Home » Public Forums » GMCnet » Re: [GMCnet] The Markbag(tm)
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| Re: [GMCnet] The Markbag(tm) [message #155712 is a reply to message #155704] |
Fri, 06 January 2012 13:50   |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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I think the hot-dog of the bag is more of a result of the side bending of
the bag due to the angle of the mounting cones. As the suspension is
raised, the angle of the bogie arm bag platform changes. As height is
increased the angle also increases and when the coach is at specified
travel height the cones are both angled upward away from parallel which
puts more compression on the bottom side of the bag. The Sullybilt air
spring plates are at a much closer angle in relation to each other (closer
to parallel) when at ride height which results in a much lower bend
(almost none) in the air bag at travel height. The Firestone spec states
that the loading capacity of each bag to be the following:
1264lbsf at 20psi
3792lbsf at 60psi
5688lbsf at 90psi
I noticed no gain in lift over 85psi. I would think reducing the compressor
cut out down to 80psi would be more than sufficient to operate the system
through its full range even with above desired tongue weight while towing.
I did not check pressure in the system at ride height. I would imagine it
is in the 60psi range from the bag specs. I measured from the bogies to the
floor during inflation and watched until no further lift was achieved but
pressure continued to increase. That was at 80psi or so. I then continued
to inflate to 120psi with no further gain in height. The Firestone engineer
I spoke with today said that the maximum service inflation pressure is
100psi. Since no gain in height is achieved above 80psi or so I see no need
to have the compressor shut off any higher than 85psi.
Sully
77 Royale
On Fri, Jan 6, 2012 at 10:12 AM, gene Fisher <mr.erfisher@gmail.com> wrote:
> On Fri, Jan 6, 2012 at 10:10 AM, gene Fisher <mr.erfisher@gmail.com>
> wrote:
>
> > Your first note said the ride height was at 90#
> >
> > the bag-llfters reduce the pressure to 70# and stop the hot-dog of the
> bag.
> > this will allow full raising of the coach with lower pressure.
> >
> > thanks
> > gene
> >
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] The Markbag(tm) [message #155725 is a reply to message #155720] |
Fri, 06 January 2012 15:01 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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Agreed Emery but if there is an issue with the height control valve it would be a nice fail safe to reduce the max output of the compressor to prevent filling the bag beyond its max service pressure.
Sully
77 royale
Sent from my Verizon Wireless BlackBerry
-----Original Message-----
From: Emery Stora <emerystora@mac.com>
Sender: gmclist-bounces@temp.gmcnet.org
Date: Fri, 06 Jan 2012 13:11:31
To: <gmclist@temp.gmcnet.org>
Reply-To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] The Markbag(tm)
On Jan 6, 2012, at 12:50 PM, Todd Sullivan wrote:
> That was at 80psi or so. I then continued
> to inflate to 120psi with no further gain in height. The Firestone engineer
> I spoke with today said that the maximum service inflation pressure is
> 100psi. Since no gain in height is achieved above 80psi or so I see no need
> to have the compressor shut off any higher than 85psi.
>
> Sully
> 77 Royale
>
If your wheel well height control levers are adjusted properly then it doesn't matter if your compressor is set at 90 or 120. The valve will determine the pressure in the bag to raise it to the height selected and no more pressure will go to the bag. Any excess pressure until the pressure switch for the pump cuts out will go into the small tank for the compressor.
Emery Stora
77 Kingsley
Santa Fe, NM
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] The Markbag(tm) [message #155727 is a reply to message #155712] |
Fri, 06 January 2012 15:06 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Sully,
It has been noted here that if the front and rear ride height are set properly you can draw a straight line through the centers of
the rear spindle, the rear bogie pin, the front bogie pin, and the front spindle.
The mounting faces of the air bag cones are 90° perpendicular to that line.
Regards,
Rob M.
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org [mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Todd Sullivan
Sent: Saturday, 7 January 2012 6:51 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] The Markbag(tm)
I think the hot-dog of the bag is more of a result of the side bending of
the bag due to the angle of the mounting cones. As the suspension is
raised, the angle of the bogie arm bag platform changes. As height is
increased the angle also increases and when the coach is at specified
travel height the cones are both angled upward away from parallel which
puts more compression on the bottom side of the bag. The Sullybilt air
spring plates are at a much closer angle in relation to each other (closer
to parallel) when at ride height which results in a much lower bend
(almost none) in the air bag at travel height. The Firestone spec states
that the loading capacity of each bag to be the following:
1264lbsf at 20psi
3792lbsf at 60psi
5688lbsf at 90psi
I noticed no gain in lift over 85psi. I would think reducing the compressor
cut out down to 80psi would be more than sufficient to operate the system
through its full range even with above desired tongue weight while towing.
