torque arm

[LS6 Tommy]

eibach springs f/r, 660lbs/in front, rear ??
GW negative roll system with Del a lum bushings top and bottom.
B body spindle with 1LE rotors
1 1/16 front sway bar with poly mounts and links.
Edlebrock IAS shocks f/r.
GW lower rear contol arms del a lum axle side, spherical frame side,
stock upper arms with stock rubber to limit bind.
stock g body rear sway bar for now, have a camaro style bar setup waiting to install.
i run the car on the street with out the rear sway bar in,
it under steers without it but handles better over rough pavement (less skipping = G's)
but when i push the car, it tends to snap over steer over rougher pavement,
hence why the torque arm set up. as it will allow me to set up the rear control arms to provide roll under steer while providing good anti squat characteristics.
torque arm setup will allow for a better performing suspension then the factory setup.
that is why i am trying to figure out proper setup for the g body.

If they're progressive rate rear springs, that may be your entire problem. The rate increases drastically when the spring compresses to the point where it reaches the stiffer rate coils & it really upsets the chassis. In any event, not knowing your rear spring rate doesn't help for tuning.

If they are single rate springs, I'm thinking they're a little too stiff, along wth a slightly undersized front bar. If the car understeers without any rear bar but has snap over steer on rough pavement, adding a rear bar won't fix it, especially going to a bigger one than stock like the Camaro bar you're intending. It'll oversteer sooner. I'd try an 1 1/8" front bar & no rear bar, that's what GW recommends with your suspension. Then to get rid of the rough pavement rear axle chatter I'd try softer rear springs, better shocks or both. You didn't mention what shocks you had, so it may just be a matter of adjusting the ones you have.

Tommy

 

[6spdmalibu]

i have a 7/8", 15/16", 1 1/16" and a 1 1/4" front sway bars and found the 1 1/16" the best for this setup.
the stock rear is useless in my opinion as it mounts to the lower arms and not the frame with links.
found a '97 camaro rear sway bar that will be experimenting with for FINAL tuning,
after i decide what/how i am going to proceed with the rear suspension setup.
whether it be a 4 link, 3 link or a torque arm rear, just want to make the best handling car possible.
as i mentioned earlier the frame will be swapped, so i am looking at other possibilities for a rear suspension design, before the body is put on. (possibly a 6-10 point cage will be used which will make it harder to change the rear setup later).
contemplating to use either the QA1 or Koni double adjustable shocks in the future.
the rear spring rates are hard to find for the Eibach springs, which are single rate not progressive.
(am going to pull and measure with weights to find out the rate).
these are my planning stages for the build,
as this car is not going to be built over night.


btw the Edelbrock IAS shocks are used now.

 

[LS6 Tommy]

Sounds like you have a pretty good grip on it. The IAS is a really good non-adjustable shock for the $$. You may find that the rear spring rate is just a tad too high. I dunno. It's hard to make any other suggestions without driving/observing the car.

Tommy

 

[liquidh8]

Have you checked out pro-touring.com yet? I asked a similar question some time ago, and did a bunch of searching around. I was gonna either go with a 3 link, or use a torque arm in my wagon, since the body will be off the frame, and I wan't it to corner better for the auto-x. Anyhow, Marc @ SC&C in Jersey, VERY nice guys and helpful, http://www.scandc.com/ was doing road testing and experimenting with a 3-link in a g-body with a bolt-in watts link, which I think is better than a panhard bar, at keeping the rear centered with-out shiftng the rear during hard conering. If anything allowing you to run the max tire possible.


Anyhow, the 4 link with the right uca's & lca's is said to be fine. You really need to have rubber bushings or johny joints in the uppers to keep the rear from binding during hard cornering. Also, you are on the right track with wanting to use a rear anti-roll bar that is NOT connected to LCA's. Marc also has one of those, as does Edelbrock now. You could make your own, there is a thread or 2 on here with someone doing it. I have all the parts already.

Lose the progressive rear coils and b-body spindles.

I know this doesn't answer your question, but there are more qualified people around, especially on pro-touring.com, at making a car corner. Mine corners fantastic, I used the suggestions and research from the guys over on PT.

