How bad is that rust? - Rusty trailing arm

[kingcrunch]

Hi,

for my project i aquired a set of trailing arms that looked good on the outside but had some rust trapped between the C-channel pieces.

I straightened them, split them and had them media blasted. The damage is like 0.07" in the deep spots, which is halfway through.

Link to a picture of the damage (too big to embed):
https://thedodgetruckblog.files.word...608_203530.jpg

I planned to use more plug welds and plate them like C20 arms (plate running 2/3 of the arm on the underside and 1/3 on the topside).


To abide local law i would really have to stick with stock arms for what i want to build.
NOS arms seem to be hard to come by (but i would buy these no matter what they cost if there were any available).


Speaking of replacement parts, does anyone have experience with the repop arms LMC sells?

http://www.lmctruck.com/Features/CB/CBCR1.htm

Thanks,
Alex

[Shaky]

Hello Alex - it seems like the guys from the southwest USA here are able to find arms with only surface rust on them. Maybe you could buy a good used set.

In my opinion, those arms are so over-designed, that you could bolt them back together and they'd be fine.

I don't have any experience with the LMC arms.

If you click my C20 thread below you can see what I did with my C20 arms. You could always add the 3/4-ton plates to the top and bottom to add integrity to your existing arms.

[mike16]

new ones are available from several vendors. I understand that that trailing arm set up is used alot unter NASCAR race cars and is very popular

[CG]

Finding parts in Germany must be a bit tricky.

[kingcrunch]

Originally Posted by CG

Finding parts in Germany must be a bit tricky.

Like a trailing arm? Next to impossible.
I buy lots of parts in the states and have them shipped.

[TrkEnvy]

I'd run them.. If you really wanna make them strong you can do what I did and use some 3/16 plate on top and bottom of it and run a slightly longer u bolt. I'm gonna turbo LS my truck and I'm not the least bit worried about the strength of my reinforced stock arms.

[jerry moss]

vintage chevy truck, fremont ca. (510)651-5874, he has nice used ones

[kingcrunch]

Thank you, i contacted them. All other comments are appreciated, keep 'em coming
I know this is a topic that has been gone through more often than one would want to count but i am really lost here.

Everybody i know just shrug their shoulders.

[Katrina/10]

Yours really don't look too bad, from the picture.

[Shaky]

Originally Posted by Katrina/10

Yours really don't look too bad, from the picture.

Aye. I'd brush primer on the contact surfaces, bolt them together while the primer is wet, and then paint the whole thing.

[kingcrunch]

Ok... still not convinced though, i will explain why:

I planned to put these in a truck with an engine producing roughly 485hp / 470lb-ft (Dodge truck with retrofit Chevy trailing arm suspension, 6.4 SRT Hemi, six speed manual).
I have not decided on the final drive ratio yet but it will be somewhere between 3.55 and 4.10 with a 285/35 R19 tire.
I expect it to run somewhere around 150mph top speed with this kind of power.
The truck will be a highway runner / track toy / autocross vehicle.
I am located in Germany where i can actually take this to 150 legally.

By law i am stuck to stock arms and cannot use built ones ...
It's probably a "piece of mind" thing more than an actual problem but i think i will refurbish these and keep hunting for pristine rust free arms.

[Jason Banks]

I puckered a little bit at the thought of going 150 in one of these trucks....

[Coley]

If the deterioration shown is the worst of it....that isn't enough to worry about....BUT, that is under stock/original operating conditions.
Again, that is based on the original context and usage that these were designed for...and original speed/load probabilities.
If you intend on 'maxing' this thing out power, torque and speed wise (150mph??)...then add, form and weld reinforcement plating (3/16" min. to 1/4" or 6mm thk.) to both the vertical and horizontal surfaces and make sure you weld and join the corners where the new plates meet at the 90° point to add a corner strength element.
....My two bits.
oh yeah, one more thing.....I don't think I would consider going over 100mph in a pickup truck unless it was seriously suspended, reinforced, set-up and designed....and that definitely is NOT most street trucks.

All Good
Coley

[PanelDeland]

I would be way more concerned with 150 on the stock front suspension than the trailing arms.

[Katrina/10]

I find it odd that it's acceptable to put a Dodge cab with a Hemi engine on a Chevrolet frame, but not change the trailing arms for something stronger.

