watts link clarification

[IMPALAMAN1]

Using a watts link on my setup on a 1968 Impala. Rear suspension is a factory 4 link style setup. My question comes at the addition of a sway bar. Is it customary to run the watts link with a sway bar?

setup:
global west custom lower control arms for air ride. umi tubular uppers not adjustable. fays 2 watts link.

Thanks for the help,
D

[XLexusTech]

NO a sway bar and a watts link are not common..

[stab6902]

I agree that it's not particularly common to see both, probably because there's usually not a lot of extra real estate available for a nice sway bar setup when you add a watts link into the mix. With a watts link, you can raise the roll center height easily, which can negate the need for a sway bar, but that comes with undesirable side effects.

If it were up to me, I'd run both a sway bar and a watts link if you have that option. Keeping the sway bar will let you get away with a lower spring rate and a lower roll center height for better grip in bumpy corners. Plus, the lower spring rate will give you a better ride.

[iadr]

If you want a Watt's link with a lower roll center then you re-configure the center link and it becomes a Mumford link

[carbuff]

I don't know about customary, I don't think that a lot of cars run a Watt's link, but the two serve different purposes and are complementary. So I would use both if you and are after performance and tunability.

The Watt's link primary purpose is side-to-side location with the secondary benefit of rear roll center height control.

The sway bar is there to help control roll/body lean, and with adjustable arms is yet another tuning tool.

I have both on my car (71 Firebird). A good bit of work went into packaging the bar install. There's not a lot of room back there but it certainly can be done.

[jetmech442]

I don't know about customary, I don't think that a lot of cars run a Watt's link, but the two serve different purposes and are complementary. So I would use both if you and are after performance and tunability.

The Watt's link primary purpose is side-to-side location with the secondary benefit of rear roll center height control.

The sway bar is there to help control roll/body lean, and with adjustable arms is yet another tuning tool.

I have both on my car (71 Firebird). A good bit of work went into packaging the bar install. There's not a lot of room back there but it certainly can be done.

^^^My thoughts exactly. I set up my 69 442 with the hellwig bars front and back and loved the improvement. Then I installed the Fays2Watts. The addition of the Watts was primarily to prevent the axles lateral shift allowed by the triangulated 4 link, but soon found that the adjustable roll center allowed me to tune the car's under/oversteer with a single 3 minute bolt change.

For what it's worth, Ive never adjusted the rear bar, I set it to SC&C's recommended hole and use the watts for tuning.

[SSLance]

First off, I suggest you watch this video of a 4 link suspension and what happens when a watts links added.

https://youtu.be/EDM9_-4kjHg

The only way to NOT restrict travel is to use super compliant rubber bushings at all control arm mounting locations. I know some have been happy with this compromise, I just never could get past it once we did the test shown in the video.

[stab6902]

First off, I suggest you watch this video of a 4 link suspension and what happens when a watts links added.

https://youtu.be/EDM9_-4kjHg

The only way to NOT restrict travel is to use super compliant rubber bushings at all control arm mounting locations. I know some have been happy with this compromise, I just never could get past it once we did the test shown in the video.

Excellent video, thanks for sharing. Makes you wonder how much of the rear roll-stiffness tuning people do with a watts link is actually due to roll center height change vs introducing / removing bind during articulation.

[carbuff]

Excellent video, thanks for sharing. Makes you wonder how much of the rear roll-stiffness tuning people do with a watts link is actually due to roll center height change vs introducing / removing bind during articulation.

Lance can correct me if I'm wrong, but I think the issue demonstrated in that video is specific to the 4-link. The 4-link itself is working to keep the axle centered, or at least under control (as it appears to move quite a bit without the Watt's). Thus the 4-link is fighting with the Watt's link unless their roll center heights are matching. When the bellcrank was lowered, the roll center heights were very different and were in contention.

On a 3-link or other suspension that doesn't have another means of side-to-side location, you wouldn't have that type of binding.

[stab6902]

On a 3-link or other suspension that doesn't have another means of side-to-side location, you wouldn't have that type of binding.

I totally agree. I was referring to the triangulated 4 link cars we've been discussing in this thread (GM A, G, and B-bodies).

[SSLance]

Look at it this way, the only way a watts link will work without binding on a triangulated 4 link setup is if the roll center on the watts is very close to the roll center of the 4 link. When you consider that...what's the sense of even putting a watts link in then?

[dontlifttoshift]

B bodies aren't triangulated enough to call them triangulated, they have a panhard bar stock.

To the OPs question: Rear sway bars or anti roll bars are tuning tools. The need for an ARB is independent of what type of lateral locating device you are using on your rear axle.

[stab6902]

Good point Donny. I had the later B-bodies in mind. I think 1971-1996 were triangulated with no panhard bar.

[SSLance]

B bodies aren't triangulated enough to call them triangulated, they have a panhard bar stock.

Thanks Donny, I did not know this...

[JustJohn]

The LCA's are parallel enough for these cars that it's a common anti-sway bar mounting point. I looked but unfortunately don't have a clear picture of the rear suspension at the moment.
Here it is:

[jetmech442]

Look at it this way, the only way a watts link will work without binding on a triangulated 4 link setup is if the roll center on the watts is very close to the roll center of the 4 link. When you consider that...what's the sense of even putting a watts link in then?

A quick observation on that really nice vid is that this situation is worsened if the car is lowered(roll center moves into the trunk, or if you have antisquat relocation bars(combined moves it reallly high in the trunk).

I have about a years worth of driving while running the triangulated 4 link and the watts installed simultaneously before I burned in a 3 link setup. Below are some of the pro's and cons I noticed.

Pros:
Lateral stability improvement was massive. When you dip into a corner with the stock triangulated 4 link, the body shifts, then the axle, then they play a small round of ping pong before stabilizing, which makes each corner a guessing game. The watts addition made jumping into corners so much more stable. I should mention by this time I was alreayd running SC&C stage 2 up front. I also had an issue with rubbing 295's because the axle was shifting over 3/4 '', which was cured by the watts.


Cons:
Two Roll centers. As you move the roll center down on the watts to gain more rear traction, it fights the roll center defined by the upper arms(this is confirmed by the video Lance linked(thanks btw). Usually, protouring cars don't run more than 3 or so inches of travel, so it's uncommon for the axle to articulate so much you start putting twist into the frame. Well. at least for most positions of the watts bolt-when I ran mine all the way down on the street and drove aggressively I noticed that before mid corner the rear end would bind, then unbind sometimes later. Really not a great feeling, but those lowest settings really shift the car heavily into Understeer, so the nice balance is up near the middle anyways.

After about a year, I converted the rear to a 3 link. although the fighting roll centers definitely played a role in the decision, I also wanted to adjustable antisquat, and new gears and a bunch of other stuff.

MY experience with it, knowing what I know now...if I couldn't add the 3 link, I would still add the watts, just for the stability it provided and a way to control the roll center to create a more favorable roll axis.

again, this is just my experience with using this setup for a while, hope it comes across that way.

Your Quarantine Pal,
Scott