Swing Arm Guides

K

Ken H.

Active member
Sep 9, 2000
19,427
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A couple of years ago one of the Sunshine Statesmen bought a set of used
rear suspension arm roller guides from Sirum's. After discussing it, he and
I decided we'd each take one pair to go on our center arms. I've never
liked the wheelbarrow-like center wheel arrangement and figure the rear
wheels are gonna have to do pretty much whatever the rest of the coach does.

The Eldorado backing plates, on which I based my 6-wheel disc brakes,
interfered with the mounting of the guide rollers so I had to replace them
with smaller caliper mounts. A deal with Terry Skinner brought me a set of
those recently so yesterday I began the conversion. Mounting Terry's
caliper mounts, the guide rollers, and the guide tracks was no problem.

Now I need advice from anyone who's installed guides before. I've got all
the holes drilled, setting the longitudinal positioning of the tracks. But
I haven't tightened any of the bolts because I need to know how to adjust
them laterally. When the suspension arms are all the way down, the rollers
rest either near or touching the outsides of the tracks. As the suspension
arms rise, the rollers bear harder and harder on the outsides of the tracks,
binding severely at the top, even with loose bolts.

Obviously I've got to shim the tracks to keep the rollers more nearly
centered throughout the arms' travel. The big question is, how much will
the weight of the coach affect their alignment when I put the wheels back on
and lower it to the ground? I think the frame will flex slightly and the
arms bend a little, thereby decreasing the binding -- but those are WAGs.
There won't be enough clearance under there to measure or adjust anything at
ride height with wheels on.

So, has anyone had experience they can share with me? Any tricks or unique
procedures to use? Or must I just do it all by trial & error?

TIA,

Ken Henderson
Americus, GA
www.GMCWipersEtc.com
76 X-Birchaven
76 X-Palm Beach

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Hi Ken

I'll bet you need to get with Bob Hooton and get his input.
www.bdub.net/hooton/

Or, give Ken Rose a call. He used to build and sell these years ago.
www.bdub.net/rose/

hth
bdub

>So, has anyone had experience they can share with me? Any tricks or unique
>procedures to use? Or must I just do it all by trial & error?

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Billy,

Thanks. I'd forgotten Bob Hooton had his instructions posted. His design
has a lateral adjustment which this one doesn't appear to have so I'll have
to use shims. He positions the suspension arm at center travel and makes
only one adjustment. Maybe that will work for me. I'll call him.

Might call Ken too.

Ken H.

> -----Original Message-----
> Hi Ken
>
> I'll bet you need to get with Bob Hooton and get his input.
> www.bdub.net/hooton/
>
> Or, give Ken Rose a call. He used to build and sell these years ago.
> www.bdub.net/rose/
>
> hth
> bdub

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Ken,
I am glad you brought this up. I remember you saying that you were going to try a set a couple of years ago. I was going to ask you how they worked out. I have spoken with Bob Hooten and was going to purchase a set, but several other people had told me that they were trouble to align and they only masked symptoms of other problems. I since replaced the whole front end including the forward frame section. Added correct tracks ( which made a Huge! differnce by the way ) and everything else I could think of. The thing still handles awfull. I seldom let my wife drive it, and as yet she has been lucky not to have the crap scared out of her the few times she did. I have certainly had to stop for a fresh change a few times. I know we tend to drive faster than most others but not faster than all. I have talked to several people that drive consistently in the seventies. ( Besides even if I said that I would never go over 65, my wife creeps up to eighty everytime I am in the back relaxing with cold one. Thats why I usualy have to wait until we arrive, lol. ) Anyway the damn thing is so twitchy. I have finally come to the conclusion that the back is steering itself. It seems that the road makes a major difference, as sometimes it seems fine and the 20 miles later, white knuckle road. This does not always seems to be from ruts either. I have checked all my rear swing arms and only one front one is on the edge of tollerance. I was going to have at least the front pins done next time I get up to Jims, but I have a feeling that I will still be in the same boat. I also began towing a Tracker which realy seemed to make it worse. I know this has been a subject many times over, but I feel that the topic is so subjective that it realy does not apply to my use. Any thing uder sixty and I can practicly close my eyes without worry. I am looking forward to hearing about your field tests with these, as I am seriuosly considering trying these up front only before putting in all new pins.
--
Lionel Vargas
73 260 CCL
FL Keys

