| [GMCnet] White knuckle ride [message #318555] |
Mon, 05 June 2017 22:31  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Senior Member |
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A word to the wise. Ask him/her if in those 35 years of experience how many times have they worked on a vehicle where both front and rear ride heights are adjustable and where one influences the other. Add to that the hysteresis in our 40 year old suspension systems that requires one to drive the coach two to five miles to let the suspension find its natural level when going down the road any time the coach is lifted. Most really experienced alignment people just tug no the suspension a bit while still on the alignment rack to try to get it to settle in. Won’t work with our GMCs so as soon as you drive it off the rack you stand to loose all the camber, caster and toe settings they so carefully set.
The proper procedure is to set tire pressure for the load carried (roughly 65psi front and 60 psi rear for most 26 foot GMCs). Now set rear ride height, block it so rear won/t move and set front ride height. Drive the coach two to five miles and recheck ride height front and rear. Takes most people two to three or more bites at the apple to get ride heigh correct after driving. Then and only then can one effectively set caster, camber and tow. Assuming you are running radial ply tires, caster should be as much as you can get with both sides equal (1.5 to 3 degrees is all most coaches can get without offset bushings). Camber should be zero with the wheels frame parallel where tow is zero. Toe should be left at zero for most coaches with a reasonably tight front end. Rear wheels should be frame parallel with just a bit of tire top in camber on all four. Hope your guy/gal can achieve that for you.
Remind them that the coach was designed around bias ply tires so the factory alignment specs are not correct now that most of us are running radial ply tires.
When you get the coach back from the alignment shop, check ride height to see if it is still correct. If it is, then go after centering the steering box and there will be no more white knuckle rides in your future.
Jerry Work
The Dovetail Joint
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
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I'm going to talk to the local motorhome alignment guys. Their alignment person has been doing this for 35 years, so may actually have done some work
on these old gals, and I have a PM into one of the local GMCers to see if he has any insight, recommendation. I WILL get her out on the road in
"Relax" mode! ;)
--
Li'l Sister
'77 Kingsley, 403, with a few mods;
TZE167V101404
It's Bigger on the Inside!
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] White knuckle ride [message #318560 is a reply to message #318555] |
Mon, 05 June 2017 23:39  |
Deb
Messages: 349
Registered: October 2016
Location: Logan Lake, BC
Karma: 2
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Senior Member |
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Thanks Jerry. I plan to ask first if he has ever done one! And if so, how long ago  And how many. If the answer is none, then I may have to reconsider. And try to find other options. It's a busy shop and they may not be willing to take the open ended time that could be required to get this done.
But, first things first. Get the tire pressures set, and get her down to the rec centre parking lot where it's nice and flat to check the ride height. (I have a sloping driveway so that is a no go). Then take her out and see if that has helped.
And go from there.
Deb McWade
Logan Lake, BC, CAN
GMC Alumnus
It's Bigger on the Inside!
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