GM’s X Frame, upon which millions of GM full-size cars sat from the years 1957 through 1964 (Buick Riviera through1970), has generated plenty of controversy, speculation, and accusations. Since there seems to be no complete survey of the X frame – at least any available on the web – let’s lift off all those handsome and finned GM bodies by Fisher, and take a closer look at what’s really under there.
Starting with a real stunner: The X frame first appeared in 1957, underpinning the new C-Body Cadillacs and Eldorado Brougham (pictured). It was obviously conceived as a way to facilitate lowering the total vehicle height, by facilitating deep floor wells for the passengers feet to drop essentially to the bottom of the car, unimpeded by frame rails.
I’m not a frame expert or historian, but Cadillac’s approach in developing the X frame seems to be rather unique, although it combines aspects of two very distinctive frame designs: the backbone frame and the X-braced ladder frame.
The backbone frame originates with Hans Ledwinka’s revolutionary Tatra T-11 of 1921 (full story here). A strong solid steel tube was the carrying member for the whole car and its (lightweight) body.
The Tatra tube frame evolved into a combination central backbone-platform frame, as seen here in the mid-thirties Tatra 97. Needless to say, a very similar route was also taken by others, including Porsche for the now very-familiar (and similar) VW platform frame. In these, the body was rigidly bolted to the platform, to create essentially a unitized structure from the two halves.
The pure backbone chassis was taken up by others, none more famously so than by Colin Chapman, with his brilliant Lotus Elan. With a very deep central section, which worked well in a sports car, the Elan had unparalleled rigidity, the ultimate goal of any frame/body structure. Rigidity is the only way that a suspension system can be designed to optimize its function.
On the other end of the spectrum, sits the ladder frame, here immortalized in the frame rails from a Ford Model T. A certain amount of flex was an intrinsic part of the equation. Its origins are obviously in the heavy timber frames underpinning wagons, but the seminal 1901 Mercedes was perhaps the first to sport something akin to what became this timeless approach to automotive frame building
Jumping ahead about a century, here is a modern ladder frame, as now used in pickups and BOF SUVs.
The origins of using an X-member to reinforce a ladder-type frame has been credited to the fwd Cord L-29, and this excerpt from its brochure substantiates that claim.
But this 1939 Buick frame shows that its adoption had expanded by then, and for obvious reasons. It undoubtedly increased rigidity, at least in certain planes.
X frame centers were also used to stiffen ladder frames specifically for convertible use. This is a sedan frame for a ’57 Chevy.
And here is the center section for the convertible version. It’s important to note that the bodies of BOF (body on frame) cars contribute substantially to the overall vehicle rigidity, which is why convertibles require additional reinforcement to their frames.
There’s no readily available background on the engineering decisions that led to the first GM X frame, on the ’57 Cadillacs (’61 Chevy frame shown here). GM claimed improvements in rigidity, as well as the lower floor. It did result in a very large central tunnel, a distinctive feature of all X frame cars.
In order to make the X frame work, Fisher Body increased the strength of the rocker sills of the bodies, as well as side-to-side stiffeners in the floor. These can be seen fairly well in this shot of a ’58 Chevy. In essence, GM was transferring a substantial amount of the overall structure’s strength to the body; certainly any side impact resistance that this intrinsically vulnerable design might have had. The problem is not only whether the body sills had enough strength for that purpose in the first place, but these rocker sills were notorious for collecting moisture and rusting prematurely.
But before we discuss the X-frame’s safety weaknesses, real or perceived, let’s do a survey of what all the GM divisions were doing frame-wise during this period. Contrary to some assumptions, not all the divisions used the X frame, either at all, or at least not during some of the time.
Vehicle design and construction at GM then was almost the exact opposite of today. Now, numerous vehicles (and brands) with distinctly different bodies share a “platform”, generally the key underbody structure, suspension and/or floor platform. Back then, Fisher body engineered a common body to be used by various divisions, but each division engineered its own vehicle otherwise, including the frame, suspension, drive train, etc. It really was ass-backwards; or it certainly came to be so, given how increasingly little folks actually appreciated what went on under the floor, at least very technically speaking. And it was inevitable that GM would eventually centralize these aspects.
But not during the X-frame’s reign. The ’57 and ’58 Buicks, which shared Cadillac’s big C-bodies, did not go with the X frame, keeping an X-strengthened ladder frame. So where did the rear foot wells go? Did the Buick C-Body ride higher than the Cadillac? If I could find overall height specs on both, it might possible to ascertain that.
Rather curiously, for 1959 Buick even dropped the X center-reinforcement, going with a strict ladder-perimeter frame, with a K-type front section. To each their own!
But beginning in 1961, Buick fell in with the X crowd, even touting it as the “Safety-X-Frame”. Full-sized Buicks stayed with the X through 1964.
And the Riviera maintained its X-Frame all the way through the 1970 MY. Here’s a 1969 Riviera showing off its skeleton.
Olds was the only member of the GM family to not use the X frame at all. The ’57-’58 Olds frame looks quite similar to the same vintage Buick frame.
But for 1959, Olds came up with what is essentially a variation the X-frame, incorporating wide side rails to do the work that the reinforced body sills were asked to do on the true X-frame cars. These side frame rails (or similar) have been widely adapted to high-performance X-frame cars, creating an overall stronger, more rigid and safer frame. And that came without any sacrifice in the X-frame’s deep floor wells. Call it the improved X frame.
The other unique aspect about the ’59 – ’60 Olds chassis is that it reverted to leaf springs in the rear suspension, the only GM full-sized rwd car to do so during the whole modern era, except for the ’71 – ’76 “clamshell” wagons, which did so for space reasons.
