trailing arms: Goodmark vs. ECE vs. OEM

[SCOTI]

Originally Posted by special-K

The rear suspension is articulated through the bushed mounts. I have no experience with tubular trailing arms, so I have to ask how drastically do they affect the suspension? What are the negative results?

Hey Aus69, I wondered if something like that was possible?

Yes, but that's in addition to the 'bars' design.

The following excerpt is copied from the SA Design book on "Muscle Car Handling Upgrades: Rear Suspension Systems":

Truck-Arm Suspensions

The truck-arm design is another suspension that was never used by OEMs under any muscle car. It was used on many pickup trucks and Suburbans, from 1960 to 1972, hence the name “truck arm.” I mention this system because it has developed a small following in the ProTouring/G Machine segment in recent years.
First adapted for use on racing cars by NASCAR legend Junior Johnson in the mid 1960s, it’s still used on every NASCAR Cup car today. The package consists of two very long arms with an I-beam cross section, rigidly attached to the axle with U-bolts and converging in plane view so they’re very close together at the frame mounting point. These arms are quite rigid longitudinally, but fairly flexible in torsion. This is no mistake! In order for the rear axle to articulate, the arms need to twist. This system is in bind whenever it moves, but the geometry and configuration of the arms makes this binding fairly linear. Mounting pads for a pair of coil springs sit on top of the arms just forward of the axle, and lateral axle restraint is almost always handled with a Panhard bar, although a Watts link would also work. Since this suspension is most often used on circle track cars that only turn left, the Panhard bar (usually called a track bar in NASCAR circles) can be used to induce jacking and tune the car’s behavior. This is perhaps the only application where a Panhard bar may be a better choice than a Watts link.

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So, using a spherical joint in place of the front rubber bushing allows articulation w/o the instant bind . That being said, spherical joints only articulate so far before reaching their limits as well but that would be extreme articulation (think 4x4 trail climb territory). The factory arms flex is still better for the system in over-all function as designed but structurally stiffer square/round tube works & is more consistent within the range of motion allowed by a front joint that articulates.

[redbaron]

Originally Posted by special-K

Let us know how they work out.

I don't buy the no flex from boxed arms being bad. I wouldn't use poly bushings since the point of the boxed arms are to give a more positive feel, as well as more strength. The trailing arm is a rigid member of the suspension. If stock are flexing in up and down motion they are also flexing side to side. They are built to be strongest on the vertical plane. For those lowering trucks, it lessens required range of motion anyway. The fact that 3/4t trucks need that plate tells me the design could use a little help. They are one part of these trucks, which I always say were designed so well, where GM cheaped out and that is showing up now even in AZ trucks. I've only ever run stock trailing arms and have only had a few trucks with them. I never had any problems. But if I needed new trailing arms I think I'd consider ECE's better design.

I second K's way of thinking. Also, CPP has a lot of poor quality products made in China. Sorry to see ECE closing up for many reasons with being made in America as one.

[special-K]

Do we know there is no flex, sounds like twisting is the key word here, with tubular/boxed design or just less? Are NASCAR arms two pieces of light channel tacked together or are they tubular? I realize roundy round on a race track at 200 mph has different requirements. Very limited requirements compared to road driving.

All I am saying is are the ECE trailing arms really such a bad idea that there is some significant negative affect on performance? Are they really a bad idea? Something we wouldn't want?

[SCOTI]

Originally Posted by special-K

Do we know there is no flex, sounds like twisting is the key word here, with tubular/boxed design or just less? Are NASCAR arms two pieces of light channel tacked together or are they tubular? I realize roundy round on a race track at 200 mph has different requirements. Very limited requirements compared to road driving.

All I am saying is are the ECE trailing arms really such a bad idea that there is some significant negative affect on performance? Are they really a bad idea? Something we wouldn't want?

Torsional flex = twist; just like a steel beam. So some allowable flex along the length but not up/down or sideways bend for the OE arrangement. As far as NASCAR, I believe they are built similarly but welded along the seams vs spot welding like OE arms. Since I actually had an OE arm come apart that's been a standard (stitch welding the seams) once I started welding. On my high school ride, I found arms from a 3/4 ton truck that had the plates. Back then I thought that's why mine had failed (because someone removed the plates). I didn't know any better @ the time.

Are solid, tubular bars bad?

Do they work? Yes.
Are they a bad idea? If you know the OE arrangement was designed to achieve their articulation through torsional flex via the front rubber bushings & I-beam construction but delete both of those options from a replacement arm you either need another method that allows articulation or they will bind sooner than the OE stuff would. It's that simple.

Will the 'Average Joe' that occasionally putts around town notice? Probably not. But, that does not make them better.

[69Tom]

This is good conversation guys. Glad we can keep a good discourse on things unlike some other forums I've been on in the past where they tend to get ugly upon the first disagreement.

In any event, I think I'll be fine with the ECE/stock appearing arms. I'm not going to beat my truck, won't probably be hauling anything over 1000 lbs. They should be good.

And while I think I could have gotten them when I first posted my question and even pulled the trigger on the CPP arms, the ECE arms are sadly no longer available.

[SCOTI]

Originally Posted by 69Tom

This is good conversation guys. Glad we can keep a good discourse on things unlike some other forums I've been on in the past where they tend to get ugly upon the first disagreement.

In any event, I think I'll be fine with the ECE/stock appearing arms. I'm not going to beat my truck, won't probably be hauling anything over 1000 lbs. They should be good.

And while I think I could have gotten them when I first posted my question and even pulled the trigger on the CPP arms, the ECE arms are sadly no longer available.

If you're referring to these arms (https://www.summitracing.com/parts/c...el/c10-pickup/) you'll be fine. Basically new aftermarket metal & fresh bushings.

The weird thing is.... The title indicates 'Stock Type Rear Trailing Arms 6072STA-K' while the overview lists them as 'Control arm style: 'tubular/boxed'. One of the two is incorrect. The image displayed is OE/stock style arms.

[ElKotze]

Originally Posted by SCOTI

If you're referring to these arms (https://www.summitracing.com/parts/c...el/c10-pickup/) you'll be fine. Basically new aftermarket metal & fresh bushings.

The weird thing is.... The title indicates 'Stock Type Rear Trailing Arms 6072STA-K' while the overview lists them as 'Control arm style: 'tubular/boxed'. One of the two is incorrect. The image displayed is OE/stock style arms.

I wonder if CPP custom-makes them for SUMMIT, because I couldn't find them on CPP's website, and that's why you have to wait 4 weeks. Those are the only stock-type arms I could find, everything else is tubular.

[special-K]

Originally Posted by 69Tom

This is good conversation guys. Glad we can keep a good discourse on things unlike some other forums I've been on in the past where they tend to get ugly upon the first disagreement.

Yeah, I'm just wanting to gain knowledge by asking my questions. I have little experience with trailing arms. I'm the type who wants to know why and wants to understand. Most all my 67-72s have had leaf spring or the ones with trailing arms never needed any attention. They were just part of the truck that always did what they were meant to. They are just fine for me, but they do tend to rust out in all the years that have passed. They seemed cheaply made to me, but I now see it's all for a reason.

Thanks Scoti