3 link vs 4 link what is the difference (1 Viewer)

[derelict]

Great thread. I was thinking about this too but for a 60. I dont want to run a SOA conversion with leafs as I would love to keep it kind of low and SOA makes for a pretty tall truck. If I could net about 4" of lift, I would be happy as that would give me room to run 34s or "small" 35s with the right backspacing. More droop than compression is alright with me. I dont do a lot of "hardcore" wheeling and the truck will have to pull a lot more road duty than trail duty so getting something that doesnt bump steer, stops straight and isnt nervous on the road is a first priority. Its mostly used for camping and fishing rather than going out and trying to tackle as rocky a trail as I can find. I was thinking about a system 3 link in the front and a 4 link in the rear. My only concern with the 3 link is that I had a Disco with a 3 link and although it flexed great, it scared the piss out of me in off camber situations. I think that was more a result of too soft springs combined with the top heaviness of the body and the skinny 255/85s than design. The front seems a little easier because there is more room than the rear. I would love to do a matching coilover setup in the rear as well but do not want to cut up the load floor in order to make room for the upper mount of the shock. Because of what I use the truck for, mounting some sort of hoop in there that would take up valuable room is not an option. I would be interested to see if something like this could be made to work without cutting up sheetmetal in the wheelwells. The 60 does have a good amount of room in the wells.
Poly Performance JEEP/TRUCK & BUGGY*::*Synergy Suspension TJ/LJ Rear Coilover Bracket Kit - 4X4 Off-Road Parts, JK Synergy Suspension Systems, Fox Racing Shox, Beard, CNC Brakes, Johnny Joints®, Currie Enterprises, Edelbrock, Pit Bull Tires, Ramsey W

 

[4WheelUnderground]

From my experience, a well designed street geometry link setup works better offroad than a "rock crawler" suspension does. I view the "rock crawler suspension as a amateur design. Long flat links that aren't designed "trictly" for ground clearance will pay dividens in all driving conditions.

Handling characteristics can be traced back to the geometry but equally important are the shocks. People dont generally give them enough credit.

 

[Mace]

From my experience, a well designed street geometry link setup works better offroad than a "rock crawler" suspension does. I view the "rock crawler suspension as a amateur design. Long flat links that aren't designed "trictly" for ground clearance will pay dividens in all driving conditions.

Handling characteristics can be traced back to the geometry but equally important are the shocks. People dont generally give them enough credit.

what exactly is a "rock crawler" suspension?

 

[4WheelUnderground]

That’s a great question, I don’t know if anyone truly knows. I just think its funny when people say I designed my suspension for rock crawling not driving on the street. But if I had to give some kind of description I'd have to say when you start lifting the truck about 5" or so and then you decide to put your lower link above the bottom of the frame for ground clearance purposes. A complete disregard for what causes the problematic jacking effect that so many associate with a linked suspension.

 

[Slowerthanu]

My buddies linked their rigs using more eyeball than calculations and their systems work well. Thing is, they work as well as my rear leafs which to me is not worth it.

If I EVER link my FJ40 (I'm sure I will around the time I stick an 80 series rear behind it) I will take my time. Having years of experience welding and fabricating makes the real hard part the design, but I am not going to cut corners which more than likely explains why I have not done it.

Wheeling where I do (Moab and local areas in Utah) is no longer "Hardcore" and leafs will work almost anywhere that a linked system will. In your situation, you are going to a linked suspension because it fits your design, but not your needs from the sounds of it.

 

[brokenparts]

3 linking the front of a 60 is a pain in the ass.

 

[Mace]

linking any framed vehicle sucks...

 

[derelict]

3 linking the front of a 60 is a pain in the ass.

Ive been watching your build. Its definitely awesome. What was tough about linking it? Was it that you needed to clear room for the long coilovers for your 42's (they are 42's, right)? What if the coilovers were shorter and the tires were more like 34- 35's? Would really love to not have to cut up the rear load area to clear shocks. Maybe tip them so that they can remain inside the wheelwell? Wouldnt work with shocks over 12" I would guess but would be more what I would be looking to do.

 

[brokenparts]

Ive been watching your build. Its definitely awesome. What was tough about linking it? Was it that you needed to clear room for the long coilovers for your 42's (they are 42's, right)? What if the coilovers were shorter and the tires were more like 34- 35's? Would really love to not have to cut up the rear load area to clear shocks. Maybe tip them so that they can remain inside the wheelwell? Wouldnt work with shocks over 12" I would guess but would be more what I would be looking to do.

What sucked and what Mace alluded to is that frame gets in the way. Tube buggies have the advantage of literally bending tube around problems and tight situations. With a frame you have to compromise things to make everything fit... that usually means height (taller), restrictions in shock travel due binding, roll axis, instant center, etc. The linking calculator is important but reality says that you will compromise whatever "magic" numbers you think are great in the calculator. I must have re-done my 3 link 5-6 times after cycling the suspension and finding problem spots. I'm still not sure I've solved all the problems and predict I'll be doing some "fine tuning" after spending some time out on the trail. I built some adjustment in my setup... I'm just hoping I built enough into it that I dont have to do any major changes.

