GMC-Steering

[dick kennedy]

>From watching the posts here it seems that some GMC's drive well and others
don't. Prior to purchasing my '75 PalmBeach I had owned two class C RV's on
GMC chassis and the handling of the GMC is awful by comparison.

The front end has new ball joints and fresh alignment. This improved things
somewhat but the handling is still poor. Everything in the front end seems
to be tight enough that it should work ok.

The rear bogies seem to be tight but on the right side the leading wheel
seems to be pointed about a half degree inward relative to the rear wheel.
It seems to me that at highway speeds as the vehicle sways to the right more
weight would transfer to this wheel which would tend to steer the rear of
the vehicle to the left creating an oversteer condition in the rear end.
This seems to fit the steering pattern I'm experiencing. The rear end has a
lot of side to side whipping that my other RV's didn't.

My manuals specify camber and toein but don't mention alignment of one wheel
relative to the other. I started out expecting to find worn bushings so
haven't actually measured toein at this point. This leading right wheel is
the one which is most likely to be damaged by running over a curb or
something so I would assume someone else has been here before.

Is a half degree difference between the wheels a problem or is there
something else I haven't found? If something is bent is it likely to be the
spindle, the arm or the mount. The spindle could be checked by chucking it
in a lathe and comparing the shaft relative to the flange but measuring the
other pieces would be much more challenging. Is there a way just to shim
everything into place?

Has anyone else been this route before? I would appreciate hearing of
anyone else' experiences.

Dick Kennedy

 

[thomas g. warner]

Dick if you have not got the maintenance manual for the coach it would be
advisable to purchase one from Cinnabar at 1-800-720-2227. All of the
alignments can be shimmed into place assuming that nothing is drastically
bent. Have you checked your tire pressures and shocks. My coach when
purchased drove exactly like you described. Replaced the shocks with KYB
gas shocks, checked the tire pressure (40# right front, 70# left front,
first rear 14#) and now drives beautifully. Large trucks passing cause very
very little disturbance, much less than with my car.

>>From watching the posts here it seems that some GMC's drive well and others
>don't. Prior to purchasing my '75 PalmBeach I had owned two class C RV's on
>GMC chassis and the handling of the GMC is awful by comparison.
>
>The front end has new ball joints and fresh alignment. This improved things
>somewhat but the handling is still poor. Everything in the front end seems
>to be tight enough that it should work ok.
>
>The rear bogies seem to be tight but on the right side the leading wheel
>seems to be pointed about a half degree inward relative to the rear wheel.
>It seems to me that at highway speeds as the vehicle sways to the right more
>weight would transfer to this wheel which would tend to steer the rear of
>the vehicle to the left creating an oversteer condition in the rear end.
>This seems to fit the steering pattern I'm experiencing. The rear end has a
>lot of side to side whipping that my other RV's didn't.
>
>My manuals specify camber and toein but don't mention alignment of one wheel
>relative to the other. I started out expecting to find worn bushings so
>haven't actually measured toein at this point. This leading right wheel is
>the one which is most likely to be damaged by running over a curb or
>something so I would assume someone else has been here before.
>
>Is a half degree difference between the wheels a problem or is there
>something else I haven't found? If something is bent is it likely to be the
>spindle, the arm or the mount. The spindle could be checked by chucking it
>in a lathe and comparing the shaft relative to the flange but measuring the
>other pieces would be much more challenging. Is there a way just to shim
>everything into place?
>
>Has anyone else been this route before? I would appreciate hearing of
>anyone else' experiences.
>
>Dick Kennedy
>
>
>

 

[bartz paul]

Dick:

Some questions come to mind that would potentially affect your handling
concern.

What brand and condition are your shocks?

Same for tires. What is your tire air pressure?

Although each to his own, I run around 55 psi tire pressure. That is
supported by the dealer tire charts as adequate to support my coach
weight.

Are you aware on how to read the age of your tires? If not, on the
sidewall, there is a code consisting of three positions, usually inside
a circle or oval shape. For example, a code of 058 would mean a
manufacture date of the fifth week of 1998. It could also mean the
fifth week of 1988, and so on. Tire rubber begins to get hard after 3-4
years and affects your ride. Unless you accumulate a lot of miles
driving, listening to tire salesmen tout high tire mileage as a selling
point, isn't worth while. I'm convinced that tire sidewall construction
(e. g. steel vs. belted ply's) also affects the wiggle factor and ride
quality. Steel being somewhat harsher. Michelin tech support says the
principal advantage to steel sidewall construction is increased weight
carrying capacity.

Although I don't know anyone who actual had a bent swing arm, it is
something a number of owners had worried about. With a straight edge,
you should be able to determine if you have a bent condition,
particularly relative to another arm.

Are you also aware that the track of the front wheels is slightly
narrower than that of the rear wheels? That normally results in the
front wheels hunting for position between the peaks and valleys when you
traverse rutted asphalt pavement, resulting in the coach wiggle you
experience.