For 1961 through 1964, Oldsmobile used a perimeter ladder frame. Note how much emphasis Olds places on the safety of “Steel Protection All Around”.
The frame Olds used those years (’63 in drawing above),
very much predicts the frame all the GM full-sized cars went to in 1965 (Riviera excepted). This one is from a ’69 Cadillac. Olds’ reputation for engineering advancements among the GM divisions seems to have gone all the way down to frame design.
Interestingly, Pontiac did not show off its frames in its brochures, unlike the rest of the divisions. John DeLorean, who was then running Pontiac, was an engineer by training, but was also an excellent marketer. He thought GM was generally lacking in modern marketing techniques at the time, and perhaps that explains why Pontiac frames didn’t make it into brochures. Who cared? Folks were much more interested in how they looked, and even how they drove. Pontiac accentuated its very visible Wide Track stance, and left folks guessing about the frames.
But as the above frame spec chart shows, Pontiac followed Chevrolet and Cadillac with X frames for ’58 – ’60, but then went to a perimeter frame for ’61 – ’64 that looks very similar to the ’61 – ’64 Olds frame. (Update: Canadian Pontiacs did keep the X frame for ’61 – ’64)
Chevrolet’s “little brother” relationship to Cadillac was more than skin deep, inasmuch as the two of them were the most consistent users of the X-frame; from ’58 through the ’64 MY, in Chevrolet’s case. Here’s the ’59 version in full display. The ’58 was unique to that MY; the ’59 – ’60 frames were identical, as were the ’61 – ’64 frames.
The ’59 Chevy became famous in 2009 when it was crashed into a new Malibu, and (not surprisingly) fared rather poorly. The X frame probably played a relatively small part in that, given all the other aspects that were so different between these cars. And who knows how rusty the Chevy frame and/or body were. Speaking of, the X-frame is rather notorious for rusting, and there is a pretty brisk business in replacement frames, often reinforced. One wouldn’t want to start throwing a Chevy low-rider hydraulically four feet into the air with a rusty frame.
In Ralph Nader’s “Unsafe At Any Speed”, the X-Frame merits some less-than flattering attention. Here’s some excerpts from that:
A case in point is the “X” or “cruciform” type chassis frame. This frame was introduced in 1957, primarily to reduce the problem of restricted headroom and difficult entry into the “low-profile” automobiles that were becoming popular after the mid-fifties. The X frame construction does not have side rails along the passenger compartment, as did most previous conventional frame designs. From the time the cruciform type frame was introduced, it was widely used by General Motors on Chevrolet, Buick, and Cadillac. The Ford Motor Company continued to use frames with side rails, and it was evident that the two companies held strongly different opinions about the two designs.
In the fall of 1959, a photograph of a Chevrolet Impala that was broken in half after striking a tree broadside was widely circulated in newspapers throughout the country. The frame had severed at the intersection of the X. The report of the General Motors investigators who rushed to the scene attributed the severance of the frame to the semi-airborne position of the car as it struck the tree. This had apparently allowed the engine mass to act as the head of a sledge hammer. At the General Motors engineering center in Michigan the conclusion was that “automobiles are not designed to withstand such tremendous lateral forces – this would be extremely uneconomical.”
General Motors spokesmen continued to defend the cruciform type frame as offering substantial resistance to side impacts because of the rocker panel and floor pan underbracing members — even though by 1965 all General Motors models except the Buick Riviera had abandoned the design in favor of the perimeter type. In 1960 the General Motors technical center offered proof that a unitized structure with side rails can also split into two pieces. A picture of a Ford Thunderbird, torn in half after slamming against a telephone pole and tree, was offered as evidence to critics of the X type frame.
This comparison enraged Ford engineers. Fletcher N. Platt, a highly talented research engineer at Ford, retorted that the Thunderbird case involved a telephone guy-wire that had “acted as a knife on the entire body structure.” In contrast, he said, “the Chevrolet that broke in half failed at the center of the X frame after hitting a tree.” Platt said, “The X frame has no advantages from the standpoint of passenger protection. It requires less material to support the four comers of the car, but it is obviously less rigid and provides little lateral [side] protection to the passenger compartment.” He suggests consulting any “‘unbiased’ structural engineer regarding these two designs.” Mr. Platt might not consider Mr. Harry Barr, vice president for engineering of General Motors, qualified for the designation ‘unbiased,’ but Mr. Barr did admit grudgingly, under questioning, that the Oldsmobile perimeter type frame had some advantages over the Chevrolet X type frame in side-impact crashes at speeds of about fifteen miles per hour. Further proof that some General Motors engineers agreed with Ford’s Platt came in the form of an internal memorandum prepared by the Oldsmobile division in 1963 in which the Oldsmobile “guard-beam” frame was described as offering an “extra margin of protection” over the X type frames of Chevrolet, Buick, and Cadillac.
I was unable to find the picture of the broken-in-half ’59 Chevy cited here. Undoubtedly, a side impact, especially against something like a tree or pole, would be the X-frame’s most vulnerable aspect. At least today, the car would be covered by classic insurance. There are other anecdotal negatives commonly cited on forums, such as cracking of the rear body sills, as well as other minor structural infirmities, especially with advanced age. The two-piece drive-shaft used with the X frame also comes for a lot of hate, especially the weakness of the center bearing, and the joys of replacing it.
