Wiggle Wagon

G

gene

New member
Sep 29, 1999
2,215
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Yep

here is some info

http://www.california.com/~eagle/front.html

gene

>OK Netters: Stay away from this issue if you want but I bet everyone has an
>opinion on it. During last night's theoretical discussion about the Gimmy
>wiggle, it was strongly suggested that the main and uncorrectable source of
>the wiggle is the different wheel spread of the front and rears. Although I
>know (being an experienced Iowa driver in the 60's with the narrow roads,
>curbs, and chain ruts) that two different wheel spreads will make it
>impossible to maintain a straight line, has anyone actually used front wheel
>spacers or such to increase the width to that of the rear bogies? And with
>what success? Anyone? Dean Hanson's 73-23-Hotrod GMC
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
Dean,
I have heard that several people have tried offset wheel combination
with varying degrees of success and there has been a discussion of this
topic earlier in the year. General thoughts were that it would be nice
to use a larger offset wheel, but the front bearing load would probably
shorten bearing life dramatically and might lead to a front hub failure.
I am sure that other have thoughts that they would like to
express on this issue again.

J.R. Wright
GMC GreatLakers
77 Eleganza II
Michigan

>
> OK Netters: Stay away from this issue if you want but I bet everyone has an
> opinion on it. During last night's theoretical discussion about the Gimmy
> wiggle, it was strongly suggested that the main and uncorrectable source of
> the wiggle is the different wheel spread of the front and rears. Although I
> know (being an experienced Iowa driver in the 60's with the narrow roads,
> curbs, and chain ruts) that two different wheel spreads will make it
> impossible to maintain a straight line, has anyone actually used front wheel
> spacers or such to increase the width to that of the rear bogies? And with
> what success? Anyone? Dean Hanson's 73-23-Hotrod GMC
 
Dean,
Consider this: The wheel and tire pivot on a line drawn
through the center of the two ball-joints which intersects
the pavement at approximately the center of the contact
patch. When you hit anything solid (chuck hole, etc.),
the force is absorbed on the pivot line and nothing
happens except the navigator screams "BLIND DUMMY!
With four and a half of unengineered off-set in the front
when you hit that solid object, you have 12,000 lbs. of
force acting on a 4 1/2 inch lever arm trying to turn that
wheel which is attached to that steering wheel that you have
in your hands. You would be well-advised to keep your
thumbs on th outside of the steering wheel. Many dirt
sprint cars (which use lots of positive offset on their
front wheels)use steering wheels with solid center to
prevent putting their thumbs in danger.
Sorry about being so long-winded but I think this is
a serious safety issue.
Thanks for listening,
Gary Kosier
- ----- Original Message -----
From:
To:
Sent: Tuesday, July 18, 2000 8:05 PM
Subject: Re: GMC: Wiggle Wagon

> In a message dated 7/18/00 4:32:46 PM Pacific Daylight Time,

>
> >
> Wait until I start the BS session tonight with this. I knew someone has
> measured-built-tested-etc. this to the nth. Thanks for the input for the
> discussion. Dean
 
> OK Netters: Stay away from this issue if you want but I bet everyone
> has an opinion on it. During last night's theoretical discussion about
the
> Gimmy wiggle, it was strongly suggested that the main and uncorrectable

> source of the wiggle is the different wheel spread of the front and
rears.
> Although I know (being an experienced Iowa driver in the 60's with the
narrow
> roads, curbs, and chain ruts) that two different wheel spreads will
make it
> impossible to maintain a straight line, has anyone actually used
> front wheel spacers or such to increase the width to that of the rear
bogies?
> And with
> what success? Anyone? Dean Hanson's 73-23-Hotrod GMC

I mentioned this before when this topic came up. An owner at the GMC MH/I
rally in NH put duals on the front. Claimed it solved that particular
problem. Looked really weird.

Since I stay off the Interstates as much as possible it isn't a problem
for me.

David Lee Greenberg
The GMC Motorhome Registry
Dedicated To The Preservation of the Classic GMC Motorhome
http://www.GMCss.com/Registry.htm
http://www.Buskirk-RushRV.com/GMC-Registry/online-registry.htm
 
>
During last night's theoretical discussion about
> the Gimmy wiggle, it was strongly suggested that the main and uncorrectable
>
> > source of the wiggle is the different wheel spread of the front and
> rears.



I wonder if the front wheels could be spread out maybe half inch and
the rears IN a half inch to get closer to "inline tracking" and have the
least extra strain on the bearings?

I wonder also why, with all their engineering genius, that Generous
Motors didn't line up all the wheels in the first place?

