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[GMCnet] Wheel Spacers [message #170726] Thu, 24 May 2012 10:51 Go to previous message
glwgmc is currently offline  glwgmc   United States
Messages: 1014
Registered: June 2004
Karma:
Senior Member
Good info, Adrien. It is important to note that all things pertaining to steering geometry on our GMCs start with proper ride height. If a coach is not at the correct factory ride height front and rear, you cannot achieve proper alignment. Things like the anti-dive geometry and proper drive shaft angle to name just two are baked into the ride height and cannot be altered. Caster, camber, toe and frame parallelism can be adjusted even if the ride height is off but your coach still will not drive correctly and might wander with or without things like spacers and aftermarket sway bars. The other critical factor is that the GMC was designed for bias ply tires and the design was not changed (as far as I can tell) when they switched to radial ply tires in 76. Bias ply tires and radial ply tires exhibit very different rolling characteristics. At speed a bias ply tire will go egg shaped and the contact patch area will shift rearward which effectively increases the caster angle
. Radial ply tires do not so additional caster must be dialed in at rest to compensate. Too much caster, however, will cause excessive steering effort and may overload the steering gear. You can read all about this in the slides from the presentation I gave at GMCWS Casa de Fruita rally last month. The presentation slides in .pdf format are available for free download on the GMCWS web site or my web site (http://jerrywork.com).

Jerry
Jerry Work
Fine furniture designed and hand crafted in the 1907 former Masonic Temple building in historic Kerby, OR
glwork@mac.com
http://jerrywork.com
541-592-5360

-------------------------
Message: 7
Date: Wed, 23 May 2012 19:21:14 -0500
From: Adrien Genesoto <fixman54@syix.com>
Subject: Re: [GMCnet] Wheel Spacers
To: gmclist@temp.gmcnet.org
Message-ID: <29ab1.4fbd7ef9@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"



Mac,

I know about the tracking differences that is built in to our coaches (LOOKS, and rut tracking), but I Keep thinking about what spacers do to the designed 'front end geometry'.

Not to mention the difference in load forces imposed on the hub bearings. I'm surprised that they're lasting like they do.

Here are some site about FEG also none as Steering Geometry.

> http://www.scribd.com/doc/15355738/Steering-Geometry-Angles <

> http://www.motor.org.uk/documentlibrary/Sep%2009/TT%20_%20Sept%2009.pdf <

> http://www.google.com/search?q=steering+geometry&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=NXa9T5LtDsqliQKorZi5D w&sqi=2&ved=0CGoQsAQ&biw=1600&bih=688 <


Just for information.





--
&#8221;When we avoid the mistakes we might have made, we sometimes make the mistakes that we might have avoided.&#8221;



Adrien & Jenny
75 Glenbrook
Yuba City,Ca.
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Jerry & Sharon Work
78 Royale
Kerby, OR

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