Home » Public Forums » GMCnet » [GMCnet] 1 ton alignment - lessons learned, part 2
| [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137587] |
Fri, 05 August 2011 11:26  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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This is a continuation of my comments following the installation of the 1 ton front end and what I learned during and following that process about alignment and ride height on our coaches.
In my previous post I said I had the ride height spot on when we took the coach to the alignment shop. When they were finished the professional alignment shop indicated they lowered ride height a bit to "even things out". When we returned from our 750 mile trip I found the ride height low by two full inches on both sides. By the time I finished putting the ride height back where it should have been I had to turn both torsion bar adjuster bolts EIGHT FULL TURNS. So, what the alignment guy said was "a bit" turns out to have been a bunch!
The point here is not to denigrate the alignment guy (even though I would like to thump him on the head), the point is if this reputable alignment shop with a tech who said he had done lots of these GMC motorhomes ignored my instruction not to monkey with the ride height and chose instead to use his "experience" to lower it that much, then what is happening with all the other alignments being done on our coaches? Is it just luck of the draw that the ride height and alignment turns out to be correct after driving the coach enough to fully settle the suspension?
My surmise is that by raising the wheels off the ground to make his adjustments the coach did not settle down when he checked the measurements so he lowered the ride height to get it to come down on his rack. After several iterations of this the ride height wound up adjusted wildly low. By the time I drove the coach the suspension settled to the point that it became two inches too low throwing caster and camber out the window and negating the whole alignment process.
So, the real lesson I learned through all of this is the requirement to drive the coach further than you think you will need to in order to settle the new suspension components before measuring the result of any change you make to either ride height or alignment. That means you will either need (1) a very patient and accommodating alignment shop and lots of time, or (2) plan on doing the alignment and ride height adjustments yourself. I don't know of an option (3).
As to the question about the need for turntables and setting/measuring caster -
I think they are necessary as we cannot be sure that 35 plus years later the frame and A arm attachment points are where they started out at the factory nor can we be sure that the two offset bushings that we have to press into the rear upper A arm go in exactly in the same spot on both sides. So, while turning the rear upper A arm adjustment cams to pull that end of the A arm as far toward the center of the coach as possible will result in maximum caster, it will not necessarily result in maximum EVEN caster. To achieve that one needs turntables and a way to measure the number of degrees the camber changes when the wheels are turned 15 to 20 degrees (determined by the measuring device itself) inward and outward. That difference is the amount of caster.
In addition to maximum even caster on both sides we also need to set the initial camber with the wheels in the straight ahead position to zero by turning the front upper A arm adjustment cams. When either cam is turned, both camber with the wheels straight ahead and resulting caster are effected. Raising or lowering the ride height will also effect both caster and camber. And, any time the wheels are jacked up off the ground we need to drive the coach quite a bit to get the suspension to fully settle before checking our measurements.
It may be fine for some to simply set the tire pressure and ride height correctly, then turn the rear upper A arm adjuster to maximum caster, and then turn the wheels straight ahead to set camber to zero and toe to zero and call it good. But, from what I learned we can only call that our initial or base line setting. Once we drive the coach a number of miles to fully settle the new suspension components, the resulting ride height change alone might well throw caster and camber both way off from where we thought they were so it is necessary in my opinion to remeasure ride height, caster, camber and toe to confirm that they are where they should be. That can only be done accurately with turntables and a device designed to measure caster as well camber and toe with the wheels in the straight ahead position.
We cannot expect or assume that an alignment shop will get this right either. I doubt that my experience is a unique one. My guess is if we measure all of the coaches in our collective fleet we will find that a high percentage of them will be off quite a bit in ride height or caster or camber or toe or all four. Hence, my conclusion that each of our clubs need to assemble the simple kit of tools and a good set of instructions that will allow all our owners to check their coach themselves. This is important for safety and for long term drivability. Hope this helps.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
Visitors always welcome!
glwork@mac.com
http://jerrywork.com
541-592-5360
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137612 is a reply to message #137587] |
Fri, 05 August 2011 13:22  |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Jerry,
49 years ago, I was the parts mangler in a brand-new dealership.
