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Old 07-01-2009, 04:56 PM   #1
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Question results of CAT Scales and WD hitch adjustments

Okay – I finally started working on improving my hitch set-up today. Last month I spent a couple hours trying to configure the hitch with my new 2000 Yukon XL (1/2 ton) and never got it quite right per the DrawTite WD setup instructions. The main problem was that the rig rode high at the hitch ---- with the trailer several inches higher at the tongue than rear bumper.

Cutting to the chase: My review of the data is as follows. I didn’t see any significant differences based on measurements at TV wheel wells alone. Scale differences are more obvious. Weigh master suggested I use the setup from my second pass (at 6 links). After calculating the percent load capacity of the axles, I’m inclined to agree. Adds a bit more to the TV Drive Axle, but I read that it is more capable of handling the extra load (vs the Steering axle).
5 links
added 130 lbs to TV Front (98% max GAWR)
added 280 lbs to TV Rear (80% max GAWR)
removed 380 lbs from TT axles (86% max wt)
6 links
added 60 lbs to TV Front (96% max GAWR)
added 400 lbs to TV Rear (84% max GAWR)
removed 420 lbs from TT axles (85% max wt)

Here’s the full scenario: Today I loaded some ballast to my TV and TT in my best effort to mimic actual weight of additional equipment that I’d have stowed during a regular trip.

I lowered the head assembly on the shank to the lowest position (essentially, lowering the ball as far as possible – which was only one hole lower than started with). I measured the TV Front/Rear wheel well heights and then hitched to the trailer. I re-measured (finding a gain at the Front and substantial loss in the Rear). I then towed the trailer about 5 miles without the spring bars engages as detailed in my Tahoe Owners Manual – for my Premium Smooth Ride option: “Level Control – Self-Adjusting”. I’m told this is, essentially, gas shocks – mechanically driven. Not Auto-leveling, not Auto-ride, not controlled by any compressor or electrical connection. (Details on this system at post # 28 at http://www.airforums.com/forums/f464/auto-leveling-on-tow-vehicle-40012-2.html .) After this short tow, I measured Front/Rear heights again and it did change. Then I engaged the spring bars so that the rig (TV/TT coupled) appeared most level and with the Front/Rear heights adequate (6 links) The 800 lb spring bars definitely moved the load and I did notice them flex/bend some.

TV uncoupled: Front 34-7/8" , Rear 36-3/16"
TV with TT (no spring bars, no travel): Front 35-9/16" , Rear 34-3/4"
TV with TT (no spring bars + 5 miles): Front 36", Rear 35-3/8"
TV with TT (spring bars at 6 links): Front 35", Rear 35-7/8"
TV with TT (spring bars at 5 links): Front 34-1/2", Rear 36'
TV with TT (spring bars at 5 + 15 miles): Front 34-5/8", Rear 36"

I left the spring bars with 5 links engaged and preceded to the CAT Scales. Below are the weights. NOTE: my front passenger (200 lbs) had to leave so I annotated in the results as pass/no pass! This accounts for the changes you may notice (esp. in ross weight). The weigh master said that he believed the second run was my best setting (at 6 links engaged).

TV Uncoupled (no pass): TV Front 2840, TV Rear 2900, Gross 5740
TT uncoupled (no pass): Tongue 700, Rear 5160, Gross 5860
max bars (5 links) (pass): TV Front 3140 , TV Rear 3220, TT 5480, Gross 11860
adj bars (6 links) (pass): TV Front 3060, TV Rear 3340, TT 5440, Gross 11840
no bars (no pass): TV Front 2580, TV Rear 3740, TT 5260, Gross 11580

Some additional info.
2000 Yukon XL, 5.3 Vortec V-8, ½ ton, 2-WD, 3.73 axle ratio, factory tow package – my giant
Bridgestone Revo, E-rated 65 psi verified (80 max)
Curb Weight 4769
GVWR 7000
Front GAWR 3200
Rear GAWR 4000
Payload 1905
Front axle capacity 3400
Rear axle capacity 5500
Front spring rating 3150
Rear spring rating 4000
Towing capacity 8000
Wheelbase 130”
Length 219”
1973 Airstream, 27’ Overlander, rear bath double – cute as a button
Henschen axles (new 2009) 3200 lbs each
Gabriel shocks (new 2007)
Marathon, D-rated tires, 60 psi max 60 psi verified
Tekonsha Voyager brake controller – pain in the ass
DrawTite WD hitch: 800 lb spring bars (rated as 800 lb max tongue weight, 12,000 max gross trailer weight) - no issues

So, do any of you have any comments, suggestions or witty comments? This has been a challenging day for me --- intimidated by the scales (and having to back off for each successive pass) and then solid rain on my way home. Thankfully my dad helped me through this!!! When I say "I" in the post, I really mean "we".
Laura
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Old 07-01-2009, 05:45 PM   #2
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Laura we be proud, ya' done good....Here's some more good reading.

