| [GMCnet] effects of torque steer [message #233925] |
Tue, 24 December 2013 19:09 |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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Hi David,
The change in wheel base is a result of needing get 16" wheels to clear the much larger front brake calipers on the one-ton. No other way to do this than to space the wheels further out or use a larger diameter wheel which, with load range D or E tires, would not fit well under the finders of our coaches. The original designers elected the wheel base they did (front track narrower than rear track) for the GMC for a whole bunch of reasons having to do with room inside and using as many stock components as possible for a limited volume production vehicle. They certainly could have widened the front track to be the same as the rear if they wanted to, but they elected not to. It is interesting to note that the front track on the 810 Cord (designed by Gordon Buehrig while he worked for GM as part of a design competition) is the same percentage narrower than the rear as it is on our GMCs. Lots of anecdotal evidence that the Toro designers were heavily influenced by Buehrig's w
ork (see Automobile Quarterly volume XVIII, number 3, page 318 for one example) but no evidence that I am aware of that the GMC motorhome designers were. But, I find it hard to believe this same percentage difference in wheel base front to rear is just a coincidence.
Many have reported good results with the stock front end with our without spacers and nearly everyone who switched to the one ton has reported good results with the spacers. I think these good results are a consequence of proper alignment of our coaches for radial ply tires (the GMC specs were all done for bias ply tires which exhibit a very different behavior at speed than radial ply tires do) far more than anything having to do with the wheel base. My take anyway.
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
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Message: 5
Date: Mon, 23 Dec 2013 19:21:24 -0600
From: David Orders <dao@oarsllc.com>
Subject: Re: [GMCnet] effects of torque steer
To: gmclist@temp.gmcnet.org
Message-ID: <3917d.52b8e194@gmc.mybirdfeeder.net>
Content-Type: text/plain; charset="ISO-8859-15"
JohnL455 wrote on Mon, 23 December 2013 17:18
> Torque steer would show up as a skittery effect under acceleration especially on uneven pavement as wheel loading changes. By widening the track with the wrong Dodge front wheels this will be, by definition, worse as the steering geometry is now out of design parameters. Looks cool, but long lever arm tugs the wheel forward that has grip turning the direction. Right grip steers left and conversely. Any slop in the front end will make this worse. Lower ball joints would be a good candidate for this as the vehicle loading 'self eliminates' slop as long as they are loaded. Get on uneven surface and the loading may come and go causing all alignment specs to shift. Having the wheels centerline outside the imaginary steering arc centerline of the ball joints will increase torque steer, bump steer,(pulls steering wheel towards the side you hit the pothole on) and make any caster pull worse. Sorry.
I'm not questioning your logic, but isn't one of the benefits of the 1-ton front end conversion that it moves the front wheels out a bit and inline with the rear wheels? Maybe doing this with the stock suspension doesn't produce the same positive results.
--
1976 Royale "Twinkie II", 1978 Palm Beach with front end fire. Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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Jerry & Sharon Work
78 Royale
Kerby, OR
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