4 link help

[Mac5005]

So, Ive searched and read almost all the threads on here, and on pirate about what number to shoot for with the 4 link calculator. I've been playing around with it, and think i am somewhere close to haveing it "right" but it seems like i can't get it perfect. The numbers I have entered now are a little off from the measurements i got from the back of the jeep, but they are still within range of what i can do. I have not welded anything yet, nor made any brackets yet, since I am trying to get all the geometry friguered out ahead of time.

heres what i'm looking at.

at ride height:
69% antisquat and 1.297 deg. Roll axis

At full bump:
69% a/s, and -7.119 roll axis

heres where it goes haywire and the part that bothers me

at full droop (w/ 18" travel)
104% a/s, and 17.627 degs roll axis

at full droop (w/ 16" travel)
85% a/s, 15 deg roll axis

at full droop( w/ 14" travel)
58% a/s and 13.555 degs roll axis

All of this travel is based off 6" compression, and the difference in travel, is only a difference in droop.

So do i sacrifice the travel to keep the numbers sane, or keep working to the 4 link to tweak the geometry better. I feel like the geometry needs to be better so that the roll axis stays close to the same thing throughout the suspension cycle.

What do you guys think.

Here is a screen shot of the measurements, and of the geometry.

Also, What do you guys think of having the lower links mounted to the "front" of the tubes instead of the bottom. To me, It seems like what i am giving up in strength, i am gaining in geometry. It worked out better to have them on the front, but i fear they reall should be on the bottom.

discuss:

 

[rockcity]

looks fine to me, but what do I know...

however, I would make the upper links a little longer.

The A/S at droop is a little misleading as you rarely ever have the axle at full droop, its usually just one side and the other side is close to full bump.

Everyone's setup is different and sometimes you have to compromise performance to what you can actually fit on your vehicle. That being said, more than likely your numbers will change as you'll prob. modify your actual mounting location once you get started.

The link mounts on the front of the axle are just fine, but you need to ensure the brackets and tabs are beefed up a little. The closer to the centerline of the axle with the mounting brackets, the greater the force directed to that bracket, etc. Think of it like a see-saw. Its easy to pick up the person on the other end, however, shorten up your end of the see-saw close to the pivot and see how much more force is needed to pick up that person. Am I making any sense?

 

[Mac5005]

thanks Rob, you definitely answered all of my questions. I took measurements off the frame and axle, and wrote down a range of what would be able to work, and i am still in that range. I think the uppers need to be a little longer as well, but

that leads me to another question. The upper links are angled so:

If i make them the same length in the X-axis ( horizontal side view of chassis) as the lowers, or really close to the same. Then this would mean that the uppers would then be longer in actual length that the lowers, going against what everyone "says".

So with that in thought, i think that i should make the uppers as long as possible ( forward from rear axle centerline) while still keeping them the same total length or shorter ( the 70-80% rule) than the lowers.

I don't know if what i said makes sense, it does in my head. I'm going to play w/ the calculator w/ longer uppers and see what happens.

 

[Mac5005]

I made the uppers longer, and the a/s goes haywire at bump. as the upper gets longer, the a/s at bump decreases more and more as i make the uppers longer and longer. If i make them so they are 80% of the lower's length, then the a/s gets more consistent than before.

ride = 69%, bump = 78%, droop = 99%.

Also, In and ideal setup, where should be the converging point on the lower links? barely forward of front axle? as far forward as possible. Center line of front axle?, or just whereever it ends up with the link mounts where they are.

Thanks guys.

 

[rockcity]

I made the uppers longer, and the a/s goes haywire at bump. as the upper gets longer, the a/s at bump decreases more and more as i make the uppers longer and longer. If i make them so they are 80% of the lower's length, then the a/s gets more consistent than before.
ride = 69%, bump = 78%, droop = 99%.
Also, In and ideal setup, where should be the converging point on the lower links? barely forward of front axle? as far forward as possible. Center line of front axle?, or just whereever it ends up with the link mounts where they are.
Thanks guys.

the a/s sounds reasonable.

I've always heard shoot for the top bolt on the bellhousing.

 

[Mac5005]

any other opinions?