Our exhaustive look at the X Frame is complete. If you made it this far, you’re now an expert. Hopefully, others will add further facts or insights.
brochure images from oldcarbrochures.com
That video with the ’59 was the first thing I thought of when you started saying how weak that frame was in a side impact. However…if you watch the video slowly, the ’59 has no engine or transmission and something’s hinky about how the right front fender just pops off on impact at about 1 minute into the vid not to mention the rust storm. Surely the crushing weight of an iron drivetrain and unrusted body and frame would have added something to how the ’59 performed here.
Not to start a debate here, but I thought that the IIHS and independent witnesses verfied that the ’59 did indeed have an engine and transmission installed during the crash test. It became necessary almost immediately after the video was released, when the fanboys of old-school iron were making that claim, as well as the claim that the ’59 was compromised due to cuts to the body and/or frame, or that it was a rustbucket.
Look carefully at the video. In the slow motion shots you can see the “Blue Flame” six’s air cleaner flying off as the hood deforms.
I don’t know if the ’59 was structurally compromised in any way, but I’m completely confident that today’s cars are safer. Perhaps one day we can get into the time machine and pull a fleet of brand new ’59s off of the assembly line…then, once and for all we can settle the question to the satisfaction of all.
Yeah, the old fan boys went nuts on this. They assume that any old car is ‘indesructible steel’ and new cars are ‘all cheap plastic’. This just from “nostolgic feelings” and they want to relive youth again.
What is most amazing, and disturbing, is that all those so-called fanboys can rattle off for hours about engine sizes, horsepower ratings, camshaft specs, carbureter jet sizes, all to exact detail, but do not appear to know the following cold, hard numbers:
Mild steel: 35,000 pounds per square inch of tensile strength
Ultra High Strength Steel : 110,000 pounds per square inch of tensile strength
Old cars, made before the mid 1990s are made of the weak mild steel, including the frames, X frame of ladder frame.
New cars are made up of up to 5 types of steel, and guess which kind of steel is used around the passenger compartment? So no 50s of 60s car is capable of “slicing through” a new car. The new car passenger compartments will demolish the old car passenger compartments once the crumple zone finishes crumbling. And you know what kind of steel the crumple zone is made of? The same mild steel the whole old car is made of.
Here is a crash test of a 2002 vs 1962 cadillac:
http://www.autoblog.com/2011/11/27/1962-cadillac-vs-2002-cadillac-in-head-on-collision/
You raise a very good point. Crashworthiness was never a primary design criteria a generation or more ago. But now, it is. It only makes sense that when you design the structure so that the occupants are most likely to safely survive a crash, that this will be a much more likely outcome than in an older model.
I did not know the strength ratings of these kinds of steels, and appreciate the info.
Sorry to burst your bubble there, dude. My grandpa was just driving along in his 1958 Lincoln one night. A drunk driver-amazingly-driving a 2006 lincoln-smashed into him. The new driver died. The 5,000 pound unibody frame design of the older lincoln allowed it to shear the entire front end off the car. ;D Just goes to show you that not all newer cars are safer, and not all older cars are unsafe. It’s probably because the newer lincoln only weighs like 3,000 pounds, smaller engine etc.
Sorry to here about your Grandpa’s Lincoln, but at least she did her job of protecting him with honor.
I am sure that some new cars are safer than many older ones, but
I strongly feel that this crash footage is biased,
As it is known that 59-64 Chevys are structurally weak, just go ask any retired collision damage worker who has worked in the 60′s and 70′s on these cars .
The crash organizers knew this fact before planning this footage, why did not they brought in a 53-54 Chevy instead ?
with a 53-54 Chevy this crash could have been a whole other scenario, the Malibu’s passenger compartment could not have survived as it did with the 59.
Assuming the picture loads properly, here is the engine in that 1959 belair after the crash. It is a straight six, you can see the blue painted valve cover.
This may seem hard to believe.. BUT, this ’59 in the video belonged to a friend of mine. In fact, I helped him sell it on my web site. (I have a ’59 Impala and I own a popular 1959 Chevy web site. I was tempted to buy this Belair, but passed.)
When we sold it, the guy from the East coast showed-up with $8,000.00 in cash and a trailer, and took it away. We had no idea it was destined for destruction.
This video has infuriated collector car people all over the world. The car was originally from Georgia, it was a six cylinder model. That red dust that comes out on impact is actually Georgia clay that had accumulated inside the frame rails. The car was not a ball of rust bondo-wagon!
I just caught this when reading the excerpt from Nader’s book.
“It requires less material to support the four corners of the car,”
Maybe it’s possible that the X frame was just an example of cost engineering and not fashion (low step in height, lower roofline, etc).
I really had to laugh at how Buick was touting the safety of the X frame and Olds was touting the safety of a perimeter frame in 1961.
Wow, great article, Paul! I always thought all the GM divisions used the X frame, but didn’t know about the system by which Fisher supplied the bodies and the divisions engineered everything underneath it uniquely.
40 years ago when in the air force and enjoying my avatar above, a 1964 Chevy Impala SS convertible, 283, 2 bbl, powerglide, when TDY on Okinawa for my second time, I left my car with a buddy for the four months I was gone at our base, Beale AFB in California.
We had planned some “upgrades” to the car. New springs, spec’d for a Chevy 409 wagon. This raised the car about 2″ higher off the ground. This caused a few issues. One, ball joint extensions were needed, no problem. The second? A serious vibration problem with the center U-joint affixed deep in the center of that X frame! This was due to the fact that the geometry had changed. No matter how much I shimmed the bearing, I could never eliminate the vibration completely. This was only apparent when starting from a dead stop, and went away – at least I didn’t notice it anymore – to 10 mph.
That car not only rode like a truck, but looked like it had 4 wheel drive! It did handle a bit better, though.
