Centering Bed Floor - Am I being too anal?

[jerimy75]

I'm going to attempt to make this as concise as possible. I appreciate any thoughts or experience on the matter. Sorry for lack of photos, I can take some and provide additional dimensions if it will help, but I'm looking for more of a general opinion. Thanks in advance!

I've installed a rear Porterbuilt weld-in Mild Notch on my ~71 C10, followed the directions and still had a few fitment issues that I didn't realize until I started mocking everything up. Generally speaking the frame is square (I think it's within tolerances? max of 1/4" off), but when I put my bed floor on (no sides, just the floor) and center the bed based on the rotor face to the edge of the bed, the dimension from the edge of the bed to the frame rail near the rear of the frame is about 3/4" off, and the front (at the second bed mount back) is about 1/4" off, both offset to the drivers side. I was able to get the front and rear measurements within a 1/16" (centered on the frame), but now the measurement at the rotor face is 3/16" offset to the drivers side. Moving the floor to center one dimension would make the other worse.

This is all with the axle and frame at approximate ride height. The axle is centered in the frame (measured diagonally from each of the front bed mounts to the center of the axle). I do not have the weight of the frame on the axle so that might be a factor. I know that I can adjust the track bar to move the ~3/32 (half of the 3/16" offset) needed to center the axle relative the bed floor.

As I write this, I'm convincing myself that it is the 1/4" out of square that is causing the 3/16" offset. I know it's the right thing to do and I will, but I'd prefer not cut the notch out and make it square (hard enough to find time to work on this as it is).

Am I over thinking this? Will this 3/16" offset haunt me as I measure and purchase tires and wheels? Will the offset, or correction of the offset with the track bar haunt me with poor handling and a dog walk when the pickup is finished? Thanks again for reading!

[BR3W CITY]

Too many fractions, and I'm not even completely clear on what the problem is. You keep mentioning centering the axle, but the bed doesn't care where the axle is as long is its not hitting the floor or tubs.

1/4" out for the entire frame is within what GM would accept, and most of ours are at least that over the years. Ignore the bed for a second. If the axle centers properly under the frame, jack it up by the axle and see that it has a proper arc and that the axle stays relatively even. If you have a full range of motion and things stay fairly straight, then mechanically you're fine.

Issue #2, the fact that the bed doesn't "seem" to fit straight. I'd start by saying that my stepside bed has a good amount of wiggle room in it. It could probably be presuaded a 1/4" at least side to side with enough bolts loosened up.

I might be interpreting it all wrong, but it seems like your chasing one problem to fix the other.

[jerimy75]

Thanks for the reply BR3W. The reason I am concerned about where the axle is relative to the bed is just as you indicated, I'm planning to measure for my wheels and I want to make sure that the bed and axle are located correctly so the wheel and tire don't rub on the bed. I was trying to get my bed as close to centered/aligned correctly based on it's location on the frame. It was throwing me off that if the bed was centered, the axle wasn't centered in the wheel cutouts and if the wheel cutouts were centered on the axle, the bed wasn't centered on the frame. Not sure if that helps clarify my intent?

With regards to issue #2 as you indicated, I agree, I have plenty of play to move the bed around on the frame, but I run into the centering issue I indicated above.

Regardless, your response gives me a little more confidence that I am being too particular about things being exactly centered.

[dec010974]

hello to all. jerimy75, brew may be right. I have an air bag suspension and my bed is if the left. as I raise the truck suspension it shifts bak to the right. the pan hard bard may hard something to with the way your looking at the bed. if you are lowering you truck, you want to look into change the pan hard bar or its mounts. if you move it from the stock location, it may need to be lengthened. good luck. clark.

[jerimy75]

Clark - thanks for chiming in! I agree, the panhard bar will shift the axle left and right as the suspension is raised and lowered, and it does for me, I checked. However, I am taking my measurements with the frame and axle at ride height (or very close to at least). I've centered my axle at ride height, so from that aspect I think I am covered, but maybe not? What I've settled on is that I may not be perfectly centered (off an 1/8" or so) and I know that I can adjust my panhard bar if needed. I just didn't want to have to make major shifts to the bed location (and have it not align with the cab and look funny) to get clearance for my tires when I'm putting everything back together again.

[PBFAB.COM]

Originally Posted by jerimy75

Clark - thanks for chiming in! I agree, the panhard bar will shift the axle left and right as the suspension is raised and lowered, and it does for me, I checked. However, I am taking my measurements with the frame and axle at ride height (or very close to at least). I've centered my axle at ride height, so from that aspect I think I am covered, but maybe not? What I've settled on is that I may not be perfectly centered (off an 1/8" or so) and I know that I can adjust my panhard bar if needed. I just didn't want to have to make major shifts to the bed location (and have it not align with the cab and look funny) to get clearance for my tires when I'm putting everything back together again.

Jerimy-

This something that always poses a challenge to those of us who always seek "perfect". It's hard to know when to say, "Yup... that'll do"... especially when it doesn't fall under the tolerances we want it to.

One thing that I have learned about these trucks over all the years I have been making parts for them is that "perfect" is not realistic. The tolerances, technologies, and processes that these trucks were built with is nothing close to what we have today. They were never intended to be taken apart, modified, reassembled and scrutanized by guys like us.

With that said, always do your best to get it perfect, but if you can only dial it in to where you are 1/4" within square... give yourself a pat on the back... that's probably as close as it will ever get!

Nate

[jerimy75]

With as busy as you are Nate, I appreciate you taking the time to comment. Full disclosure, I'm a Civil Engineer which makes me my own worst enemy with respect to this discussion. If I were a Mechanical I think I'd be even worse. I am going to live with what I have, the comments herein have helped me get to this point, so thanks again all!