3 link vs 4 link what is the difference

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Dieseler

Dieseler

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I have done some searches for this topic but have come up short so hopefully someone can educate me on the difference between the 3 link and 4 link.
-This would be for a 90% DD and 10% moderate and up wheeler.
the two types look similar in appearance is there an advantage/disadvantage to one over the other.
-Which one is the easiest to install without having and engineering degree for calculating mounting points and axis points.
-Which one offers the best ride characteristics on the road mainly.
-Is it best to buy a install kit or can a 80 or 70 series suspension be adapted with similar results.

The purpose for this would be to stretch out my wheel base to the furthest point on the frame for my next project.
 
3 link requires a panhard rod or trac bar to keep the axle from moving left to right. The 3 linl is easier to fit around engine/exhaust/etc...

4 link with dual triangulation done well will locate the axle without panhard rod but is sometimes a bear to fit the upper links and the frame end of lowers.

If retaing the cruiser frame I would suggest searching Medusa's build as his fj45 has a front link set up with stock frame still there and works, been tried and tested and it works so that would be a great baseline to follow. IMO.
 
I assume you're referring to a (double) triangulated 4-link and not a parallel-style 4-link?

For a DD, spring rate and shock valving will make far more of a difference than what type of suspension you choose, since they behave quite similarly in straight up and down movement.

However, assuming you're using a drag-link style steering, a 3 link is typically the preferred option so that you minimize bump steer. (panhard rod similar length/height as the drag link)

Packaging a straight upper link can also often be easier on a vehicle like ours rather than a triangulated upper setup.
 
that's for your DD front and rear or one of both .?

In both cases ( F&R ) I would use a panhard .. if it's gonna be your DD . .. 3 front / 4 link rear

It could even be radius arm in front .. like 8 series front suspension ..
 
Dieseler said:
I have done some searches for this topic but have come up short so hopefully someone can educate me on the difference between the 3 link and 4 link.
-This would be for a 90% DD and 10% moderate and up wheeler.
the two types look similar in appearance is there an advantage/disadvantage to one over the other.
-Which one is the easiest to install without having and engineering degree for calculating mounting points and axis points.
-Which one offers the best ride characteristics on the road mainly.
-Is it best to buy a install kit or can a 80 or 70 series suspension be adapted with similar results.

The purpose for this would be to stretch out my wheel base to the furthest point on the frame for my next project.
Click to expand...

For a 90% DD driver, I would not do a 3 or 4 link. I'd run leaf springs.
 
Dieseler said:
I have done some searches for this topic but have come up short so hopefully someone can educate me on the difference between the 3 link and 4 link.
Click to expand...

One has 3 links (or 4 if it uses a panhard) and the other has 4 links (or 5 with a panhard). There are many different types of 3 and 4 link setups out there as well. Just saying "3" or "4" links does not describe the suspensions you are investigating well enough.

Dieseler said:
-This would be for a 90% DD and 10% moderate and up wheeler.
the two types look similar in appearance is there an advantage/disadvantage to one over the other.
Click to expand...

Not really, it all depends on the amount of room you have and what you can fit.

Dieseler said:
-Which one is the easiest to install without having and engineering degree for calculating mounting points and axis points.
Click to expand...

Both are pretty much equal. It is sitting down and doing the calculations that give you the best preformance.

Dieseler said:
-Which one offers the best ride characteristics on the road mainly.
Click to expand...

Ride is dependant on whatever you are using for shocks and springs. Not the link setup. That being said. A panhard in the front that matches the orientation and length of the Draglink will reduce bump steer the most. So driveability can be altered. Also, rotation of the axle on the three link can cause some interesting things to happen under braking.

Dieseler said:
-Is it best to buy a install kit or can a 80 or 70 series suspension be adapted with similar results.
Click to expand...

If a kit is already built for your rig that would be the easiest way. Less engineering and stuff then.. However, it may not have the characteristics you want..

Dieseler said:
-The purpose for this would be to stretch out my wheel base to the furthest point on the frame for my next project.
Click to expand...

knowing what you have right now and what your "next plans" are is kinda important.

I agree with Charles tho..
 
Ride is shocks and springs.

Handling is geometry. Poor front or rear geometry on a link suspension will make cornering exciting and emergency handling downright dangerous.

I researched a full year on Pirate4x4 prior to tackling my rear 4-link suspension on my FJ40. It got one minor adjustment, but has largely worked. Even the heims are all still original.

I've yet to consider myself smart (or dumb) enough to tackle a front link setup. The leaf setup works too well. 100" wheelbase, great poser RTI scores, and predictable on the trail. I know what it can't do, and when to back out (usually...)

My rig handles excellent at 60mph and around town...well, as excellent as 39" bias tires can anyways...
 
fj40charles said:
For a 90% DD driver, I would not do a 3 or 4 link. I'd run leaf springs.
Click to expand...

