Suspension Watts Link Question(s)

After a trip to Road Atlanta back in June, I'm considering ditching the Panhard bar for a Watts link, but at this stage Im not sure on which brand or type just yet...hence this post.

I understand the function of the watts link, and the advantages it has over the panhard bar setup, but there are some things that I dont understand about the mechanics:

From my understanding, the watts links operates around a "central" pivot point that allows the axle to articulate around a fixed point, allowing the axle to follow an equal arc when cornering left or right(unlike the panhard setup). What I dont understand is what happens when both the left and right side go up and down at the same time, as when hitting a speed bump with both wheels...how is this motion being transferred into the suspension for dissipation?

Also, I notice that some watts links brands allow for the adjustment of the roll center for vehicles that have been lowered. What I dont understand - is there a limit on how much you can lower the rear of the vehicle, and the effective roll center, without negatively affecting how much suspension travel you have??

Any input would be greatly appreciated.

SpartaPerformance said:

What do you mean? All articulation is done through center pivot whether its a turn or the rear os going over bumps it acts the same way by keeping the rear end fully centered. I too am looking into Watts link setup for my personal car, Steeda is good, Griggs is a reputable company but I haven't heard anything really about them, Cortex seems to a really good unit too. I want to go torque arm and was leaning Cortex but they say adjustable LCA's are required and I'm not looking to get rid of my CHE's.

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I'm having a difficult time understanding the articulation mechanics when both sides of the axle are moving up and down at the same time. I understand there is an impeller/propeller shaft in most models of watts link, but I am having a hard time visualizing the movement path of the rear end - as far as straight up and down movement goes, and the design mechanics involved with what triggers the propeller shaft to rotate one direction or the other when all the pivot links are supposedly the -same- length.

It would seem that suspension travel would be the determining factor on which design would best fit a mustang...??

timjimmy said:

There is one pivot point, which is centrally located on the axle, that has one arm rising upwards and one arm dropping down. These arms attach to a link which bolts to the rear frame: one above the horizontal centerline of the axle and one below it. It does not allow the axle to shift laterally but allows the axle to rotate when one tire hits a bump and when both tires hit a bump, the axle raises straight up and the pivot point rotates on the axle. There are slightly different variations, but they all function the same. Hopefully this explanation helps, but if not, I'll get on my computer tomorrow and try to make some illustrations.

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For the sake of clarity, let's use the example of a watts link where the pivot point is actually mounted on the rear-end housing. The units that I've seen all have a propeller shaft mounted on the pivot point, with a fixed length link connected to the top of the propeller assembly, with the other end connected to the car body, and a fixed length link connected to the bottom of the propeller and connected to the opposite side of the car body. Now, seeing as how the links are connected to the body on one end, that means that the other end is required to travel on an arc for any up and down motion, hence the reason for the propeller unit being able to turn - to account for the arcing effect.

Now, on a lowered vehicle, the body is lower to the ground - which also means that the rear end is also is closer to the body, which means a reduction in suspension travel, right? It's this reduction in suspension travel that has me flumoxed as it pertains to a watts link, as it would seem that when you lower a vehicle and install a watts link, that you lose valuable compression travel, but rebound travel doesnt seem to be limited by anything...so it would seem that there would be a point of binding somewhere between compression and rebound where the watts link is concerned..because the propeller assembly is only allowed to travel so far left or right(90 degrees maybe?).

Hopefully this explains the reason for my question. If I'm glaringly overlooking a function of the watts link operation, please point it out....I'm here to learn.

timjimmy said:

Ah, I see your point now. The problem can be solved by adjusting the length by using adjustable links. Adjusting the length of the links would allow you to set the pivot in a neutral position while the suspension is under ordinary load. Once this baseline is established, there is plenty of leeway for both compression and rebound.

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Ahh..ok. So adjustable links would allow for the baseline to be set relative to the vehicles stance at normal load? So if I understand this correctly, that would mean that a lowered vehicle would(should?) also require a watts link that has a roll center adjustment at the pivot point?