I did not check pressure in the system at ride height. I would imagine it
is in the 60psi range from the bag specs. I measured from the bogies to the
floor during inflation and watched until no further lift was achieved but
pressure continued to increase. That was at 80psi or so. I then continued
to inflate to 120psi with no further gain in height. The Firestone engineer
I spoke with today said that the maximum service inflation pressure is
100psi. Since no gain in height is achieved above 80psi or so I see no need
to have the compressor shut off any higher than 85psi.
Sully
77 Royale
On Fri, Jan 6, 2012 at 10:12 AM, gene Fisher <mr.erfisher@gmail.com> wrote:
> On Fri, Jan 6, 2012 at 10:10 AM, gene Fisher <mr.erfisher@gmail.com>
> wrote:
>
> > Your first note said the ride height was at 90#
> >
> > the bag-llfters reduce the pressure to 70# and stop the hot-dog of the
> bag.
> > this will allow full raising of the coach with lower pressure.
> >
> > thanks
> > gene
> >
>
> --
> Gene Fisher -- 74-23,77PB/ore/ca
> “Give a man a fish; you have fed him for today --- give him a URL and
> -------
> http://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] The Markbag(tm) [message #155732 is a reply to message #155727] |
Fri, 06 January 2012 16:23 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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As you will see in the photo, when the spindles are aligned with bogie pins
the vertical upright s of the arms are parallel but the mounting surfaces
for the bag are not. They are splayed outward from center vertically from
the top to the bottom.
https://picasaweb.google.com/lh/photo/_hgX84BEnFolvkHldpq6rA1Piv9hnV4Ggxc2P_hqJgQ?feat=directlink
Sully
77 Royale
On Fri, Jan 6, 2012 at 1:06 PM, Rob Mueller <robmueller@iinet.net.au> wrote:
> Sully,
>
> It has been noted here that if the front and rear ride height are set
> properly you can draw a straight line through the centers of
> the rear spindle, the rear bogie pin, the front bogie pin, and the front
> spindle.
>
> The mounting faces of the air bag cones are 90° perpendicular to that line.
>
> Regards,
> Rob M.
>
>
>
> -----Original Message-----
> From: gmclist-bounces@temp.gmcnet.org [mailto:
> gmclist-bounces@temp.gmcnet.org] On Behalf Of Todd Sullivan
> Sent: Saturday, 7 January 2012 6:51 AM
> To: gmclist@temp.gmcnet.org
> Subject: Re: [GMCnet] The Markbag(tm)
>
> I think the hot-dog of the bag is more of a result of the side bending of
> the bag due to the angle of the mounting cones. As the suspension is
> raised, the angle of the bogie arm bag platform changes. As height is
> increased the angle also increases and when the coach is at specified
> travel height the cones are both angled upward away from parallel which
> puts more compression on the bottom side of the bag. The Sullybilt air
> spring plates are at a much closer angle in relation to each other (closer
> to parallel) when at ride height which results in a much lower bend
> (almost none) in the air bag at travel height. The Firestone spec states
> that the loading capacity of each bag to be the following:
> 1264lbsf at 20psi
> 3792lbsf at 60psi
> 5688lbsf at 90psi
>
> I noticed no gain in lift over 85psi. I would think reducing the compressor
> cut out down to 80psi would be more than sufficient to operate the system
> through its full range even with above desired tongue weight while towing.
> I did not check pressure in the system at ride height. I would imagine it
> is in the 60psi range from the bag specs. I measured from the bogies to the
> floor during inflation and watched until no further lift was achieved but
> pressure continued to increase. That was at 80psi or so. I then continued
> to inflate to 120psi with no further gain in height. The Firestone engineer
> I spoke with today said that the maximum service inflation pressure is
> 100psi. Since no gain in height is achieved above 80psi or so I see no need
> to have the compressor shut off any higher than 85psi.
>
> Sully
> 77 Royale
>
>
>
> On Fri, Jan 6, 2012 at 10:12 AM, gene Fisher <mr.erfisher@gmail.com>
> wrote:
>
> > On Fri, Jan 6, 2012 at 10:10 AM, gene Fisher <mr.erfisher@gmail.com>
> > wrote:
> >
> > > Your first note said the ride height was at 90#
> > >
> > > the bag-llfters reduce the pressure to 70# and stop the hot-dog of the
> > bag.