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Lionel,
There are a number of factors to be considered here. The tracking
channels are not meant to be a fixall, just keep the bogeys traveling
in a vertical plane only. Saves wear and tear on the pins and
prevents the rear wheels from traveling in and out on variable road
surfaces.
What kind of tires are you running?
In the travel position, what is the measurement from either the
factory specified frame slots or the center of the rear bogey pin
grease zerk?
OEM bag setup or 4-bag?
If your rear alignment is correct, there should be no problem with
alignment of the bearing to the channels. When my coach is all the
way down, the large bearing is just above the channel. It slips in as
the coach is raised. Hooten's kit has a large bearing riding on a cam
bolt so the position of the bearing in the guide can be adjusted.

I am looking forward to hearing about your field tests with these, as
I am seriuosly considering trying these up front only before putting
in all new pins.
> --
> Lionel Vargas
> 73 260 CCL
> FL Keys
>
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--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source

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Steve I am running BFG Commercial TA. These tires have been great, I had Jim B round then for me and they are nice, tight and smooth as glass with out any hard jolting. They were another big handleing improvement. I still am holding out with the factory bags as they are both less than 5 years old, But I plan to get the new stlye 4 bag sometime in the near furure money permitting. I have never had the coach on a six wheel machine but it was checked out by a GMC shop and is supposed to be in tolerance even though the two front rear wheels have a little to much camber. I beleive it is from hitting stuff in the distant past as the frame is not drooping. I am not sure what measurement you are refering to , especialy the slot part, I have somehow missed this section of the book evidentally. Probably the only section. I have raised the coach and checked the swing arms with no weight at the travel position by pulling in an out, this is what I was referring to as the front left being on the edge of tolerance.
--
Lionel Vargas
73 260 CCL
FL Keys

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Lionel Vargas writes...

> I know this has been a subject many times over, but I feel that the
> topic is so subjective that it realy does not apply to my use. Any
> thing uder sixty and I can practicly close my eyes without worry.

I think it's time for another of my pedantic statements about Basic
Truth. No offense to any one person intended, but I think we need to
keep these in mind to avoid going astray.

1. The speed limits when GMCs were designed (not when they were built)
were as high or higher than they are today.

2. GMCs handled beautifully when they were new, compared to
truck-based motorhomes.

ERGO, there is no deficiency in the design of the GMC that should
preclude being driven at highway speeds, if the standard of comparison
is characterized by truck-based motorhomes.

I've heard that the roads aren't as good. They aren't in some places.
but they are better in many other places, and rutting on asphalt
pavements is nothing new.

It seems to me if a GMC does not handle beautifully compared to a
truck-based motorhome, one can only conclude that there is a reason
based on some difference between its current condition and its new
condition.

Therefore, I think trying to add a bunch of ex-factory improvements
will likely do no more than empty our wallets until the suspension has
been fully restored to like-new condition as designed by GM.

My rear pins are worn and have some play in them. I will not add
Tru-Track or sway bars or anything like that until I get that fixed. I
might find that I don't need those other things to achieve my handling
goals, and I'm unlikely to find that those will make a good bandaid on
worn pins.

Pin wear is easy to measure and evaluate. Put blocks under the bogie
frames at normal ride height, and then let the air out of the bags.
Grab the middle tire and push it into and away from the coach, measure
the amount of travel at the front edge of the wheel. I seem to recall
the factory tolerance was 1/8". Mine is more.

Another thing that can cause bad handling is poor balance. In my
opinion, you can't evaluate front balance unless the rear is at normal
load and properly leveled--the leveling system will affect the front
balance. And if the rear is way out of balance, the leveling system
will transfer that out-of-balance condition to the front to achieve a
level coach.

