Why is twin I-beam the worst of independent suspensions?

[rusty ol ranger]

The 450s have always had a monobeam even clear back to 87

 

[19Walt93]

The Ford Twin I-Beam suspension is essentially a heavy swing-arm design with the pivots mounted outboard instead of in the center of the vehicle as some small sports cars had for rear suspensions years ago. On the small cars the swing arms could cause a wheel to try to tuck under the car during hard cornering, possibly causing loss of control or component failure. The outboard pivots on the Ford trucks helped prevent tuck-under.

The Ford TIB is very rugged and gave an independent front suspension that was good for the time it was first introduced. These are the biggest problems:
1. The suspension beams are very heavy and there is a lot of undesirable unsprung weight.
2. The engine had to be raised because the beams ran under it, which raised the center of gravity of the vehicle. Not good. Ford was able to lower the engine and center of gravity after switching to more conventional suspension designs. Note that every Ford truck that had TIB, including the Econoline vans, switched over just a few years in the late 1990s–early 2000s.
3. Radius arms running under the cab were necessary to locate the beams. This was essentially a 1920s throwback in some ways, and those radius arms had to be fairly heavy themselves.
4. The whole system, especially the radius arms, had rubber bushings that aged and deteriorated over time. Driving with bad bushings on those arms was dangerous. We had to get them replaced on a '72 F-100 we had years ago.
5. Some shops had difficulty aligning TIB trucks properly.

The whole Explorer and Firestone story was more complex than most remember today. Ford had dictated to Firestone the tire specs, which were grossly substandard for the vehicle, in addition to the underinflation. That's not to say Firestone's hands were clean. But Ford knew the Explorer was prone to rollover with the proper tire at the proper inflation, partly because of past experience with the Bronco II, so it played games with the tires to disguise the issue. The high center of gravity from the TIB front suspension was a contributing factor in the rollover problem in Bronco IIs and early Explorers, and those models also had weak roofs that would buckle or collapse if the worst happened. There are reasons Ford and Firestone were both held accountable for the results.

The Ranger did not have the same rollover problem as the Explorer because it didn't have so many passengers raising the center of gravity, and also because the suspension was designed for a pickup, not an SUV. The load characteristics are different between the two types of vehicles.

Edit to correct a word typed in error.

Close but no cigar. The only Firestones that actually failed were from the Aitkin plant- Firestone built the "same" tire at 4 different plants and turned out tires with 4 different size wedges and 4 different tear strengths. The tear strength is the amount of force it takes to pull the belts apart, while 3 plants passed muster, a new tire from Aitkin had lower tear strength than a 5 year old Goodyear.
That being said, we changed an absolute mountain of Firestones- enough so I hired a young guy from a tire shop- and never saw a failed tire. I worked at the dealer-and we had a body shop- from 1975 until 2017 and never saw a rolled over Explorer. So much for "prone to roll over".

 

[19Walt93]

VW built cars from 1937 until the 1967 model year with swing axle rear suspension, those were "prone to roll over" and I proved it in late August of 1970 while going 30-35 mph. Jeep CJ's were accused of the same thing but most people knew they were driving a short, high ground clearance vehicle with buggy springs from the 1930's and drove accordingly.

 

[4x4junkie]

The whole Explorer and Firestone story was more complex than most remember today. Ford had dictated to Firestone the tire specs, which were grossly substandard for the vehicle, in addition to the underinflation. That's not to say Firestone's hands were clean. But Ford knew the Explorer was prone to rollover with the proper tire at the proper inflation, partly because of past experience with the Bronco II, so it played games with the tires to disguise the issue. The high center of gravity from the TIB front suspension was a contributing factor in the rollover problem in Bronco IIs and early Explorers, and those models also had weak roofs that would buckle or collapse if the worst happened. There are reasons Ford and Firestone were both held accountable for the results.

I remember quite well when all this was making the news and them showing Explorers rolled and debris all over the place at each crash scene. Every one I saw involved the '95-'99 models of Explorer. I didn't notice any Twin-Beam Explorers making the news because of the tires (that's not to say that none were ever involved in the rollovers, but they certainly were much less common).
I also remember a media outlet doing a "test" on a twin-beam Ex by remotely blowing out one of it's tires (I forget what kind of apparatus they used or which media outlet it was... one of the major OTA networks). I thought it odd because most of the Explorers involved in these rollovers had the tire tread separate from the carcass, not the whole tire go flat... So it didn't seem like an apples-apples comparison to me (and yes, the twin-beam truck remained stable and in-control when they released the air from the tire).

The 450s have always had a monobeam even clear back to 87

Our E-450 motorhome had twin-I-beams. F-450 Super Duty trucks ('99&up) I'm not so sure about (I do remember a "F-Super Duty" truck pre-'99, which had a monobeam axle)

 

[Eddo Rogue]

I think its the steering that's the problem.

 

[franklin2]

VW built cars from 1937 until the 1967 model year with swing axle rear suspension, those were "prone to roll over" and I proved it in late August of 1970 while going 30-35 mph. Jeep CJ's were accused of the same thing but most people knew they were driving a short, high ground clearance vehicle with buggy springs from the 1930's and drove accordingly.