> > > this will allow full raising of the coach with lower pressure.
> > >
> > > thanks
> > > gene
> > >
> >
> > --
> > Gene Fisher -- 74-23,77PB/ore/ca
> > “Give a man a fish; you have fed him for today --- give him a URL and
> > -------
> > http://gmcmotorhome.info/
> > Alternator Protection Cable
> > http://gmcmotorhome.info/APC.html
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] The Markbag(tm) [message #155733 is a reply to message #155732] |
Fri, 06 January 2012 16:27 |
sgltrac
Messages: 2797
Registered: April 2011
Karma: 1
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Senior Member |
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The angle in the mounting area of the bogie has been compensated for by the
angle of the standoff plates on the Sullybilt system (Mark G came up with
the angle). The oem bag has no such provision in its mount and I believe
this to be the most likely cause of the hot doging
Sully
77 Royale
On Fri, Jan 6, 2012 at 2:23 PM, Todd Sullivan <sgltrac@gmail.com> wrote:
> As you will see in the photo, when the spindles are aligned with bogie
> pins the vertical upright s of the arms are parallel but the mounting
> surfaces for the bag are not. They are splayed outward from
> center vertically from the top to the bottom.
>
>
> https://picasaweb.google.com/lh/photo/_hgX84BEnFolvkHldpq6rA1Piv9hnV4Ggxc2P_hqJgQ?feat=directlink
>
> Sully
> 77 Royale
>
>
> On Fri, Jan 6, 2012 at 1:06 PM, Rob Mueller <robmueller@iinet.net.au>wrote:
>
>> Sully,
>>
>> It has been noted here that if the front and rear ride height are set
>> properly you can draw a straight line through the centers of
>> the rear spindle, the rear bogie pin, the front bogie pin, and the front
>> spindle.
>>
>> The mounting faces of the air bag cones are 90° perpendicular to that
>> line.
>>
>> Regards,
>> Rob M.
>>
>>
>>
>> -----Original Message-----
>> From: gmclist-bounces@temp.gmcnet.org [mailto:
>> gmclist-bounces@temp.gmcnet.org] On Behalf Of Todd Sullivan
>> Sent: Saturday, 7 January 2012 6:51 AM
>> To: gmclist@temp.gmcnet.org
>> Subject: Re: [GMCnet] The Markbag(tm)
>>
>> I think the hot-dog of the bag is more of a result of the side bending of
>> the bag due to the angle of the mounting cones. As the suspension is
>> raised, the angle of the bogie arm bag platform changes. As height is
>> increased the angle also increases and when the coach is at specified
>> travel height the cones are both angled upward away from parallel which
>> puts more compression on the bottom side of the bag. The Sullybilt air
>> spring plates are at a much closer angle in relation to each other (closer
>> to parallel) when at ride height which results in a much lower bend
>> (almost none) in the air bag at travel height. The Firestone spec states
>> that the loading capacity of each bag to be the following:
>> 1264lbsf at 20psi
>> 3792lbsf at 60psi
>> 5688lbsf at 90psi
>>
>> I noticed no gain in lift over 85psi. I would think reducing the
>> compressor
>> cut out down to 80psi would be more than sufficient to operate the system
>> through its full range even with above desired tongue weight while towing.
>> I did not check pressure in the system at ride height. I would imagine it
>> is in the 60psi range from the bag specs. I measured from the bogies to
>> the
>> floor during inflation and watched until no further lift was achieved but
>> pressure continued to increase. That was at 80psi or so. I then continued
>> to inflate to 120psi with no further gain in height. The Firestone
>> engineer
>> I spoke with today said that the maximum service inflation pressure is
>> 100psi. Since no gain in height is achieved above 80psi or so I see no
>> need
>> to have the compressor shut off any higher than 85psi.
>>
>> Sully
>> 77 Royale
>>
>>
>>
>> On Fri, Jan 6, 2012 at 10:12 AM, gene Fisher <mr.erfisher@gmail.com>
>> wrote:
>>
>> > On Fri, Jan 6, 2012 at 10:10 AM, gene Fisher <mr.erfisher@gmail.com>
>> > wrote:
>> >
>> > > Your first note said the ride height was at 90#
>> > >
>> > > the bag-llfters reduce the pressure to 70# and stop the hot-dog of the
>> > bag.
