Home » Public Forums » GMCnet » Weight distribution adjustment
| Weight distribution adjustment [message #356917] |
Sat, 18 July 2020 04:27  |
MarkR
Messages: 13
Registered: September 2019
Location: Pennsylvania
Karma: 0
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Junior Member |
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I don’t know how to ask this question without sounding like an idiot, so here goes:
A few weeks ago I was fortunate enough to have Ken Frey narrating the underside of my 75 Eleganza II when he pointed out a couple of weight distribution adjustment points near mid ship. They looked like large threaded bolts (the one I could see). He thought it odd the the driver’s side “bolt” was all the way out exposing all its threads and the passenger Side was all the way in and he suggested I figure out why. And then it was quickly on to the next thing and we never got back to it.
My original purpose of seeing Ken was to get a six wheel alignment and the benefit of his experience. I wanted the alignment mainly to benchmark what a properly aligned Motorhome should feel like. It already handles SO much better than any other RV that I’ve owned or driven, but I’m pretty sure it can be even better. Honestly, I don’t even know if it needed an alignment. On a flat smooth stretch, it tracks pretty straight. It gets a little squirrelly in the tail sometimes, probably from my inexperienced over-correcting steering mostly, but I can just feel that rear end trying to get away from time to time. I also have a toolbox rear bumper full of tools and petroleum products that may enter into it.
My interior is pretty stock. It’s been prettied up, but the layout inside is the same 26-3 it always was, so why might the adjustments be so extreme? Does it make sense to anyone but me to try to put the adjustment points back to a more neutral setting to see if handling improves? I understand I need to weigh the coach at each wheel, but until then...?
Keep in mind we looked at the suspension And everything seems to be in good working order Those adjustments were the only thing that appeared to be out of whack.
So I’m sorry to ask a question about something I don’t even understand, but we went through things too quickly. How difficult is it to make those adjustments? And please tell me if it’s something I shouldn’t touch — I’m trying to do as much myself as I can, but I don’t want to break any more than necessary while learning.
Thanks in advance for your thoughts
The Portwagon, ex 1975 Eleganza II, Harrison quad bags, 6 wheel disk brakes, 455 w/EFI, serpentine belt, 3.7 final drive
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| Re: Weight distribution adjustment [message #356919 is a reply to message #356917] |
Sat, 18 July 2020 07:19  |
Ty Hardiman
Messages: 43
Registered: April 2017
Location: Norman, Oklahoma
Karma: 0
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It’s a good question and I’ll take a first run at it.
What you’re really wanting to know is if your front torsion bar suspension system is adjusted properly. This comes down to two measurements - is the front ride height correct on the left and right sides, and is the front weight evenly split between the left and right sides. If you measure these and find something is out of spec, then you could adjust it to the correct setting with those bolts that Ken showed you.
Many GMC owners have done the adjusting themselves but it takes some special tools and knowledge to ensure that neither the coach nor the mechanic become harmed in the process. This is something you could tackle with a GMC club friend or you could take it to a GMC specialist.
Norman, OK / August 1977 Kingsley / 403 / 3.55 / 16" / Quadrajet
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| Re: Weight distribution adjustment [message #356922 is a reply to message #356917] |
Sat, 18 July 2020 09:09 |
bdub
Messages: 1578
Registered: February 2004
Location: Central Texas
Karma: 5
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Senior Member |
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MarkR wrote on Sat, 18 July 2020 04:27I don’t know how to ask this question without sounding like an idiot, so here goes:
A few weeks ago I was fortunate enough to have Ken Frey narrating the underside of my 75 Eleganza II when he pointed out a couple of weight distribution adjustment points near mid ship. They looked like large threaded bolts (the one I could see). He thought it odd the the driver’s side “bolt” was all the way out exposing all its threads and the passenger Side was all the way in and he suggested I figure out why. And then it was quickly on to the next thing and we never got back to it.
My original purpose of seeing Ken was to get a six wheel alignment and the benefit of his experience. I wanted the alignment mainly to benchmark what a properly aligned Motorhome should feel like. It already handles SO much better than any other RV that I’ve owned or driven, but I’m pretty sure it can be even better. Honestly, I don’t even know if it needed an alignment. On a flat smooth stretch, it tracks pretty straight. It gets a little squirrelly in the tail sometimes, probably from my inexperienced over-correcting steering mostly, but I can just feel that rear end trying to get away from time to time. I also have a toolbox rear bumper full of tools and petroleum products that may enter into it.
My interior is pretty stock. It’s been prettied up, but the layout inside is the same 26-3 it always was, so why might the adjustments be so extreme? Does it make sense to anyone but me to try to put the adjustment points back to a more neutral setting to see if handling improves? I understand I need to weigh the coach at each wheel, but until then...?
Keep in mind we looked at the suspension And everything seems to be in good working order Those adjustments were the only thing that appeared to be out of whack.
So I’m sorry to ask a question about something I don’t even understand, but we went through things too quickly. How difficult is it to make those adjustments? And please tell me if it’s something I shouldn’t touch — I’m trying to do as much myself as I can, but I don’t want to break any more than necessary while learning.