We purchased a new Bear alignment rig. It came with
an instruction class. The instructor was an old guy who knew his
stuff. His first mandate was center the steering and see
if the last guy did it right. Then, he said, you must do an
alignment in the correct order. Caster first then camber and
then
toe-in. The reason being caster affects everything. Camber(done
correctly) doesn't affect caster and toe-in doesn't affect
anything else. I don't think I've ever seen anyone, except Tom
Hampton, do it right since then. And he made me do all
the grunt work. That's been my experience.
Gary Kosier
77EII & 77PB
Newark, Ohio
----- Original Message -----
From: "Work Jerry" <glwork@mac.com>
To: <gmclist@temp.gmcnet.org>
Sent: Friday, August 05, 2011 12:26 PM
Subject: [GMCnet] 1 ton alignment - lessons learned, part 2
> This is a continuation of my comments following the
> installation of the 1 ton front end and what I learned during
> and following that process about alignment and ride height on
> our coaches.
>
> In my previous post I said I had the ride height spot on when
> we took the coach to the alignment shop. When they were
> finished the professional alignment shop indicated they lowered
> ride height a bit to "even things out". When we returned from
> our 750 mile trip I found the ride height low by two full
> inches on both sides. By the time I finished putting the ride
> height back where it should have been I had to turn both
> torsion bar adjuster bolts EIGHT FULL TURNS. So, what the
> alignment guy said was "a bit" turns out to have been a bunch!
>
> The point here is not to denigrate the alignment guy (even
> though I would like to thump him on the head), the point is if
> this reputable alignment shop with a tech who said he had done
> lots of these GMC motorhomes ignored my instruction not to
> monkey with the ride height and chose instead to use his
> "experience" to lower it that much, then what is happening with
> all the other alignments being done on our coaches? Is it just
> luck of the draw that the ride height and alignment turns out
> to be correct after driving the coach enough to fully settle
> the suspension?
>
> My surmise is that by raising the wheels off the ground to make
> his adjustments the coach did not settle down when he checked
> the measurements so he lowered the ride height to get it to
> come down on his rack. After several iterations of this the
> ride height wound up adjusted wildly low. By the time I drove
> the coach the suspension settled to the point that it became
> two inches too low throwing caster and camber out the window
> and negating the whole alignment process.
>
> So, the real lesson I learned through all of this is the
> requirement to drive the coach further than you think you will
> need to in order to settle the new suspension components before
> measuring the result of any change you make to either ride
> height or alignment. That means you will either need (1) a
> very patient and accommodating alignment shop and lots of time,
> or (2) plan on doing the alignment and ride height adjustments
> yourself. I don't know of an option (3).
>
> As to the question about the need for turntables and
> setting/measuring caster -
>
> I think they are necessary as we cannot be sure that 35 plus
> years later the frame and A arm attachment points are where
> they started out at the factory nor can we be sure that the two
> offset bushings that we have to press into the rear upper A arm
> go in exactly in the same spot on both sides. So, while
> turning the rear upper A arm adjustment cams to pull that end
> of the A arm as far toward the center of the coach as possible
> will result in maximum caster, it will not necessarily result
> in maximum EVEN caster. To achieve that one needs turntables
> and a way to measure the number of degrees the camber changes
> when the wheels are turned 15 to 20 degrees (determined by the
> measuring device itself) inward and outward. That difference
> is the amount of caster.
>
> In addition to maximum even caster on both sides we also need
> to set the initial camber with the wheels in the straight ahead
> position to zero by turning the front upper A arm adjustment
> cams. When either cam is turned, both camber with the wheels
> straight ahead and resulting caster are effected. Raising or
> lowering the ride height will also effect both caster and
> camber. And, any time the wheels are jacked up off the ground
> we need to drive the coach quite a bit to get the suspension to
> fully settle before checking our measurements.
>
> It may be fine for some to simply set the tire pressure and
> ride height correctly, then turn the rear upper A arm adjuster
> to maximum caster, and then turn the wheels straight ahead to
> set camber to zero and toe to zero and call it good. But, from
> what I learned we can only call that our initial or base line
> setting. Once we drive the coach a number of miles to fully
> settle the new suspension components, the resulting ride height
> change alone might well throw caster and camber both way off
> from where we thought they were so it is necessary in my
> opinion to remeasure ride height, caster, camber and toe to
> confirm that they are where they should be. That can only be
> done accurately with turntables and a device designed to
> measure caster as well camber and toe with the wheels in the
> straight ahead position.