Poor alignment can, of course, cause handling problems. That can be
evaluated, and it should be corrected before adding any aftermarket
gadgets. It could be a misaligned bogie frame, or a bent bogie.
Missing or ruined body mounts can twist the frame enough to create
issues, it seems to me. Tracking guides or four-bag systems, etc.,
will not solve those problems.

Once the system is restored to original factory spec so that it drives
like it did new, then I think it's possible to contemplate improving
on GM's intended design to achieve something better than beautiful
handling compared to a truck-based motorhome. The point of the
tracking device on the forward-pointing bogies is not to take up slack
in the pins, but to control misalignments caused by flexing of the
bogie arm as tire and road anomalies trying to pull it off track.

Rick "whose coach handles well, compared to a truck-based motorhome,
even with loose bogie pins" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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you forgot tires,
the biggest improvement in handling in the last 10 years has been to go
back to Rag wall tires like they used on the OEM GMCs.

gene

>Rick "whose coach handles well, compared to a truck-based motorhome,
>even with loose bogie pins" Denney
>
>'73 230 Ex-Glacier "Jaws"
>Northern Virginia

Gene Fisher -- 77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and -------
http://gmcmotorhomeinfo.com/
Alternator Protection Cable
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SOOR summer rally
http://gmcmotorhomeinfo.com/SOOR.html

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On Mon, 5 Jun 2006 15:41:50 -0400 Rick Denney
writes:
> Lionel Vargas writes...
>
> > I know this has been a subject many times over, but I feel that
> the
> > topic is so subjective that it realy does not apply to my use.
> Any
> > thing uder sixty and I can practicly close my eyes without worry.
>
> I think it's time for another of my pedantic statements about Basic
> Truth. No offense to any one person intended, but I think we need
> to
> keep these in mind to avoid going astray.
>

While I never put th swing arm guides on my GMC their use is valid in my
considerable experience.

Their use has nothing at all to do with speed limits-then or now, nor
does road pavement quality play into this, or the quality GMC handling.

An owner found that when the passenger's side rear bogies dropped off the
pavement, the rear wheels would have a contest to see which direction
each one would follow in getting back on the pavement.

These were designed to 'harness' the two rear wheels in going in the same
lateral direction.

That's my story and I am sticking with it. VBG

Dave Greenberg
Port Saint Lucie, Florida
GMC Motorhome Registry "Dedicated To The Preservation of The Classic
GMC!"
www.GMCss.com/Registry.htm
http://www.picturetrail.com/gmcregistry

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mr.erf writes...

> you forgot tires,
> the biggest improvement in handling in the last 10 years has been to go
> back to Rag wall tires like they used on the OEM GMCs.

Yup. But the biggest change as been in our expectations. We don't
compare the GMC with a truck-based motorhome--we compare it with a
car. Not only that, but to today's lighter, radial-equipped,
rack-and-pinion-equipped, aluminum-wheel-equipped cars. But trying to
satisfy that higher calling requires us to first satisfy the factory's
intentions, it seems to me.

Rick "who goes 75 and who only needs one hand (two when the steering
CV joint is binding)" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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Lionel,
Section 4-34 of the maintenance manual has the ride height setting
specs. From the center of the bogey casting, measure 56 3/8" back on
the frame. You'll see a slot (easiest on the pass side). The correct
ride height setting is measured from the top of this slot to the floor
and should be 11-11/16, + or - 1/4 inch. Keep in mind that in order
to set the ride height correctly, the front needs to be correct as it
has an effect on the rear. Some pull the front tires, jack the front
to the correct height in the front, then set the rears. Hard to go
wrong with this method. I suggest that once you get the ride height
set correctly, find an easier place to take your measurements from. I
carry a stick with graduation marks on it and use the rearmost bogey
grease zerk as my reference point. Some use the beltline trim etc.
Anything is easier that those slots, especially on the Onan side. The
above is for a 26. On a 23, the slot is 40-3/8 back from the center
of the casting.

