| [GMCnet] Another example of different wheel tracks front to rear [message #333363] |
Mon, 11 June 2018 16:45  |
glwgmc
Messages: 1014
Registered: June 2004
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I will chime back in here too. Bill is correct about many vehicles having differential track. Among them are the 1955 Corvette and the MB 300 SL, both front engine, rear wheel drive cars, one with a solid axle and one with swing axles, and the Porsche 356 rear engine, rear wheel drive car with swing axles. Most suspension publications I have read focus on reducing over steer by the front track being narrower than the rear track. In the case of these three cars, the Corvette and the 300 SL were front end heavy cars while the Porsche was rear end heavy. And, in the Porsche case the track was wider at the front, 1306mm to 1270mm at the rear and that car was loved by professional drivers who wanted the rear end to come out to get through corners faster, but it was disliked by amateurs for that same reason - they had a hard time controlling it. Both the Corvette and the 300 SL were known as plowing cars that you had to really crank over to get them around corners but were very stable at high speeds going straight. And, bias ply tires on the motorhomes likely led to wanting the vehicle to under steer instead of over steering which would argue for narrower front track.
For the 1966 Toronado, a car with 54%/46% front/rear weight distribution, Olds designed in 63.5 front and 63 rear track as a car with that weight distribution would not over steer to begin with.
A 2010 Motor Trend article had an interesting observation about the 1966 Toronado that might shed some light on all this:
quote - Olds designed it for 15-inch radial tires, but tests revealed unusually high wear, and 14-inch bias-plies were substituted at the last minute. Ultimately, the Toronado didn’t get radials until most every American car did during the first gas crises in the 1970s. - end quote Another source says the production cars had 8.85 x 15 inch bias ply tires. I don’t know which is correct, but I think we can put to bed any question about whether the designers knew what they were doing when they dialed in a narrower front track on our motorhomes. All evidence suggests they did.
Jerry
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
===============
Message: 1
Date: Mon, 11 Jun 2018 12:08:49 -0600
From: Bill Bryant
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Another example of different wheel tracks front
to rear
Message-ID:
Content-Type: text/plain; charset="utf-8"
Rob,
To do what you suggest would have required new stampings for the L&R front frame section which was already an existing Toronado part (as well as
stabilizer bar, torsion bar cross member support & possibly other things I didn't think of).
I suspect that "matching the front & rear treads" may be of importance to us at this point, but I doubt if it made the list in 1972. If we looked at
the many makes and models of vehicles currently on the market my bet is that a large number of them have a different front vs. rear track.
I still believe the factors that determined the original design were:
1- use existing parts wherever possible.
2- costs, costs, costs
That is pretty much what I heard from the original GMC MH Engineers I spoke with.
PS. should be a good auction, no I won't be going. Have fun if you do. (looking for a mate for the T&C?)
Bill
--
Bill Bryant
1976~PB
1914 Ford
1965 Corvette
GMC MH History CD & GMC Showroom DVD
Workprint DVD GMC development 11-70 to 3-71
http://bdub.net/billbryant/
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Jerry & Sharon Work
78 Royale
Kerby, OR
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