3/4link info

[GRNOVA]

Just toying around with my rear susp. Going with a 3/4 link set up.
Do you guys think this will work with a 4 bar set up instead of a 4 link.

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[RobNoLimit]

check into a program called 'suspension geometry pro' you can test ideas on the laptop first. its easy to use and not very expensive.

[MrQuick]

i'd recommend running the upper bars a few inches over the axle centerline. With at least 3 mounting positions. Run the program Rob listed for correct geometry.


Vince

[Bryce]

short answer, yes it can work. Just packaging and geometry to make it work good.

[Rhino]

i'd recommend running the upper bars a few inches over the axle centerline.

Vince, why do you recommend running the bars high? Since the 4 link would be (I'm assuming) more drag focused, is it simply for higher AS?

[Bryce]

Running the upper bars higher giver more leverage on the axle housing and gives a longer instant center with the same high antisquat. Also you would have finner adjustments in antisquat. For drag somewhere between 95% and 150% would be good range of adjustments. WIth coilovers the ride height can even be adjusted to help with the A/S tunning.

[exwestracer]

Just toying around with my rear susp. Going with a 3/4 link set up.
Do you guys think this will work with a 4 bar set up instead of a 4 link.

https://static1.pt-content.com/images/noimg.gif

Having 2 parallel links AND a top link is going to be a fiddly thing to get right. Every link that attaches the housing to the chassis contributes to the arc that the housing goes thru during suspension travel. If the links are trying to force the housing into 2 different travel arcs, you have bind. If the 2 outer links are parallel (like a 4 bar) and the top link is angled down for A/S, the top link is trying to change pinion angle whereas the parallel links don't want it to. Unless you run a birdcages on the housing, I don't see that setup operating smoothly through very much travel. Even if you match up the static IC locations, the IC progression won't be the same and it will still try to bind on you before things move very far.

Just curious why you feel it needs the extra links on the housing? In that location, the uppers are doing almost nothing to resist axle wrap compared to the center link.

[Bryce]

I think he is doing what art morrison did and remove the UCA of the four link for a tru 3-link and remove the upper 3-link for a true 4-link.

[MrQuick]

Vince, why do you recommend running the bars high? Since the 4 link would be (I'm assuming) more drag focused, is it simply for higher AS?

bryce is spot on.....adjustability is king, especially if you are building from scratch. Running the geometry with the program will cut your fabrication time and you can map out double check your clearance before cutting your car up. check thrice and weld once.

[GRNOVA]

Bryce, that is exactly what I was trying to achieve. Also trying to save some coin and a complete tear out of my currant suspension.

[exwestracer]

DOH! :lol:
Nevermind......

[Rhino]

Running the upper bars higher giver more leverage on the axle housing and gives a longer instant center with the same high antisquat. Also you would have finner adjustments in antisquat. For drag somewhere between 95% and 150% would be good range of adjustments. WIth coilovers the ride height can even be adjusted to help with the A/S tunning.

That makes total sense. I hadn't thought of it that way. I did notice, when planning my rear geometry, that when lowering the upper bars for packaging I had a much harder time tuning the AS to what I wanted. The positive side of this is my brackets could be more compact due to tighter bolt hole placement.

It's also funny you mention adjusting ride height. My shock mounts are adjustable, and I plan on raising the rear between 1-2" for "drag mode" if/when I decide to do the 1320 :)

[GRNOVA]

MrQuick

i'd recommend running the upper bars a few inches over the axle centerline. With at least 3 mounting positions. Run the program Rob listed for correct geometry.
I do not understand about having these two bars raised above the axle housing. These will be taken out for the 3 link, unless you are talking about the 4 bar side of this? And as of now the 4 bar works great.
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[6spdcamaro]

I'm pretty sure they mean the upper bars in the four bar application. The red ones in the first picture. Having these bars higher above the housing will give you better rear suspension geometry.

[Bryce]

Tim,

Reread my explanation. I was refering to the 4-link mode. I assume you want a 4-link for drag racing. The four bar you show is more of a hotrod parralel four bar. I would raise the UCAs and angle them down slightly. If you send me pick up points, wheelbase, and CG height, I can give you an idea of you IC and A/S.

Ken,

You are correct.

[GRNOVA]

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[Bryce]

Nice, at first glance it looks sufficient. I like it!

[JRouche]

Hey Tim, interesting thread. I gotta ask. Why do you want to change from the 4-link to a 3-link. I have an art morrison 4-link and have thought about making it a three link. This was even before I got to drive the car. I was getting ahead of myself.

But now after driving it the 4-link seems to be doing just fine.

Im not putting down as much HP as you and wonder if thats the reason, to get a better hook-up off the line. As for the turns I havent seen any ill manners popping up yet. Everything is predictable and pretty darn controlled. And I havent even played with ALL the adjustability of the 4-link yet. So many variables its just funny, and fun. I like to have some adjustments to play with. And with the Art Morrison 4-link the adjustments are endless.

We have very similar suspensions so Im gonna be following this thread. Im just curious as to why? Do you have some binding? I use some heavy duty QA1 spherical rod ends and they DO allow for more displacement.