Sherline Trailer Tongue Weight Scales


HowStuffWorks "How Tongue Weight Works"


Trailer Loading and Towing Guide
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Old 07-01-2009, 06:28 PM   #3
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Laura, I think you're fine as hitched with the 6 link showing... but, let you be the judge. I'm not sure if you notice any difference, but I felt my van's steering just a TAD (small bit here) more secure with slightly more weight on it... I do believe you're right at the sweet spot. I think I'm just within the 10% difference rule (if I remember the posts I've read here) of front / rear weight differences. You are as well.

I'm glad you got it all hitched up. Happy motoring (and I still feel bad about those beauty rings for your baby.)

I'm also curious about your brake controller... are you having issues? I know my drums are a bit grabby until they heat up. I usually just "drag" the brakes a bit when I first p/u the trailer by using my manual brake controller to heat them up.
Take care!
Marc
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Old 07-01-2009, 06:59 PM   #4
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Weight Distribution Hitch

funkill
Here is a post I did about setting up my dual cam Reese.

Setup

Disable any auto ride, auto leveling etc system on your vehicle and deflate any air shocks to minimum pressure. This is the only way you can set it up and let it do its job properly.
The best way to set up the Airstream is with scales.
You need to go to a CAT Scale and expect to spend some time.
First you must adjust the ball height (up or down) to make the weight on both axles of the trailer the same (yes weigh each axle separately). Make a reference mark on the tongue (Take a piece of masking tape, stick it on the tongue if you don’t want to mark on the tongue with the magic marker and put a line on it parallel with the ground. When the weight on both axles are the same plus or minus 100lbs measure the distance from this line you made to the ground while on the scales). Pull off the scales and find a flat hard surface to park.

This is what your tongue height must always be when you are on a flat level surface.


Next adjust the spring bars/trunion bars until the weight on the front axle and rear axle of the tow vehicle is the same with the tongue height noted before.
Then tweak the number of links under tension, angle of the ball mount and ball mount position on the drawbar until the weight on all four axles is within 100 pounds of each other AND the line on the masking tape is at the distance from the ground is the same as the tongue height as measured above.
The change in overall handeling is dramatic.


If you have the dual cam straight line setup:

Lastly pull straight for at least 50 yards.
Loosen the u bolts on the arms (two u bolts per side, they will usually self adjust with a bang). Re tighten the nuts on the ubolts.

Your ready to go.


Remember:
1. Equal weight on the two trailer axles is the first and most important consideration reguardless of appearance. There is no equalizer link between the front and rear axle so the ball height is what determines the load on each axle. It must be the reference height determined above when finished no matter how many times you have readjust the angle of the ball mount/position of the ball mount on the shank.
2. Equal weight on all four axles is the best setup for braking and stability. This may not be attainable so get as close as possible.
Put your heavist toys in front of the rear axle of the pickup truck (between the front and rear axle).
3. The truck and trailer might be a little off level when the weights are right. This is caused by the different ACTUAL load capacity of the old axles on your trailer (after several years they get tired, mine are).
4. Use the lightest spring bars you can get away with. There should be 1 to 2 inches deflection from rest (on the spring bars) to be best to attain the reference mark height and equal weight on all axles. My tongue weight is 850 lbs and I use 750 lb bars. These spring bars provide a flexable link between the truck and the trailer. I learned years ago that unless you provide a flex point between the trailer and the truck, if not, the trailer or the truck will find one on its own and I guarantee you will not like it.



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Old 07-01-2009, 08:44 PM   #5
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Quote:
Originally Posted by 3Ms75Argosy View Post
I'm also curious about your brake controller... are you having issues? I know my drums are a bit grabby until they heat up. I usually just "drag" the brakes a bit when I first p/u the trailer by using my manual brake controller to heat them up.
Take care!
Marc
Awesome idea!!! I have the same problem - grabby at first and then a little soft. Seems like I'm forever playing with it until I just give-in with it on the grabby side.