>
> We cannot expect or assume that an alignment shop will get this
> right either. I doubt that my experience is a unique one. My
> guess is if we measure all of the coaches in our collective
> fleet we will find that a high percentage of them will be off
> quite a bit in ride height or caster or camber or toe or all
> four. Hence, my conclusion that each of our clubs need to
> assemble the simple kit of tools and a good set of instructions
> that will allow all our owners to check their coach themselves.
> This is important for safety and for long term drivability.
> Hope this helps.
>
> Jerry
>
> Jerry Work
> The Dovetail Joint
> Fine furniture designed and hand crafted in the 1907 former
> Masonic Temple building in historic Kerby, OR
> Visitors always welcome!
> glwork@mac.com
> http://jerrywork.com
> 541-592-5360
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137613 is a reply to message #137612] |
Fri, 05 August 2011 13:29 |
 |
WD0AFQ
Messages: 7111
Registered: November 2004
Location: Dexter, Mo.
Karma: 207
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Senior Member |
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His first mandate was center the steering and see
if the last guy did it right. Then, he said, you must do an
alignment in the correct order. Caster first then camber and
then
toe-in. The reason being caster affects everything. Camber(done
correctly) doesn't affect caster and toe-in doesn't affect
anything else. I don't think I've ever seen anyone, except Tom
Hampton, do it right since then. And he made me do all
the grunt work. That's been my experience.
Gary Kosier
77EII & 77PB
Newark, Ohio
----- Original Message -----
From: "Work Jerry" <glwork@mac.com>
To: <gmclist@temp.gmcnet.org>
Sent: Friday, August 05, 2011 12:26 PM
Subject: [GMCnet] 1 ton alignment - lessons learned, part 2
> This is a continuation of my comments following the
> installation of the 1 ton front end and what I learned during
> and following that process about alignment and ride height on
> our coaches.
>
> In my previous post I said I had the ride height spot on when
> we took the coach to the alignment shop. When they were
> finished the professional alignment shop indicated they lowered
> ride height a bit to "even things out". When we returned from
> our 750 mile trip I found the ride height low by two full
> inches on both sides. By the time I finished putting the ride
> height back where it should have been I had to turn both
> torsion bar adjuster bolts EIGHT FULL TURNS. So, what the
> alignment guy said was "a bit" turns out to have been a bunch!
>
> The point here is not to denigrate the alignment guy (even
> though I would like to thump him on the head), the point is if
> this reputable alignment shop with a tech who said he had done
> lots of these GMC motorhomes ignored my instruction not to
> monkey with the ride height and chose instead to use his
> "experience" to lower it that much, then what is happening with
> all the other alignments being done on our coaches? Is it just
> luck of the draw that the ride height and alignment turns out
> to be correct after driving the coach enough to fully settle
> the suspension?
>
> My surmise is that by raising the wheels off the ground to make
> his adjustments the coach did not settle down when he checked
> the measurements so he lowered the ride height to get it to
> come down on his rack. After several iterations of this the
> ride height wound up adjusted wildly low. By the time I drove
> the coach the suspension settled to the point that it became
> two inches too low throwing caster and camber out the window
> and negating the whole alignment process.
>
> So, the real lesson I learned through all of this is the
> requirement to drive the coach further than you think you will
> need to in order to settle the new suspension components before
> measuring the result of any change you make to either ride
> height or alignment. That means you will either need (1) a
> very patient and accommodating alignment shop and lots of time,
> or (2) plan on doing the alignment and ride height adjustments
> yourself. I don't know of an option (3).