Unless you notice an abnormal tire wear problem, normally an alignment
is not necessary. I know of several owners who were disappointed after
obtaining an alignment, which didn't change the coach handling. Also,
there are a couple of coach owners I'm aware of from Texas who have
experimented with the toe-in angle and make claims for the settings they
find better. A local coach owner has recently gone to those settings
and claims he doesn't notice a pulling to the right condition that he
previously combated.

Another item which helps tremendously, one I installed in 1995, is the
four air-bag rear suspension system.

Although I haven't solved your condition yet, hang in there and lets
keep the communication going to see if it can be solved, as I believe it
can. Perhaps others will join in the conversation with their views too.

Paul Bartz


> -----Original Message-----
> From: Dick Kennedy [SMTP:rakennedy]
> Sent: Monday, June 01, 1998 9:09 AM
> To: gmcmotorhome
> Subject: GMC: GMC-Steering
>
> From watching the posts here it seems that some GMC's drive well and
> others don't. Prior to purchasing my '75 Palm Beach, I had owned two
> class C RV's on GMC chassis and the handling of the GMC is awful by
> comparison.
>
> The front end has new ball joints and fresh alignment. This improved
> things somewhat but the handling is still poor. Everything in the
> front end seems to be tight enough that it should work ok.
>
> The rear bogies seem to be tight but on the right side the leading
> wheel seems to be pointed about a half degree inward relative to the
> rear wheel. It seems to me that at highway speeds as the vehicle
> sways to the right, more weight would transfer to this wheel which
> would tend to steer the rear of the vehicle to the left creating an
> oversteer condition in the rear end. This seems to fit the steering
> pattern I'm experiencing. The rear end has a lot of side to side
> whipping that my other RV's didn't.
>
> My manuals specify camber and toe-in but don't mention alignment of
> one wheel relative to the other. I started out expecting to find worn
> bushings so haven't actually measured toein at this point. This
> leading right wheel is the one which is most likely to be damaged by
> running over a curb or something so I would assume someone else has
> been here before.
>
> Is a half degree difference between the wheels a problem or is there
> something else I haven't found? If something is bent is it likely to
> be the spindle, the arm or the mount. The spindle could be checked by
> chucking it in a lathe and comparing the shaft relative to the flange
> but measuring the other pieces would be much more challenging. Is
> there a way just to shim everything into place?
>
> Has anyone else been this route before? I would appreciate hearing of
> anyone else' experiences.
>
> Dick Kennedy

 

[dick kennedy]

Didn't get home 'til late last night so haven't done too much. Work for a
living keeps getting in the way. Have taken the shocks off of right rear.
The forward one is frozen so it won't move any and the rear one is too loose
to damp anything. I've never seen shocks this bad, these could be my whole
problem

The shocks are Bilsteins which I've read here have a lifetime warranty,
although I didn't find any mention of warranty at their web site. I just
bought the coach so don't have receipts. How do I go about getting the
warranty? Or should I just order the KYB's from Proam?

Also where can I get more detail on the four bag system. I pull a boat so
the idea of being able to transfer weight forward by taking weight off the
inner wheel is intriquing. Who sells the air bag kits? how much do they
cost? What is the mechanical configuration? More importantly; are all the
components off the shelf items that can be found on the road. These old
beasts are difficult enough to find parts for without going oddball.

I'm in Kokomo, In if someone has one close enough for me to take a look.

Dick Kennedy

 

[bartz paul]

Dick:

In earlier e-mail responses this A.M., I provided my thoughts, answered
some questions and listed a URL (subsequently updated) about the system
that you can read.

I live in Kalamazoo MI and welcome your visit if interested. I'll even
take you for a demo if desired.

Paul Bartz

> -----Original Message-----
> From: Dick Kennedy [SMTP:rakennedy]
> Sent: Tuesday, June 02, 1998 8:33 AM
> To: gmcmotorhome
> Subject: Re: GMC: GMC-Steering
>
> Didn't get home 'til late last night so haven't done too much. Work
> for a living keeps getting in the way. Have taken the shocks off of
> right rear. The forward one is frozen so it won't move any and the
> rear one is too loose to damp anything. I've never seen shocks this
> bad, these could be my whole problem
>
> The shocks are Bilsteins which I've read here have a lifetime
> warranty, although I didn't find any mention of warranty at their web
> site. I just bought the coach so don't have receipts. How do I go
> about getting the warranty? Or should I just order the KYB's from
> Proam?
>
> Also where can I get more detail on the four bag system. I pull a boat
> so the idea of being able to transfer weight forward by taking weight
> off the inner wheel is intriquing. Who sells the air bag kits? how
> much do they cost? What is the mechanical configuration? More
> importantly; are all the components off the shelf items that can be
> found on the road. These old beasts are difficult enough to find parts
> for without going oddball.
>
> I'm in Kokomo, In if someone has one close enough for me to take a
> look.
>
>
> Dick Kennedy