't pretend to understand the math you're using but I'm really grateful for the analysis.

Plug & Play Excel Worksheet by nickcrowhurst. Post #69

Weight Distribution Hitches: An Analysis

More Plug & Play:

Weight Ratios. Post #6

.
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Old 04-28-2013, 03:29 PM   #49
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Amending My Previous Posts

I missed the fact that Steve also was standing on the steer axle pad when the "truck only" measurements were made.
The following is to correct my previous post made at 7:44 am today.
Changes are shown in red.

Your data indicate that, at 7", the steer axle still is 4540-4420 = 120# lighter than when unhitched.
So, if you want to restore the steer axle to the unhitched value, you need to transfer another 120#.

The 7" data and the adjusted 6" values indicate that 1" of jack travel caused an additional 80# to be transferred to the steer axle.
That suggests you'd need to raise the jacks approximately an additional 1.5 inches to return the front to the unhitched load.

I assume the jacks don't have an additional 1.5" of travel remaining,
so it appears that having zero washers behind the rivet will not allow full steer axle load restoration.

In addition to the above changes, the adjustment to the "truck only" weights impacts the estimated tongue weight and load transfer to the trailer axles.
The adjusted values now indicate:
for 6": -- tongue weight = 1031# with 111# transferred to TT axles and 920# on TV,
for 7": -- tongue weight = 1033# with 153# transferred to TT axles and 880# on TV.

The indicated tongue weight percentage is about 1030/6280 = 16.4%.
That value seems a bit high, but that's what the adjusted numbers indicate.

Ron
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Old 04-28-2013, 09:27 PM   #50
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A nice job by Mr Gratz, as usual.

FYI: TT TW is generally in the range of 10-15%, with 12.5-15% being considered close to ideal. 18% is possible (and increases tend to help with sway issues), but TW that heavy doesn't work out well in practice. Alternately, a boat trailer travels at 5-7% TW.

Forgot to ask earlier, does the TT as shown also have full fresh water and full propane for the weights recorded?

And how do the scale ticket trailer weights compare with AIRSTREAM published figures for model/year?

.
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Old 04-28-2013, 10:04 PM   #51
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Quote:
Originally Posted by SteveSueMac View Post
Thanks Robert. I do but I'm always afraid of just how far I can lift it before all hell breaks loose!!

I've redone the numbers (see pic below) so I have (from left to right) max capacity, TV alone (me in the seat), TV+TT w/6" WD, delta that created against TV alone, TV+TT w/7" WD and last the delta that created.

I included Ron's TW calculations too.

If the goal is to return the steer axle to unloaded weight, I'm thinking of trying 7.5" and re-weighing.

Very much appreciate the help on this forum!!

Attachment 184390
Steve,

Get on the road and try-it.....

120# light at 7" If the trailer is LEVEL I wouldn't be too concerned.

We are 100# light at the WD setting I use most often with no towing concerns at all.

I have transferred that 100# with no discernible improvement in towing.
But AS was 2" low at rear bumper, not good.

I doubt if you'll notice any difference with your D-Max either.

Bob
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Sandra wanted to go to Cleveland on vacation,
but Iím the Husband, so we went to Cleveland.
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Old 04-29-2013, 04:59 AM   #52
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Quote:
Originally Posted by slowmover
A nice job by Mr Gratz, as usual.

FYI: TT TW is generally in the range of 10-15%, with 12.5-15% being considered close to ideal. 18% is possible (and increases tend to help with sway issues), but TW that heavy doesn't work out well in practice. Alternately, a boat trailer travels at 5-7% TW.

Forgot to ask earlier, does the TT as shown also have full fresh water and full propane for the weights recorded?

And how do the scale ticket trailer weights compare with AIRSTREAM published figures for model/year?

.
Agreed - very much appreciate Ron's insight and help!

TW of 15% seems high to me - AS manual says it shouldn't exceed 1000# but then weasels out a bit saying but in any case shouldn't exceed hitch manufacturer's limit (which according to the hitch placard on the Chevy is 1500#).

At that weigh in, fresh water was probably more than 1/2 but definitely not full. Will do that on next weigh in. One propane tank full, the other I'm guessing at 75%??

The published max trailer weight for this trailer is 7600# and the placard says it left the factory at 5821#.



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Old 04-29-2013, 05:06 AM   #53
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Quote:
Originally Posted by ROBERT CROSS

Steve,

Get on the road and try-it.....

120# light at 7" If the trailer is LEVEL I wouldn't be too concerned.

We are 100# light at the WD setting I use most often with no towing concerns at all.

I have transferred that 100# with no discernible improvement in towing.
But AS was 2" low at rear bumper, not good.

I doubt if you'll notice any difference with your D-Max either.

Bob
Thanks Bob. Another thought is that if my goal is actually not 100% restoration of the front axle load but more like 50%, that was achieved at 6" (long offline discussion with Ron about that).

Still, I'm going to lower the rear of the WD bars by putting the jacks on the top hole of the 3 (currently in the middle hole) which should help me put more weight up front.

Just don't want to go back to porpoising either so I want to dial this in right. :-)

Really enjoying the process (does that make me odd?) and very grateful for the support and insight of everyone in the forum. I'm going to have to contribute and get another set of stickers :-)
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Old 04-29-2013, 05:18 AM   #54
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Odd Airstream'rs....it's part of our DNA.

Once you get a base setting you'll be able to adjust for different loads by using all the info you've stored in the "seat of your pants".

Becomes second nature after awhile.

One CAT stop at the beginning of the Season just to make sure nothings changed has worked well for me.

Bob
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Sandra wanted to go to Cleveland on vacation,
but Iím the Husband, so we went to Cleveland.
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Old 04-29-2013, 06:31 AM   #55
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Quote:
Originally Posted by ROBERT CROSS
Odd Airstream'rs....it's part of our DNA.

Once you get a base setting you'll be able to adjust for different loads by using all the info you've stored in the "seat of your pants".

Becomes second nature after awhile.

One CAT stop at the beginning of the Season just to make sure nothings changed has worked well for me.

Bob
Oddly enough, my goal for getting this set correctly is specifically to avoid a moment where something has to be stored in the seat of my pants! :vaudeville:

I feel like I'm getting closer now that I understand it better!!!
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Old 04-30-2013, 10:30 PM   #56
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Quote:
Originally Posted by ROBERT CROSS View Post
Odd Airstream'rs....it's part of our DNA.

Once you get a base setting you'll be able to adjust for different loads by using all the info you've stored in the "seat of your pants".

Becomes second nature after awhile.

One CAT stop at the beginning of the Season just to make sure nothings changed has worked well for me.

Bob
X2

A stack of scale tickets with notes about various loadings takes the guesswork out of things. Change the tires on the TV and be prepared -- as Boondockdad was not -- for a significant change in feel (an excellent diagnostic thread ensued).

Having verifications across the board brings problems-solving to a level of satisfaction, not chronic frustration.

.
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