Porterbuilt Questions (Noob)

[GoaterAz]

Hi guys, I had a few questions that came up during my suspension research that I was hoping to learn more about.

Trailing Arms:

I was wondering how exactly the Porterbuilt trailing arms lower the rear of the truck by 1" or 3". Is the lower coil spring perch lowered by either of those amounts to achieve that drop?

Has anyone weighed these compared to stock trailing arms? If so, what was the weight savings?

I want to run a 6" static drop and was curious if there were any advantages of running the 3" lowered trailing arms with a 3" drop spring compared to the 1" lowered trailing arms with a 5" drop spring?

Adjustable Trailing Arm Crossmember:

I can understand how the multiple mounting fore-aft frame mounting points dial in the rear wheels being centered in the wheel well, but I can't seem to wrap my head around what the multiple trailing arm mounting locations dial in? What exactly is 'instant center'? Are the multiple frame mounts the 'big adjuster' and the multiple trailing arm mounts the 'little adjuster' for the wheels being perfectly centered?

Also, Has anyone weighed this compared to stock trailing arm crossmember? If so, what was the weight savings?

Thanks in advance!

[Shooters_7]

Get on the porter built website and read through the descriptions of there stuff. Its mainly tailored for air bags and not really for coil springs. There isn't any weight savings going from stock to porter built. If I remember the porter built trailing arms were heavier. This works for me since its more weight to keep the back end planted to the ground.

If you plan to do coils then keep your stock stuff. Just replace the bushings and add a c-notch. It'll be cheaper on you in the long run unless your a closet millionaire.....

Spend some time reading through builds and type in "porter built" into the search engine to see what others have done. Good luck!

[ol_skool_chevy]

I beleive they have a drop welded Into the trailing arms same as if you added Blocks.
If Im not mistaken

[Pro Performance]

The Porterbuilt arms do have an integrated lowering block, for lack of a better term, built into them. You can see here the Porterbuilt vs. stock. They do work with coil springs, but not a necessity to lower the truck. It does have it's advantages of the built in drop, better looks, etc..... it is all personal preference.




As for the adjustable trac bar, the longer bar will have less axle movement through the suspension cycle. It will also center of the axle when lowered down vs. a stock non-adjustable trac bar. As for adjustability on the trailing arm side where it connects, that is so you can adjust more precisely depending on how low your truck is. I don't see it as completely necessary for those adjustments, since the drop bracket on the frame side will make that bar almost parallel the ground and have you very well set for a lowered or bagged truck.

This picture shows the bar when an air bag suspension is deflated, so at ride height, it would be basically parallel to the ground offering the least amount of side to side movement.

[GoaterAz]

Originally Posted by Pro Performance

The Porterbuilt arms do have an integrated lowering block, for lack of a better term, built into them. You can see here the Porterbuilt vs. stock. They do work with coil springs, but not a necessity to lower the truck. It does have it's advantages of the built in drop, better looks, etc..... it is all personal preference.

Makes perfect sense now, Thank you.

It would be purely aesthetics for my truck, and hopefully weight savings.

Originally Posted by Pro Performance

As for the adjustable trac bar, the longer bar will have less axle movement through the suspension cycle. It will also center of the axle when lowered down vs. a stock non-adjustable trac bar. As for adjustability on the trailing arm side where it connects, that is so you can adjust more precisely depending on how low your truck is. I don't see it as completely necessary for those adjustments, since the drop bracket on the frame side will make that bar almost parallel the ground and have you very well set for a lowered or bagged truck.

That is great information to have as well!

Maybe I wasn't clear on my exact question, I was talking about the Tubular Trailing Arm Crossmember (PB-63-72-TACM). It has 4 vertical holes for adjustment where each trailing arm bolts up to, I'm trying to understand their purpose. Just to better dial in the centering of the rear wheels?

[ddubbs]

The tubular trailing arm crossmember is used in a few different kits by porterbuilt. The holes in the crossmember help to center the axle in the different kits. For instance the extreme kit I believe uses the bottom holes on the crossmember and the mild uses a different set of holes. Hope this helps and that I'm not misleading you. It's been awhile since I put mine together.
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[STPrider]

I believe the adjustments in the trailing arm crossmember serve a similar purpose as the holes in the trailing arms for the crossmember. You can adjust the trailing arms to the best hole to minimize movement front to back. As for the trailing arms themselves, they are much more than a stock replacement. I didnt weigh mine either, but I would say they were equal or more weight than stock. However, the stock arms are 2 c-shaped tubes riveted together to make an I-beam, and water and road crap settle in the middle, compromising the bars when it rots and rusts. That's the reason my stockers broke, so watch out that you're not stranded one day... The PB arms are top quality, and the best part is getting rid of those old loose rubber bushings!

[lolife99]

The "Vertical Row" of holes in the trailing arm crossmember was to help adjust pinion angle of the rearend.

Real description:
The Porterbuilt Fully Adjustable Trailing Arm Crossmember is designed to eliminate multiple rear suspension concerns that are presented when lowering the rear of a 1963-1972 truck.
It is a direct bolt-in, utilizing the factory mounting locations.
It also allows for multiple fore-aft mounting points, along with multiple mounting points for the front trailing arm mounts.
The advantage of the multiple fore-aft mounting points is to allow the wheels to be centered in the rear wheel well opening with various drops.
The multiple front trailing arm mounting locations allow allowing for adjustments to the instant center, resulting in better performance.
It is available for both one piece and two piece driveshaft configurations and will allow for a 3" exhaust to pass between the tubing.

There are two versions:
First picture is the 2-piece driveshaft verson.
Second picture is for a 1-piece driveshaft.

[Pro Performance]

My apologies on the adjustable trac bar description, I completely mis-read that! lol. I have no idea why I instantly thought adjustable trac bar. Anyhow, glad the description got posted though.

[GoaterAz]

Originally Posted by STPrider

As for the trailing arms themselves, they are much more than a stock replacement. I didnt weigh mine either, but I would say they were equal or more weight than stock.

Thank you! So you wouldn't mind pulling yours off and grabbing a fish scale to compare the two would you? lol...just kidding.

Originally Posted by lolife99

The "Vertical Row" of holes in the trailing arm crossmember was to help adjust pinion angle of the rearend.

There are two versions:
First picture is the 2-piece driveshaft verson.
Second picture is for a 1-piece driveshaft.

Yeah, I had read that description on their website but didn't know what 'instant center' was. But I also stared at those two pictures for 25 minutes and never noticed the difference, lol.

It makes sense (from what I have read) that the two piece driveshaft version would have the flat lower tube and that base plate to rest on the ground.

What exactly is instant center? I'm assuming it has something to do with the pinion angle from your post?

Thank you, Sir!

Originally Posted by Pro Performance

My apologies on the adjustable trac bar description, I completely mis-read that! lol. I have no idea why I instantly thought adjustable trac bar. Anyhow, glad the description got posted though.

No apologizes necessary, It was good information. I would have opened the trac-bar box and immediately started a new thread about those holes, ha.