As far as the 42s.... I did enough fender trimming that the tire size wasnt really an issue. Heck, I think I could fit 46s (maybe larger) under there without any major changes to the suspension. The height of the "shock hoops" and drivetrain positioning have more to do with the vehicle height than anything IMO. I had to find a balance between wheelbase and ride height that I thought was reasonable (122" wheelbase/26"ride height @ frame). Any lower and I think I would be scraping alot on breakovers in the area that I'm in.

I cut the rear area to accommodate the longer shocks because I originally planned to 4 link the rear end. Those "shocks" are actually coliovers. In the next "stage" of my build I'm going to lose the springs and go to a 4 link and back half it with tube. I'll wait for the sheet metal to disintegrate before going there though. Shorter shocks could have certainly been used there to avoid the direction I took. Tipping them too far reduces the efficiency of the shock so watch out for that.

To sum it up... linking a framed rig is a compromise and is a pain in the ass. Think long and hard about how you will use the vehicle. Be honest with yourself and account for how much time you are willing to spend to make it work.

 

[bustanutley]

Great thread. I was thinking about this too but for a 60. I dont want to run a SOA conversion with leafs as I would love to keep it kind of low and SOA makes for a pretty tall truck.

A sprung over truck doesn't have to be tall. If you put a little effort in and french the hangers you can end up with very minimal lift.

 

[derelict]

What sucked and what Mace alluded to is that frame gets in the way.

...The height of the "shock hoops" and drivetrain positioning have more to do with the vehicle height than anything IMO. I had to find a balance between wheelbase and ride height that I thought was reasonable (122" wheelbase/26"ride height @ frame).

...I cut the rear area to accommodate the longer shocks because I originally planned to 4 link the rear end. Those "shocks" are actually coliovers... Shorter shocks could have certainly been used there to avoid the direction I took. Tipping them too far reduces the efficiency of the shock so watch out for that.

...Think long and hard about how you will use the vehicle. Be honest with yourself and account for how much time you are willing to spend to make it work.

Oh I know that they are "coilovers." I have a good amount of experience with them but on cars instead of trucks. I know that the most efficient way for them to be mounted is straight up and down but, like you said, compromises sometimes have to made. You have to be able to work with what youve got. If I didnt hate the 80 series like I do, I would just pick one of those up and be done with it.

The 60s long wheelbase has its disadvantages. Ive bumped and drug ass across enough obstacles to know that that is true. Tons of room comes with the disadvantage of dragging ass unless you go pretty high. Your wheeling is a lot like the trails over here on the East Coast where things are pretty tight. The solution is to go tall but then I have to look at it also having to be driven on the road and parked in areas where space is at a premium. 35s would be the happy place I think and that could be achieved with leafs, sure, but coils would let me keep the CoG lower and offer a better ride. Not to mention more adjustable when it comes to loads. I lived with a crappy 3 link on my Disco for about a year. Dont want to ever go there again. It was scary in about 90% of driving. You felt like it was going to flop over most of the time and God help someone that might have caused a panic stop situation.


I know you can make a low SOA but then you are still hanging over 400 pounds off of a spring pack making it prone to axle wrap/ wheel trounce and other problems associated with that type of setup. A coil set up with radius arms or a set up of links would make for a better, although admittedly more labor intensive, setup.


Im very interested in feedback and personal experience with things like this. My next rig, not sure if its going to be another 60 or a 2nd gen 4Runner (leaning more towards the latter though) will end up being linked.

 

[derelict]

What are the advantages/ disadvantages of a radius arm/ long arm system like this? Its a play off of a 4 link and panhard rod, correct? Very popular with the Heep guys.

 

[Mace]

great for street truck but limited flex without removing one of the Y links.

 

[Gumby]

It's more of a play off a radius arm than a four link. As mace says they bind if both sides have the upper arm.

 

[4WheelUnderground]

great for street truck but limited flex without removing one of the Y links.

Agreed and i'd like to add that it doesnt use as much room on the frame, which makes routing exhaust easier at times.

 

[derelict]

I figured it limited flex. Is that why the links always end up being so long? Is it simpler to set up than a 3 or 4 link system? The reason why I said it seemed like a play off of 4 links is a lot of the Heeps start out with 4 links and end up with a long arm system like the home brew one I linked up. I would think that with a system like this, axle travel wouldnt be ideal, right?

 

[4WheelUnderground]

Personally I don’t think its any easier, many people how have never set up one do think that just because they don’t have to build one extra bracket for the frame. But in the end, they are they same to build. The difference is in the performance and the ability to tweak. A radius arm design is missing the ability to change the amount of anti dive or anti squat the vehicle has. Another side effect is not being able to control torque lean.

 

[Eskimo]

What are the advantages/ disadvantages of a radius arm/ long arm system like this? Its a play off of a 4 link and panhard rod, correct? Very popular with the Heep guys.

TJ's are also notorious for having so much anti-dive that on every rock they come to bigger than 6", the suspension extends to full droop before it even thinks about climbing.

On a low rig where the radius arms are mostly flat, they seems to work well enough on a limited travel vehicle though.

 

[4WheelUnderground]

TJ's are also notorious for having so much anti-dive that on every rock they come to bigger than 6", the suspension extends to full droop before it even thinks about climbing.

On a low rig where the radius arms are mostly flat, they seems to work well enough on a limited travel vehicle though.

Exactly my point, thank you.

 

[derelict]

I guess I need to do more reading into what anti dive, anti squat, etc... means. Any good sources out there?