>> > > this will allow full raising of the coach with lower pressure.
>> > >
>> > > thanks
>> > > gene
>> > >
>> >
>> > --
>> > Gene Fisher -- 74-23,77PB/ore/ca
>> > “Give a man a fish; you have fed him for today --- give him a URL and
>> > -------
>> > http://gmcmotorhome.info/
>> > Alternator Protection Cable
>> > http://gmcmotorhome.info/APC.html
>> > _______________________________________________
>> > GMCnet mailing list
>> > Unsubscribe or Change List Options:
>> > http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>> >
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>>
>
>
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Sully
77 Royale basket case.
Future motorhome land speed record holder(bucket list)
Seattle, Wa.
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| Re: [GMCnet] The Markbag(tm) [message #155736 is a reply to message #155704] |
Fri, 06 January 2012 17:08 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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Engineers must have had a reason for this. Perhaps to allow enough travel in compression mode??? Or the non parallel surfaces at correct ride height would give a softer ride?? maybe??
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] The Markbag(tm) [message #155744 is a reply to message #155740] |
Fri, 06 January 2012 17:49 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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It looks like the mounting pads are angled at 6 degrees.
So if each arm was rotated upward 6 degrees, that would
lower the coach 2 inches from where the bogie arms are
parallel to the ground. And the airbag mounts would be parallel
to each other.
That makes sense because with a 30 inch diameter tire,
the spindle would be 15 inches above the ground.
And you want the bogie pins to be lower than that, don't you?
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] The Markbag(tm) [message #155747 is a reply to message #155744] |
Fri, 06 January 2012 18:12 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Bill,
Ken Frey showed me a quick way to check if the rear ride height was correct was to look at the bogie vertical arms and if they were
parallel vertically the horizontal arms would be parallel to the ground and that's the right ride height.
Basically that's what Sully's picture shows.
My mistake was to assume that the cone mounting flanges were parallel too!
The front ride height is set at 13 1/8" and the rear is set at 11 11/16' (both +/- 1/4").
I want to keep the front set at 13 1/8" as that keeps the axles level.
13.125
- 11.6875
1.4375
I want the bogie pins to be 1.4375 inches lower that way the frame would be level and parallel to the ground from front to rear.
Well that's what I figger!
Regards,
Rob M.
-----Original Message-----
From: Bill Wevers
It looks like the mounting pads are angled at 6 degrees.
So if each arm was rotated upward 6 degrees, that would
lower the coach 2 inches from where the bogie arms are
parallel to the ground. And the airbag mounts would be parallel
to each other.
That makes sense because with a 30 inch diameter tire,
the spindle would be 15 inches above the ground.
And you want the bogie pins to be lower than that, don't you?
Regards,
Bill
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] The Markbag(tm) [message #155748 is a reply to message #155704] |
Fri, 06 January 2012 18:27 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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Rob,
So 1.4375 inches lower in the back will level the frame?
If I look at the bogie photo, the bogie vertical arms
would have to be leaning inward to each other (not parallel)
in order to make the bogie pins lower than the spindles (axle center).
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] The Markbag(tm) [message #155754 is a reply to message #155704] |
Fri, 06 January 2012 18:43 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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Rob,
Ok, got it.
Thanks,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] The Markbag(tm) [message #155758 is a reply to message #155736] |
Fri, 06 January 2012 19:06 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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| JohnL455 wrote on Fri, 06 January 2012 16:08 |
Engineers must have had a reason for this. Perhaps to allow enough travel in compression mode??? Or the non parallel surfaces at correct ride height would give a softer ride?? maybe??
|
All of the geometry and ride height issues are a balance that is juggled up to the last minute. Whe I designed suspensions and chassis for Chevrolet, I started with a relatively pure engineering approach that was compromised in amy ways by the time of SOP came around. Things like bumper heights, handling, packaging, durability, anti lift/squat, tire size changes, etc etc are all balanced many times before the design is locked in. I wouldn't read to much in to why things may or may not be parallel or vertical. BTW, the rear suspension harshness is determined by the geometry, not the airbag pressure.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] The Markbag(tm) [message #155790 is a reply to message #155758] |
Fri, 06 January 2012 22:36 |
hal kading
Messages: 642
Registered: February 2004
Location: Las Cruces NM
Karma: 4
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Senior Member |
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One reason to have a higher compressor set pressure is you will get faster response when raising the rear for clearance going into a filling station.
Hal Kading 78 Buskirk Las Cruces NM
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