[kingcrunch]

Gary,
the trailing arms will be added to the Dodge chassis.
That's the only non-Dodge thing on this truck, engine, trans, front suspension, rear axle - all parts taken from other Dodge vehicles (Viper, SRT-10 Ram, etc.).

But i want the C10 rear suspension because it's far superior over leaf springs.

[Grumpy old man]

You want to run 150 on rusty old trailing arms bolted together ? Your one brave soul ! Buy new NASCAR style , going fast on old used parts is how guys die .

[Fatherflash]

Huh? I thought with TUV you had to show or document improvement when compared to new?

Must be me....

Does anyone know how "Sancho Truck" which is in Germany got away with using aftermarket trailing arms? Didn't Delmo build that truck using Porterbuilt with PB trailing arms? I looked at Delmo's website however, nothing really shows the rear end of the truck after his shop built it.

http://67-72chevytrucks.com/vboard/s...516801&page=17

[kingcrunch]

@Fatherflash:
The TUV has problems with aftermarket built components and i understand why.
"Built" to them means:
An piece of unknown quality metal has been shaped to physically fit but has unknown mechanical qualities.
It gets worse if you start to weld stuff and even alter the already unknown metal or mechanical qualities.


That's why they usually don't like and accept brake adapters (remedied that by using spindles out of a Dodge Viper) or tubular UCA/LCAs, etc.

Honestly, i would have my doubts as well, seeing some of the built trailing arms available on the market.
The most horrible thing i saw are the ones that replicate the bend by welding two box section pieces or I-beam sections together at an angle, close to the spring.

To me it looks like all of these "stiffer" and "stronger" arm constructions ignore the fact that these arms have to be able to flex.


My build relies on mostly stock components:
Stock Gen 3 Viper spindle / UCA / brakes (14"!), stock Ram SRT-10 rear axle and brakes (14"!), stock '15 Challenger 6.4 SRT drivetrain, otherwise stock 85 Ram + containment seats, harnesses and FIA spec welded construction cage (not doing it myself!).


Ok, i will have to build the crossmember that attaches the trailing arms to the frame and the one that accepts the rear springs.
But i have a known quality material (known in the industrial world as S355) and all i do to it is bend it to shape and bolt it to the frame.
No welding involved.


I believe the stock C20 (the reinforced arms) trailing arms are strong enough to handle what i throw at them.


@Grumpy:
This thread stems from my reluctance to die

I am doubtful about using these arms in my vehicle.
For mockup, sure. For a stock C10 doing no more than 55, all day long.

I won't use them for the road ready vehicle...

How did you get to the impression i wanted to BOLT them back together?
There was a handful of spot welds holding them together and i doubled the number of plug welds, that's why there is holes in the half-piece in the picture.

This is a finished arm:

[kingcrunch]

Reviewing the Sancho C10 i am pretty sure this thing is not registered.

[Katrina/10]

Originally Posted by kingcrunch

Gary,
the trailing arms will be added to the Dodge chassis.
That's the only non-Dodge thing on this truck, engine, trans, front suspension, rear axle - all parts taken from other Dodge vehicles (Viper, SRT-10 Ram, etc.).

But i want the C10 rear suspension because it's far superior over leaf springs.

I see. As long as all your parts are original equipment items, you can use them. I just thought your inspectors might have a problem using these items on a vehicle that never came with them. Are you using the 85 Dodge cab also?

[kingcrunch]

Gary,

body and frame will not be altered (well, except for carbon fenders, hood and bumper, a cage and of course the trailing arm crossmember).
For my plan to work it has to stay a Dodge truck for the most part.
I will not be messing with the frame except for some bolt-ons.


I have got another question about the trailing arms.

Measuring on the arms on my bench i see a distance of 4.13" (center to center) between the holes for the u-bolt.
The known-to-me width of the axle u-bolt is 3.5" though. I am bit confused right now...

[Katrina/10]

This should be a really cool ride, would like to see some pictures of it.

[snipescastle2]

Yeah, mine had minor rust issues, I sand blasted them, ground out the surface rust on the split seam top and bottom, then welded the entire seam front to rear, I had a couple of missing rivets in a few places, I just plug welded them up and had the welds ground smooth and powder coated them. Should be way stronger and last longer than the stock ones.
Ben

[snipescastle2]

Sorry, double post