trailing arms: Goodmark vs. ECE vs. OEM

[69Tom]

After doing some research on here, I'm beginning to think my trailing arms are a little too rusty to keep using.

Therefore, I'm looking for a set of new (to me) ones.

I was considering pulling the trigger on a pair of the ECE arms. However, people say not to used boxed arms, as they don't flex enough. Not sure how true this is or not.

If it's true, that leave me with a) finding a clean set of OEM arms, or b) buying some Goodmark repops on RockAuto.

Any opinions here? I'm a little confused based on all I've read. At the end of the day, I'm a pretty original guy so I guess maybe I should go with a nice set of OEM arms if I can find some nice ones close by.

Thanks.

[Richard]

A pair of sandblasted trailing arm on the parts board https://67-72chevytrucks.com/vboard/...d.php?t=786364

[Mike C]

Not using boxed arms because they don’t flex enough is a bizarre statement. Eliminating flex allows the suspension to do the work it is supposed to.

IMO, the more rigid the better when it comes to things like trailing arms. I would run the ECE with no worries if that is what you want.

[SCOTI]

Originally Posted by Mike C

Not using boxed arms because they don’t flex enough is a bizarre statement. Eliminating flex allows the suspension to do the work it is supposed to.

IMO, the more rigid the better when it comes to things like trailing arms. I would run the ECE with no worries if that is what you want.

The engineers designed the Truck Arms to allow some flex. That flex & rubber bushings in the front mounts are what helped keep things cheap yet still survive the articulation stresses of daily use. The T/A arrangement binds @ the limits in OE form. Take away those areas of flex & you get bind much sooner.

By swapping in hard poly bushings up front vs. rubber, the set-up will bind sooner or will require more flex of the arm.
By swapping the I-beam arrangement that allows for some twist in it's length to a solid steel beam that doesn't will induce bind sooner.

There are ways to improve the original for sure. The solid steel beam (tubular or square) promotes consistency vs. 'unwanted' flex when subjected to more aggressive loads (side loads/cornering or straight line/drag strip launches). The key to prevent the bind issue is to use a bushing that allows for some flex. Either the OE style rubber (which defeats the intent of eliminating flex) or something that allows articulation w/o being sloppy (a spherical joint).

Yes, steel tube arms & poly bushings are a common 'upgrade'. That doesn't mean they are better just because the materials are stronger.

[bigmac73]

i have a set of tubular rectangle trailing arms I installed with new poly bushing , simple and easy install, just make sure you get the correct lube for the bushings. I have had no issues with them at all. I think i got them at ECE.

[69Tom]

So has anyone ordered the reproduction Goodmark arms? They're $200 each at RockAuto, so a little cheaper than the ECE box arms.

[SCOTI]

Originally Posted by 69Tom

So has anyone ordered the reproduction Goodmark arms? They're $200 each at RockAuto, so a little cheaper than the ECE box arms.

Seeing your avatar suggests you're in/around AZ? I would think you'd be able to find a clean, rust free pair of T/A's easy.

[69Tom]

Originally Posted by SCOTI

Seeing your avatar suggests you're in/around AZ? I would think you'd be able to find a clean, rust free pair of T/A's easy.

One would think! Heck, I can't even find a rust free cab at a decent price anymore. I think the stock is getting lower out here and is harder to find part-outs.

[SCOTI]

Originally Posted by 69Tom

One would think! Heck, I can't even find a rust free cab at a decent price anymore. I think the stock is getting lower out here and is harder to find part-outs.

Wow. That's a scary thought if you're struggling to find rust free stuff. I guess it's harder here in TX as well but suspension stuff usually isn't bad.

I'm parting out the OE suspension from my 64 now & will likely clean the crust off the parts & sell them locally. Didn't notice any rust , but wasn't necessarily looking for it either. I suppose I'll look closer just to be sure.

[69Tom]

Well, I decided on "none of the above."

I wanted to retain the stock look. I don't really trust Goodmark. I also didn't want to be attempting to sand EDP coating off these things.

So I went with these. https://www.summitracing.com/parts/c...el/c10-pickup/

CPP seems to have a decent reputation, I maintain my stock look, and they're bare steel so I don't have to sand anything. Plus, Summit is close by, has super cheap shipping, have a discount going now, and I had a coupon. So win - win, I think.

Hopefully they work out. Thanks all for the comments.

[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.

[SCOTI]

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.

Define "bad"? The T/A set-up is basically a triangle right? When looking @ it from a birds-eye view, it utilizes horizontal front mounting points & angled c-channel links that are solidly attached to the rear end/rear mounting point.

If the rear mounting points are @ different heights (driver side goes up 3" & the pass side droops 3") vs both sides moving equally up/down in relation to the front mounts (which remain constant to each other), the triangle needs to be able to flex somewhere to allow the changes. Where does the flex occur to allow the different heights for each side when the suspension cycles?

The C-channels can twist slightly along their length (not bend up/down or side/side). That's why I-beams are used. That ability to twist plus the front mounting points encapsulated w/rubber allows the flex. The aftermarket rigid bars/arms don't allow the flex along the length. Poly bushings limit the ability to flex. Stack the two together & it's worse.