That was my one regret with that car, as it wasn’t “perfect” in my eyes and mind. Should have just replaced the springs with the proper ones…
The year before (1971), my friend rebuilt the engine and installed a 327, 350 hp cam and dual exhausts with glass packs – full tail pipes, of course. Man, did that car sound and run sweet. Not much off the line, but it would literally take off if you punched it at 50 mph!
Overall, it was a great car and I miss it to this day – X-frame and all!
What a great article. Gotta love the tech stuff!
I still recall a memory of my car-mentor Howard. He recalled a co-worker who bought a new 60 Impala convertible. The employees parked in a gravel lot. Howard recalled that the guy with the Impala had to find a fairly level place to park, or else the doors would not open on the car.
I can also provide a bit more info on Ford Model T and Model A frames. Both were designed to have some measure of flex. On the A in particular (and I would presume on the T as well), the frame members were held together by rivets, and not with welds. A restorer’s guide that I read warned not to weld the frame members, because the welds would either fail or the surrounding metal would likely tear from stresses that the frame was not engineered to take.
My last piece of frame trivia for today involves the 1951 Kaiser, which used a ladder frame with a stiffening X member. The frame, coupled with an unusually large number of body mounting points, made for one of the stiffest structures of any BOF car made at the time.
It is clear that you did a lot of research on this piece, and it is appreciated! An enlightening and informative piece.
This is a great showcase for American engineering talent. While I am sure there was a lot of trial and error and revisions made after field testing practically everything we see in this article was designed by guys using slide rules and mechanical calculators. There were no computers at all until the last of these frames were designed and finite element analysis was years away. Of course, many of the engineers had gotten lots of experience in aircraft work in WWII.
I hope you (or someone) will do a similar article on Chrysler unibodies.
Thanks for a great writeup.
We had a ’60 Impala, a ’64 Buick wagon and later a ’64 Impala in the family, all with the X frame and all with a common riding experience.
The hood and fenders would shake with road imperfections and you would sense and hear that “crash/boom” effect with each bump and pot hole.
In general, it made the body feel like a bucket of bolts, as though the whole thing would collapse with a good jolt.
X frame related or just P’s OS? Who knows. The powertrains, especially the Buick were quite durable though.
I hear this a lot, but I never had any issue with my avatar. The doors never failed to close, never flung open, never binded and the car never rattled. I learned to drive in dad’s 1960 Impala 4 dr. hardtop. Same thing. No muss, no fuss – ever. My second car was a 1961 Bel-Air 2 dr. sedan. No issues there, either. A friend had a 1959 Chevy 4 dr. hardtop. No problems. Dad also had a 1966 Impala 4 dr. hardtop. No issues. I could go on, but I just don’t understand all this about “issues” with the X frame.
Your ’66 doesn’t have an X frame. Title is misleading.
Your comment is interesting to me. I am dredging up long dormant memories of a 63 Cad Fleetwood Sixty Special that I owned back in the late 1970s. I vividly recall what a solid feeling car it was, and am amazed that they could get that kind of stiffness out of the X frame (a design feature that I paid no attention to at the time). The car was getting pretty rusty, however. One day I found a BIG broken-off bolt in the driveway. One of the body-to-frame mounting bolts had broken off from around the middle of the car, probably as a result of jacking up a corner. The car had a noticeable decrease in structural stiffness, and picked up a teeny bit of quiver and squeak when going over rough roads. But it never displayed (at least as I remember it) the doghouse quiver that you describe. (It was my 85 Crown Victoria that suffered from doghouse quiver more than any other I recall.)
One thing about GM cars in the 1950s and 1960s was that divisions still made significant changes to a vehicle even if they shared the basic body with another division.
At one of the Hershey Antique Automobile Club of America (AACA) shows, a 1959 Chevrolet, Buick and Cadillac were all parked in a row, with their hoods open.
You could easily see that, as you climbed the GM price ladder, you also got a car with more bracing and beefier overall construction in those days.
I remember watching the hood and fenders of my parents’ 1976 Oldsmobile Delta 88 Royale four-door hardtop quiver over even minor bumps. This didn’t only happen with cars that had the X-frame.
We had a ’61 Chevy Bel Air as the family car, bought new. It had the X-frame, and I remember the central hump in the floor was huge, both front and rear. It didn’t make sitting in the center position very comfortable.
My brother and I rode in the back and we often climbed over that hump in the course of getting in or out of the car (it was a 2-door sedan like Zackman’s). By the time the car was sold in 1967 (with only 30K miles), part of the hump’s carpeting was worn through to the jute-like backing.
In regard to a perimeter frame providing intrusion resistance in a vehicle-to-vehicle side impact crash, there really wasn’t any, because the front end of the impacting vehicle would hit the lower part of the struck vehicle’s doors and B-pillar. The body would largely be shoved off the frame.
This can be seen in this photo of a Crown Vic after an IIHS side impact test (doors removed after test for better view of structure):
Oldsmobile actually had a TV commercial in ’59 about their frames:
http://www.youtube.com/watch?v=ijNJSqOx6Q8
I know it’s been beaten to death, but I think because the engine in the 59 Chevy was a straight six it didn’t strike the Malibu in a corner to corner crash so in effect helped to pull the sheetmetal part of the car through the Malibu.
At any rate it’s no secret that today’s cars are vastly safer. When family members ask me (the family car guy) what a good safe car is I tell them to buy anything made during the last 15 years.
Great article, I had no idea of the whole X frame thing until that crash test came out. I wonder what would’ve happened if they’d used a Lotus Elan?
