Setting up a 4 link

[PrerunnerRob]

Hey guys,
I picked up a new 4 link for my truck at the local car show, and was wondering if anyone has set one up properly with a dropmember. Any input would be greatly appreciated, especially geometric stuff!

[leftcoast66]

Originally Posted by PrerunnerRob

Hey guys,
I picked up a new 4 link for my truck at the local car show, and was wondering if anyone has set one up properly with a dropmember. Any input would be greatly appreciated, especially geometric stuff!

Is it parallel or triangulated. I'm guessing triangulated but figured I would clarify.

Triangulated, you need the triangular bars to be greater than 30 degree angle to keep it from going side to side, unequal length obviously for top and bottom will create a change in pinion angle throughout the range of travel, which can be good or bad, depending on what you want to use it for. Those are a few things that pop into my mind right now, its midnight and I've studied 6 hours for tests so might have a few more thoughts when I'm awake again haha.

[PrerunnerRob]

Originally Posted by leftcoast66

Is it parallel or triangulated. I'm guessing triangulated but figured I would clarify.

Triangulated, you need the triangular bars to be greater than 30 degree angle to keep it from going side to side, unequal length obviously for top and bottom will create a change in pinion angle throughout the range of travel, which can be good or bad, depending on what you want to use it for. Those are a few things that pop into my mind right now, its midnight and I've studied 6 hours for tests so might have a few more thoughts when I'm awake again haha.

Thanks for the info, it is triangulated.

[leftcoast66]

Originally Posted by PrerunnerRob

Thanks for the info, it is triangulated.

Sweet. Let me know if you need more details than that. One other thing is the longer the arm the better it is for the geometry. The axle will change the pinion angle a lot less with a longer arm.

[Captainfab]

I'm almost done with a Morrison Tri-4 bar in a '67.....is there something specific you need to know? What brand is yours? I had to do some fabbing to make it work. I can get you some pics if it will help.

[PrerunnerRob]

I think I may be putting more into this then I really need to. I was going to use a 4 link calculator to set up the handling perfectly, but I'm thinking that is no necessary. I.m wondering how far the lower link must be placed from the frame to keep good frame clearance, but not so far out it get near the tire. Any pictures would be greatly appreciated!

[joe231]

nice work Capt.
is that truck finished? if so how does that setup handle?

[Captainfab]

Originally Posted by joe231

nice work Capt.
is that truck finished? if so how does that setup handle?

No unfortunately it isn't done yet.....I took those pics just today. The goal is to have it finished for next summer. Should be a blast to drive with a 620hp 572 under the hood

[scotts62]

Originally Posted by Captainfab

No unfortunately it isn't done yet.....I took those pics just today. The goal is to have it finished for next summer. Should be a blast to drive with a 620hp 572 under the hood

Yeah i can see how that would be fun to drive!!!
Setup looks good

[Captainfab]

Originally Posted by scotts62

Yeah i can see how that would be fun to drive!!!
Setup looks good

Thanks for the compliment Scott

[RunninLo]

cap'n,
I may be wrong here but it was always my understanding on the tri 4-link that the "longer" bars were the uppers and were longer to compensate for being mounted at angles instead of straight like on a parallel 4 bar. It was also always my understanding that it was done that way to keep the pivot points on the frame the same distance from the axle and to minimize pinion change.

I see by looking at your pics you went with the short bars up top and have a pretty good distance between your pivot points.

I'm not saying right or wrong just curious why you chose that way and what the benefits are?
TIA,
Josh

[Captainfab]

Originally Posted by RunninLo

cap'n,
I may be wrong here but it was always my understanding on the tri 4-link that the "longer" bars were the uppers and were longer to compensate for being mounted at angles instead of straight like on a parallel 4 bar. It was also always my understanding that it was done that way to keep the pivot points on the frame the same distance from the axle and to minimize pinion change.

I see by looking at your pics you went with the short bars up top and have a pretty good distance between your pivot points.

I'm not saying right or wrong just curious why you chose that way and what the benefits are?
TIA,
Josh

I'm far from an expert on link suspensions, but I think what you're thinking would definitely be the direction to go with a vehicle that needs substantial suspension travel, like in offroad, but could be used on the street as well. On a street driven vehicle with a more limited travel suspension, you can get away with a little more. The principals and design of link suspensions is quite complex and involved. The 4 link calculator that Rob already used is a very useful tool and can certainly be applied to street use.

The '67 that I'm building is for a good customer, and with my limited link suspension experience, I decided to play it safe and just order the kit from Art Morrison. The Tri-4 bar suspension was designed by the engineers at AME and is a proven setup, which is one of the reasons I went with it. The bars come already welded and the kit comes with instructions giving parameters for installation. Here is the kit that I ordered
http://artmorrison.com/layout.php?y=...i4bar/&x=index

I am by no means saying that this is the best triangulated 4 link for the street, it is just one that is proven and was the 'safe' way for me to go at the time. If it was my own truck I probably would have built one from scratch.

Let me know if I can be of any help Josh

John

[leftcoast66]

Originally Posted by RunninLo

cap'n,
I may be wrong here but it was always my understanding on the tri 4-link that the "longer" bars were the uppers and were longer to compensate for being mounted at angles instead of straight like on a parallel 4 bar. It was also always my understanding that it was done that way to keep the pivot points on the frame the same distance from the axle and to minimize pinion change.

I see by looking at your pics you went with the short bars up top and have a pretty good distance between your pivot points.

