Home » Public Forums » GMCnet » Re: [GMCnet] Alignment-Height Setting
| Re: [GMCnet] Alignment-Height Setting [message #78766] |
Wed, 31 March 2010 16:21  |
Gary Casey
Messages: 448
Registered: September 2009
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Ken,
I think leaving the rears in "automatic" will complicate the issue. If you change one torsion bar to tweak the front, the rear valves will attempt to bring it back the way it was (level or not). So I think the way to do it is to jack the front in the center, adjust the bag pressure to get the coach level (side to side) and then lock the rears in the hold position. Now when you adjust the fronts you can tilt the coach side to side, allowing you to get it back level again. Then both fronts will have the same weight - close anyway. Now put it back in automatic and if the coach tilts, one or the other control valves will have to be adjusted.
Gary (going over this in my head for when I do it)
Paul,
I thought about lifting the coach under the center rear for front alignment,
as you suggest. Then someone reminded me that doing that would allow any
rear weight imbalance to bias the front ride heights. By setting the rear
ride height first and then keeping it in Auto during the front alignment,
the rear suspension compensates for any weight imbalance, leaving the front
free to compensate only for front imbalances not cancelled out through the
body stiffness.
Ken H.
Americus, GA
'76 X-Birchaven
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| Re: [GMCnet] Alignment-Height Setting [message #78789 is a reply to message #78766] |
Wed, 31 March 2010 18:03  |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
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| Gary Casey wrote on Wed, 31 March 2010 14:21 |
Ken,
I think leaving the rears in "automatic" will complicate the issue. ... << snipped >> ... Then both fronts will have the same weight - close anyway. Now put it back in automatic and if the coach tilts, one or the other control valves will have to be adjusted. ...
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At first I was in agreement with you about the rear being in hold, but the more I think about it... I am not sure.
When adjusting the torsion bars, You are NOT trying to get the same weight on both front tires. You are trying to get the correct HEIGHT on both sides of the coach. If you have a weight imbalance and adjust the torsion bars to get equal weights, the coach WILL NOT be level.
If you set the ride heights correctly and the there is a weight imbalance, you may have to redistribute the weight in the coach.... THEN recheck the ride height.
I would go with Ken's recommendations.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Alignment-Height Setting [message #78814 is a reply to message #78789] |
Wed, 31 March 2010 20:57 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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If you tinker long enough, any of the methods will work -- or get things so
screwed up you'll have to start over. :-)
Ken Burton's coach got into that situation, whether by PO's, shops', or his
doings: He found his wheel weights to be so discombobulated that he
resorted to using Alex Sirum's scales to do all of the adjustments. I'll
leave it to him to tell you the details now that I've ratted him out.
But the real point of that disclosure is an idea that hit me this afternoon:
At times all of us wish scales were immediately available to us. During
ride height adjustments, that's especially true. What occurred to me is
that we have differential scales built in on the rear. How about this:
Install an accurate air pressure gauge at each rear bag (very easy if
you've got permanently installed Shrader valves). Raise the front center to
establish front ride height (average). Adjust the rear ride heights by
adjusting pressure in the bags -- either by doing a complete rear ride
height adjustment or just using Raise/Lower. Block In/Out air flow to the
bags, by valve or Hold, so that any change in rear loading will result in a
change in the gauge readings.
Now, adjust the front ride heights, monitoring the rear gauge readings; if
the differential between them changes, your front adjustment has biased the
rear loading so it's not right -- you need to back off on the front
diagonally opposite the rear increase in loading. It should be possible to
achieve the correct front ride heights without affecting the rear
differential pressure. If not, the body/frame's got to have a twist in it
-- I'm not going into that!
Huh? Does any of that make sense?
Ken H.
On Wed, Mar 31, 2010 at 7:03 PM, Mike Miller <m000035@gmail.com> wrote:
>
>
> Gary Casey wrote on Wed, 31 March 2010 14:21
> > Ken,
> > I think leaving the rears in "automatic" will complicate the issue. ...