 

[6spdmalibu]

i agree with you about the watts link being a better form of axle control.
though the pan hard bar is just as effective and cheaper to implement,
not ruling out the use of the watts link, mind you
just that it'll be harder to put a dual exhaust without some tight bends.
i know the b body spindle gets a bad rap also
the braking improvement with better handling, minus the bump steer of course
are still cost effective.
will be pulling the whole car apart and can play with probable solutions for the bump and ackerman steering issues then. could always pull the front clip and mess with the front after the car is assembled.
as i want to concentrate on the rear suspension, which will be harder to modify once the body is placed back on permanently.
i have a spare chassis and body that i can use for mock up anyways.
was also considering the 3 link, but the decoupled torque arm is a 3 link under braking and has better geometry for anti squat that should still fit under the g body chassis, by my calculations.

and yes i want this car to end up a monster at the auto X
also thanks, will check out sc&c & pro touring.

 

[liquidh8]

Sounds like you have a sound plan. Definitely check out those sites. And whichever route you go, take lots of pics and keep us posted. I also have 2 wagons, My turbo Buick wagon is getting a body off, with suspension upgrades happenening then. Taking what I have off the chevy, and changing more. But this won't be or 6+months. Have to get the house done.

I had thought about using an aftermarket Camaro Torque arm, ala BMR, and the watt's link from SC&C. But I have a turbo6 and I dunno if the Y-pipe would clear the torque arm. IMO that would be the cheapest route to go if you wanted to lose the factory 4-link set-up. Especially if you were using a ford-9 since you could weld on whatever bracketry was need to mount the arm.

There is a member on the turobuick boards, username tcharged, who was all his suspension done up with pieces from SC&C. Though I don't know if he has tailpipes or not. From what I understand, you cound run tailpipes with the watts-link from SC&C. You would have to make em fit, but they'll fit. Also, the watt's from them is like 600 bucks. Does cost more that a panhard, but it's completely adjustable.

Your right about the low cost big brake swap with the b-body spindles. Instead of buying that adjustble center link, maybe you could sell what you have, and use the 2000's blazer/s-10 spindle and sealed hubs. You could run the big rotors and use the 2 piston calibers. There have a been a few over on the pro-touring board who done this swap also on g-bodies. Then get the tall upper ball joints. Unless you have the tubular uppers already.

Good luck and keep us posted, I am definitely interested so see what direction you go in!

 

[6spdmalibu]

Forgot to mention that most of these suspension pieces where bought before Y2K.
Except the shocks.
Thought there would be a rack and pinion set up by now for the B body spindle in G bodies. lol
Wishful thinking on my part, i guess.
And yes thought about the S10 spindle swap, as I've only have 30K miles on everything why swap it now, it works well except for the rub at full lock.
But, its the rear that I've got to concentrate on first.

 

[Norm Peterson]

if you want handling go watts link,the panhard bar setup makes the chassis respond differently to left and right hand turns,as for the torque arm I see no benefit from changing the factory four link,the only reason it is on the fbodys is for packing problems there is simply no room for a triangulated four link with the stock floorpan.I have both currently an 02SS as my DD and have had a slew of gbodys and with a decent set of aftermarket trailing arms and bushings I really do believe the four link is the way to go.

A couple of things with respect to PHBs vs WLs.

In anything resembling sane street driving most folks would be hard pressed to tell the difference. You do have to be "leaning on it" pretty hard. Another is the initial inclination of the PHB (let's assume with the driver only aboard, or perhaps driver + half a passenger :lol: ). I have a feeling that as the PHB inclination gets greater, so does the asymmetrical behavior.


The factory 4-link does its job reasonably well for most reasonable driving, but no better. Keep in mind that it was designed at a time where 0.75 lateral g was a pretty decent number (the 'bu's were getting 0.70-ish), as was a 60 mph R&T slalom speed (58.2). And it is not very "tuneable" for cornering. Unless you can move all of the control arm pivots (as in both ends of the LCAs and the UCAs) you are almost always compromising away something when you tweak it to gain something else. Don't forget, the inclinations of the links completely determine the rear roll center height, anti-squat, and axle roll steer. And that with cylindrical bushings, this arrangement is technically "over-constrained", meaning that bushing stiffness will indirectly add suspension stiffness.

