4 link set up decisions?

FnStrkn6.4

New member
Joined
Feb 8, 2012
Messages
19
Reaction score
0
Can't decide which to go with. The RCD links or PMF short arm. I have a lowered ccsb, anyone running either with any input would be great.

Sent from my SM-G900V using Tapatalk
 

Breaking Habits

New member
Joined
Feb 11, 2012
Messages
6,158
Reaction score
0
Location
Mapleton, Illinois
I would advise an Adjustable Radius Arm over a 4 link

The front end of the vehicle was designed around a radius arm and the components performance and survive better with a good radius arm. The truck will also drive much better and not bump steer or body roll as bad.

If you'd like any information about the One Up Offroad Adjustable Link Arms feel free to give me a shout.

If your mind is made up on the 4 link, RCD has been building theirs for quite some time and usually have them in stock. They are a very nice piece!

-Jared
 

BOSS450

New member
Joined
Sep 19, 2011
Messages
940
Reaction score
0
Location
Concord, NC
Pmf short arm is what I went with. Good price and I don't have any problems mr rice is talking about. If I did it again Id do the same thing.
 

FnStrkn6.4

New member
Joined
Feb 8, 2012
Messages
19
Reaction score
0
I'm not opposed to going another direction I'm mostly looking for input, I guess I should of worded a little differently. I do drive around relatively bumpy highways and want to avoid as much bump steer as possible.

Sent from my SM-G900V using Tapatalk
 

Layson

New member
Joined
May 18, 2011
Messages
1,638
Reaction score
0
257_Product_Cards_Page_13.jpg


I don't know if you can read this but I would go the OUO ALA route over the 4-link. They are a great addition to these trucks and in my opinion the only option for these trucks. Should come with them from the factory this way with their traction bars....LOL

Adjustable for lowered or lifted to 6". You can dial in the caster perfectly. It isn't going to have bumpsteer since your steering on your axle was designed around a radius arm setup. You don't need to add sway bars or revalve your shocks for them. The arms are offset so you can actually have tighter turning radius over stock or run wider tires without rubbing. The same dang joints that are in these front arms are on this truck...which are pretty much the best you can get.

FB_IMG_1428361293107_zps3xuwx1rg.jpg

FB_IMG_1428124650343_zpsuexgdase.jpg

photo4_zps88796462.jpg
 

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
Not sure what you guys are considering bump steer. The drag link and track bar which are arching together have nothing to do with 3 or 4 links. So unless you have the drag link and track bar out of parallel than you don't get bump steer.
For ride, a 4 link will ride smoother across uneven passenger side to driver side road/terrain because the linkage is not fighting each other trying to twist the axle in opposite directions. Hence why 4links are the professionals choice for offroad articulation. Team a four link with a high end shock absorber and your laughing (especially for lifted trucks that need to counter additional body roll). The other added bonus is a castor angle that stays very close to where it should be throughout travel.
Three links are great for higher speed handling/cornering because of the linkage binding from uneven travel side to side. Its like having an additional sway bar. An after market 3 link with heim joints is going to bind even more because it lacks the rubber bushings the stock radius arm use. So on the plus side, body roll will be much more limited and a less aggressive shock and swaybar can be used. As far as castor angle is concerned, its all over the place while the axle is traveling away from static.
You being a lowered superduty will be fine with either setup since offroad is not an issue.
Personally I prefer 4 links, especially in lifted trucks. Quite happy with mine, makes a significant difference in articulation and ride on uneven roads. But that's apple to oranges for you.
 

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
I'd say you have other issues. Linkage adjustment is not set the same length side to side, a castor angle out to lunch, and/or an obviously compromised axle mount which should not happen.
 

weekendwarriorfsw32

New member
Joined
May 22, 2011
Messages
1,626
Reaction score
0
Location
Central California
I have checked everything twice and all the link arms are the correct distance, castor is perfect. Every 4 link I have drove has just not been right driving down the road, last week I was doing coolers on a 6.0 and it had a BDS 4 link on it and it was down right terrifying to drive. On the flip side I drive a OUO 12 inch lifted 6.4 pretty regularly and I can drive that one handed with no issues doing 75 - 80 here on the freeways. That BDS truck I was scared with 55. Not that this was ideal at all but I was towing with my F-450 and lost a trans last year and all I had was the OUO truck which is 3 link and even at the height it still towed my trailer fine.

I'd say you have other issues. Linkage adjustment is not set the same length side to side, a castor angle out to lunch, and/or an obviously compromised axle mount which should not happen.
 

FnStrkn6.4

New member
Joined
Feb 8, 2012
Messages
19
Reaction score
0
Thanks for the input. It's looking more like I'll be going OUO 3 link.