> << snipped >> ... Then both fronts will have the same weight - close
> anyway. Now put it back in automatic and if the coach tilts, one or the
> other control valves will have to be adjusted. ...
>
>
> At first I was in agreement with you about the rear being in hold, but the
> more I think about it... I am not sure.
>
> When adjusting the torsion bars, You are NOT trying to get the same weight
> on both front tires. You are trying to get the correct HEIGHT on both sides
> of the coach. If you have a weight imbalance and adjust the torsion bars to
> get equal weights, the coach WILL NOT be level.
>
> If you set the ride heights correctly and the there is a weight imbalance,
> you may have to redistribute the weight in the coach.... THEN recheck the
> ride height.
>
> I would go with Ken's recommendations.
> --
>
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| Re: [GMCnet] Alignment-Height Setting [message #78824 is a reply to message #78814] |
Wed, 31 March 2010 22:03 |
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So, who'd going to do a session on ride height, torsion bar adjustment, load
balancing, etc. at DuQuoin? It seems that a show-and-tell could be done
there.
Byron Songer
1978 Royale by Coachmen
Louisville, KY
Personal - http://web.me.com/bnsonger
Eastern States - http://www.gmceast.com
Ken Henderson wrote:
> If you tinker long enough, any of the methods will work -- or get things so
> screwed up you'll have to start over. :-)
>
> Ken Burton's coach got into that situation, whether by PO's, shops', or his
> doings: He found his wheel weights to be so discombobulated that he
> resorted to using Alex Sirum's scales to do all of the adjustments. I'll
> leave it to him to tell you the details now that I've ratted him out.
>
> But the real point of that disclosure is an idea that hit me this afternoon:
> At times all of us wish scales were immediately available to us. During
> ride height adjustments, that's especially true. What occurred to me is
> that we have differential scales built in on the rear. How about this:
> Install an accurate air pressure gauge at each rear bag (very easy if
> you've got permanently installed Shrader valves). Raise the front center to
> establish front ride height (average). Adjust the rear ride heights by
> adjusting pressure in the bags -- either by doing a complete rear ride
> height adjustment or just using Raise/Lower. Block In/Out air flow to the
> bags, by valve or Hold, so that any change in rear loading will result in a
> change in the gauge readings.
>
> Now, adjust the front ride heights, monitoring the rear gauge readings; if
> the differential between them changes, your front adjustment has biased the
> rear loading so it's not right -- you need to back off on the front
> diagonally opposite the rear increase in loading. It should be possible to
> achieve the correct front ride heights without affecting the rear
> differential pressure. If not, the body/frame's got to have a twist in it
> -- I'm not going into that!
>
> Huh? Does any of that make sense?
>
> Ken H.
>
>
> On Wed, Mar 31, 2010 at 7:03 PM, Mike Miller <m000035@gmail.com> wrote:
>
>>
>>
>> Gary Casey wrote on Wed, 31 March 2010 14:21
>>> Ken,
>>> I think leaving the rears in "automatic" will complicate the issue. ...
>> << snipped >> ... Then both fronts will have the same weight - close
>> anyway. Now put it back in automatic and if the coach tilts, one or the
>> other control valves will have to be adjusted. ...
>>
>>
>> At first I was in agreement with you about the rear being in hold, but the
>> more I think about it... I am not sure.
>>
>> When adjusting the torsion bars, You are NOT trying to get the same weight
>> on both front tires. You are trying to get the correct HEIGHT on both sides
>> of the coach. If you have a weight imbalance and adjust the torsion bars to
>> get equal weights, the coach WILL NOT be level.
>>
>> If you set the ride heights correctly and the there is a weight imbalance,
>> you may have to redistribute the weight in the coach.... THEN recheck the
>> ride height.
>>
>> I would go with Ken's recommendations.