There are some old crash test videos on YouTube that involve other cars from that era. Even some of the Mopar Unibodies do not fare well in crashes. I think that the biggest problem was that crash safety was not a significant design criterion at the time. Mercedes was about the only one really touting safety in this period of time.
Actually, in ’56, Chevy and Pontiac, were bragging about the “plenum arch” (body section at the firewall) and that, in ’56, in Pontiac, safety was “enginerred in”. Then, of course, the ’56 Ford with “Lifeguard Design” and American Motors’ single unit-body and frame; “safer . . . . stronger.”
The two cars hit corner to corner the engine block is irrelevant the sheet metal on the 59 takes the impact and deforms. The passenger compartment crushes which is what kills people whether belted in or not the doors crush and burst open. These old Chevs werent very strong at all and very weak in crucial places when it comes to occupant safety
Probably the safest recently made car you can buy if you still subscribe to the ‘mass is good’ theory is the last year Crown Victoria or Marquis. Crumple zones, airbags, all the other safety goodies and 4,000 pounds down low to the ground. Someone survived hitting a wall at 90 mph in one recently IIRC. Note I did not say SUV or truck, as handling and resistance to rolling over is important to me.
This is a great article, and another reason why this site is head-and-shoulders above other car sites!
Interestingly, Ford made some hay over the X-frame. In a 1961 issue of Popular Mechanics, a Ford ad shows the frames of the 1961 Ford and Mercury, along with an X-frame, with a transparent line drawing of a car body superimposed over each frame. The car superimposed over the X-frame looks somewhat like a 1961 Chevrolet, although no brand is mentioned. The ad emphasizes that the Ford frame surrounds the entire passenger compartment, while the X-frame doesn’t, and also has more body-mounting points for a quieter ride.
On another thread, jpcavanaugh noted that GM had enough resources to continually “shave” costs and materials out of components until they were just good enough. Thus, the car felt solid on the showroom floor and when it was still new, and rode very well over smooth roads (and the interstate highway system was brand-new in those days), but may not have felt the same over time, or under more extreme conditions. GM had the resources and talent to exploit the advantages of the X-frame work and make it work when the car was brand-new, but it wasn’t necessarily a better solution over the long haul.
Ford, on the other hand, tried unit-body construction on the post-1957 Thunderbirds and Lincolns, but didn’t have the resources to continually shave the car until it was just good-enough. The result was a unit body car that was as strong as a tank, but weighed as much as one, too, despite smaller exterior dimensions. One of the advantages of unit-body construction – lighter weight – was lost.
If you traded your car every 2 years, as many GM owners at that time did, you wouldn’t have cared too much, especially given GM’s obvious talent for making the car much more appealing on the showroom floor than comparable Chryslers, Fords and AMCs.
GM pioneered unitary mass production cars with Opel and Vauxhall in the late 30s and by 1960 only their US cars were BOF making it much easier to make annual model changes. Both GM and Ford by 1960 were expert at unitary cars outside the US Ford with the English Zephyr/Zodiac range which were tough durable well engineered cars and GM with its Holden cars both able to withstand Australian conditions.. My point is this is a brilliantly researched and presented article as usual Paul but it hardly represents the then current cutting edge on body/Chassis technology more an expedient way of being able to constantly update cars easily rather than engineer them properly. A unitary structure is stronger from a chassis tuning and safety angle but hey it was the age of big lazy cars cruisers etc not precision cornering or crash worthyness.
Bryce, couldn’t agree with you more. and I hope to move on to more modern technology in the future! These frames really are old-school. But don’t tell the Panther crowd that!
Looking forward to it.
Growing up in that era, in a GM-owning family, this is a great topic for me. Thanks Paul. Olds and Buick seemed like the engineering innovators back then. The ’39 Buick frame and suspension looks almost like the ’57. I had no idea any mass-produced car had all-coil suspension that early. In the ’50′s and ’60′s, I never liked Olds styling compared to the others, but I can also see that better engineering was underneath.
Wow. this is my favorite article so far. Thanks for shedding some light on this subject. Its also interesting to note the autonomy that each division truly had and the engineering muscle of Oldsmobile.
RIP Olds… Still my favorite dead GM division.
Paul, this is a magnificent article! Thanks for researching it in such detail. I’m intrigued by the combination X/perimeter frame that Oldsmobile developed. Seems like a great way to get a nice low floor without too much safety compromise. (Though in the end, door beams are obviously the way to go.)
I’m amazed to learn how badge engineering got its backwards start. The “quirks” of GM’s structure will never cease to amaze me.
Thanks for this info Paul. I can actually put late 50s to mid 60s Oldsmobiles back on my “own someday” list.
Why does the title say that the X frame lasted “until 1970″? GM’s 1965 full sized cars got full frames.
EDIT *Riviera only had it to 1970. But title assumes that it was in wide use for the later years.
I’ve amended the text in the first sentence to clarify that only the Riviera used the X frame after 1965. But I don’t think I’ll change the title, because technically, it’s correct.
Ok, thanks, I learned something new. Had no idea E body Riv used X frame pre-1971.
Was there a particular reason Buick hung onto the X frame for the Rivieras that long? I guess I always thought that underneath they were structurally the same as other full-size Buicks.
I don’t know how important it truly is today. With the speed we drive on the interstates, an old car would probably explode with a big impact. I feel though, that I would not want an X frame. I don’t care about the hump so the X reinforced ladder frame might be the best.
I owned a 50 olds. They turned into gas hogs in 56 as far as I am concerned. 49 through 55 were probably the highlights with the 442 being nice as well. Never owned another but admired them a lot except for the gas thing. Glad to see there was a basis for that even if I was ignorant of it.
