chevynation

iTrader: (8)

Just wondering what you guys think about the f-body rear suspension design (not the components... everyone already knows they suck). Seems to me like GM put a lame setup under the car to gain a bit of interior room and maybe save an extra buck or two. Compared to say an irs or even a nascar truck arm design, the f-bods (with their short LCAs) encounter serious geometry issues as the rear end goes through its travel, causing mean wheel hop under accel or even a "jacking effect" in sharp corners that I think heard Mr. Strano mention, plus all the unsprung weight of the solid axle keeping the tires from being planted in bumps.

Seems like the truck arm design (with its looong trailing arms) would be a better way to go. Its cheaper than an irs to make strong (ls1 torque likes to break stuff), maintains better geometry through susp travel than current f-bod design, can pretty much eliminate the need for a slip yoke in the driveshaft (maybe not a big deal?), and doesn't need a torque arm (no more stress on tranny tail). Of course, it too has a lot of unsprung weight, and also doesn't keep the rear perfectly centered during travel due to the arc of the panhard. The irs doesn't have these problems, but there's obviously something difficult about it, look at the wheelhop/traction/strength issues with the GTO and 03-04 Cobra (Vette the exception?).

Maybe someone could elaborate on other designs, ie four link (which I know nothing about), or ways to make the f-body design drag well and road race well AT the same time.

Erik

SIK02SS

iTrader: (11)

do a search, this has been beat to death

trackbird

iTrader: (4)

He's right, it's been covered here before.

The Mustang guys change their fox bodies over to a torque arm suspension (Griggs) in many cases for road course duty. The F-body suspension design is probably more capable for drag and road race as it is designed than it would have been to use most other available options. A watts link (replacing the PHB) would help the jacking issue. Longer control arms will need to be stiffer to avoid flexing, so you're going to add weight. The torque arm on the transmission housing isn't a big deal for most people. I'm sure someone has broken one, but I can't think of any that I've seen posted anywhere (but I don't look too hard for such things, you might find 20 threads in a quick search that I haven't read).

The Mustang IRS isn't too good for drag and the geometry isn't too good for road racing. It's heavy and complicated without much gain (it seems to ride better, my old room mate swapped his 99 gt to the IRS setup....which he got from a friend who was drag racing a Cobra and wanted rid of it).

The Mustang stock suspension is a modified 4 link that binds during body roll. They can drag race ok, but it's not a great setup for handling performance.

The 3 link in the F-body is probably the best compromise of all of them, even Ford seemed to agree since they put it under the new Mustang.

Just my random thoughts.

subtlez28

iTrader: (15)

trackbird covered every thing I was going to say.

And saved interior room and cost matters to most F-body owners....otherwise they would have a Vette, right?

eLTwerker

Watt's link...is that a form of IRS?

trackbird

iTrader: (4)

It's to keep the axle centered under the chassis. It's like having two short panhard bars that connect to the center of the axle (often the differential cover or a bracket that connects to the axle housing in the center). That way the loads are balanced and the car can't rise or squat as it loads the phb.

Here's a watts link (added to a Fox body or later Mustang):

eLTwerker

Few questions about that pic. Is it a 4-link? What are the "links"? Also, is that a strut? Is it also a coilover?

slick1851

I want this thread to keep going

chupr0kabra

iTrader: (10)

Maybe this will help with some of the terms. I know I found it helpful.

http://www.popularhotrodding.com/tec...pension_guide/


-Mike

trackbird

iTrader: (4)

Actually, that's a Mustang that's been converted to a basically a 3 link (like the F-bodies), but they replaced the PHB with a Watts link. If you look at the side view, the torque arm is bolted to the bottom bolts of the rear end cover and up to the preload studs in the center of it as well as being bolted to the webbing on the axle housing next to the pinion gear/yoke. They use lower control arms like we do, a torque arm and remove the top links from the axle. It is also using a coil over conversion in the rear to get the rear springs off of the normal Mustang location of putting them on the LCA's.

The linkage you see where we'd have a PHB is called a "Watts link". It's like a PHB that's connected to the chassis on both sides. The place it's connected to on the cover is a pivot point, as one side pulls, the other pushes and that is a bar that has a bolt through the center to balance the force. It's another way to center the axle under the car, but you don't see the "jacking" problems that a PHB has. And, the rear roll center will be where ever that pivot bolt is. You can see that there are several locations for it and it is adjustable to tune the chassis.

eLTwerker

That's bad ***.

Dragula

iTrader: (5)

Here's a standard Panhard and Watt's link in motion:

eLTwerker

that pic looks like its got a standard PHB and a Watt's link.

Dragula

iTrader: (5)

yep, the left one is standard panhard and the right is Watts

eLTwerker

No I mean the pic that Trackbird posted.

chupr0kabra

iTrader: (10)

That upper brace isn't a panhard bar, if that's what you mean. It's just to reinforce the mount points where the Watts link bars connect. The rearend is in front of that and moves up and down freely.


-Mike

eLTwerker

Thanks for clearing that up.

So, are shocks/struts/coilovers ever considered a "link"?

Dragula

iTrader: (5)

They also say the lower the pivot point on the Watts system or the lower the panhard bar = lower roll center. You want to becareful because you want the rear and front roll centers close or the car will pitch and yaw when cornering.