[Aus69c20]

If anyone’s worried about the lack of flex in the trailing arms I thought these were a great idea. They replace the bush in the trailing arms and allow less restrictive articulation.
https://www.hotchkis.net/product/196...k=&yr=&md=&sm=

[scottofksu]

Originally Posted by Aus69c20

If anyone’s worried about the lack of flex in the trailing arms I thought these were a great idea. They replace the bush in the trailing arms and allow less restrictive articulation.
https://www.hotchkis.net/product/196...k=&yr=&md=&sm=

Those were what I was thinking about... Clean up, seam weld, and plate stock arms and use these for more predictable articulation.

[SCOTI]

Originally Posted by scottofksu

Those were what I was thinking about... Clean up, seam weld, and plate stock arms and use these for more predictable articulation.

Exactly.

[ElKotze]

Originally Posted by SCOTI

Define "bad"? The T/A set-up is basically a triangle right? When looking @ it from a birds-eye view, it utilizes horizontal front mounting points & angled c-channel links that are solidly attached to the rear end/rear mounting point.

If the rear mounting points are @ different heights (driver side goes up 3" & the pass side droops 3") vs both sides moving equally up/down in relation to the front mounts (which remain constant to each other), the triangle needs to be able to flex somewhere to allow the changes. Where does the flex occur to allow the different heights for each side when the suspension cycles?

The C-channels can twist slightly along their length (not bend up/down or side/side). That's why I-beams are used. That ability to twist plus the front mounting points encapsulated w/rubber allows the flex. The aftermarket rigid bars/arms don't allow the flex along the length. Poly bushings limit the ability to flex. Stack the two together & it's worse.

Dear fellow enthusiast, please allow me to respectfully disagree. You say: "the triangle needs to be able to flex somewhere to allow the changes", and that's where I think you are wrong. That kind of flex is unwanted, why else would one install a rear anti-sway bar? Just my opinion, correct me if I'm wrong. P.S. I'm planing on fabricating my own T/A out of square tubing.

[SCOTI]

Originally Posted by ElKotze

Dear fellow enthusiast, please allow me to respectfully disagree. You say: "the triangle needs to be able to flex somewhere to allow the changes", and that's where I think you are wrong. That kind of flex is unwanted, why else would one install a rear anti-sway bar? Just my opinion, correct me if I'm wrong. P.S. I'm planing on fabricating my own T/A out of square tubing.

So we respectfully agree to disagree.

Yes & no.... Flex beyond articulation is unecessay. Flex for articulation is quite necessary & the triangle (the rear T/A susension on C10's) used the original material choices for that. No flex for articulation means binding. Binding vs. smooth articulation can unsettle the suspension. A suspension that gets disturbed @ the wrong time is unpredictable.

On the subject of rear sway bars.... Rear bars are used for specific reasons. Many install a rear sway bar 'because'. Because why? Because it's necessary? Because other guys have one? Because different vehicles have them & this GEN of C10 didn't so adding one is 'better' vs. not having one? If you install a rear sway bar, what size bar are you specifying?

A rear bar if needed is supposed to compliment the front so the size up front matters when deciding what rear bar. Adding a sway bar to a T/A set-up that utilizes solid tube arms & non-flex style front bushings won't hurt simply because the set-up is already limiting articulation.

It's your truck so use whatever you think is best (solid tube arms, poly bushings, & add a rear bar). Normal driving down the street to the burger joint, Cars & Coffee, or local show won't stress the suspension enough to notice a difference.

[ElKotze]

Originally Posted by SCOTI

So we respectfully agree to disagree.

Yes & no.... Flex beyond articulation is unecessay. Flex for articulation is quite necessary & the triangle (the rear T/A susension on C10's) used the original material choices for that. No flex for articulation means binding. Binding vs. smooth articulation can unsettle the suspension. A suspension that gets disturbed @ the wrong time is unpredictable.

On the subject of rear sway bars.... Rear bars are used for specific reasons. Many install a rear sway bar 'because'. Because why? Because it's necessary? Because other guys have one? Because different vehicles have them & this GEN of C10 didn't so adding one is 'better' vs. not having one? If you install a rear sway bar, what size bar are you specifying?

A rear bar if needed is supposed to compliment the front so the size up front matters when deciding what rear bar. Adding a sway bar to a T/A set-up that utilizes solid tube arms & non-flex style front bushings won't hurt simply because the set-up is already limiting articulation.

It's your truck so use whatever you think is best (solid tube arms, poly bushings, & add a rear bar). Normal driving down the street to the burger joint, Cars & Coffee, or local show won't stress the suspension enough to notice a difference.

Good points, and I agree in part. For my next build I was planing on tube arms because in my (simple) mind they would partly act like a sway bar IF used with poly bushings, regular rubber would support binding, as you stated. This pickup will be a street truck, no off-road use, that can go down the straight line slightly quicker than stock. And I agree, a binding suspension would be undesirable in any circumstance, while a rather stiff rear end would (hopefully) enhance traction.

[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]

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?

[Metaldoc]

Custom made by me with lowering angle included. I've put over 7000km on the truck without an issue.

[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.

[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.