While doing some simple roll checking of the rearend while on jack stands, (checking for clearance issues and forcing 5 degrees of roll) I was unscrewing the poly rod ends. Even with the jamb nuts very tight. It was binding too much for 5* of roll with the poly rod ends. Switched them out for 5/8" QA1 spherical rod ends and it is silky smooth. I could get at least 6* (I didnt got further cause that was a pretty deep roll, I cant see it getting close to that with any type of driving).

Im just curious is all. JR

[GRNOVA]

Hey JR,
I did have a lot of bind in the rear keep splitting the bushings. I am not running a 4-link only a four bar. I thought I could have less bind with a 3 link. Also it gives me options. I was looking at ordering Jonny Joints for all the links. any other suggestions?

[GRNOVA]

Thanks Bryce!

[Bryce]

Hey JR,
I did have a lot of bind in the rear keep splitting the bushings. I am not running a 4-link only a four bar. I thought I could have less bind with a 3 link. Also it gives me options. I was looking at ordering Jonny Joints for all the links. any other suggestions?

Tim,

I run rod ends. I didnt want the weight penalty of johny joints. Plus other delrin swivels I have used have much higher stiction. Which would add to your roll and suspension stiffness.

Aurora has the best rod ends. If you can afford them. I am using the aurora aluminum ones on my watts links.

[Rhino]

Bryce, what kind of life expectancy do you have out of those rod ends? I've been planning on running spohn delrin ends just due to the number of carefree miles you can run. As a side benefit, it seems to cut down on NVH.

Since my car will be predominately street, with some AutoX mixed in, I felt it was a good trade off.

[Bryce]

Rhino,

That sounds like a good plan for you. When I design something I build for my goals. And weight it a huge issue for me. I make every piece as light as possible for the applied loads. But my car will not see too many miles. It will never be my DD. It will see as much track time as I can afford. I have run rodends on all attachment points for my front suspension for a year and a half now with no issues and no NVH issues. The rod ends will last as long as they need to. They will be checked before and after every track day to ensure there is no slop or fatigue issues. I am thinking I will have a different set of arms for drag racing and run lighter ones for other events.

[MrQuick]

Hey JR,
I did have a lot of bind in the rear keep splitting the bushings. I am not running a 4-link only a four bar. I thought I could have less bind with a 3 link. Also it gives me options. I was looking at ordering Jonny Joints for all the links. any other suggestions?

the new spohn ends are better just due to thread and through bolt size, plus you can adjust the "stiction". http://www.spohn.net/shop/Del-Sphere-Pivot-Joints/

pictured is the difference between the two.....jj with a 9/16" through bolt and the del-sphere with 3/4" through bolt and threads.

[JRouche]

Hey JR,
I did have a lot of bind in the rear keep splitting the bushings. I am not running a 4-link only a four bar. I thought I could have less bind with a 3 link. Also it gives me options. I was looking at ordering Jonny Joints for all the links. any other suggestions?

Still splitting bushing. Not cool.

I for one would have gone with the spohn rod ends if money wasnt holding me back. I have heard nuthing but good stories from folks that use them. They really are meant for a street/track car where IMO the JJs are great for off road and some heavy duty applications. Its amazing how large some of them are. Made for some serious rock crawler apps. That includes some of the ends like JJs that say Ballistic sells.

But for a road car the spohn ends would be my choice, if I had the money, and they arent all that bad for cost. Im just a lil thin on cash these days.

My QA1 joints are very strong. I also use Seals-it rod end seals. They are pretty nice. Tight fitting so no dirt can get into the ball. And the lips of the seals feel like they are poly, so they will last and stay flexible and not dry out. I wont be driving in the rain and weather but just some added protection for the dust and dirt and water splashes.

As far as road noise NVH (Noise, vibration, and harshness) Im screwed anyway. Not for the long term, its not permanent if I cant live with it. But I have steel bushings up front, wanted to make my own and give it a shot, I can still put rubber bushings in the arms if I want. My air springs are poly mounted (pretty stiff). I made aluminum bushing for my rack and pinion rack. The engine has pretty stiff poly mounts as does the trans. And the back half is all pretty much metal on metal bearing surfaces (sway bar, 4-link arms, watts link arms and poly for the air springs).

Its a rattle box for sure. Might get old, prolly not cause I only take the car out when I want to have fun and wake up. It does ALL of that and then some.

Oh, and its loud (wasnt my plan, I didnt want an obnoxiously loud car, but I didnt have any idea how the muffs would sound, they are too loud, but fun for the time being). Idling through the parking lot of the big box store and setting off car alarms is fun, for a second. But thats gonna get old fast. JR

[BillyShope]

I am not running a 4-link only a four bar. I thought I could have less bind with a 3 link. Also it gives me options.
As far as binding is concerned, the 3link is no better than a 4bar. This is not true of a 4link, of course.

Have you made the 4bar adjustable? (That's an adjustability of both bars at once, while keeping them parallel to each other.) If so, you already understand that an antisquat adjustment means placing the bars parallel to the desired line of constant percent antisquat.
http://www.racetec.cc/shope