I have to agree with this statement as well if the linked setup is designed for trail (rock) use. If your engineering the rig to be DD first and occational off highway then a well designed link set up would be superior but what would be the point of spending the money and time unless your planning on rally or high speed dirt road racing. Link geometry is particular to the environment you design it for. Leafs work and they are cheap! Links are awesome but are not for the novice wheeler/mechanic.
 
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To get the wheel base I am looking for ....staying with leafs is not an option I have to go to a coil suspension on the rear so the axles sit below the rear cross member.
I need to get to aprox 112" wheel base to achieve the modification that I am working on , the frame is a 44 frame with a 102' base and if I chose the leafs the axles will be to far forward plus the front hanger will sit inside the frame arch if I was to do a leaf reversal and move the leafs to the furthest point towards the rear of the frame.
When geometry is mentioned I am totally lost on this topic when I look at suspensions like an 80 or a HEEP it looks to be straight forward the axles are linked to the frame and the panard goes from axle end to opposing frame rail is there something in this I am missing,I am not sure how driveability is affected if this is not calculated properly, to my thinking the connecting point at the frame rail is the pivot point and the axles move up and down in relation to this pivot point and the panard stops the axle side movement,so to my pea sized brain it would be up to the coils to control the ride whether it is rough or soft.
 
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Dieseler said:
When geometry is mentioned I am totally lost on this topic.
Click to expand...

You need to do a lot more reading and asking questions before you tackle the conversion.

That or pay someone that has done it before to do it again.
 
if you are currently at 102" and want 112", then my math tells me that's 10" of added length.

stock FJ40 is 90", and mine with leafs front and linked rear is now 100"...

The 'phrases' to look for when researching are 'roll center' 'instant center' and 'antisquat'...and probably a few others...understand those and you can build a suspension that won't flop over on the first corner, and won't lift a front tire as you accelerate thru an intersection (both of which I've witnessed with poor designs...)
 
Agreed

Springs and shocks will determine the ride in a straight up down motion but there are too many other factors. You need to research and fully understand squat/ anti squat, roll height, roll axis, over/ understeer and how changing the geometry of each individual link will impact each of those numbers. The variables are too many for a one size fits all solution, it is highly vehicle and application dependent.

And anybody that says a properly designed link suspension wont be superior on and off road is misinformed.
 
Woody my measurement may be a little off but I have a 44 frame which is longer than the 40 frame IIR it is 8" longer than 40 and a longer base, I have to get enough stretch for an extended cab and leave enough wheel base to fit a shortened 45 box.
I will be adding to the frame to fit the box and adapt a rear winch but do not want to place the load of the leafs on the frame extension... my welding is profesional rated but I am concerned if I misscalculate I could be putting a death trap on the road.
Maybe I have to look at seeing if a frame specialist will do the job for me and calculate if the cost is worth it.
 
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Have you considered putting you body/tub on an FJ80 frame/chassis?

You'd get the longer wheelbase with factory designed drivetrain and suspension.
 
80s are not plentiful here at a reasonable price as in the US that was a consideration I would like to work with what I have my neighbours wont like another cruiser in the driveway 6 is their limit.
 
I believe my front suspension is pushed forward about 3"...simply reversing the stock springs adds 2.5ish, and redrilling the perches on the axle/u-bolt plate can add another inch. All relatively 'no brainer' modifications. That gives you a stockish front suspension setup and maintains the OEM stability and handling. (which we all know is stellar...lol) This will also work with the stock body/cab as well, tho if you push the suspension too far forward, you'll be into the fenders pretty hard on compression/turning

Linking the rear is 'less' of a headache than the front, and a simple set of splayed lower links and triangulated upper links will do a good job of positioning and controlling the axle. There is a 60% guideline, where the length of the uppers is 60% of the lowers, and the separation at the frame is 60% of what it is at the axle mounts. I broke all those rules, and mine still works.

IIRC, Ruff Stuff Specialities has a rear link 'kit' for FJ40's...Proffitts Cruisers does as well I believe...both shops have good reputations and their products work. Proffitts also has a front kit, running an 80-style design...not sure if it's public yet tho :) (so, don't tell them I leaked the info...I'll deny it...really...)
 
woody said:
IIRC, Ruff Stuff Specialities has a rear link 'kit' for FJ40's...Proffitts Cruisers does as well I believe...both shops have good reputations and their products work. Proffitts also has a front kit, running an 80-style design...not sure if it's public yet tho :) (so, don't tell them I leaked the info...I'll deny it...really...)
Click to expand...


Cut, copy paste...
 
woody said:
Linking the rear is 'less' of a headache than the front, and a simple set of splayed lower links and triangulated upper links will do a good job of positioning and controlling the axle. There is a 60% guideline, where the length of the uppers is 60% of the lowers, and the separation at the frame is 60% of what it is at the axle mounts. I broke all those rules, and mine still works.
Click to expand...

I heard 70%... Maybe I will just do 65% to shoot in the middle :lol: No really tho...
 
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