How's your four link doing?

[skullandbones]

I don't have a lot of miles on my car yet. What I have read tells me I should expect some erratic behavior when pushing it in the turns. I will be doing a lot of street driving and a little bit of track activity but I sure don't want to have any nasty surprises while on the track. I can't complain so far. It launches nicely. Several people have commented on that. I really haven't had the opportunity or "seat time" to find out what it does on turns other than gentle highway stuff.

Can you share your experiences with this rear end setup with me? I want to know what happened and what you did to make it better. I am eventually going to change to a 3 link or 5 link (not interested in IRS). But there are a few things higher on the priority list before that happens. So I would like to do whatever I can to make this setup work until then. I have heard a lot of comments about upgrading but can't find anything specific. I did hear about a three part bushing that might help. So let's hear what you have to say. As usual: thank you in advance for your input, WEK.

[edwardb]

Would help if you described your setup a little more. I see coil overs in your sig line, so assume no donor quad shocks or whatever? What upper and lower control arms, bushings, coilovers, springs, etc. are you running now?

My Mk3 has the full FFR upper and lower arms, bushings, springs, Koni coil overs, etc. Nothing donor. With all the negative comments and press 4-link gets I'm not sure what I was expecting. I'm approaching 3,000 miles now in my second season. While I don't track the car, I'm very pleased with how it rides, drives, etc. I doesn't ride like my grandpa's Impala, but didn't expect it to. But the ride is very controlled, stiff but not harsh, launches fine, and on some pretty fast twisties a few weeks ago, does very well. For my purposes, I'm more than happy with it. My Mk4 has the Gordon Levy 5-link setup, Eibach springs and FFR Koni coilovers. Looking forward to what the difference may be. Won't find out for at least a year.

[Mike N]

I ran the 4 link for a couple of years and did a lot of street driving and drag racing and was very happy with it. Then I started Auto X-ing the car and found it frustrating to find the limits of the car consistently. As you approached the limits of the tires rather than getting a nice graceful slide the car would spin. In the factory 4 link the lateral location of the rear end is achieved by the triangulation of the control arms but as you apply lateral cornering loads the bushings also try to move sideways so they deflect a bit like a spring and build up a pre load. When the tires start to slide this pre load gets released which allows the rear end to start moving back to its unloaded position changing the weight distribution and geometry in the process. This is not dramatic but when you are trying the get the car right to the traction limit of the tires it makes it very challenging to actually hit the sweet spot and then keep it there. Also through lots of reading I learned that the 4 link geometry actually binds up as the car rolls. The factory rubber bushings flex when this binding occurs but the urethane ones (like I had) don't flex so much so as the car rolls it also builds up a pre load in the suspension and then as the tires start to slip it releases that pre load as well and all of a sudden the balance of the car changes and you can't catch it. The FFR 3 link replaces the 2 factory upper links with a single link and that eliminates the binding condition, at the same time the lateral loads are transferred directly through the lateral link (panhard bar) rather than through the triangulation of the stock 4 link vastly improving that condition as well. The 5 link works exactly like the 3 link except that the lateral link is replaced with a watts linkage. A panhard bar describes an arc as the suspension extends and compresses and can also induce jacking forces if it is not aligned parallel with the ground. The center pivot of a watts linkage geometry travels in a straight line up and down and does not follow an arc like the panhard rod. I put a 5 link set up in mine more than 6 years ago and it works very well. It also improves the ride quality on uneven pavement as the suspension is able to follow the contours of the road more freely without the binding.

[CraigS]

Both my mkI and mkII started out as 4 links. They had the FFR UCAs and LCAs w/ the plastic bushings. While talking to Levy about rear shocks he mentioned it would be better to change the UCAs to Ford Motorsport parts which had rubber bushings that were harder than stock but softer than plastic. I did that and felt it handled better in corners but did wheel hop if I tried a burnout. SO I just didn't do burnouts. Adding a front swaybar really helped a lot especially in autocrosses. As Mike mentions, the basic problem of it binding isn't good and Ford got away w/ it due to all the rubber bushings. Since you are going to stay w/ 4 link for a while, I would order a 7/8 front swaybar from Forte. I think you will be glad you did.