No problem about the bling - I thinK I've found some. Hopefully it will turn out!
Laura
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Old 07-02-2009, 07:07 PM   #6
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A little Grabbie is hard to avoid, if wet or dirty.

Make sure the shoes and drums are clean and the brakes are adjusted properly. They really shouldn't grab or lock if set up properly.

I havent experienced the "grabs" since installing the Tru-control.
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Old 07-02-2009, 11:09 PM   #7
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How Is The Loaded Ride?

So, how does it ride loaded?
We deliver firewood, one cord at a time, in a double axle trailer with our diesel Jeep liberty.
The trailer acted fine empty but when loaded it got squirrely, it just felt wrong.
I raised the hitch an inch to compensate for the instability I felt based on what I saw.
My point: Your analysis seemed rigorous, thorough and balanced but there is no substitute for seat of the pants experience and common sense.
I know, I had some, some where.......
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Old 07-04-2009, 11:43 AM   #8
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Hi Laura, I just went thru the same process, only I was lined up between big rigs at the Cat scale on a busy day, very intimidating.
The only suggestion i have, is the TV should drop equal amounts from unhitched to hitched, with 1/2" drop greater on the rear, according to what I have read. Your 5th link may be closer.

TV uncoupled: Front 34-7/8" , Rear 36-3/16"
TV with TT (no spring bars, no travel): Front 35-9/16" , Rear 34-3/4"

TV with TT (no spring bars + 5 miles): Front 36", Rear 35-3/8"
TV with TT (spring bars at 6 links): Front 35", Rear 35-7/8"
TV with TT (spring bars at 5 links): Front 34-1/2", Rear 36'
TV with TT (spring bars at 5 + 15 miles): Front 34-5/8", Rear 36"

The real test is to tow it for a few miles, and see which feels better.

GOOD JOB!!
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Old 07-11-2009, 02:05 PM   #9
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Weights at the Scale

Spent the morning at the local Love's CAT scale.

Excursion Weight 7540 lbs (no occupants).

Trailer Total Weight 7320 lbs.

Front Trailer Axle 3180 lbs, Rear Trailer Axle 3280 lbs, Tongue Weight 860 lbs

I usually run at just about the #2 weight bar setting - seems to be happy there.
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Old 07-11-2009, 07:08 PM   #10
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Funkill
Just forget about those fender heights they mean nuffin. The actual axles weights look good. With a difference of only 300 lbs or so between steering and drive I dont think you can get much better. U really dont want them equal. That is about where I stand with the 1 ton,about 300 lbs difference and 6 links under tension. We use 550 or 600 lb bars .We get a really good soft ride.
You DID GOOD My favorite sayin is "THE TAIL IS IN THE SCALE" Now you know where you are. I have tried other settings for the chains but dont get the ride I do from 6 links under tension. You have to have bars that flex,large bars take so much energy to flex that when they do bend the rebound is awesome,and at some point the rebound I think can cause loss of control.
Good luck with your setup
Roger
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Old 07-11-2009, 07:35 PM   #11
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Quote:
Originally Posted by Mikethefixit View Post
Funkill
Just forget about those fender heights they mean nuffin. The actual axles weights look good. With a difference of only 300 lbs or so between steering and drive I dont think you can get much better. U really dont want them equal. That is about where I stand with the 1 ton,about 300 lbs difference and 6 links under tension. We use 550 or 600 lb bars .We get a really good soft ride.
You DID GOOD My favorite sayin is "THE TAIL IS IN THE SCALE" Now you know where you are. I have tried other settings for the chains but dont get the ride I do from 6 links under tension. You have to have bars that flex,large bars take so much energy to flex that when they do bend the rebound is awesome,and at some point the rebound I think can cause loss of control.
Good luck with your setup
Roger
Thanks for the vote of confidence Roger!!! I am leaving for a trip tomorrow and will get a good feel for the ride. I have been thinking about maybe going with lower rated bars -- maybe the 600 pounders -- if I don't see the flexing I hope. That will be under consideration after my trip! Now I need to focus on getting the last minute stuff stowed - yawn.

Laura
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