>> --
>>
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
--
Byron Songer
Full-timing to enjoy the USA
Former owner but still an admirer
GMC paint schemes at -
http://www.songerconsulting.net
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| Re: [GMCnet] Alignment-Height Setting [message #78832 is a reply to message #78814] |
Thu, 01 April 2010 00:40 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| GMCWiperMan wrote on Wed, 31 March 2010 20:57 |
If you tinker long enough, any of the methods will work -- or get things so
screwed up you'll have to start over. 
Ken Burton's coach got into that situation, whether by PO's, shops', or his
doings: He found his wheel weights to be so discombobulated that he
resorted to using Alex Sirum's scales to do all of the adjustments. I'll
leave it to him to tell you the details now that I've ratted him out.
But the real point of that disclosure is an idea that hit me this afternoon:
At times all of us wish scales were immediately available to us. During
ride height adjustments, that's especially true. What occurred to me is
that we have differential scales built in on the rear. How about this:
Install an accurate air pressure gauge at each rear bag (very easy if
you've got permanently installed Shrader valves). Raise the front center to
establish front ride height (average). Adjust the rear ride heights by
adjusting pressure in the bags -- either by doing a complete rear ride
height adjustment or just using Raise/Lower. Block In/Out air flow to the
bags, by valve or Hold, so that any change in rear loading will result in a
change in the gauge readings.
Now, adjust the front ride heights, monitoring the rear gauge readings; if
the differential between them changes, your front adjustment has biased the
rear loading so it's not right -- you need to back off on the front
diagonally opposite the rear increase in loading. It should be possible to
achieve the correct front ride heights without affecting the rear
differential pressure. If not, the body/frame's got to have a twist in it
-- I'm not going into that!
Huh? Does any of that make sense?
Ken H.
|
Well I originally was going to stay out of this but I guess I started it by posting and then I let Ken H. suck me in.
It is my contention that each system (front and rear) should be adjusted independently of the other. I suggest that opposite coach ends should be held as closely as possible regardless of loading to it's correct ride height while adjusting the other end. Ken, Alex, and I had quite a discussion over this approach at a GMC Eastern States rally that culminated with a picnic table rolling over on top of Alex.
I guess in the end we really need to know is the end objective. Is the objective equal height side to side regardless of weight applied to each wheel, or is it equalizing the weight on each pair of wheels while trying to get the height as near as equal as possible?
One compounding factor in adjusting the fronts or using scales is that the coach will be heavier on one side than the other. So if balancing the weighs side to side is your objective then this offset in side to side weight needs to be taken in to account.
What started all of this discussion with Ken and Alex was my attempt to adjust the ride height using Ken H's methods. I got all of the ride heights within specs, but the weights were way off on opposite corners of the coach. I mean hundreds of pounds off on the left rear and right front. This problem was caused by the automatic action of the rear air system and it's affect on the adjustment of the front.
So it is my contention that the rear heights should be set first. The rears adjust by height only no matter how much weight is applied to them. The automatic air system adjusts the air pressure to compensate for any imbalance in weight side to side. Jacking in the exact center by weight is just about impossible in the front and I see nto way to do it in the rear.
I contend that the rears should be held in place at the correct height on blocks or stands while adjusting the fronts. This keeps the coach rear in perfect balance (height wise) no matter what the weight is applied to the rear suspension while adjusting the fronts.
The fronts being a different system do NOT automatically adjust as the weight applied to them changes. In fact as you start cranking in additional screw turns on the torsion bar pork chops, the torsion starts to bend absorbing additional weight until it reaches a point that it actually starts raising the coach. So there is no direct relationship to the number of turns and the height of the coach. To keep the rears from affecting the front adjustment the rears must be held stable in their desired height while adjusting the fronts. Adjusting the fronts while the rears are blocked can now be done by height or better yet by scales or both without any interference for the rear suspension system.
If the adjustment of the fronts changes the amount of weight on each side of the rear, it will make no difference when you are finished. The rear is an automatic system based on height only and not the weight applied to it. The compressor and leveling switches will add or reduce air pressure in the bags accordingly when the blocks are removed and the key turned on again.