Sent from my SM-G900V using Tapatalk
 

sootie

Well-known member
Joined
Oct 3, 2012
Messages
11,854
Reaction score
29
Not sure what you guys are considering bump steer. The drag link and track bar which are arching together have nothing to do with 3 or 4 links. So unless you have the drag link and track bar out of parallel than you don't get bump steer.
For ride, a 4 link will ride smoother across uneven passenger side to driver side road/terrain because the linkage is not fighting each other trying to twist the axle in opposite directions. Hence why 4links are the professionals choice for offroad articulation. Team a four link with a high end shock absorber and your laughing (especially for lifted trucks that need to counter additional body roll). The other added bonus is a castor angle that stays very close to where it should be throughout travel.
Three links are great for higher speed handling/cornering because of the linkage binding from uneven travel side to side. Its like having an additional sway bar. An after market 3 link with heim joints is going to bind even more because it lacks the rubber bushings the stock radius arm use. So on the plus side, body roll will be much more limited and a less aggressive shock and swaybar can be used. As far as castor angle is concerned, its all over the place while the axle is traveling away from static.
You being a lowered superduty will be fine with either setup since offroad is not an issue.
Personally I prefer 4 links, especially in lifted trucks. Quite happy with mine, makes a significant difference in articulation and ride on uneven roads. But that's apple to oranges for you.

wrong. bad castor can give you bump steer.
 

Rubenk

Member
Joined
May 18, 2011
Messages
725
Reaction score
0
Location
KCMO
I have a 4 link and it does great. Truck handles and rides much better than stock. I am factory height on relatively small tires though.
 

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
wrong. bad castor can give you bump steer.

No sir, "bump steer" is specifically the axle shifting side to side in a different arch/rate than the drag link throughout travel. Therefore the axle is moving side to side following the track bar arch, and the draglink (on a slightly different arch swing) is ever so slightly pushing the knuckles in and out (based on the degree of difference) as you hit bumps. It literally making you steer left and right just by hitting bumps when the steering wheel is held perfectly still. A parallel track bar and drag link is the only way to fix it in our situation.

Bad caster angle is just bad caster angle. Positive caster is good because its the self centering force that keeps you feeling stable and straight. Bumps or not, it lets you drive more passively. Extra positive caster beyond spec usually doesn't hurt anything either as far as handling, in fact it helps handling within reason. It just further reduces the steering wheel input required to keep the tires centered. Negative caster is the issue we have with stock radius arms and lift kits though. Negative caster is bad for any modern vehicle. It removes the caster effect and forces the person holding the steering wheel to keep the tires straight at all times. It's effects are further exaggerated when hitting bumps which is what your getting at. These are the vehicles that are scary to drive and make the vehicle wonder/ steer where they shouldn't.

Either way, a four link or three link can fix the caster issue that stock radius arms can't. A four link though is the only way to keep the caster virtually the same throughout travel (unless the 4link geometry is way out) in comparison to a three link that varies significantly. To the average person, most wouldn't know the difference if they are set up correctly.
 
Last edited:

Layson

New member
Joined
May 18, 2011
Messages
1,638
Reaction score
0
No sir, "bump steer" is specifically the axle shifting side to side in a different arch/rate than the drag link throughout travel. Therefore the axle is moving side to side following the track bar arch, and the draglink (on a slightly different arch swing) is ever so slightly pushing the knuckles in and out (based on the degree of difference) as you hit bumps. It literally making you steer left and right just by hitting bumps when the steering wheel is held perfectly still. A parallel track bar and drag link is the only way to fix it in our situation.
.

I do like some of what you are saying. But there is way more to this then parallel and same length drag link/track rod relationship. The steering linkage really needs to be at a different spot on the axle/knuckle to make it work correctly on a 4-link. When your axle moves through the suspension cycle it also moves forward, up and over. Where the drag link connects on the axle works great with a radius arm setup. You install a 4-link on there and your axle doesn't go through the same exact motion since the caster hardly changes and that exact point where the drag link connects to the axle is now at a different spot then where it would be on a radius arm setup. It is a slightly different path in the 3D world. When you actually draw this in 3D software you will notice the difference.

One other thing that sucks about a 4-link is the lack of caster change. What do you think happens to a front driveline when your front axle droops out. It needs to stay straight out of the axle and only change angle at the transfer case. Then when you droop out your front suspension the driveline will just blow up at the axle end and take out your oil pan, your transfer case and beat the piss out of the bottom of your truck until it falls off. So if you are building your superduty for going offroad you really need to address the front driveline if you run a 4-link.

Look that front driveline looks happy with this setup.
E8EB557C-33A4-434A-B73B-BC5688ADEF24_zpstj6bwoww.jpg



Look at POS dodges. They went to a 4-link setup and now what do the trucks come with....it is very similar to a Ford now. Dodge couldn't even get it correct.

This is my truck. My track rod is like half the length of my drag link. There is a lot more to the equation then just the drag link/track rod relationship.
photo-2159.jpg
 
Last edited:

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
I do like some of what you are saying. But there is way more to this then parallel and same length drag link/track rod relationship. The steering linkage really needs to be at a different spot on the axle/knuckle to make it work correctly on a 4-link. When your axle moves through the suspension cycle it also moves forward, up and over. Where the drag link connects on the axle works great with a radius arm setup. You install a 4-link on there and your axle doesn't go through the same exact motion since the caster hardly changes and that exact point where the drag link connects to the axle is now at a different spot then where it would be on a radius arm setup. It is a slightly different path in the 3D world. When you actually draw this in 3D software you will notice the difference.

