Stomis' Return of the Truck Build

[Fred_M1010]

So it's winter surgery this time

Cool, that you changed your mind.
It's much more fun with a full-size

Why do you wanna swap the 52's for 56's in the front?
My main reason for 56" was pure laziness, as I didn't want to move the shackle mount
But you've already done that...

I'm not sure the difference in flex is big enough to be worth it.
With 56" you'll need degree shims,
and even with that the pinion angle will get worse at droop, since the axle isn't centered.

And I think you'll need longer shackles as well, which will make it wander more, and add to the problem with the pinion angle.

 

[Stomis]

Well I honestly need longer shackles with the 52s as it is right now. I'm running 6" eye to eye shackles with a pretty good angle but its definitely bias towards droop (which is my opinion it should be).

Regardless I'm switching to 7.25" shackles because theres tons more flex left in the springs and I'm only using like 4 or 5in of the down travel I have in my square tube shaft out of the 12 or 14in thats there.

I was going to go to 56s for a few reasons. The first being that I wanted to do 64s in the rear. So I have two good 56 packs. Second being that my 52 pack is clunking, some of the leaf springs are showing their age and arent exactly the straightest. And thirdly because I had thought that 56s did offer more flex over 52s

Its kinda like one of those, eh well I got em so I might as well do it things. As far as the pinion angle I figured when I got my dana 60 I'll be turning the knuckles anyway.

 

[Fred_M1010]

Unless you're using lift springs I don't think you'll need to turn the knuckles though.
I used 6 degree shims and still have 6 degree of caster at ride height

It will probaby give some more flex but I wouldn't expect a ****load more of it.
I think properly set up shackles (lenght and angle) plays in more than the 4" difference in length.

But I can relate to the "use what you have" filosophy

 

[Stomis]

Unless you're using lift springs I don't think you'll need to turn the knuckles though.
I used 6 degree shims and still have 6 degree of caster at ride height

It will probaby give some more flex but I wouldn't expect a ****load more of it.
I think properly set up shackles (lenght and angle) plays in more than the 4" difference in length.

But I can relate to the "use what you have" filosophy

Only reason I was gonna turn them is to get the pinion pointing straight at the tcase. I guess it doesnt really matter with the square shaft anyway though lol.

 

[Fred_M1010]

Yeah, I just angled it up just enough to be sure it couldn't bind even at full droop.
It sure wouldn't hurt if the pinion pointed straight at the TC...
But I thought what the heck, I'm not going to do highway speed in 4wd with this truck anyway.
(not in 2wd either for that matter)

 

[Stomis]

So the new addition to my "Hmmm I should do that" is a 4 link in the rear to alleviate the departure angle issues that come with long leaf springs...

I already bang the **** out of of my shackles with them hanging out back with 56s....

What say the brother hood?

 

[odin]

I vote yes on 4 linking the rear....

I'll lend a hand.

 

[Stomis]

I vote yes on 4 linking the rear....

I'll lend a hand.

What kind of coils did you use in the back? I was thinking TJ fronts.

And on a side question why do all the pre-made trusses sit up so high? Is it for the antisquat etc numbers when doing a 4 link?

O and another question. Whats the advantage of a single triangulated vs double triangulated. And is there anything wrong with using a 3link in the back? Only cause if I dont have to truss it I'd rather not.

 

[Stomis]

Ok so I've been doing alot of reading tonight. The single triangulated 4 link is out just because of the rear steer it causes.

I want something thats going to drive really well on the road. From my research a 3 link and panhard will be best for keeping body roll under control with no sway bar.

I'm looking at doing triangulated lowers so I can keep the mounts up high on the frame and keep my roll axis angle down.

I'm also looking into doing a raised panhard to keep my rollaxis up high effectively eliminating the typical body roll a 4 link would have w/o a sway bar.

 

[Greg72]

Ok so I've been doing alot of reading tonight. The single triangulated 4 link is out just because of the rear steer it causes.

If you think this is true, you should keep reading...

For a street truck, design the suspension for a slight amount of roll understeer. Roll oversteer will be a handful to drive. Play with the online calculators to get the link positions correct and you can do either a 4 link or 3 link out back.

 

[Stomis]

If you think this is true, you should keep reading...

For a street truck, design the suspension for a slight amount of roll understeer. Roll oversteer will be a handful to drive. Play with the online calculators to get the link positions correct and you can do either a 4 link or 3 link out back.

I've read numerous places that the single tri setup allows for a good bit of rear steer when fully articulating.

Please inform me because I'm new to this. I know your using a single tri on your mog truck right? I figured the 3 link would be best for street driving because of how easy it is to keep the roll center high with the panhard in the back.

Asfar as the roll oversteer I'm aware of that from reading. Screwing with the calc I've been triangulating my lowers like some people on pirate suggested to keep the mounts high and roll negative.