In the end what I would like to see is a coach set at the proper heights (front and rear) while keeping the weight as close as possible to being balanced side to side. I also contend that if coach is heavy on one side in the rear then it should probably also be slightly heavy on that same side in the front. It definitely should not be heavy on opposite corners which is what I had using Colonel Ken's system.
I should also comment on calling Ken, Colonel Ken. I respect Ken Henderson for his time and rank in the service. I also respect him for all he has for us in the GMC community since then. So when I call him Colonel Ken it is out of respect.
It this case it is my way of saying I disagree but still respect you and your work, assistance, and conclusions.
Colonel Ken, I salute you but I disagree with you on this subject. I salute not your rank, but you the person.
I think is an interesting idea to measure the bag differential pressure to determine the rear weight balance.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment-Height Setting [message #78871 is a reply to message #78843] |
Thu, 01 April 2010 10:14 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| g.winger wrote on Thu, 01 April 2010 06:10 |
Ken B,, was the picnic table overturning an example of improper weight distribution, is that not a strange omen considering the topic???HMMMM,,,PL
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Exactly. It was the type of table that has the seats attached to to the sides. There was too much weight on one corner (kind of like my GMC) and the whole thing flipped over on Alex when both Ken H. and I got up.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment-Height Setting [message #78872 is a reply to message #78766] |
Thu, 01 April 2010 10:29 |
g.winger
Messages: 792
Registered: February 2008
Location: Warrenton,Missouri
Karma: 0
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Senior Member |
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Made progress this morning. Got up at 3:45 {boy I wish I was retired} and worked on the height. Last nite I put on the rear wheels and tires. Raised the rears to the correct height w/air and 1/4" above safty blocks. Raised the front. Jackstands. Set both screws so they were the same stickout. 1". To low, 7/8",,still low,,3/4",,very close,, 5;10 and have to leave for work. Did check and I,ve now have 4degrees caster on the right side and 3.25 on the left side. More to do.,,,PL
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| Re: [GMCnet] Alignment-Height Setting [message #78876 is a reply to message #78872] |
Thu, 01 April 2010 10:46 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| g.winger wrote on Thu, 01 April 2010 10:29 |
Made progress this morning. Got up at 3:45 {boy I wish I was retired} and worked on the height. Last nite I put on the rear wheels and tires. Raised the rears to the correct height w/air and 1/4" above safety blocks. Raised the front. Jackstands. Set both screws so they were the same stickout. 1". To low, 7/8",,still low,,3/4",,very close,, 5;10 and have to leave for work. Did check and I,ve now have 4degrees caster on the right side and 3.25 on the left side. More to do.,,,PL
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You do not want to retire. You will not have enough time to get anything done for yourself. Everyone knows you are retired and you will have more projects than you ever expected. As an example I ran into a friend at Two Wheel Tuesday that reminded me that I promised to roto-till about 1 acre for him this spring. That reminded me that I need to go down the street and move a couple of truck load of dirt for a neighbor. Then another friend reminded me I need to go to his place and mount an antenna on a barn for a about a 1.25 mile WiFi hop for him.
Do not retire. You will never find enough time to get your own projects done for yourself.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment-Height Setting [message #78877 is a reply to message #78871] |
Thu, 01 April 2010 10:47 |
C Boyd
Messages: 2629
Registered: April 2006
Karma: 18
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Senior Member |
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| Ken Burton wrote on Thu, 01 April 2010 11:14 |
| g.winger wrote on Thu, 01 April 2010 06:10 |
Ken B,, was the picnic table overturning an example of improper weight distribution, is that not a strange omen considering the topic???HMMMM,,,PL
|
Exactly. It was the type of table that has the seats attached to to the sides. There was too much weight on one corner (kind of like my GMC) and the whole thing flipped over on Alex when both Ken H. and I got up.