Excellent article. Keep em coming.
We drove that fast on the interstates then. In fact after many years of improvement, deaths per million miles started going up again in 1960. Lots of interstates were opening then. Lots more power under American hoods. Lots of these X-frames on the road then too. Without the stats we’ll never know whether the X-frames were a factor or not.
Safety going the wrong way got the attention of the public, and safety requirements started with lap belts in 1965.
(Data from National Safety Council, Injury Facts, 1999, graph from davidbarber.org)
Yes speed has increased but was it modern X frame cars killing people or older cars being driven beyond their capabilities causing deaths.
I think the reason for the increase was more mundane – in the early 1960s, the first of the baby boomers were getting their licenses. In some states at that time, the driving age was 14 or 15 years old.
The country had a huge uptick in young, inexperienced drivers behind the wheel of some very powerful cars designed and engineered when crash safety wasn’t even on the radar. The demand for safer cars was the result, and this, combined with better roads, helped reverse the increase in the death rate.
People didn’t keep cars that long in those days. The main reasons for the increases in deaths, according to anything I have read, were drum bakes, bias ply tires, generally unsafe cars and drunk drivers.
People many not remember, but driving around juiced used to be common. I can remember my dad filling up my empty paper cup with beer and sucking on it with a straw while he drove. He was not the only dad I saw doing it, either. Even 25 years ago, at bar break-up time, hundreds of good ole boys would stagger to their cars and trucks and head on, and maybe get to, home.
Distances in Aussie used to be measured in stubbies or cans
Bryce, I really love your comments on this site. Don’t invite me to your house. I’d go in no time. All I need to visit NZ is an excuse.
Drunk driving did play a big role in highway deaths, but the death rate began falling again in the mid-1960s, while the real move to reduce drunk driving didn’t start until the early 1980s, when MADD was formed.
Even in the late 1970s, I can remember people laughing about how they managed to drive home despite being legally drunk. In both high school and college, it wasn’t unheard of for people to drive drunk after a party. The push to change this began around 1983.
I have been watching these comments with interest, and as the day has progressed, something hit me. These cars were all over the place when I was a kid growing up i the midwest. Thinking back, I cannot remember anyone being critical of the X frame. I think that part of it was that they were made by GM, which was considered almost devine by a lot of people back then. If GM did it, it must be good.
The only discussion I remember hearing about frames was nagging prejudice against cars that did not have one. I remember more than one person being dismissive of unit construction, because where I was, it was considered as something less than a real car. Unit bodies were viewed with suspicion as somehow less strong and less substantial than BOF cars.
As time passed, there were these X frames that were bad in side collisions, and the 60s Ford rusting perimeter frames which sometimes proved that a “full traditional frame” could be less substantial than a decent Unibody.
I think that one of the reasons people were suspicious of unit-body vehicles was that, once rust did set in, it could quickly destroy the structural integrity of the entire vehicle. Early unit-body vehicles often trapped water on the inside, and the rust started from there, so that by the time it was visible from the outside, major damage had already occurred. Simply patching an exterior panel was not enough.
AMC attempted to address this with its multi-step, deep-dip rust-proofing process in the late 1950s.
With a body-on-frame vehicle, the rust often started on the exterior panels, and thus could be more easily repaired without worrying about whether the entire structure was sound. Even rust on a frame could often be more easily repaired than rust on a unit-body.
Truly great article. First read about the X-frame when the Malibu v. Malibu vid came out and it’s great to read such a great extrapolation. Knocked another one out of the park, Paul.
I don’t know if the ’59 Buick was lower overall than its GM cousins, but I seem to recall contemporary reviews complaining that headroom and ease of entry had been sacrificed for the sake of a stylishly low roof. (Maybe not specifically Buick; that was a common complaint in that era.) There were probably tradeoffs in that respect.
Worth mentioning as an alternative approach to the lower ride height/adequate headroom challenge is the “cowbelly” frame adopted by Ford for its BOF cars. If I’m remembering correctly, it was introduced on the Continental Mark II for 1956. Instead of pushing the side rails inward, as the GM X-frames did, it bowed them outward, achieving the same effect of allowing the foot wells to sit lower. At least on the Mark II, that approach was quite heavy, which may have been a reason GM went another direction.
In terms of rigidity, when GM returned in a big way to the perimeter frame in ’64 (on the A-bodies) and ’65 (on the B- and C-bodies), the new frames were specifically designed to be flexible, while the body shells were as stiff as possible. The way Car Life described it in its technical analysis of the ’65 big Chevrolets, the idea was to let the frame twist, with rubber bushings at each body mounting point to soak up vibration and harshness. It was kind of like having a unitized body with a full-length, bolt-on subframe. I haven’t seen any comparative bending/torsional rigidity figures, but Car Life claimed when the ’66 Riviera came out that the self-supporting X-frame was stiffer than the contemporary perimeter frame unit.
An interesting comparison, vis-à-vis the semi-unitized approach, was the first Toronado and Eldorado. They shared the RIviera’s shell, but where the Riviera had a separate frame, the Olds and Cadillac were basically unitized, with a long front subframe that extended almost to the rear wheelhouses. Olds engineers said at the time they didn’t think that was quite enough, so the ’71 cars adopted a full perimeter frame. I don’t think it was so much a reversion as an expansion of the already-sizable subframe to full length.
That argument in favor of flexible frames seems to have been around for awhile. I have read that this was a factor in the 53 Studebaker, which was quite willowy. I also recall reading at the time that this was a design factor in the 1971 full sized Ford. Up through 1970, the perimeter framed Ford was quite a rigid vehicle (at least until the rust got the better of it). But the 71 quite shaky. The 71-76 GM B and C bodies were shaky as well.