>
> As to the question about the need for turntables and
> setting/measuring caster -
>
> I think they are necessary as we cannot be sure that 35 plus
> years later the frame and A arm attachment points are where
> they started out at the factory nor can we be sure that the two
> offset bushings that we have to press into the rear upper A arm
> go in exactly in the same spot on both sides. So, while
> turning the rear upper A arm adjustment cams to pull that end
> of the A arm as far toward the center of the coach as possible
> will result in maximum caster, it will not necessarily result
> in maximum EVEN caster. To achieve that one needs turntables
> and a way to measure the number of degrees the camber changes
> when the wheels are turned 15 to 20 degrees (determined by the
> measuring device itself) inward and outward. That difference
> is the amount of caster.
>
> In addition to maximum even caster on both sides we also need
> to set the initial camber with the wheels in the straight ahead
> position to zero by turning the front upper A arm adjustment
> cams. When either cam is turned, both camber with the wheels
> straight ahead and resulting caster are effected. Raising or
> lowering the ride height will also effect both caster and
> camber. And, any time the wheels are jacked up off the ground
> we need to drive the coach quite a bit to get the suspension to
> fully settle before checking our measurements.
>
> It may be fine for some to simply set the tire pressure and
> ride height correctly, then turn the rear upper A arm adjuster
> to maximum caster, and then turn the wheels straight ahead to
> set camber to zero and toe to zero and call it good. But, from
> what I learned we can only call that our initial or base line
> setting. Once we drive the coach a number of miles to fully
> settle the new suspension components, the resulting ride height
> change alone might well throw caster and camber both way off
> from where we thought they were so it is necessary in my
> opinion to remeasure ride height, caster, camber and toe to
> confirm that they are where they should be. That can only be
> done accurately with turntables and a device designed to
> measure caster as well camber and toe with the wheels in the
> straight ahead position.
>
> We cannot expect or assume that an alignment shop will get this
> right either. I doubt that my experience is a unique one. My
> guess is if we measure all of the coaches in our collective
> fleet we will find that a high percentage of them will be off
> quite a bit in ride height or caster or camber or toe or all
> four. Hence, my conclusion that each of our clubs need to
> assemble the simple kit of tools and a good set of instructions
> that will allow all our owners to check their coach themselves.
> This is important for safety and for long term drivability.
> Hope this helps.
>
> Jerry
>
> Jerry Work
> The Dovetail Joint
> Fine furniture designed and hand crafted in the 1907 former
> Masonic Temple building in historic Kerby, OR
> Visitors always welcome!
> glwork@mac.com
> http://jerrywork.com
> 541-592-5360
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
_______________________________________________
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[/quote]
Interesting Gary. I may try to get by Tom's to have him check my one ton allignment. Glad to hear he does it that way.
Dan
3 In Stainless Exhaust Headers
One Ton All Discs/Reaction Arm
355 FD/Quad Bag/Alum Radiator Manny Tran/New eng.
Holley EFI/10 Tire Air Monitoring System
Solarized Coach/Upgraded Windows
Satelite TV/On Demand Hot Water/3Way Refer
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137618 is a reply to message #137587] |
Fri, 05 August 2011 14:04 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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Senior Member |
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> Hence, my conclusion that each of our clubs need to
>> assemble the simple kit of tools and a good set of instructions
>> that will allow all our owners to check their coach themselves.
For what it's worth, I'm trying to assemble these instructions. That obviously
depends on people contributing their knowledge and experience. I'll keep adding
to what I've got until/unless somebody else comes up with a better idea. I've
been trying to focus on doing a basic but competent alignment with a minimal set of
tools and techniques. From what I've seen so far, even that simple and imperfect
approach will typically give better results than many "pro" shops. I think the
main difference is that we care about the results.
I believe your point about the suspension settling is true with the OEM front end as well.
All the manufacturers instructions I've seen state that the vehicle (any vehicle) must be
bounced or driven to settle the suspension before taking measurements.
Karen
1973 23'
1975 26'
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137665 is a reply to message #137640] |
Fri, 05 August 2011 19:53 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Karen,
You've done a great job, but the section on measuring caster is a little
erroneous: Turning the wheels and measuring the change in camber is
correct, but the result is NOT caster -- its relative to caster; that is,
Caster=K X (Camber Change), where K depends on the angles to which the
wheel is turned. For best accuracy, the wheel being measured should turn
the same number of degrees left and right. I can provide the formula for
computing K, but for simplicity, fixed angles such as 15* and 20* are
usually used. For 15*, K=1.91; for 20*, K=1.43. Now if we don't care WHAT
the caster is, just that it's the same on both sides, K=1 is as good a
number as any other. We just don't want to mislead ourselves into thinking
we've actually measured caster (unless K=1, which would require a turn angle
of 28.7* -- more than the GMC allows).
