[GoremanX]

This is something I've been pondering for a while, and I keep wanting to forget it, but it keeps nagging at me.

I have a complete Fays 2 watts link setup in my garage. It's intended for 2nd gen F-bodies, but I decided to stick with leaf springs on mine, so it's useless to me. It just sits there, taunting me...

Our B-bodies use a triangulated 4-link setup, which also doesn't lend itself very well to a Watts link (dueling roll centers and all that). That 4-link setup is comprised of weak, flexy bits and soft rubber bushings which don't do the best job of locating the axle laterally, but they need to be flexy and soft to accommodate the geometry. It's all very frustrating.

Then I remembered that B-bodies used to come with a 3-link setup, once upon a time. And those cars used a panhard bar to locate the axle laterally. In fact, UMI sells aftermarket top links and brackets for those cars:

1959-1964 GM B-Body Adjustable Upper Control/Trailing Arm- "Banana Arm" - UMI Performance Inc.

UMI Performance offers one of the only on-car adjustable control arms for the rear of the GM B-Body vehicle. This

www.umiperformance.com

So if I converted the rear suspension to a 3-link setup using those bits, then a watts link suddenly makes sense. I can use it to set my own roll center, and the axle would remain perfectly centered all the time without any binding.

As far as I can tell, the only thing I would need to do this is bolt a bracket to the frame crossmember, and weld a bracket to one of the axle tubes (the 3rd link doesn't need to be centered, and historically hasn't been). The only real complication I see is finding room between the rear end and the gas tank to accommodate a watts link. I suppose I should probably also weld the axle tubes to the center section if the top link will be acting on a tube.

I dunno, it seems so simple, surely I must be missing something?

 

[95wagon]

"(the 3rd link doesn't need to be centered, and historically hasn't been)"

Picture the single upper link all the way over to one side , like in line with one the lowers.
That wouldnt work at all, agree ?
The side with no link would move ahead on acceleration. Still agree?

Any position other than dead center will result in varying degrees of the above issue.

It was common practice to add the
" missing " left arm in performace and high horsepower cars.
I have never seen a purpose built custom susp with a single upper that wasnt centered.
Maybe some dedicated only turns one way they might try something weird but that would not apply here.

 

[GoremanX]

This is true, but in that case, a pair of parallel uppers would work, too

 

[Caddylack]

Just a reminder that 2nd gen Dodge Durango uses a factory Watts link.

Also, there are some vehicles that have like an "A-arm" in the center, which is sort of a compromise between a 3rd and 4th link. Older Grand Cherokee, for example.

 

[GoremanX]

Yeah I have a Dodge Durango Watts link here. It's not workable for our purposes. I'm pretty sure they have a parallel 4-link setup, too. And in this case, I'm specifically wanting to make use of the Fays 2 kit I have on hand. I prefer that layout because the bracket bolts to the car so the roll center stays at a fixed point on the car rather than moving relative to the rear end height. But this isn't so much a discussion about Watts links as it is about converting from triangulated 4-link to parallel 3- or 4- link so that a Watts link actually makes sense.

 

[Fred Kiehl]

Like you said, locating it is a problem. There is no space for it. The only thing you can do is make a custom gas tank that costs you about 3-4 gallons of available fuel. If you put stronger arms and poly bushings in the rear, you should have plenty of stability.

If you remove one of the arms, you must increase the strength of all the other parts of the suspension including the mounts for the arms. You could use a "V" arm for the lower that attaches at the top and bottom of the axle to control rotation, eliminate the upper arms, and put your watts link at the front of the center section. The rear brake lines could be rerouted to each arm at the front pivot with a flexible hose, allowing more space for the watts link at the front of the center section. The lower arm front pivots would require strengthening.

 

[SSandman]

I'm not so sure a watts link WOULDN'T work with the factory style triangulated 4 link. You would have to raise the roll center of the watts link to match the triangulated 4 link which would put the bell crank pretty high, but with a rubber bushing in the UCA's to give a little bit more wiggle room it might articulate without bind. Fitting it, especially with the bell crank as high as it needs to be, is another story.

I just don't know what the advantage would be.There would probably provide a little better control of the diff against lateral forces, but if you needed to use rubber bushings then you'd be gaining that at the cost of more deflection/pinion angle movement under acceleration.

I know i've installed watts links on F bodies before and it makes a world of difference compared to panhard bar setups, but panhard bar setups leave something to be desired with the arc movement of the rear during articulation so i think that may be why the Watts provides a much more neutral feel after installation.

I don't see that kind of inherent disadvantage with a triangulated 4 link though, at least not when using spherical bushings at all ends. I think the only major downside to a triangulated four link is the NEED to use spherical bushings to really achieve the best possible axle control without bind and that just isn't very street friendly (for some anyway, driving conditions, tolerance to vibration, how quickly you're OK with having to service suspension parts all plays a role there).

