The eccentric upper control arm bushings, can be used in either forward or
rearward control arms, depending upon the effect desired. In our
application, they are installed to enable the rearward control arm to
travel towards the frame, and in effect, move the upper ball joint towards
the rear of the coach. That has the effect of moving the contact patch of
the front tire towards the front of the coach. Draw a straight line
directly through the centerline of the upper and lower ball joints to
illustrate this effect. It makes the front tire want to travel in a
straight line, rather than turn right or left. Ergo: more hands off
handling rather than less so.
Obviously, many other forces are at work here. Not part of this
subject. Not wanting to get into a big "Hoo-Haw" about this.
Jim Hupy
Salem, Oregon
On Wed, Jan 20, 2021, 7:01 PM Ken Henderson via Gmclist <
> Well, I guess I've had my head screwed on backward for quite some time:
> I've been thinking, and discussing, the use of offset bushings in the UPPER
> REAR of the upper A-arm. Tonight, I've been researching offset bushing
> part numbers. LO and BEHOLD: Moog (and everyone else) ONLY mentions
> eccentric (offset) bushings for the upper FRONT! NOT the rear! Holy Moly,
> why hasn't someone called me on that? Or have we GMCers been "doing our
> own thing"?
>
> Here are the ONLY Moog part numbers I've found for '76 Toronado (and by
> extension GMCMH):
>
> Standard Offset(Eccentric)
> Upper Front K7006 K7104
> Upper Rear K6111
> Lower Front K5222
> Lower Rear K6116
>
> Does this mean that the K7104 will ONLY fit the Upper Front, or merely that
> that's where they're recommended (but CAN fit the rear?).
>
> Come on, somebody straighten this mess out.
>
> Ken H.
>
>
> On Wed, Jan 20, 2021 at 9:01 PM Ken Henderson
>
> > I've got another question (or more) for this survey:
> >
> > 1. Is it feasible to use offset bushings in both the rear AND front of
> > the upper A-arms? Seems to me it should be perfectly OK and potentially
> > give about twice as much caster increase as using them only in the rear.
> >
> > 2. Seems to me installing the offset bushing in the rear, to increase
> > caster, would inevitably tend to move camber toward negative. By the
> same
> > rationale, using offset bushings front and rear would have less effect on
> > camber because the front would tend toward positive camber about equal to
> > the rear's negative effect.
> >
> > 3. Has anyone considered or tried the offset upper A-arm shafts? Like
> > this:
> > bit.ly/3obunmp
> > or
> >
> >
> https://www.globalwest.net/billet-steel-stock-upper-control-arm-offset-cross-shaft-camaro-67-68-69-global-west.html
> >
> > I have no idea whether those are available to fit the GMC, but we've got
> > plenty of folks capable of designing and building them. It might be
> easier
> > than modifying A-arms, as Lenzi does. What are the pros & cons?
> >
> > 4. Other options?
> >
> > Rest assured, I'm just trying to learn something here -- I'm happy with
> my
> > 1-ton front end -- and it was installed before Manny decided to increase
> > the caster. (I THINK I did use offset bushings in the rear though --
> tooo
> > long ago for my old memory to be sure.)
> >
> > Thanks for all your inputs/ideas.
> >
> > Ken H.
> >
> >
> > On Thu, Jan 14, 2021 at 11:42 AM Ken Henderson
> >
> >> Time for a survey of those using Dave Lenzi's upper A-arms modified for
> >> increased caster:
> >>
> >> What's your opinion after using them for a while? Do they significantly
> >> increase the steering stability? Did you try the offset bushings before
> >> going to modified A-arms? How do they compare? Did either affect the
> >> steering effort significantly? Which is the "better buy" -- or is
> either
> >> worth the trouble/cost?
> >>
> >> Thanks for your opinions.
> >>
> >> Ken H.
> >>
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
rearward control arms, depending upon the effect desired. In our
application, they are installed to enable the rearward control arm to
travel towards the frame, and in effect, move the upper ball joint towards
the rear of the coach. That has the effect of moving the contact patch of
the front tire towards the front of the coach. Draw a straight line
directly through the centerline of the upper and lower ball joints to
illustrate this effect. It makes the front tire want to travel in a
straight line, rather than turn right or left. Ergo: more hands off
handling rather than less so.
Obviously, many other forces are at work here. Not part of this
subject. Not wanting to get into a big "Hoo-Haw" about this.
Jim Hupy
Salem, Oregon
On Wed, Jan 20, 2021, 7:01 PM Ken Henderson via Gmclist <
> Well, I guess I've had my head screwed on backward for quite some time:
> I've been thinking, and discussing, the use of offset bushings in the UPPER
> REAR of the upper A-arm. Tonight, I've been researching offset bushing
> part numbers. LO and BEHOLD: Moog (and everyone else) ONLY mentions
> eccentric (offset) bushings for the upper FRONT! NOT the rear! Holy Moly,
> why hasn't someone called me on that? Or have we GMCers been "doing our
> own thing"?
>
> Here are the ONLY Moog part numbers I've found for '76 Toronado (and by
> extension GMCMH):
>
> Standard Offset(Eccentric)
> Upper Front K7006 K7104
> Upper Rear K6111
> Lower Front K5222
> Lower Rear K6116
>
> Does this mean that the K7104 will ONLY fit the Upper Front, or merely that
> that's where they're recommended (but CAN fit the rear?).
>
> Come on, somebody straighten this mess out.
>
> Ken H.
>
>
> On Wed, Jan 20, 2021 at 9:01 PM Ken Henderson
>
> > I've got another question (or more) for this survey:
> >
> > 1. Is it feasible to use offset bushings in both the rear AND front of
> > the upper A-arms? Seems to me it should be perfectly OK and potentially
> > give about twice as much caster increase as using them only in the rear.
> >
> > 2. Seems to me installing the offset bushing in the rear, to increase
> > caster, would inevitably tend to move camber toward negative. By the
> same
> > rationale, using offset bushings front and rear would have less effect on
> > camber because the front would tend toward positive camber about equal to
> > the rear's negative effect.
> >
> > 3. Has anyone considered or tried the offset upper A-arm shafts? Like
> > this:
> > bit.ly/3obunmp
> > or
> >
> >
> https://www.globalwest.net/billet-steel-stock-upper-control-arm-offset-cross-shaft-camaro-67-68-69-global-west.html
> >
> > I have no idea whether those are available to fit the GMC, but we've got
> > plenty of folks capable of designing and building them. It might be
> easier
> > than modifying A-arms, as Lenzi does. What are the pros & cons?
> >
> > 4. Other options?
> >
> > Rest assured, I'm just trying to learn something here -- I'm happy with
> my
> > 1-ton front end -- and it was installed before Manny decided to increase
> > the caster. (I THINK I did use offset bushings in the rear though --
> tooo
> > long ago for my old memory to be sure.)
> >
> > Thanks for all your inputs/ideas.
> >
> > Ken H.
> >
> >
> > On Thu, Jan 14, 2021 at 11:42 AM Ken Henderson
> >
> >> Time for a survey of those using Dave Lenzi's upper A-arms modified for
> >> increased caster:
> >>
> >> What's your opinion after using them for a while? Do they significantly
> >> increase the steering stability? Did you try the offset bushings before
> >> going to modified A-arms? How do they compare? Did either affect the
> >> steering effort significantly? Which is the "better buy" -- or is
> either
> >> worth the trouble/cost?
> >>
> >> Thanks for your opinions.
> >>
> >> Ken H.
> >>
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