Thanks in advance for your thoughts
==============================================
* Admin note:
Mark is now a part of the GMCnet email list as well.
bdub
'76 Palm Beach/Central Texas
www.bdub.net
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www.gmcmotorhomemarketplace.com
www.gmcmhregistry.com
www.facebook.com/groups/classicgmcmotorhomes
www.facebook.com/groups/gmcmm
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| Re: Weight distribution adjustment [message #357003 is a reply to message #356917] |
Mon, 20 July 2020 03:39 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The best way to do this is with a set of scales. I have a set but you will have to come to NW Indiana to use them. The first thing to do is to check and set the rear ride height EXACTLY to spec. I use a set of 2x4's cut to the exact height and slip them under the frame. Make sure the tires pressures are set to the correct cold inflation numbers before beginning. Then adjust the air leveling switches in the rear wheel well to get them exactly correct. Then drive it for 10 miles or so and check and adjust if necessary again. It usually takes about three times until you get the rear switches to stabilize at the correct height.
Now run the coach over the scales and see how far off the weights are between left and right of each pair of wheels (front and rear). Now you will know what has to be corrected. The rears are set by height switches so as things change from adjusting they will automatically adjust after a short drive.
Now for the front. Take those 2x4 measuring blocks you have for the rear and slide them under the rear frame. Then let the air out of the rear bags just enough to get the frame to sit on the 2x4s. This will lock the rear in place at an equal height while you start correcting the front.
If there is nothing broken or worn in the front then you will find the fronts are not equal in weight and height. Based in the numbers you now have, adjust the front torsion bars to get them close to equal in weight and height as possible. You will find at that point that they are also equal in height too. At this point when they are equal, you can adjust them both up and down the same number of turns to get to the correct ride height. At this point you should be done.
A side note being off by 1/4 in front height will transfer 125 pounds in front side to side in the front wheels. We usually try to get the front with about 100 to 150 pounds of each other.
Beside needing scales, you will need a torsion bar unloader tool to adjust the fronts. If you try to do it without it, you will strip the bolts and will have to wait to get another one from Jim K. Also lube the threads on the tool liberally before using it. I use anti-sieze on the threads but oil will do.
With those two bolts being different you have a badly adjustment or you have a mechanical problem with the torsion bar or sockets the bars fit in.
I will bet someone that did not know what they were doing just tried to adjust it. It is imperative that the rears be locked in at the correct EQUAL height BEFORE attempting to adjust the fronts. Fix the rear heights first.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Weight distribution adjustment [message #357081 is a reply to message #356917] |
Wed, 22 July 2020 10:31 |
Scott Nutter
Messages: 782
Registered: January 2015
Location: Houston/San Diego
Karma: 4
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Senior Member |
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Mark,
Make sure both of the front torsion bar adjustment bolts are the same length. There are aftermarket bolts that are longer than the original ones. Maybe the PO put in one longer bolt? But I’m sure Ken would of noticed that.
Scott.
Scott Nutter
1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final drive, Quad bags, Dave Lenzi super duty mid axle disc brakes, tankless water heater, everything Lenzi. Alex Ferrera installed MSD Atomic EFI
Houston, Texas
[Updated on: Wed, 22 July 2020 16:39] Report message to a moderator |
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| Re: [GMCnet] Weight distribution adjustment [message #357082 is a reply to message #357081] |
Wed, 22 July 2020 10:53 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Length of the adjustment bolts does not reveal much about weight and
balance of the right vs the left on the front end. Most coaches have an
imbalance, partly due to the batteries all being on one side. Some people
install the drivers side Ragusa battery tray and then load it up with
stuff. So, weight side to side should be taken into account before ANY
ATTEMPT is made to establish correct ride height. Goes without saying that
the rear of the coach must be spot-on and blocked to immobilize it from
reacting to any changes in torsion bar adjustments.
Jim Hupy
Salem, Oregon
On Wed, Jul 22, 2020, 8:32 AM Scott Nutter via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Mark,
> Make sure both of the front torsion bar adjustment bolts are the same
> length. There are aftermarket bolts that are longer than the original ones.
> Maybe the PO put in one longer bolt?
> Scott.
> --
> Scott Nutter
> 1978 Royale Center Kitchen, Patterson 455, switch pitch tranny, 3.21 final
> drive, Quad bags, tankless water heater, everything Lenzi. Alex Ferrera
> installed MSD Atomic EFI
> Houston, Texas
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Weight distribution adjustment [message #357100 is a reply to message #357073] |
Thu, 23 July 2020 06:18 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Jim is right on with his advice. From weighing coaches at the rallies (I have forgotten how many we have done now) we have found a lot of the two diagonal corners being heavy. I did it to mine one time before I got these scales. I borrowed Alex Sirum's scales at an Eastern States rally and corrected my problem there.
The problem is most people do not realize is that the are two different types of suspension on our coaches that operate differently. The front is a static adjustment (torsion bars) and the rears are a dynamic adjustment that changes by the weight applied at any given time. So what you do to the rear also affects the front and vice versa. Putting blocks under the rear and locking it down at the correct rear height eliminates that interaction of front to rear while adjusting you are the front. We are given a ride height number in the manual to set the front to. The problem is as you crank up on the torsion bar adjustment it does not immediately move the coach higher or lower. It flexes / twists the bar first as it takes on more weight. If the rears are not blocked in to the correct position the, diagonal bag also collapses some as it takes on more weight. If the leveling switches are set correctly on an unblocked coach the bag will automatically adjust to accept more weight and that just exacerbates the diagonal imbalance problem. So fix the rears first and BLOCK THEM BEFORE TRYING TO SET THE FRONTS.
We have had long discussions over this at some of the rallies and not all of the "experts" including one GMC maintenance business agree with this. But some of us including, Me, Chuck, Richard, two Jims, Bob, and a few others that I have loaned by scales to, all agree that this is the way to get it right.
I have only seen one coach that the torsion bar adjustment bolts were not similar in length after setting their adjustments according to this procedure. That one coach had a bad torsion bar socket in the lower A-frame.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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