I really wouldn't think the Watts would provide any huge benefit to a well built triangulated 4 link, but then again there was a member on here Tad (ProTools) who ran a panhard bar and reported a big improvement in handling on the autocross track. I wonder how much of that was the panhard bar inducing bind and possibly acting as a sway bar/stiffer spring all in one? Also wonder how well it articulated/handled/drove on the street.


I know i'm pretty happy with my triangulated 4 link setup. I've been through a few different suspension setups to get it right, but I've gotten to the point where I lose my buddy's C6 vette on cloverleafs. My tuner who is a big road race guy and is usually working on ZL1 Camaros and CTSV's couldn't believe how well the car handled while still articulating well over rough roads. .I think part of the comfort part is just the body on frame design, you can really stiffen these cars up without FEELING stiff the way an F body would, rattling your teeth over rough roads, but I also put a lot of care into setting up the rear suspension in a way where I think i found a great compromise between reducing bind, controlling the axle and reducing harshness/vibration. The end result is a rear that seems to articulate better than any of my previous setups over rough roads , insanely comfortable to drive yet allows the car to corner great and seems to handle the 700whp pretty well when the pedal is to the floor.

 

[95wagon]

While I get the roll center ( I work on this stuff)
There are high center cars such as ours and A bodies that defy the perceived logic they could never work well.
Given you make room for it , your Fas2 kit, about the time you deal with it is made for a narrower frame, narrower diff, smaller axles tubes, leaf mount one side, wouldn't it make more sense to sell it and start from scratch ?
Fighting roll centers, opinion, a solid mount rod end watts verses rubber upper arms , I feel the actual working roll center would become the watts height.
Three link , you could build a bolt on bracket that used the two upper bushing bosses plus pick up the rear cover holes .
People have done this.
The real question is does this accomplish anything real world or does it become an engineering exercise?

 

[GoremanX]

I'm not so sure a watts link WOULDN'T work with the factory style triangulated 4 link. You would have to raise the roll center of the watts link to match the triangulated 4 link which would put the bell crank pretty high, but with a rubber bushing in the UCA's to give a little bit more wiggle room it might articulate without bind. Fitting it, especially with the bell crank as high as it needs to be, is another story.

Oh I'm not saying it wouldn't work, I just really don't see the point. Without the adjustable roll center, I might as well just use Johnny Joints in the uppers to get the axle located more positively. And getting the Watts link to match roll centers with the existing geometry seems like a pointless exercise. But none of that is street-friendly.

I don't see that kind of inherent disadvantage with a triangulated 4 link though, at least not when using spherical bushings at all ends. I think the only major downside to a triangulated four link is the NEED to use spherical bushings to really achieve the best possible axle control without bind and that just isn't very street friendly (for some anyway, driving conditions, tolerance to vibration, how quickly you're OK with having to service suspension parts all plays a role there).

That's exactly my issue, spherical bearings and Johnny Joints aren't very street friendly. I don't track this car, but I often drive it aggressively on the street. Nasty, chewed-up Vermont streets, especially at red light intersections or highway on-ramps. I've driven cars with a variety of rear suspension designs, from triangulated 4-link to parallel 4-link with panhard bar to leaf springs to independent suspension. By far, the 4th Gen F-body with a Watts link was the most composed in fast turns. It was like a revelation, and that car wasn't even setup for the track, it had stock control arms with rubber bushings. I'd be perfectly happy with rubber bushings on (boxed) control arms, regular coil springs, a good swaybar, soft-ish shocks, and a Watts link keeping the rear end centered.

Given you make room for it , your Fas2 kit, about the time you deal with it is made for a narrower frame, narrower diff, smaller axles tubes, leaf mount one side, wouldn't it make more sense to sell it and start from scratch ?

The Watts link I have is meant for a parallel 4-link 2nd-gen F-body. It doesn't use a leaf spring mount, both the arms use an axle mount intended for 3" axle tubes, so all of that is bolt-in for most B-body wagons. The entire assembly needs about 3.75" of space behind the rear end. I think that's achievable by dimpling the protrusion at the front of the gas tank, re-routing the exhaust and doing without heat shields. The frame rails (that the bracket attaches to) are farther apart than an F-body, but that's just a simple modification to the bracket. It even accommodates the exhaust pipes already.

Fighting roll centers, opinion, a solid mount rod end watts verses rubber upper arms , I feel the actual working roll center would become the watts height.

The problem there is the binding. When the roll centers don't match on these chassis, the binding becomes bad enough to twist the entire frame.

Three link , you could build a bolt on bracket that used the two upper bushing bosses plus pick up the rear cover holes .

I was considering something like that. Then the 3rd link would be centered, and I wouldn't need to weld the axle tubes. Not sure if there's enough room available to accommodate a 3rd link that's long enough, though.

The real question is does this accomplish anything real world or does it become an engineering exercise?

If it's anything like that Camaro I drove, the difference is pretty amazing.