The thing I dont understand is instant center and how it affects the truck. I've played with the calc to what seems like awesome numbers with like 50% AS, -1 roll steer, 25in high roll center and my links tucked up really well and around 35in long. Except my instant center is like super far out infront of the truck.

Only solid approximation of where it should be that I found was on a desert racing website. They say for the rear suspension the IC should land around the water pump. But then I read on pirate that IC really only is part of what affects how your AS is calculated so I'm confused a bit on that...

 

[Greg72]

I've read numerous places that the single tri setup allows for a good bit of rear steer when fully articulating.

Please inform me because I'm new to this. I know your using a single tri on your mog truck right? I figured the 3 link would be best for street driving because of how easy it is to keep the roll center high with the panhard in the back.

Define "good bit"...

Any link that travels in an arc is going to have to deal with some axlesteer, but the longer the link is the less of an effect it has. When you're talking about street driving, the concern about axlesteer is limited to the first few inches of travel....not at 16" of droop.

My 4-link has less than 1/8" of axlesteer through it's 6" of bump travel, and 2" of steer at the full 10" of droop. There is only about 7/8" of axle steer in the first 6" of droop, so those last few inches of droop travel is where it really starts to go non-linear. My upper links are 31" and my triangulated lowers are 45"....having the longest links you can (within practical limits) helps a lot too.

Personally, I think the 3-link is the ugliest option because of the side-to-side shifting of the axle when the suspension droops. For street driving (those first few inches of travel) it's not a big deal, but with big travel the axle can move to one side 2" or 3" because of the arc of the panhard bar. I've never liked that characteristic of a 3-link....but again, there's plenty of examples of guys using it successfully, so there really aren't any absolutes when it comes to suspension design.

The more you know, the better you can choose the attributes that are most important to you and sacrifice in the areas where you are willing to compromise. There is no suspension that will give you 100% perfect values in all areas.

 

[odin]

The coils I used in the rear were off a 68 ElCamino...I had them on the shelf and decided to give them a shot. Theyre not too soft and flex like mad. I like them so much Im reusing them on my new build.

My dual triangulated 4 link has/had no axle steer and about 75 percent A/S.
And the instant center was about 110 percent of my wheel base.
Handling on and off road was awesome. No excessive body roll and NO anti sway bars.
IMO a dual triangulated 4 link is the best option.

 

[Stomis]

The coils I used in the rear were off a 68 ElCamino...I had them on the shelf and decided to give them a shot. Theyre not too soft and flex like mad. I like them so much Im reusing them on my new build.

My dual triangulated 4 link has/had no axle steer and about 75 percent A/S.
And the instant center was about 110 percent of my wheel base.
Handling on and off road was awesome. No excessive body roll and NO anti sway bars.
IMO a dual triangulated 4 link is the best option.

See my main reason for thinking a 3 link PH bar would be best is for body roll w/o a sway bar.

Will a single triangulated 4 link have more roll than a double? I was somewhat trying to avoid trussing the entire axle not that its the end of the world. Doing a single would allow me to mount my uppers outside the frame rail and then triangulating the lowers from a crossmember behind the cab.

 

[Stomis]

So heres the screen shot of my first good attempt at a 4 link for the truck. Its it is double triangulated but no severely on the lowers.

The numbers seem good and the mount points are roughly where I can get them in the real world.

 

[odin]

That looks pretty good...very similar to mine.
Body roll would be an issue if your springs were too soft. Like I said its not an issue with my truck.

 

[Stomis]

That looks pretty good...very similar to mine.
Body roll would be an issue if your springs were too soft. Like I said its not an issue with my truck.

Yeah I plan on using the stock spring hangers moved forward on the outside of the frame for the lowers angled out to the outer end of the axle.

The uppers will be the typical crossmember in the frame to a truss over the axle. I'll more than likely make the truss just like yours Odin cause the ballistics one seems really over priced...

As far as body roll I figure that at 28in its just about the same as my 3 links were winding up...

 

[BGKYK5]

Ok so I've been doing alot of reading tonight. The single triangulated 4 link is out just because of the rear steer it causes.

Leaf sprung rear axles with rear shackles cause roll oversteer as well.

It just isn't an issue with the small amount of suspension travel you get on-road.

 

[Stomis]

Alright so I got some pics for you all...

Some shots of the bumper I built last week, battery box from a couple weeks ago and my new awesome battery. Theres also just some "how it sits now" shots of the truck as a reference for where it winds up this time around.

I didnt do much on the truck this weekend, just an oil change. I went to my metal supplier early saturday to find out hes no longer open saturdays so tube rockers didnt happen...

 

[ryoken]

dood... resize your pics! it makes the thread unreadable...