Back to Basics - Chassis Question

[Huffstutler]

Since Cadillac Commercial vehicles are based on a special bare chassis, I am wondering something about the "style" used for the 1957-1964 versions. I say this because they are not the same design as the Limousine frames. The rear section that would usually fit under a trunk area is the original non Eldorado Brougham design - triangulated rather than squared off as with the 4 point control suspension. I had always wondered why Cadillac only used these sharply angled rear fork rails which restricted trunk space for only one year - 1957 but now see them under Commercial cars. Was this planned or something as a left-over?

I also see that Pontiac used a similar version between 1958-1960.

Any help with any background history about these frames would be greatly appreciated!

Eric

[Dickey]

I'm not sure I follow the context of your question.

Here is a typical 1957 Cadillac frame:


Here is a typical 1958 Cadillac frame:


Here is a 58 Pro-car setup:





The pictures are for my benefit, would you mind using them to clarify a bit further what you're asking?

[Psychoholic]

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[60Crown]

Not certain I'm following exactly what you're asking either. Can add the following:

Limos are Series 75. CC are Series 86. Although the same gas tank was used in CC from '59-'68, it is basically a slightly modified '58 passenger car unit.

http://www.ebay.com/itm/350562321650?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

Here's a '59 CC:



Would history of the X frame help?

http://www.curbsideclassic.com/automotive-histories/automotive-history-an-x-ray-look-at-gms-x-frame-1957-1970/

[Huffstutler]

Yes, the subject can be a bit confusing but Atti kind of hinted that there was something different with the gas tanks, especially the 1957-1958. Those gas tanks were also used on the standard Cadillac's of 1957 (which dictated that odd gas tank shape) but not 1958 because the rear chassis design had changed. Here is another example drawing I made which will help visualize what I am saying. It actually shows in red the outline shape of the rear of the frame for regular Cadillac's as well as the 1958 and the 1957-58 Eldorado Brougham. But what you need to pay attention to is the 1957 shape which apparently carried over on "Commercial" frames between 1957-1964 and not only 1957 as with standard models. And from what I can tell production line limousines frames followed non commercial chassis and changed as did the regular cars. Dickey your first picture example is not a Cadillac but a 1950s Mercedes Benz 300 series.

[Huffstutler]

To expand for those who may be curious, the 1957 style frame official called a Tubular Center X-Frame, was initially designed for the Cadillac Eldorado Brougham and GM had toyed with the idea of going with a unibody design for the rest of the 1957 Cadillac line. Early testing of the frame (which had been in development since 1950) showed that it would not work with the air suspension setup being pushed for introduction so changed the rear rail shape and routed them outward to accommodate the 4-point control setup and the torque with them (Brougham only). With the deeper trunks on these cars it also opened up the trunk space that on the standard 1957's the trunk the space was also triangle shaped and the spare tire almost in the middle of it. For 1958 Cadillac dropped the leaf spring setup and went with across the board with the 4-point control arm coil spring setup and the frame also changed with it. But possibly since A.O. Smith had already made up a ton of these early 1957 style frames must have used them on Commercial chassis since the wheelbases were altered between models by the center tunnel section? Which brings up the question, why did GM use leaf springs under commercials as opposed to the coil springs?

[Dickey]

Dickey your first picture example is not a Cadillac but a 1950s Mercedes Benz 300 series.

You're right. It comes up under the wrong heading when googling "1957 cadillac chassis". That's my mistake, I should have noticed the engine. The picture offered part of my confusion.


I'd venture they used leaf springs for durability's sake. At that time, metallurgy wasn't what it is today and I'm not sure you could get a coil spring strong enough to support the added heft of a commercial vehicle's needs while keeping a small enough footprint to use the normal sedan style perches. Springs would have been the easiest method of accommodating the rear suspension.

[60Crown]

^x2. I'd also guess additional CC weight was determining factor in using leafs. Everything on a CC was burlier to handle the additional rigors (no pun intended). Even though '57-'58 Brougham may have used same tire size as CC (820 or 840 x 15) there was a proportionately significant curb weight difference. Broughams were 5300# +/-, limos 400# + more coming in between 5700-5800#, and depending on configuration hearses/ambulances in this year range started around 6200# approaching 6900# empty. There are a couple high top rigs decked out with gear out there that breech 8000# before humans figure in!

And for clarification Huffstutler, when you say '57-'64 CC frame you do mean through '65 limo (only), right? Although '65 saw an all new CC (which forced coach builders to completely redeisgn their offerings), '64 limo carried design over through '65. Only visible discernible difference between '64 and '65 limo is hubcap. As I have not spent much time crawling under any '65 limo, factoring in your knowledge base and line of questioning, I'm wondering now if the chassis may have changed yet skins remained the same. (Leaning toward not.) Like you I do enjoy learning this stuff.

[Huffstutler]

Atti, you are correct and I left the limousine factor open ended a bit. For those not familair with what we are talking about, there was no 1965 Cadillac body style limousine (from the factory). They used the 1964 model throughout - including chassis. The only way you could tell a 1964 and 1965 limo apart was by VIN, wheel covers, and double stripe factory whitewalls. They are identical to the 1964 cars while all other 1965 models changed. There was a 1966 limo of the new design.

That said, the 1965 Commercial frame was of the new 1965 Cadillac perimiter design.

As for chassis, other than springs, the rear rails could have been changed to reflect the standard 1958 frame design, but maintained the unique 1957 configuration throughout the 1957-1964 years on Commercial frames but guess the leaf springs dictated that it stayed the same and of course didn't matter since the floor was flat over that area anyway and no spare tire well.

Eric

[Huffstutler]

Is there any historians here that may have the S.A.E. Paper from Technical Journal 66 of 1958 (paper 580014) which discuses the development of the chassis in question? Thanks.

[Huffstutler]

Bringing this back to the top to see if anyone has access to microfilm, hard copy or has in their own personal library the mentioned S.A.E. paper concerning the development of the 1957 Cadillac chassis? Thanks in advance!