By the way, with the digital level I use, no math is required to determine
the camber change: With the 15* left turn set, and the digital level
attached to the jig, press the Zero button. Turn the wheel 30* to set 15*
right, then read the level. Multiply the reading by 1.91 to yield the
caster.
HTH,
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI+ & EBL
www.gmcwipersetc.com
On Fri, Aug 5, 2011 at 6:11 PM, KB <kab7@sonic.net> wrote:
> I've just updated the instructions again. There are small changes
> throughout,
> but the one of most interest here is the alignment section. I've
> incorporated
> the recent discussions, I hope correctly.
>
> Again, this is a work in progress:
>
>
> http://www.machinesoflovinggrace.net/gmc/frontend/index.php?p=Alignment
>
> thanks,
> Karen
> 1973 23'
> 1975 26'
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137684 is a reply to message #137640] |
Fri, 05 August 2011 22:04 |
Kosier
Messages: 834
Registered: February 2008
Karma: 1
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Senior Member |
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Karen,
Another method for checking camber is to use a common framing
square.
Cut the short arm off at 14". Then set it with the short(14")
arm on the floor
and the long arm against the wheel. At zero camber it will be
flat on the
floor. If not, measure the distance the high end is off the
floor. My notes
are out in the shop, but I think it is 1.8" = 1/4*. I just
couldn't cut up a good
framing square, so I used chalk marks at the 14" mark. JWID
Gary Kosier
77EII & 77PB
Newark, Ohio
----- Original Message -----
From: "KB" <kab7@sonic.net>
To: <gmclist@temp.gmcnet.org>
Sent: Friday, August 05, 2011 6:11 PM
Subject: Re: [GMCnet] 1 ton alignment - lessons learned, part 2
> I've just updated the instructions again. There are small
> changes throughout,
> but the one of most interest here is the alignment section.
> I've incorporated
> the recent discussions, I hope correctly.
>
> Again, this is a work in progress:
>
> http://www.machinesoflovinggrace.net/gmc/frontend/index.php?p=Alignment
>
> thanks,
> Karen
> 1973 23'
> 1975 26'
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137686 is a reply to message #137587] |
Fri, 05 August 2011 22:15 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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Senior Member |
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Oops, you're right (of course). I'll see if I can straighten it out
without making it too complicated. I like the digital level idea; I bet a lot
more people have one of those than a caster/camber tool.
A question I've been pondering: can we just use the maximum turn angle
on both sides? That is, can we simply say "turn the wheels all the way to
the right and measure, now turn them all the way to the left and measure"?
I'm thinking we don't have be very precise with wheel angles to just get
relative caster. (Though it's good to include how to calculate actual caster too).
thanks!
Karen
> You've done a great job, but the section on measuring caster is a little
> erroneous: Turning the wheels and measuring the change in camber is
> correct, but the result is NOT caster -- its relative to caster; that is,
> Caster=K X (Camber Change), where K depends on the angles to which the
> wheel is turned. For best accuracy, the wheel being measured should turn
> the same number of degrees left and right. I can provide the formula for
> computing K, but for simplicity, fixed angles such as 15* and 20* are
> usually used. For 15*, K=1.91; for 20*, K=1.43. Now if we don't care WHAT
> the caster is, just that it's the same on both sides, K=1 is as good a
> number as any other. We just don't want to mislead ourselves into thinking
> we've actually measured caster (unless K=1, which would require a turn angle
> of 28.7* -- more than the GMC allows).
>
> By the way, with the digital level I use, no math is required to determine
> the camber change: With the 15* left turn set, and the digital level
> attached to the jig, press the Zero button. Turn the wheel 30* to set 15*
> right, then read the level. Multiply the reading by 1.91 to yield the
> caster.