I am not sure what measurement you are refering to , especialy the
slot part, I have somehow missed this section of the book
evidentally. Probably the only section. I

--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source

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That says it for me also Dave. When Arch mentioned it, I too set my
mirrors so I could watch my rear wheels at a glance. I was
dumbfounded at how far in and out they travel. My pins are in
excellent condition and I believe that the guides will help keep them
that way. BTW, that in and out travel is gone now and so is the
shoulder snatch that came with it. No longer does driving off the
edge of pavement wake me :>)

Dave Wrote:
I know this has been a subject many times over, but I feel that
the topic is so subjective that it realy does not apply to my use.
Any thing uder sixty and I can practicly close my eyes without worry.
I think it's time for another of my pedantic statements about Basic
Truth. No offense to any one person intended, but I think we need
to keep these in mind to avoid going astray.
While I never put th swing arm guides on my GMC their use is valid in
my considerable experience.
Their use has nothing at all to do with speed limits-then or now, nor
does road pavement quality play into this, or the quality GMC handling.
An owner found that when the passenger's side rear bogies dropped off
the pavement, the rear wheels would have a contest to see which
direction each one would follow in getting back on the pavement.
These were designed to 'harness' the two rear wheels in going in the
same lateral direction.
That's my story and I am sticking with it. VBG
--
Steve Ferguson
'76 EII
Sierra Vista, AZ
Urethane bushing source

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>
> you forgot tires,
> the biggest improvement in handling in the last 10 years has been
> to go back to Rag wall tires like they used on the OEM GMCs.
>
> gene

Gene - the RADIAL "ragwall" tires being used today are nowhere near
the bias ply ragwalls that they used on the older model OEM GMCs.

Emery Stora
77 Kingsley
Santa Fe, NM



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but a big step up from the steel walls we were led down the garden path
with for 10 years.

gene

>Gene - the RADIAL "ragwall" tires being used today are nowhere near
>the bias ply ragwalls that they used on the older model OEM GMCs.
>
>Emery Stora

Gene Fisher -- 77PB/ore/ca
"Give a man a fish; you have fed him for today --- give him a URL and -------
http://gmcmotorhomeinfo.com/
Alternator Protection Cable
http://gmcmotorhomeinfo.com/APC.html
SOOR summer rally
http://gmcmotorhomeinfo.com/SOOR.html

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Rick,

I agree with your concern about getting everything "right" before attempting
changes. But I've had everything right and still wasn't as happy as I want
to be with the GMC's handling. Maybe all I really need is bias ply tires,
but I'm not going to get 'em even if I'd have 'em. So, I've got to try to
overcome the rear end wander some other way. Since I think pushing the
center tires around the way we do is sorta like trying to push a wet noodle
from the end, I'm going to try the track guides. What the heck, I've only
got $75 in them -- not even one GMC Unit.

It would be nice to get the GMC to the condition of most modern cars and
trucks: Nudge the wheel every now and then with one finger tip to keep it
in the center of the lane, regardless of road condition. That's not going
to happen, especially with a towed tail back here wagging the dog. But I
would like to get close when not towing.

By the way, the accumulated wear in my bushings (one center now has about
1/4", mostly axial) has not caused much steering degradation in 60,000+
miles.

You'll be getting a note off-net about your pins & bushings.

Ken H.

> -----Original Message-----
> ...
> Therefore, I think trying to add a bunch of ex-factory
> improvements will likely do no more than empty our wallets
> until the suspension has been fully restored to like-new
> condition as designed by GM.

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In a message dated 6/5/2006 2:56:15 P.M. Central Daylight Time,

>you forgot tires,
>the biggest improvement in handling in the last 10 years has been to go
>back to Rag wall tires like they used on the OEM GMCs.

Gene

I agree with that. The all steel RIB tires rode like a stiff legged pony.
They also had very little traction. Pump them up to 80 PSI and
it was disaster. I know I drove them that way for 5 years.

Take Care
Arch


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Ken Henderson writes...

