| [GMCnet] Alignment question [message #163077] |
Thu, 15 March 2012 13:49  |
Gerald Work
Messages: 102
Registered: June 2010
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hi Ken,
I'm sure you have already checked ride height, but also take a look at weight loading. A slight pull can sometimes be caused by a torsion bar loading imbalance offset by differential air in the rear bags. Start by checking the air pressure in each bag when your coach is at correct rear ride height. If they are not the same, then block the center of the rear at correct ride height, dump 15psi out of both bags and recheck front ride height. If that checks out ok then recheck tire pressure and even wear. Swap the front tires side to side and see if that helps. Start playing with differential camber only if all else checks out. Road crown is not consistent so it is hard to set the "right" amount of differential for that reason.
Jerry
Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
Http://jerrywork.com
................
Steven Ferguson wrote on Thu, 15 March 2012 10:10
> Play with one, you'll have to play with the other. Easiest way is to shoot for as much caster as possible and still get zero deg camber.
That is what I have now. Maximum EQUAL caster side to side and 0 camber on both sides. I was just looking for what to tweek a bit. This is just a slight pull that was not there before I started. I'll drive it some more on 4 lane and 2 lane roads before I make any adjustments.
I just wanted to know what to change if necessary.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
..............
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| Re: [GMCnet] Alignment question [message #163082 is a reply to message #163077] |
Thu, 15 March 2012 15:47  |
KB
Messages: 1262
Registered: September 2009
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Per my genius mechanic brother-in-law:
caster pulls to the negative side but 1.5* caster pulls the same as 1* camber.
Eg if it pulls to the right, either set the right side more positive, or set the left side more negative.
Karen
1973 23'
1975 26'
> finally took the GMC out of winter hibernation in my hanger and took it for a ride for the first time since I put the bushings in. I have a slight pull to the right. Not much but enough to be irritating.
>
> I am assuming that I need to add a bit of camber to the right side to correct this. I'm thinking about 1/2 degree but my question is which way.
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Karen
1975 26'
San Jose, CA
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| Re: [GMCnet] Alignment question [message #163087 is a reply to message #163077] |
Thu, 15 March 2012 16:13 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Ride heights are set correctly.
I have a set of scales and the difference on the front is 50 pounds. The rears are within 100 pounds side to side. Both front and rear are slightly heavier on the left (driver's) side.
I have the 22,000 pound scales that we have used at the rallies to weight coaches. I can not get any closer than 50 pounds with these scales.
I set the front ride heights by weight with the rears blocked at the correct height. Then I set the rears using the leveling sensors. It is amazing how much 1/4" difference in ride height makes in weight on the diagonally opposite wheel(s).
That is why I can not imagine how anyone gets this anywhere near correct using cutoff valves or or this wireless system people are pushing these days.
As I stated before I'm only trying to change a SLIGHT pull to the right. I thought this could be done with camber but every on one is saying caster.
Thanks
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment question [message #163089 is a reply to message #163082] |
Thu, 15 March 2012 16:22 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| KB wrote on Thu, 15 March 2012 15:47 |
Per my genius mechanic brother-in-law:
caster pulls to the negative side but 1.5* caster pulls the same as 1* camber.
Eg if it pulls to the right, either set the right side more positive, or set the left side more negative.
Karen
1973 23'
1975 26'
> finally took the GMC out of winter hibernation in my hanger and took it for a ride for the first time since I put the bushings in. I have a slight pull to the right. Not much but enough to be irritating.
>
> I am assuming that I need to add a bit of camber to the right side to correct this. I'm thinking about 1/2 degree but my question is which way.
|
You are reenforcing what I thought I knew about Camber. I might try that after I have driven the coach about 150 miles on different roads next week to make sure it really needs adjusting.
Thanks.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alignment question [message #163102 is a reply to message #163077] |
Thu, 15 March 2012 19:38 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Hey, Jerry,
Are YOU coming to Shawnee? If so, I'll be glad to cede the floor to
you for the seminar. Maybe show my jigs as an alternative to yours to
achieve the same result. Of course, one hour won't be enough to go
into all the in's & out's like diagonal biases, ride height
variations, etc. My intention is to postulate most of that as
prerequisite and concentrate on pure alignment using our simple
equipment.
Ken H.
On Thu, Mar 15, 2012 at 2:49 PM, Gerald Work wrote:
> I'm sure you have already checked ride height, but also take a look at weight loading. A slight pull can sometimes be caused by a torsion bar loading imbalance offset by differential air in the rear bags. Start by checking the air pressure in each bag when your coach is at correct rear ride height. If they are not the same, then block the center of the rear at correct ride height, dump 15psi out of both bags and recheck front ride height. If that checks out ok then recheck tire pressure and even wear. Swap the front tires side to side and see if that helps. Start playing with differential camber only if all else checks out. Road crown is not consistent so it is hard to set the "right" amount of differential for that reason.
>
> Jerry
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www.gmcwipersetc.com
Large Wiring Diagrams
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