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137688 is a reply to message #137587] |
Fri, 05 August 2011 22:17 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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Senior Member |
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> It would be good to add a statement that the ride height should be adjusted if the coach has larger than stock tires such as LT245/75R16 or LT235/85R16. The ride height should be increased by the difference in the rolling radius for the installed tires vs the original equipment tires which were 8.75/16.5 or the current equivalent LT225/75R16.
Will do.
thanks,
Karen
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137691 is a reply to message #137686] |
Fri, 05 August 2011 22:43 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Karen,
IIRC, one of the many caveats involved in simplifying a mind-numblingly
complex solid trigonometry equation is that the wheel must turn the same
number of degrees in each direction. Because of the Ackerman geometry of
the front suspension, that doesn't happen at full lock -- the "outside"
wheel is turned less than the "inside" wheel. But I suppose that would work
for being sure the caster is the same on both sides -- IF you believe that
the installed steering box (and knuckles) have the same stops on both sides.
I don't have that confidence at all.
Ken H.
On Fri, Aug 5, 2011 at 11:15 PM, KB <kab7@sonic.net> wrote:
> Oops, you're right (of course). I'll see if I can straighten it out
> without making it too complicated. I like the digital level idea; I bet a
> lot
> more people have one of those than a caster/camber tool.
>
> A question I've been pondering: can we just use the maximum turn angle
> on both sides? That is, can we simply say "turn the wheels all the way to
> the right and measure, now turn them all the way to the left and measure"?
> I'm thinking we don't have be very precise with wheel angles to just get
> relative caster. (Though it's good to include how to calculate actual
> caster too).
>
> thanks!
> Karen
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137712 is a reply to message #137587] |
Sat, 06 August 2011 02:48 |
Richard Brown
Messages: 281
Registered: May 2009
Karma: 1
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Question; If there's a specification that the wheels should be measured at a certain angle, why not go to a sheet metal shop & have a piece of sheet metal cut with a straight side & a side with the specified angle made into a triangle? I once saw a tool set made for checking the caster, camber, & toe-in that used a tool that bolted between the wheel bearing & the bearing nut. It used a pendulum and pointer to measure angle of deviation from plumb. It also contained a sheet metal triangle with a 20° angle on it It was for checking declination of the kingpin on a solid beam axle.The instructions said to use chalk to draw a line parallel to a tire & use the gauge plate to turn tire 20° in each direction & take a reading to find caster.
Richard & Carol Brown
1974 Eleganza SE
"DILLIGAF"
Lindale, Tx. 75771
903-881-0192
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Richard & Carol Brown
1974 Eleganza SE
1174 Hickory Hills Dr.
Murchison, TX. 75778
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137717 is a reply to message #137712] |
Sat, 06 August 2011 04:18 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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My camber/caster gage has a template included with it that looks like a
flattened X. It is used to set camber, after caster has been set. The
template is centered under the center of the front tire, and the lines of
the X are at + 20 degrees, and - 20 degrees. The front steering is turned
to +20, a reading taken on the digital scale, the steering turned to -20,
another reading taken, & do the math etc. I do not think that lock
to lock on a GMC would be the same on all coaches, as there are no positive
stops in either direction built into the components. A notched stick, string
and incense might work too but this is a precision adjustment. Some accurate
parameters are probably in order, like a level floor and corrected ride
height, and a straight GMC frame, and a couple of hundred others like not
worn out suspension, unbent control arms, straight wheels and/or tires. You
get the idea. In the final analysis, when the coach is being driven, does it
require a light touch on the wheel at 70 mph, does it "bump steer" when
negotiating corners or bridge seams, does it track straight when passing a
truck, or follow truck grooves in the pavement? All indicate a suspension
that is in need of attention.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sat, Aug 6, 2011 at 12:48 AM, Richard Brown
<wings77sporty@sbcglobal.net>wrote:
> Question; If there's a specification that the wheels should be measured at
> a certain angle, why not go to a sheet metal shop & have a piece of sheet
> metal cut with a straight side & a side with the specified angle made into a
> triangle? I once saw a tool set made for checking the caster, camber, &
> toe-in that used a tool that bolted between the wheel bearing & the bearing
> nut. It used a pendulum and pointer to measure angle of deviation from
> plumb. It also contained a sheet metal triangle with a 20° angle on it It
> was for checking declination of the kingpin on a solid beam axle.The
> instructions said to use chalk to draw a line parallel to a tire & use the
> gauge plate to turn tire 20° in each direction & take a reading to find
> caster.