[skullandbones]

Would help if you described your setup a little more. I see coil overs in your sig line, so assume no donor quad shocks or whatever? What upper and lower control arms, bushings, coilovers, springs, etc. are you running now?

My Mk3 has the full FFR upper and lower arms, bushings, springs, Koni coil overs, etc. Nothing donor. With all the negative comments and press 4-link gets I'm not sure what I was expecting.

I have the same setup as you with no donor parts except Bilsteins and 250 # springs and the FFR tubulars. I know that the bushings can make quite a bit of difference in various suspensions but wasn't sure if it would make enough difference to be worth changing them out on this application.

Wish your 5 link ride would be ready sooner so we could do a side by side comparison.

Thanks for the explanation Mike. I always wondered why that complicated Watt's linkage. Now it makes sense. I will consider those softer bushings on the V arms CraigS. I suppose the LCA doesn't present a problem. I have some testing to do on my front suspension before I add any more variables like a sway bar but I will keep that as a possible step down the line. I need some "serious seat time" to compare my reactions to your comments to get a better understanding. I think I will reread everything right before my next drive which is supposed to be this week if we get a little relief from the heat. Thanks a lot, WEK.

[CraigS]

I never took the bushings out of my UCAs to see what they were but I have replaced them in the LCAs. They are actually a three piece set. The center 5/8 inch or so is a super hard plastic. The outer pieces are a softer plastic. This allows the twist that is needed. It's not a rod end but it's better than the usual super hard two piece bushing.
I am still running them w/ my 3 link.

[Mike N]

Wish your 5 link ride would be ready sooner so we could do a side by side comparison.

I pretty much guarantee that you (or I) wouldn't be able to tell the difference between the 3 link and 5 link driving the cars on the street. The differences you would feel would be due to other things like shocks, springs and tires and not the suspension. On the track or at an auto x you may be able to feel the difference but even then it is more likely to be because the roll center of the 3 link is going to be lower than the 5 link and not the fact that you have a watts versus the panhard bar. Not to say that a seasoned auto x-er or spec racer couldn't tell the difference, he (or she) probably could.

[skullandbones]

If you installed a pan hard bar on a 4 link that was parallel to the diff and spanned the width of the diff (to reduce the arc) would it have a positive effect on the 4 link? Do you think it would reduce the binding of that V shaped configuration of the upper arms? I've been thinking about this for some time. We used to use this sort of setup on hot rods. Can't say it is an apples to apples comparison but we did get some improvement in handling with the addition of the bar. To rephrase that, we got some stabilization from the bar and at that time most people called it a stabilizer bar. WEK.

[Mike N]

If you installed a pan hard bar on a 4 link that was parallel to the diff and spanned the width of the diff (to reduce the arc) would it have a positive effect on the 4 link? Do you think it would reduce the binding of that V shaped configuration of the upper arms? I've been thinking about this for some time. We used to use this sort of setup on hot rods. Can't say it is an apples to apples comparison but we did get some improvement in handling with the addition of the bar. To rephrase that, we got some stabilization from the bar and at that time most people called it a stabilizer bar. WEK.

Only one way to find out and that's to try it. Personally I have a feeling that it probably would help as it would take the lateral loading completely off the rubber bushings. The bind in roll would still be there and you could argue that you just made it worse as you have introduced yet another link into the 'mechanism' but I have a feeling that even with the bind that the rear suspension would be more stable under cornering loads.

However unless you are a tinkerer the FFR 3 link package is hard to overlook. It's well engineered and hard to duplicate for the price unless you have access to a fab shop.

[Jeff Kleiner]

If you add a panhard bar I believe it is going to try to dictate a different roll center than the existing 4 link and at some point the rear suspension will end up fighting with itself :( As an aside some of the Mustang guys used to add a panhard bar and remove one of the upper control arms to create what was often called the "poor man's 3 link". I can't say what the result might be if one were to try this on one of our cars.


... I learned that the 4 link geometry actually binds up as the car rolls. The factory rubber bushings flex when this binding occurs but the urethane ones (like I had) don't flex so much so as the car rolls it also builds up a pre load in the suspension and then as the tires start to slip it releases that pre load as well and all of a sudden the balance of the car changes and you can't catch it...

I remember having a conversation with Mark Daugherty a few years ago regarding snap oversteer in the 4 link. He said the best way to minimize it is to "get a set of donor upper control arms with the loosest most worn out rubber bushings you can find"!