I'm not saying right or wrong just curious why you chose that way and what the benefits are?
TIA,
Josh

From what I understand, yes your right, but its so tiny unless you run a lot of lift, then its not a big deal. If its pretty much set up close to ride height, and the pinion angle is set up right for ride height, which I'm sure captn fab did, then its all good.


Captain, looks very impressive, even though its a kit, the install is incredible. Where in cda are you, I keep hearing your out there, I'm stuck at gonzaga, not too far away.

[Captainfab]

Originally Posted by leftcoast66

From what I understand, yes your right, but its so tiny unless you run a lot of lift, then its not a big deal. If its pretty much set up close to ride height, and the pinion angle is set up right for ride height, which I'm sure captn fab did, then its all good.


Captain, looks very impressive, even though its a kit, the install is incredible. Where in cda are you, I keep hearing your out there, I'm stuck at gonzaga, not too far away.

Yeah if you're at Gonzaga you're not too far away. My shop's kinda on the west side of CdA. Shoot me a pm if you're coming this way sometime.

[kdrodworks316]

I must chime in here, I have seen the captians work first hand, and he is a artist. That frame is just beautiful and I wish it was under my rig.
Now just to clear up a few things, A properly setup double triangulated four link will not change the pinion angle, ever. Now that is only the case when you are dealing with insane amounts of up and down travel. In a street truck app. it is not near as important because your talking 2"-10" of travel as an example vs 30"-50". I am not claiming to know it all about 4 links, but I have dealt with super long travel monster truck suspension to mild travel low rider stuff. A few inches in bar length and and a few degrees in angles can make huge changes at the pinion. I know I will probably get a lashing for this, and I am not saying anyone is wrong or right, but you cant argue with the math and the finished product.

[PrerunnerRob]

Double triangulated? As in both the uppers and lowers are triangulated?

Originally Posted by kdrodworks316

I must chime in here, I have seen the captians work first hand, and he is a artist. That frame is just beautiful and I wish it was under my rig.
Now just to clear up a few things, A properly setup double triangulated four link will not change the pinion angle, ever. Now that is only the case when you are dealing with insane amounts of up and down travel. In a street truck app. it is not near as important because your talking 2"-10" of travel as an example vs 30"-50". I am not claiming to know it all about 4 links, but I have dealt with super long travel monster truck suspension to mild travel low rider stuff. A few inches in bar length and and a few degrees in angles can make huge changes at the pinion. I know I will probably get a lashing for this, and I am not saying anyone is wrong or right, but you cant argue with the math and the finished product.

[kdrodworks316]

Originally Posted by PrerunnerRob

Double triangulated? As in both the uppers and lowers are triangulated?

yep, top and bottom. its monster truck tech for extra long travel and strength. It would work on street stuff as well with shorter bars. thats why the pinion angle dont change with this setup, the 2 triangles have to work together to travel. The standard setup on most monster trucks is top: frame to center axle and the lower is outside axle to center frame. This also allows massive articulation, so a street app would almost require a swaybar, or properly valved shocks mounted at the correct angle forward and to center. the powerblock site has a 4 link geo download that is a big help for all the math.

[PrerunnerRob]

Originally Posted by kdrodworks316

yep, top and bottom. its monster truck tech for extra long travel and strength. It would work on street stuff as well with shorter bars. thats why the pinion angle dont change with this setup, the 2 triangles have to work together to travel. The standard setup on most monster trucks is top: frame to center axle and the lower is outside axle to center frame. This also allows massive articulation, so a street app would almost require a swaybar, or properly valved shocks mounted at the correct angle forward and to center. the powerblock site has a 4 link geo download that is a big help for all the math.

I have seen that before on off road 4x4 trucks, and wondered why they trangulated both. It seems to me you would end up with alot of articulation due to the triangulation pivot points, but could induce some non-street friendly handling. My offroad expeierience is more with the 2wd desert trucks, thanks for the info!

[kdrodworks316]

Originally Posted by PrerunnerRob

I have seen that before on off road 4x4 trucks, and wondered why they trangulated both. It seems to me you would end up with alot of articulation due to the triangulation pivot points, but could induce some non-street friendly handling. My offroad expeierience is more with the 2wd desert trucks, thanks for the info!

Your right about the street manors, the length of the bars and a good sway bar should take care of this.

[RunninLo]

No arguement here! sorry if it came off that way. I was mostly trying to continue my own education and am well aware there being more than one acceptable way to "get 'er done"
Josh

PS I"M A DADDY..... 5:32PM sat sealed the deal I'll try to get some pics in Gen D soon.

[PrerunnerRob]

Congratulations!

Originally Posted by RunninLo

No arguement here! sorry if it came off that way. I was mostly trying to continue my own education and am well aware there being more than one acceptable way to "get 'er done"
Josh

PS I"M A DADDY..... 5:32PM sat sealed the deal I'll try to get some pics in Gen D soon.

[Captainfab]

Originally Posted by RunninLo

PS I"M A DADDY..... 5:32PM sat sealed the deal I'll try to get some pics in Gen D soon.

Congrats Josh! I hope all is well with Mom and the little one....

[kdrodworks316]

And a huge congrats to the new low rider Daddy! I cant wait to see her Josh

[joe231]

yeah, they are in his crew cab thread

[1Bad62Pro/Street]

Sorry Joe,

I was in the wrong tread. Doe! Me needs to pay attention!