>
> Richard & Carol Brown
>
> 1974 Eleganza SE
>
> "DILLIGAF"
>
> Lindale, Tx. 75771
>
> 903-881-0192
> _______________________________________________
> GMCnet mailing list
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137757 is a reply to message #137587] |
Sat, 06 August 2011 13:04 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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> Good changes, Karen. The only additional change I would suggest is to make the language about driving the coach to settle the suspension any time the front wheels are jacked off the ground even stronger. I think the drive has to be measured in miles, not city blocks.
Thanks Jerry. I'll see if I can add some emphasis to that point.
thanks,
Karen
1973 23'
1975 26'
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137762 is a reply to message #137587] |
Sat, 06 August 2011 13:31 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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> Another method for checking camber is to use a common framing
> square.
> Cut the short arm off at 14". Then set it with the short(14")
> arm on the floor
> and the long arm against the wheel. At zero camber it will be
> flat on the
> floor. If not, measure the distance the high end is off the
> floor. My notes
> are out in the shop, but I think it is 1.8" = 1/4*. I just
> couldn't cut up a good
> framing square, so I used chalk marks at the 14" mark. JWID
And if you're just going for 0 camber, you wouldn't even have to get that fancy.
Use the framing square against the flat floor and the face of the wheel
and adjust until they line up. Wouldn't help with checking caster, but fine for camber.
I guess if you know the coach is level, you could even use a plumb line.
thanks,
Karen
1973 23'
1975 26'
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137763 is a reply to message #137587] |
Sat, 06 August 2011 13:41 |
KB
Messages: 1262
Registered: September 2009
Karma: 0
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> Question; If there's a specification that the wheels should be measured at a certain angle, why not go to a sheet metal shop & have a piece of sheet metal cut with a straight side & a side with the specified angle made into a triangle?
I've even seen some versions done with a piece of cardboard. I bet a pretty simple
thing could be used to get "close enough".
Karen
1973 23'
1975 26'
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1975 26'
San Jose, CA
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| Re: [GMCnet] 1 ton alignment - lessons learned, part 2 [message #137893 is a reply to message #137876] |
Sun, 07 August 2011 14:44 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Karen, maybe I need to explain what I meant by the "shotgun" approach. It is
in reference to the attitude that seems to prevail in the non GMC community
when it comes to alignment. If you have ever had experience with a shotgun,
you do not need to be very precise with aiming one. Just pointing it in the
general direction is close enough, and that is the kind of mind set
prevelant in alignment. I do not feel that this attitude will yield a very
precise alignment.
My second reference to "incense" has to do with the mystery and myths
surrounding wheel alignment. There are many things that affect wheel
alignment. If you are dealing with a ladder type frame, like the GMC, where
the suspension members are attatched with bushings and fasteners. If the
frame is not parallel with the ground, the alignment will not have much
value. It isn't witchcraft, it is precise measurement that is needed, not
speculation and incense. You have the right attitude about it."Close" only
works well in horseshoes and hand grenades, not in precision measurements.
If reference to shotguns and incense will drive home the point that I was
trying to convey, we will have accomplished much towards the understanding
of alignment. Having the frame of the motorhome at the factory recommended
ride height just can not be close. It must be right on + or - 1/4" like the
factory says. Then caster, then camber, then toe. I like your step by step
approach and your sincere attempt to come up with clear, concise proceedures
for alignment. Hang in there, don't be distracted by the incense burners out
there.<Grin>
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sun, Aug 7, 2011 at 9:40 AM, KB <kab7@sonic.net> wrote:
> > "shotgun and incense", that's an interesting term I've never heard
> before.
>
>
> Well we had "shotgun" alignment in one message, and "notched stick and
> incense" alignment in
> another, so what the heck, combine them both for a really good home
> alignment! :-)
>
> Karen
> 1973 23'
> 1975 26'
>
>
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