Jeff

[efnfast]

Wish your 5 link ride would be ready sooner so we could do a side by side comparison.


There's no comparisson between 5 link and the others. With 500rwhp my 5link stays planted and I've NEVER run into an instance where I thought I was going to lose control of the rear. It always feels planted and straight, even when spinning at 100mph. On the other hand I've driven a 302 4link car and thought I was seriously going to spin out and die.

[CraigS]

WEK, my feeling is that your idea of a panhard bar combined w/ the Dougherty idea of worn out UCAs might have some merit. This could be step one in a conversion to a 3 link. You would, of course, need to put up w/ wheel hop or skip burnouts. I agree w/ MikeN that it is hard to beat FFRs 3 link but it would also be easy to do you own if you want. I have done a 4 link to 3 link conversion twice and my one recommendation is that you commit to removing the passenger seat and cutting a nice big access hole in the aluminum for that chassis mount. I considered the 5 link because I thought it would be gun to mess w/ the pivot/roll center height. But one thing I didn't like was adding all that weight to a solid axle that already has way to much unsprung weight.

[skullandbones]

If you add a panhard bar I believe it is going to try to dictate a different roll center than the existing 4 link and at some point the rear suspension will end up fighting with itself :( As an aside some of the Mustang guys used to add a panhard bar and remove one of the upper control arms to create what was often called the "poor man's 3 link". I can't say what the result might be if one were to try this on one of our cars.



I remember having a conversation with Mark Daugherty a few years ago regarding snap oversteer in the 4 link. He said the best way to minimize it is to "get a set of donor upper control arms with the loosest most worn out rubber bushings you can find"!

Jeff

Did a little search on the PM3L. It's fascinating how hot rodders will find a way even if they don't have the coin to do it conventionally! The funny thing is, there was almost no bashing of the PHB. Just a consensus more or less to do something along with that. I had seen the acronyms but didn't know what it was all about. Thanks Jeff. BTW: have you had similar results in AX as Mike with the 4 link or have you always had something else?

One thing this discussion tells me is you probably need to give your 4 link some TLC periodically. I will be under it, lubricating often. Also, I saw something interesting yesterday at this fabrication shop I do business with. It is a small racer with all sorts of technology on it. I was looking at it's three link which gave me a possible idea for making the 4 link work a little better. QA1 makes a heim joint that has 36% misalignment capability and it is rebuildable. I was wondering if I installed those at the diff end of the UCAs would that give the arms a chance to pivot more when bound in a hard turn. I've seen the complete adjustable UCAs with heims at both ends but they are almost half the price of the FFR 3 link. So it puts the argument for the 3 link in a very good light.

[Jacob McCrea]

If you installed a pan hard bar on a 4 link that was parallel to the diff and spanned the width of the diff (to reduce the arc) would it have a positive effect on the 4 link? Do you think it would reduce the binding of that V shaped configuration of the upper arms? I've been thinking about this for some time. We used to use this sort of setup on hot rods. Can't say it is an apples to apples comparison but we did get some improvement in handling with the addition of the bar. To rephrase that, we got some stabilization from the bar and at that time most people called it a stabilizer bar. WEK.

For what it's worth: I have a 1994 Nissan Pathfinder; the rear suspension is a 4-link setup with a Panhard bar spanning most of the width of the differential. The lower links are parallel and the upper links are "triangulated" at a slight angle, maybe 15 degrees. Apparently there isn't enough triangulation in the upper links to locate the differential laterally, unlike the old Fox Mustang, etc. suspension, hence the need for the Panhard bar.

The rear suspension has always been very harsh, despite pretty soft springs. After reading Jeff's comments about the "poor man's three link" I removed the left upper control arm, making the suspension, at a basic level, about the same as an FFR three link. The result is that the suspension is much smoother over railroad tracks and the like. It seems like there is a little more body roll, which I would guess is because the 4-link and the Panhard bar are no longer binding/fighting each other. Bottom line: it was a noticeable improvement, with no noticeable downside, and I am not putting it back on.

Here is a question for the suspension experts: in the best-case scenario, should the Panhard bar be perfectly level? On the Pathfinder it is not, and I seem to rememeber something in a Carroll Smith book suggesting that it should be level. I will take a second look at the book but would appreciate any insight.