Well I'm glad you like a little. And yes there is slightly more to the equation of bump steer but I'm keeping things simple and pointing out the direct main cause of "bump steer". By saying parallel drag link and track bar sets the foundation(for the less knowledgable) for solving bump steer. As for your point about caster angle changing less on a four link, which in turn puts the draglink/knuckle pivot in a slightly different location due to the lack of axle rotation, you are correct. What your saying is the draglink/knuckle pivot is farther from the axle caster center of rotation than the track/axle pivot. So when the axle roatates the draglink/knuckle location moves a further distance than the track/axle pivot. The arch path gets larger(dis-proportionally to the track bar)the more the axle rotates. That fact all on its own makes it very difficult to sync the track bar and draglink motion on a three link. A 5 link (if you want to get technical because a true 4link is a whole other ball game) eliminates this added geomerty calculation by eliminating caster change. If the distance between the pitman arm pivot in front of the frame/track bar pivot is roughly the same as the distance from draglink/knuckle pivot in front of the axle/track pivot, along with parallel/similar length track bar and draglink (on a five link setup), the archs will be virtually the same with no bump steer.
On a side note, were talking moderately lifted/no lift/ lowered superdutys. So the suspension travel/angles are pretty minimal to any average superduty drivers out there. The whole bump steer due to caster fluctuation is hardly an issue because their isn't enough suspension travel to feel small geometry flaws at the end of the day. Hence why their are happy guys with properly setup 3 and 5 link setups under the same ol superduties.


One other thing that sucks about a 4-link is the lack of caster change. What do you think happens to a front driveline when your front axle droops out. It needs to stay straight out of the axle and only change angle at the transfer case. Then when you droop out your front suspension the driveline will just blow up at the axle end and take out your oil pan, your transfer case and beat the piss out of the bottom of your truck until it falls off. So if you are building your superduty for going offroad you really need to address the front driveline if you run a 4-link.

The ujoint angle is not an issue on moderately lifted (8") to lowered superduties. If we were talking about +10-12" lifts then yeah we might be concerned. That's very far from the majority. The drivline does NOT need to be addressed for the majority, even if they off road. My 7" front lift/4 link bars set with a degree of extra caster above spec(which further hurts my driveline argument) goes to full droop without binding. If i pull the shocks, brake lines, sway bar i can push the axle down another 6-8 inches before the yokes start to kiss. The driveline dilema is a non issue.


Look at POS dodges. They went to a 4-link setup and now what do the trucks come with....it is very similar to a Ford now. Dodge couldn't even get it correct.

I could be wrong but I'm pretty certain ford uses a 3 link setup for simplicity, wear, and cost. It has two pivot wear points plus track bar on a 3 link vs eight pivot wear points plus track bar on a 5 link

This is my truck. My track rod is like half the length of my drag link. There is a lot more to the equation then just the drag link/track rod relationship.

Like I said, trying to keep things simple and touch on the main points for the majority.
 

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
That pinion seems a little high btw. So i would say your caster is set too low. It sits higher than stock and much higher than mine which is a degree above spec. Heres a pic for anybody that's curious. 7" lift springs/4link upgrade.
IMG_3901.jpg
 

Layson

New member
Joined
May 18, 2011
Messages
1,638
Reaction score
0
Those were installation pictures. The caster had not been set yet.

Here is a fabtech 4-link setup on the dunes....6-8" lift...

image001-2_zps6xqru0lf.jpg

image004_zpsojtvm0mf.jpg

image003_zps6iur2ayh.jpg

image002-2_zpswp985bqn.jpg



Other things to consider about a 4-link is the rubber bushings on the axle. They were not designed to be twisted the way 4-links move. That is why they kept pushing the bushing out of the axle on the other persons truck.

If the axle now does not follow the arc that was designed into the suspension it will cause the wheels to turn when the suspension moves. Even if you don't feel the bump steer in the steering wheel your suspension components do. It is just wearing out all your steering components and your steering box. So even if it feels fine and you can't feel it. After 15-20,000 miles and you need new steering components and people rarely connect the dots and understand what is causing the premature wear.
 

footlong70

New member
Joined
Nov 1, 2012
Messages
115
Reaction score
0
Location
Whitecourt AB
Well I don't see the point in arguing with you because it won't get me anywhere special. That truck was clearly not setup correctly with limiting straps in a coilover setup (if a binding driveshaft was the cause) and was more than likely in the air. I highly doubt a big company like fabtech puts out 6000 dollar coilover/4link kits only to explode guys driveshafts the first time they put it to use. Funny how I can have a properly set up 4 link that doesn't even come close at full droop to binding a driveshaft. And my 350 is far from a pavement princess. But I guess my my superduty must have been built differently from factory.

And I'm sorry but your wear and tear is ridiculous and very exaggerated. If you can't feel it in the steering wheel, than it isn't moving any more than bumps on the road are already cycling the components. And you miss the point that 3 links move steering components more because of the axle rotation over a 5 link.
 

Latest posts

Members online

Top