Weight distribution adjustment

[tyhardiman]

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

 

[bdub1]

> 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

==============================================

* Admin note:
Mark is now a part of the GMCnet email list as well.

--
bdub
www.bdub.net

 

[Ken B]

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

 

[MarkR]

Thank you
--
Nearing the summit of Mount Stupid In my new 1975 Eleganza II

 

[scott nutter1]

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

 

[Jim Hupy]

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 <

> 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
>

 

[Ken B]

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