> I agree with your concern about getting everything "right" before
> attempting changes. But I've had everything right and still wasn't
> as happy as I want to be with the GMC's handling.

Folks may be misunderstanding me, so let me be clear:

I'm not saying there are no improvements to be made. I'm saying (as
you correctly interpret) that a coach that has really bad handling
needs to be properly repaired *first*, before attempting those
improvements. No coach in factory condition should have really bad
handling.

I was responding to a complaint about a coach that handles badly at
highway speeds, where the person had attempted at least one
aftermarket improvement and was considering more *before* having the
pins overhauled and going through proper ride height and front
geometry checks and adjustments.

I myself may consider those improvements once I've restored factory
condition, but I may find I don't need some or all the things people
are trying to meet my goals.

I personally think the track guides are a good idea in principle for
the reasons you mention, if they can be kept clean enough not to bind.
I will probably look at them seriously--AFTER I redo my pins and
bushings and get everything else up to spec.

> It would be nice to get the GMC to the condition of most modern cars
> and trucks: Nudge the wheel every now and then with one finger tip
> to keep it in the center of the lane, regardless of road condition.

I wish it was that way even with modern cars. I find my newer cars
require much more steering input than did my older cars, and they have
noticeably less centering action. I think it's in part because of the
sportier suspensions, and in part because of the slot-car tires. But
it is also the way the suspensions are designed and tuned. I kind of
like that the GMC doesn't have to be fiddled with constantly, but it
would be nice if what fiddling was required happened at more
predictable times. It's the little surprises that I think bother folks
who have otherwise good-handling coaches.

My 1974 GMC pickup had exactly the same handling issues as my coach: A
pavement drop-off will pull the back end in that direction, and nudge
the front end in the opposite direction, causing a sway. The other
issue on my coach is that the coach leans before turning, given the
feeling of incipient oversteer which is uncomfortable. I suspect a
tighter rear end would help with that problem.

> By the way, the accumulated wear in my bushings (one center now has
> about 1/4", mostly axial) has not caused much steering degradation
> in 60,000+ miles.

That's good to know in my case, since the cost of redoing the pins is
a little out of reach at quoted prices just now.

> You'll be getting a note off-net about your pins & bushings.

Received--thanks.

Rick "who has removed enough 'improvements' applied as bandaids to
worn-out parts" Denney

'73 230 Ex-Glacier "Jaws"
Northern Virginia

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Well said Rick, The GMC was meant to Cruise.

I have pretty much covered all this, however there is some room for improvement. I could benifit from a six wheel alignment but the nearest I know of is 10 hours away, it is on the list. I have however had it done to the best of a tape measures abilities and the assistance of a laser rig my buddie came up with. My coach other than being an ealry 73 is runs very empty and light generally, as I am a fanatic on what comes and where it goes. Got the frame issues covered. The rear Bogies tested as you described are all under probably a 1/16 except for the front left, which is just as 1/8. I have been told by more than one person that thier coach handles fine with more than this. ???????? Everytime I have corrected something it did get better, but still not it.
--
Lionel Vargas
73 260 CCL
FL Keys

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Wow, old age is truly catching up with me Duh. Of course I have set my ride height. I even have the air system working as intended. I was thinking how does slots apply to the bogies and where are they? Now I know which slots you mean. No not that. By the way I ahve experimented with this and found little or no handleing differene. even if I several raked it forward such as in a high airbag condition or had the front almost two inches low. With that said I have added the offset bushings front and rear and probably have plenty of caster to make it up even though I don't know the exact number.
--
Lionel Vargas
73 260 CCL
FL Keys

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> Anyway the damn thing is so twitchy. I have finally come to the conclusion that the back is steering itself.Any thing uder sixty and I can practicly close my eyes without worry.
Sounds like you are aero-loose. How is your ride height? If your front end drops at speed you could get into oversteer, whiich is what it sounds like. Also could it be your torsion bars have gone soft over time?

--
Hardie Johnson "Crashj"
1973 26 foot Glacier, White Thing
Enola PA

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