In tems of auto-X, the G-body rear suspension has way too much axle roll steer (which adds to the amount of vehicle understeer and in particular makes these cars hate slaloms and offset gates/lane change features). A 4th Gen Firebird (torque arm/PHB) that I drove at one auto-X and the '08 Mustang GT (3-link/PHB) that's now my DD are both far more willing to make abrupt maneuvers such as those. The Fox/SN95 Mustangs, with a rather similar rear suspension at least have a front suspension with an above-grade roll center and a camber gain curve that goes the right way and is better at auto-X for that reason.

The G-body rear roll center is way too high, even for the circle track racers who don't normally run a rear sta-bar. That forces you into using relatively more front roll stiffness to bring the car into balance up towards its cornering limit. It also means that if for any reason you suddenly have better overall grip (concrete vs asphalt, R-compound tires vs all-seasons) you'll suddenly have more 'push'.

I know of at least one individual who has experimented with lowering the rear RCH on a 4th Gen F-body down below axle centerline height, apparently with positive results. I'm not sure what else he did other than swap in stiffer rear springs and a rear sta-bar modified to be adjustable, but I'm sure that he considered the consequences of dropping the PHB on axle steer. Vehicle roll oversteer for a car used in open-tracking = seat-puckering moments at a minimum.


Norm

 

[liquidh8]

Norm, we were hoping you would chime in here.

We were discussing the torque arm I think for the reasons you stated:

A 4th Gen Firebird (torque arm/PHB) that I drove at one auto-X and the '08 Mustang GT (3-link/PHB) that's now my DD are both far more willing to make abrupt maneuvers such as those.

I don't personnaly didn't want to loose floor pan space so I was leaning towards a torque arm set-up, and Watts (I am gonna run as big a tire that fits with out side-side rub), instead of the 3 link. Though the though crossed my mind to get a steeda kit for a newer 'stang and convert it over. I am also gonna keep using the AFCO springs and adjustable spring cups I already have. I like the adjustability in ride height, and the wide variety of spring rates. Maybe upgrade the bilstiens to something adjustable. I also have a narrower rear sta-bar that uses frame mounts for the end links, instead of mounting the the LCA's.

 

[Norm Peterson]

Actually, I'd think that it would be easier to package a 3-link. The pumpkin already has ears that could be at least part of the axls-side attachment, and the frame crossmember has brackets that you could attach a chassis-side attachment to. There's a bit more to it, but the hard points already exist. At most, you might end up clearancing the trunk floor depending on where you actually spot the axle side pivot.

As to that not being an optimum 3-link arrangement - that's entirely true. "Optimum" would likely include frame mods radical enough to fit lowers of perhaps 40" long and maybe a 30" long upper. But working with the existing G-body hard points won't make it at all a 'poor' arrangement. The S197 Mustang works very well with very similar link lengths (the 2009 Track-Pack equipped cars are good for mid 0.9x lateral g and somewhat better than 65 mph slalom speed on 255-wide tires. On the aftermarket side of things, a 3-link that was designed around lower arms that converge much like the OE lower G-body arms do is part of Steve Rupp's very competitive 1968 Pro-touring Camaro (it goes under the name "Bad Penny" and has been either mentioned or featured in a number of the magazines). Marcus' upper link prototype was very similarly configured.

In the Mustang, I've been into the brakes hard enough to invoke ABS action and even an "ice mode" of sorts and it hasn't brake-hopped on me. There's a slight chance that that could change if I was at all oriented toward drag racing and relocated the rear lowers with relo brackets for more anti-squat. But I haven't heard any complaints of this happening on two or three forums that cater to or are oriented toward Mustangs.

I think that as long as you aren't looking for big anti-squat numbers, brake hop may be less of a problem with a 3-link than with a torque arm. I'm looking at rates of change in antisquat per inch of suspension movement here, and the general thought is that a suspension that gains (say) 50% antisquat per inch of upward suspension movement is at far greater risk of developing brake hop than a suspension that only gains 5% per inch. The geometry simply yanks more load off the tires faster.


Norm