Bill Tyrrell
 
>Remember that GM designed this coach from scratch as evidenced by the
>different CV shaft lengths between the Toronado and the GMC coach. They
>could have made the track widths the same but did not. They made the tracks
>different for a reason, it handles and rides better. The wiggle factor does
>not come from the different track widths, or the air bag system, it comes
>from improperly set up and maintained coaches. Ask some of the owners that
>have an almost new,low mileage, original coachs and see. None of the
>steering or wiggle problems others are trying to solve. Just what i have
>found out by talking to others at rallys and on the net.
>regards,
>
>tom

Tom, it also comes from truck ruts. I'd bet that even the most perfectly
maintained and aligned GMC would "wiggle" as its driver tried to maintain a
straight course while the front vs. rear track width tried to follow these
ruts.

Dave (advisor/navigator) & Dege (ALL else), '76 Royale, Santa Barbara, CA
 
> The wiggle factor does
>not come from the different track widths, or the air bag system, it comes
>from improperly set up and maintained coaches. Ask some of the owners that
>have an almost new,low mileage, original coachs and see.

Last week I rode in a coach with 9,000 original miles on it. Same problem
as I had on my Palm Beach when it came to wiggle. The owner was positive
that the miles were original - I saw the maintenance records to prove it.

> None of the
>steering or wiggle problems others are trying to solve. Just what i have
>found out by talking to others at rallys and on the net.

I'm relatively convinced that the problems with the wiggle-waggle are
many-fold. First, the interstates of the early 60s/ late 70s when the GMC
was designed were generally in much better shape than what we contend with
today. I don't remember as a kid ever riding on an interstate that was
heavily rutted. It's a pretty common occurrence today in many western
states. I've watched trailers on semis wiggle the same as our coach -
climbing up the ridge in the pavement, changing direction and coming back
down the ridge.

I do recall that early front wheel drive vehicles had problems with bump
steer and torque steer. Maybe someone who knows the details can comment -
it wasn't something that I followed.

As a final comment I believe that if there are 4,000 coaches on the road,
then there are 4,000 different complex problems that account for the
wiggle. For example, I'm willing to bet that if we were to measure
torsional stiffness of the frame and plywood diaphram we would find
dramatic differences between coaches. Some of it comes with usage as the
plywood is flexed. Some of it comes from water damage. Some of it is due to
the physical properties of individual pieces of plywood. The degradation of
the polyurethane insulation also influences stiffness. Add to that the
differences in tire construction and sidewall stiffness and it gets pretty
complicated in a hurry. Don't forget that the GMC was designed originally
to run on bias ply tires which have a much less stiff side wall.

Your basic point that it's best to get the GMC to meet factory spec first
is key. Many handling problems do go away or become less pronounced when
the coach is set up right. Still, even with making everything on my coach
meet spec or better I had the annoying experience of getting launched on
some roads - like I10 in the panhandle of Texas. I've found a way to solve
that problem on my coach, for me. It may not work for everyone. It may not
be needed for every driving circumstance. It's what I did - and I'm not
saying that everyone should do it. It was right for me.

Henry
PS Anybody interested in what I did and why send me an e-mail.
 
> I had the annoying experience of getting launched on
> some roads - like I10 in the panhandle of Texas.
>
> Henry
> PS Anybody interested in what I did and why send me an e-mail.

Always interested, even though I like the way mine drives.

About that launch - did it involve a fourth dimension? I's borned in
Texas, and I didn't know you could get to the panhandle on I10.
(Quibble, quibble; that's all this list does, I know.)

Walt Taylor
Austin, TX
 
Walt,
Don't forget, Californians aren't good with Interstate numbers, they name
their exits rather than having numbers. Then, they get out into the rest of
the country and have problems with the numbering systems.>

Maybe it was an I-10 bypass up there. A Texas sized bypass, like around the
whole state. {:>)

Roger
 
you got that right, for a high tech state, I don't see how we can be so
stupid with our gas and our roads. course, greed and corruption don't help.

gene

>Walt,
>Don't forget, Californians aren't good with Interstate numbers, they name
>their exits rather than having numbers. Then, they get out into the rest of
>the country and have problems with the numbering systems.>
>
>Maybe it was an I-10 bypass up there. A Texas sized bypass, like around the
>whole state. {:>)
>
>Roger
>
>
gene fisher 76 PB/OR/CA
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
>Walt,
>Don't forget, Californians aren't good with Interstate numbers, they name
>their exits rather than having numbers. Then, they get out into the rest of
>the country and have problems with the numbering systems.>
>
>Maybe it was an I-10 bypass up there. A Texas sized bypass, like around the
>whole state. {:>)

Arghh... Of course I meant I-40?

In my own twisted defense, I had just finished looking at the southern
route for our trip across the US starting next week. Guess with the temps
that I saw predicted that we won't go that way. Guess it's back across the
panhandle on I-40.

BTW, I grew up in Maine. No need to number the roads when I was a kid - at
least that's what kids stealing road signs thought so I'm told. We just
told people what their destination was. When there's only one road or one
way to get somewhere what do you need numbers for? Now they went and
screwed it all up. There's two ways to get into Maine from the south.

