| [GMCnet] Some observations on ride height [message #140061] |
Fri, 19 August 2011 16:46  |
glwgmc
Messages: 1014
Registered: June 2004
Karma:
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Senior Member |
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During the development of the do-it-yourself front end alignment kit and in developing the GMC history and genealogy presentation I have given at several GMC rallies in the past, I took the opportunity to read as much as I could find on issues surrounding ride height on our GMCs. While I was not able to find any definitive explanation for the specified ride height, it is clear that it was based on design decisions and not whim. Remember that the GMC as designed and tested had a very low cd, some say it was actually lower than the Corvette of the day initially. It is possible, but unconfirmed, that the ride height might have been raised a bit at the last minute as part of the asserted Corporate edict to raise the cd a bit above the Corvette. Whether that is true or not I do not know. But, two things are certain from what I have learned.
1) Rear ride height effects front ride height in not always predictable ways. 2) Front ride height effects every other alignment setting. If you want to play around with ride height because you think something other than the factory specs look better to your eye, be prepared to measure and change the camber, caster and toe settings on the front to be correct once your coach settles into the ride height you set and also check and possibly reset the camber and parallelism settings on the rear bogies. All of those things are subject to change with a change in ride height.
Side to side weight balance also plays a role and you can only set front ride height correctly if you have about the same weight on both sides front and rear. Once you do, block the center of the rear at whatever ride height you selected, drop 15 or 20 pounds out of each air bag and then measure/set the front ride height you want following appropriate safety procedures and using the correct torsion bar unloading tool. Readjust the automatic ride height controllers on the rear, drive the coach five to ten miles and check ride height again. It may take you several tries to get it right. Once that is correct, then start in on all the custom alignment adjustments, drive the coach five to ten miles and recheck again. Eventually you will probably get it right and stable but it is not something to do just on a whim.
Based on everything I have learned during this project, I will stay with the factory spec ride height and be happy with the "look".
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
Founder of the Southern Oregon Guild
www.southernoregonguild.org
Member of the Siskiyou Guild
www.siskiyouguild.org
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Jerry & Sharon Work
78 Royale
Kerby, OR
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