I like to think that everyone has learned one lesson from this: a flexible structure does nothing but result in a juddering, squeaking, rattling loosey-goosey car that doesn’t ride any better than a stiff one. The day of the car serving as a farm utility vehicle and thus needing to be flexible as it traverses plowed fields (such as a Model T) is long gone.
One of the most significant developments of the past couple of decades has been the rigid body structure, available to all classes of cars. The concept that a rigid structure would best allow the suspension to do its job was known quite a while back, and explains why the Germans (in particular) were such big fans of fully independent suspensions (including swing axles, for better or for worse). Cars like a Porsche 356 feel relatively “modern” precisely for that reason, unlike the polar opposite, the English sports cars of those times.
It took advanced computing power (CAD) to finally bring superior body rigidity to all cars 20-15 years ago. Back then, it took an extreme measure, like the Lotus backbone frame, or the tubular frames of many racing cars in the fifties or sixties, to create that rigidity without CAD.
My article is actually a bit frustrating for me, because there’s not ready information available for what the engineers were shooting for in their efforts.
There’s no question that these BOF cars were compromises in their general body/frame structures, a result of tradition and lack of better knowledge. What Aaron refers to in his description of the ’65 GM frames designed to allow some frame flex, that was undoubtedly a necessary Band-Aid, allowing the rubber mounts to absorb as much of the frame’s flex as possible.
These were all compromised structures, from today’s point of view (except the Elan), but that’s what progress is all about.
I agree with you on the CAD computing. But even without it, the Chrysler Unibody managed to be a pretty rigid structure. I owned several, and they were certainly the “tightest” structurally of anything I owned from that era. The unit T bird of the early 60s was quite tight as well, although the one that I had experience in had become compromised by rust.
That German “engineering” gene seems to have been a good thing, as that rigid structure mindset served them quite well.
“The concept that a rigid structure would best allow the suspension to do its job was known quite a while back… Cars like a Porsche 356 feel relatively “modern” precisely for that reason, unlike the polar opposite, the English sports cars of those times.”
I’m not sure you can tar all old English sports cars with the same brush – the Lotus given as an example of a rigid design was of course English, and the MGB also had a reasonably rigid unibody starting in 1962.
I do agree that structural rigidity has improved all modern cars. 20 years ago there were big differences between how “solid” different makes felt, now they all seem pretty tight – and all are better than anything produced back in the ’90s or earlier. Progress through technology I guess. Now if they could just find a way to deliver the same solid structures without blind spots and excessive weight…
I clearly pointed out the Lotus as an example of superb chassis rigidity. Yes, the MGB was an improvement; I was mostly referring to the older BOF sports cars before it, that still espoused the flexible flyer approach.
I read somewhere that the Elans’ backbone chassis was a Chapman shortcut to allow R+D work on the powertrain and suspension before the production chassis ( spaceframe ? ) had been designed.The previous Lotus, the Elite, used a fibreglass monocoque with no chassis to donate to new-model development. In the event the backbone chassis worked so well they decided to adopt it for production.
Great point. I often say that about my saab, which had it’s underbody designed in the mid-80, and it way way too flexibe.
Would be interesting to find someone who can talk about the software available to car designers and how that took off.
Maybe thats why my ’65 Impala wagon was a decent off-road vehicle. We took it on camping trips in open desert. It was much more comfortable on washboard desert trails than the Dodge A-series and Econoline we sometimes used.
Brilliant piece of research, Paul. Just fascinating. All those pictures! You must have a stash of body shop manuals.
I’m glad the X-Files are in such good hands!
Manuals? Thank you google images! Keeps my library small.
People didn’t keep cars that long in those days. The main reasons for the increases in deaths, according to anything I have read, were drum bakes, bias ply tires, generally unsafe cars and drunk drivers.
People many not remember, but driving around juiced used to be common. I can remember my dad filling up my empty paper cup with beer and sucking on it with a straw. He was not the only dad I saw doing it, either. Even 25 years ago, at bar break-up time, hundreds of good ole boys would stagger to their cars and trucks and head on, and maybe get to, home.
“People didn’t keep cars that long in those days.”
True for many – if you got two years out of a new car before rust appeared, you had a keeper! If you found a nice used car like dad’s 1966 Impala in February 1968, you bought it. He did. Man, that was one cool car!
If my father were still alive, he’d probably be needling me over how I can possibly sleep at night, with – heavens! – 72,000 miles on that car I keep driving!
He’d probably turn in his grave to know that I consider it less than halfway to the point where I plan to eventually buy a new one. My last Nissan went almost 200,000 miles with only minor repairs, and probably had at least another 30,000 trouble-free miles in it…and that one was built during the dark, near-bankruptcy days of Nissan, where corners were obviously cut.
I’d like to see an “after” shot of the frame of that crash-test ’59 Chevy. I’ve been thinking that the X frame played a big part in the scary results of that crash.
Due to the offset nature of the crash, forces were concentrated heavily on the left front “horn” of the frame. At the same time, all the mass of the car rearward of the crossing point of the X has plenty of inertia and wants to keep moving straight ahead. Wouldn’t the result be that the X becomes a fulcrum point and the frame wants to fold up there?
That looks like what happened. The passenger compartment gets squeezed on the driver’s side and the floor buckles up under the driver’s side of the seat pushing the driver into the roof. Meanwhile, on the other side of the car, the passenger front fender rotates AWAY from the door — toward the left side of the car — and the gap between the passenger door and the B pillar widens, like it is about to be pulled away.