Henry
 
>About that launch - did it involve a fourth dimension?

Na, just a few beers under the LBJ law.

>I's borned in
>Texas, and I didn't know you could get to the panhandle on I10.
>(Quibble, quibble; that's all this list does, I know.)

I do know where I-10 and I-40 run. Guess I shouldn't post late at night
after planning trips across the US.

Spent three pretty miserable years in Houston. Didn't like the humidity.
DId like the one day of fall and one day of spring when I didn't have to
have either my heater or air conditioning working. Found it odd to have a
fireplace - I had to run the A/C whenever I had a fire in the fireplace.

Loved San Antonio and Austin. Would likely still be in the state if I had
lived either place.
 
The wiggle factor does not come from the different track widths, or the
air bag system, it
> comes from improperly set up and maintained coaches. Ask some of the
> owners that have an almost new,low mileage, original coachs and see.
None of
> the steering or wiggle problems others are trying to solve. Just what
i
> have found out by talking to others at rallys and on the net.
> regards,
>
> tom
>

Well this is news to me, Tom. My 1st Palm Beach a brand spankin' new 1975
model wiggled but ONLY when I tried to run in the ruts that overloaded
trucks lay on sub standard asphalt on the Interstates. My current coach
still tries to climb out but the rear track wants to stay in the ruts.

I agree the steering mechanism needs to be in top condition and mine is
probably not, but I never have a wiggle on roads without truckers ruts.

David Lee Greenberg
The GMC Motorhome Registry
Dedicated To The Preservation of the Classic GMC Motorhome
http://www.GMCss.com/Registry.htm
http://www.Buskirk-RushRV.com/GMC-Registry/online-registry.htm
 
Tom,
Here's what I've done. New spline shaft, new GMC power steering box, new
relay arm, checked all other moving parts and they are tight, aligned
several times to spec on camber and toe in, tried increased caster last
time(2.5 and 3.5 degrees), changed over to KB shocks from Caspros', ride
height front and back on the money, Alcoa wheels, G159 tires. Haven't found
anyone locally to check bogey alignment but sight lineup looks good. Drives
like a dream except on I40 truck ruts (crosswinds are a pain but no launch).
Funny thing (to me) is, it's fine in the ruts below about 50 mph but as I
push it up towards 65-70 it gets wild.
I hope you are right that there has to be an answer. I've only got the
bogey alignment as a last try. I will ask Jim Bounds to do it next time I
get to Florida. As you can see, it is exasperating to those of us who would
like to solve it.
Bob McLaughlin

- -----Original Message-----
From: owner-gmcmotorhome
[mailto:owner-gmcmotorhome]On Behalf Of tom warner
Sent: Saturday, July 22, 2000 5:50 PM
To: gmcmotorhome
Subject: Re: GMC: Wiggle Wagon

Justin have you driven in these canyon truck ruts everyone is talking about
or is your driving all on table top smooth roads? There has to be an answer
if even one coach has normal suspension and does not experience this wiggle!

regards,

tom

>Tom, I have to agree with you. I've never had the wiggle wagon problem.
I've
>always insisted that the alignment be according to recommended specs. More
>than once I've had a front end man say to me "that's too much castor. I've
>been doing this 30 years and you don't need that much, I'm going to set it
so
>and so." I insist on recommended specs. Perhaps some alignment people have
>just gone ahead and set the castor to what they think it should be and
caused
>the wiggle wagon factor.
>Justin
>
>
 
Tom,
Thanks. I'll give it a try.
Bob McLaughlin

- -----Original Message-----
From: owner-gmcmotorhome
[mailto:owner-gmcmotorhome]On Behalf Of tom warner
Sent: Sunday, July 23, 2000 12:17 AM
To: gmcmotorhome
Subject: RE: GMC: Wiggle Wagon

Bob you can do the rear alignment at home using the string method detailed
by alex sirum and a few others. It is very accurate.
You might want to try this it works:

http://www.web-access.net/~bmassey/rear_wheel_alignment.html

warmest regards,

tom
 
How did you see it was gone ??

gene

>In a message dated 07/22/2000 5:50:45 PM Central Daylight Time,

>
> Justin have you driven in these canyon truck ruts everyone is talking about
> or is your driving all on table top smooth roads? There has to be an answer
> if even one coach has normal suspension and does not experience this wiggle!
>
> >>
>Yes, I've driven all over the country. Over 175K since I've owned it. East
>coast, west coast, Canada, and even to Alaska. All my GMC buddies who have
>driven my coach always comment on how well it handles. However after
braggin
>about how well my rear boggie pins have held up, I noticed that an O ring
has
>blown out of one. So that has to be replace before another trip.
>Justin
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
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