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Kinda like this one?
http://www.gmcmhphotos.com/photos/showfull.php?photo=28135
C. Boyd
76 Crestmont
East Tennessee
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| Re: [GMCnet] Alignment-Height Setting [message #78886 is a reply to message #78877] |
Thu, 01 April 2010 12:07 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| C Boyd wrote on Thu, 01 April 2010 10:47 |
| Ken Burton wrote on Thu, 01 April 2010 11:14 |
| g.winger wrote on Thu, 01 April 2010 06:10 |
Ken B,, was the picnic table overturning an example of improper weight distribution, is that not a strange omen considering the topic???HMMMM,,,PL
|
Exactly. It was the type of table that has the seats attached to to the sides. There was too much weight on one corner (kind of like my GMC) and the whole thing flipped over on Alex when both Ken H. and I got up.
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Kinda like this one?
http://www.gmcmhphotos.com/photos/showfull.php?photo=28135
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That is the table and me and Alex. Ken H. Is missing.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment-Height Setting [message #78887 is a reply to message #78886] |
Thu, 01 April 2010 12:08 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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| Ken Burton wrote on Thu, 01 April 2010 12:07 |
| C Boyd wrote on Thu, 01 April 2010 10:47 |
| Ken Burton wrote on Thu, 01 April 2010 11:14 |
| g.winger wrote on Thu, 01 April 2010 06:10 |
Ken B,, was the picnic table overturning an example of improper weight distribution, is that not a strange omen considering the topic???HMMMM,,,PL
|
Exactly. It was the type of table that has the seats attached to to the sides. There was too much weight on one corner (kind of like my GMC) and the whole thing flipped over on Alex when both Ken H. and I got up.
|
Kinda like this one?
http://www.gmcmhphotos.com/photos/showfull.php?photo=28135
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That is the table and me and Alex. Ken H. Is missing.
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I just noticed that is my GMC on the left in the back ground.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment-Height Setting [message #78890 is a reply to message #78886] |
Thu, 01 April 2010 12:10 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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I assigned Fred to balance you two. Looks like he's barely up to the job.
:-)
Ken H.
On Thu, Apr 1, 2010 at 1:07 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
> C Boyd wrote on Thu, 01 April 2010 10:47
> > Ken Burton wrote on Thu, 01 April 2010 11:14
> > > g.winger wrote on Thu, 01 April 2010 06:10
> > > > Ken B,, was the picnic table overturning an example of improper
> weight distribution, is that not a strange omen considering the
> topic???HMMMM,,,PL
> > >
> > >
> > > Exactly. It was the type of table that has the seats attached to to
> the sides. There was too much weight on one corner (kind of like my GMC)
> and the whole thing flipped over on Alex when both Ken H. and I got up.
> >
> >
> >
> >
> >
> >
> > Kinda like this one?
> > http://www.gmcmhphotos.com/photos/showfull.php?photo=28135
>
> That is the table and me and Alex. Ken H. Is missing.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
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>
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| Re: [GMCnet] Alignment-Height Setting [message #78897 is a reply to message #78893] |
Thu, 01 April 2010 13:31 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| Tom Lins wrote on Thu, 01 April 2010 12:52 |
or retire and tell people your on vacation catching up on your honey-do list
people don't mind interrupting your projects but will not think about asking you to interrupt HER list
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Are you telling me that some individuals have a list OTHER than HER list. Note here, the GMC is HERS, I'm just the mechanic.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Alignment-Height Setting [message #78905 is a reply to message #78902] |
Thu, 01 April 2010 15:08 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| Robert Mueller wrote on Thu, 01 April 2010 14:38 |
Steve,
The good news is that you can add a second title when you get Smurfie on the
road:
"Mechanic AND chauffeur!"
Regard
Rob Mueller
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Nah - she is a terrible rider, goes nuts in the passenger seat. It always ends up with her driving if the trip is over an hour or so. She also goes nuts when I sleep in the passenger seat, goes more nuts when I sleep in the drivers seat. We'll see how she handles me going to the back bed when she is driving.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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