Great article Paul!
Anyone know how Canadian Pontiacs were built during ’58-’64? I’m guessing since they had a Chevrolet wheelbase to go with their Chevrolet drivetrains, they got Chevy’s X-frames.
Yes, the Canadian Pontiacs rode on X frames. Perhaps I should have put that in the text.
Explains what happened to a friends 61 Pontiac years ago sideways into a pole bananad it, left side was stoved in, right side had a definite curve along it, still a runner but a real bad thumping sound under neath if driven it went for scrap
Intuitively, the X-Frame looks to me like flexibility was desired. I can see adding the X to a perimeter frame doing the opposite. I had a ’76 Eldo in which the body was rusted almost beyond belief. Holes in the rear quarters were handy for disposing empty beer cans… Luckily the beefy open C-section frame could not trap water and kept things together. I even used it to tow a 3,000 boat & trailer with ease but used to wear out the (4 wheel disk) brake pads in a hurry. I’m sure the frame on it extended the full length of the car (I installed the trailer hitch). Was this different on late 60′s Eldos?
The Cadillac Ranch offers good close-up views of the X-Frame. The back half anyway.
http://en.wikipedia.org/wiki/Cadillac_Ranch
Yes, this is a 1957.. only year they used the triangle shaped rear end. Note where the spare wheel well is located. Almost in the middle of the trunk!
Great piece Paul. “The ’57 and ’58 Buicks, which shared Cadillac’s big C-bodies, did not go with the X frame, keeping an X-strengthened ladder frame. So where did the rear foot wells go? Did the Buick C-Body ride higher than the Cadillac? If I could find overall height specs on both, it might possible to ascertain that.”
Here are some Buick RM 70 / Cad 62 (C-Body) dimensions from the 1957 “Automotive News Almanac,” FYI…
Wheelbase – 70-127.5″ / 62-129.5″
Length – 70-215.3″ / 62-215.9″ / 62 Coupe DV-220.0″ (important when measuring your 1950′s garage!)
Height – 70-59.6″ / 62-59.1″
Width – 70-77.6″ / 62-80.0″
Rear Axle Clearance – 70-6.74″ / 62-6.2″
Headroom (front seat to headliner) – 70-35.8″ / 62-35.0″
Legroom (front floor to front seat back) – 70-43.1″ / 62-45.2″
Too bad they didn’t break out rear head & legroom. Still, conclusions can be drawn.
Tom… The rear floor pans will be different but you can see under this 1957 Buick, the rear part of the X brace is channeled so the recess is not affected and the driveshaft torque tube goes over the X and not through it.
Eric (X-Frame) Huffstutler
Richmond, VA
Great article, read it with interest!
Here’s a link to one of the newspapers that published the story of the Impala that was cut in half by the tree:
http://newspaperarchive.com/ogden-standard-examiner/1959-11-28/
Alex, the car in the Utah newspaper is actually a Pontiac convertible. The one mentioned in Ralph Nader’s book as a 1959 Chevy Impala is actually a 1958. I have seen the picture and getting a copy soon.
As far as the crash test between that plasticky Malibu and the ’59 Impala, any Chevy of that period would hardly be a shining example of passenger safety… I would be curious how a similar test between a modern Chevy and a late fifties Cadillac or Lincoln would play out. Or even a ’58 Buick with it’s full ladder frame with X member.
I trust either of those cars would plow the Malibu right off the road, and fair far better on impact than that base ’59 Chevy, which was among the least expensive cars one could get from GM at the time. As it is true today, you did get what you paid for in those days.
In 1952, my old 1939 Chrysler C-23 Royal sedan was a shocker when first jacked up; it had an X-frame! Dad and I even jacked it up on a single jack by the center plate of the X. We always assumed it had been assembled on a frame intended for a convertible (sorry I never took a picture of that).
I was here trying to find out when Oldsmobile used steel crossed protection in the side doors etc. because I was in an accident(on my birthday!) in my ’77 Olds Delta 88 Royale Brougham Coupe hit directly on the driver’s side door head on. A brand new Korean Hyundai slammed full speed into my side slamming the Delta up on the sidewalk hard into a brick wall. Didn’t even crack my power window. I pushed the button and lowered it to see a pile of Korean junk on the side of my Olds. I don’t know how those kids lived! Well I merely drove away with minor sheet metal damage-cosmetic. I’m living testimony to the big Oldsmobiles safety and thank my lucky stars for that wonderful tank-like Car, G ride, red velour plush seats and tough steel frames. I know it had two steel beams in the door also. Any other car and I think I would have been dead or seriously messed up for life. God Bless those huge Oldsmobiles. Aren’t airbags merely balloons?
I believe that the steel beams in the doors came in the 1973 models. I cannot recall, but believe that these were federally mandated.
Yes, they were mandated by NHTSA under motor vehicle safety standard 214. This was a requirement for all vehicles built after Jan 1, 1973, but many had implemented the changes before this occured. Off the top of my head, teh 1970 Chrysler E-bodies had them. Some cars that were redsigned before 1973 but were plan to last past 1973 got them early. The 1971 Torino didn’t have any, while the 1972 Torino did. The Chevelle didn’t get them until the 1973 redesign. I guess GM figured why waste money to retrofit an old body that wouldn’t be around past 1972.
Although I do not have an index in front of me, Special Interest Autos had an excellent write up on GM’s body sharing program title “Body Politics”. It was written regarding the 1950′s vehicles stating that each division used their own engines, frames, suspension set-ups, and exterior panels. S.I.A. was published by Hemming’s and no longer in publication, but they may have an index for the magazine.