[Mike N]

Here is a question for the suspension experts: in the best-case scenario, should the Panhard bar be perfectly level? On the Pathfinder it is not, and I seem to remember something in a Carroll Smith book suggesting that it should be level. I will take a second look at the book but would appreciate any insight.

If the panhard bar is not parallel to the ground you will get vertical (jacking) forces under cornering loads. For a 4x4 with typical off road (low traction) tires the bar would probably have to be quite a way off before you would notice it. The vertical force would be the tangent of the angle multiplied by the lateral force so for 10 degrees at 1G on the roadster with 1200 lbs on the back axle you could get more than 200 lbs vertical force which at the limit you will definitely feel.

[skullandbones]

I read similar info in two racing articles I found. Don't remember how the FFR PHB is placed. BTW, was that "Tune to Win" you read about the PHB? I am going to get that book even if it is a little old. That's pretty neat to be able to experiment by doing the PM3L on your Pathfinder.

I have recently gotten some inspiration to eventually try modifying the 4 link. It's a little Mod Light racer (1100#). It's small but has a lot of cool technology on it. Notice the PHB is parallel with the solid axle.


Enjoying the input on this subject,

WEK.:cool:

[Jacob McCrea]

Mike, I appreciate that detailed explanation. If I get some free time in the next few months I may level the Panhard bar and also switch the upper control arm to the other side and see what happens. Oddly enough, one of the custom links I made for the IRS on my Coupe is the same length as the upper control arm, and I may also install that to see what happens.

WEK, yes, the book was "Tune to Win." Unlike "Prepare to Win," some of the book was "over my head" as I don't have the engineering background (or racing background) to fully appreciate some of the content. Still, it is a good book and I would suggest it.

[Johnc1]

I have that set up on my MKll, 4 link with a pan hard that is parallel with the axle and the bottom links are parallel with the ground. The upper links are triangle and coil overs. Ford 9 inch and webbed housing.
All street driving but handles good. It dose ride hard on railroad track crossing and such. For drags it work great. The launch is striate every time and wheel spin is easy to control.
I would like to try a 5 link. All I have talk to like it.

[Mike N]

Hi Johnc1, where in NC are you located?

[skullandbones]

Hi John,

Do you have any pics of your setup that you could post? It's pretty tight under there. I would like to see how you accomplished that task.

Thank you,

WEK.

[Johnc1]

Hi Johnc1, where in NC are you located?

I am over in Currituck about 12 miles north of Nags Head. I see you are in Mooresville.

[Johnc1]

20294
Hi John,

Do you have any pics of your setup that you could post? It's pretty tight under there. I would like to see how you accomplished that task.

Thank you,

WEK.
Does this help? Some one out there may know this set up.

[Johnc1]

Hi Craig how are things up in Shady Side?

[skullandbones]

Yeah, that does it. I like that. Not much stock. Looks like the triangle bracket is the most efficient way to put the PHB down where it needs to be to get it parallel with the diff. Nice job!

Thanks, WEK.

[Johnc1]

Yeah, that does it. I like that. Not much stock. Looks like the triangle bracket is the most efficient way to put the PHB down where it needs to be to get it parallel with the diff. Nice job!

Thanks, WEK.

The upper links are adjustable to get the pinion angle.
You want to make sure you install your upper link mounts so you can get the adjustment you want. I could use a little more adjustment.

[skullandbones]

I'm still thinking the spherical rod ends at the differential end of the UCAs will be a good first step to see if the binding can be alleviated for the stock 4 link. I have seen a good candidate to replace those ends.

http://www.qa1.net/qa1_motorsports/industrial/rock-ends/mr-rock-ends.html

They may be a little overkill at 1 1/4 inch but I'd rather be safe than sorry. I will cut the end off and weld nuts to accommodate the "rock ends". Then we will have to see if there is any observable difference. What I'm thinking is it may be more difficult to catch the 4 link doing bad things until it's too late (from some of the comments: snap steering and sudden release that throws the rear around). Don't know how to check that out without getting into trouble. Any practical advice on how to demonstrate issue such as what speed and conditions that repeat bad behavior? Any help will be appreciated. Thanks, WEK.