I don't know if you guys realize this, but we have had "fake news" for a long time, longer than I ever thought. It has come out on the corvair swing arm thing that they were actually faking some of that and making the cars lose control on purpose. Knowing now what I know about the news, I am thinking while there may have been a minor problem with the Explorers, the news most likely blew it way out of proportion like they do now. Only thing is they have blown their cover now and no one believes anything they say (most sane people anyway).

 

[rusty ol ranger]

I


Our E-450 motorhome had twin-I-beams. F-450 Super Duty trucks ('99&up) I'm not so sure about (I do remember a "F-Super Duty" truck pre-'99, which had a monobeam axle)

I should have clarified...the 450 trucks (F-superduty pre 97) always had mono. The E-Superduty/450 had I beams. Although i have seen some E450s with monos, They also have a goofy looking front clip.

 

[19Walt93]

I don't know if you guys realize this, but we have had "fake news" for a long time, longer than I ever thought. It has come out on the corvair swing arm thing that they were actually faking some of that and making the cars lose control on purpose. Knowing now what I know about the news, I am thinking while there may have been a minor problem with the Explorers, the news most likely blew it way out of proportion like they do now. Only thing is they have blown their cover now and no one believes anything they say (most sane people anyway).

Exactly. I read Nader's Unsafe At Any Speed as a kid and was able to pick out some b/s even then. My cousin had a bunch of Corvairs in high school- even one with 4 carbs but he didn't have a turbo car. They were a sweet handling little car. A woman told Nader she turned into her cul de sac at 30 mph and the car just rolled over. You bet, and Bill Clinton didn't inhale.
The biggest problems with Explorers were oil leaks in the early OHV engines and valve train noise in the early SOHC's. As I posted, I was working at the dealer when Explorers were introduced and still there after they went to the front wheel drive chassis and never saw a roll over. Nor did I ever see a first gen Bronco or a Bronco II roll over.

 

[85_Ranger4x4]

I think its the steering that's the problem.

The loose nut on the steering wheel specifically...

 

[dvdswan]

The loose nut on the steering wheel specifically...

Don't you mean behind the steering wheel?

Really the only bad thing the TIB/TTB suspension is... It looks like you got kicked in the twins when its off the ground...

 

[rusty ol ranger]

Don't you mean behind the steering wheel?

Really the only bad thing the TIB/TTB suspension is... It looks like you got kicked in the twins when its off the ground...

View attachment 83726

Atleast when I beams land they dont look like this...

 

[dvdswan]

Atleast when I beams land they dont look like this...

View attachment 83727

Toyota and their ball joints...

 

[Josh B]

I liked the hell out of mine. A 73 Econoline E300 Super Van with a straight 300 Six I bought in 1978.

It had 10 ft from back of drivers seat to inside back door. For years I traveled around with an easy chair behind the drivers seat and a box spring and mattress back there somewhere.

The steering was a TIB and after a few years it had gotten rather loose. I was closer to home then but it was still full of tools and such

The coils were easy to break loose and release with a floor jack under them.
I took them to a machine shop and had the bearings and maybe kingpin too, I really can;t remember it well, all pressed in. I put some 50 year roofing rubber everywhere anything touched tight enough to hold it and bolted it all back up.

Not a major chore at all, I really guess thinking about it was the hardest part
.
Not long before I made it back home after dad had began to lose his memory a scrapper came by and talked my father out of it, knowing my father had no clue what he was talking about :/

 

[rusty ol ranger]

l

I liked the hell out of mine. A 73 Econoline E300 Super Van with a straight 300 Six I bought in 1978.

It had 10 ft from back of drivers seat to inside back door. For years I traveled around with an easy chair behind the drivers seat and a box spring and mattress back there somewhere.

The steering was a TIB and after a few years it had gotten rather loose. I was closer to home then but it was still full of tools and such

The coils were easy to break loose and release with a floor jack under them.
I took them to a machine shop and had the bearings and maybe kingpin too, I really can;t remember it well, all pressed in. I put some 50 year roofing rubber everywhere anything touched tight enough to hold it and bolted it all back up.

Not a major chore at all, I really guess thinking about it was the hardest part
.
Not long before I made it back home after dad had began to lose his memory a scrapper came by and talked my father out of it, knowing my father had no clue what he was talking about :/

I had a 94 E150 Mark III conversion at one point...and dad had a 78? I think club wagon when i was preteen/teen.

Vans are pretty sweet once you get past the obvious jokes.

ran across a pic of the big green bastard a while ago. Think i saved it off my old cardomain page. Had a 302 in it.

 

[ekrampitzjr]

Exactly. I read Nader's Unsafe At Any Speed as a kid and was able to pick out some b/s even then. My cousin had a bunch of Corvairs in high school- even one with 4 carbs but he didn't have a turbo car. They were a sweet handling little car. A woman told Nader she turned into her cul de sac at 30 mph and the car just rolled over. You bet, and Bill Clinton didn't inhale.
The biggest problems with Explorers were oil leaks in the early OHV engines and valve train noise in the early SOHC's. As I posted, I was working at the dealer when Explorers were introduced and still there after they went to the front wheel drive chassis and never saw a roll over. Nor did I ever see a first gen Bronco or a Bronco II roll over.

IIRC, that woman was an inexperienced (new) driver, had put some heavy load on the roof, and had not properly inflated the tires when she rolled the Corvair. That came out after Nader's book appeared.