G body suspension help....

[85GPLEf41]

It's been awhile since I've posted on this forum and i'm tired of searching figure I would ask the experts on their opinions...here is what i'm working with, its a 1985 Grand prix:



99 ls1 all stock except for ls6 intake
t56
g body jounce bars, and GP bar brace and gp fender braces
18x8 245/40/18 front nitto nt555
18x9.5 275/ 40/18 rear nitto nt555
Vette C6 front on 98 zq8 spindles rear c6 as well
36mm 1le front sway bar no rear at this time have stock one though
8.5 GN rear stock gearing
stock front end rebuild consisting of energy suspension bushings Napa problem solver balljoints upper and lower, Brand new moog inner/outer tie rods, center link and idler, stock f41 gear box unknown drop F body drop springs but do have new Hotchkis front 1in drop springs as well didn't install them as I like the rake it has now..
rear:
Hotchkis springs 1in drop springs, Hotchkis upper and lower drag race control arms with support braces Edelbrock ias shocks front and rear with rear homemade relocation brackets.

Here is my dilemma, It handles real nice BUT steering is real "twitchy" high speeds and car bangs at every crack in the road... rear left side tire rubs when making a hard left turn... almost to the point of ruining my tires! So I got a decent deal on some spc adjustable upper a arms and, planning on getting the lowers to compliment them as well. From what I've read ride tech is a good coilover conversion shock spring, what ball joints? spring rates? double or single adjustability.... should I keep my current springs? I'm somewhat on a budget but if need be i'll save my pennies and get decent stuff been eying the afx spindles!!, but I would rather spend it on my Future 408.. any tips or advice greatly appreciated I've searched and my head hurts! i

[marolf101x]

http://www.ridetech.com/store/musclecars/?subcats=Y&features_hash=V283.V328

[carguykeith]

If I had it all to do over again I'd go ridetech truturn/musclebar with shockwaves all around, but it is a lot to swallow all at once.

Here would be my suggestions from cheapest to most expensive:

1. Tall "pro forged" upper and lower ball joints and those hotshkins spring you have already in the front with a hellwig adjustable antisway bar (p/n 55809 and amazon was the cheapest when I got mine) and Edelbrock adjustable UCAs in the rear.

2. Same as above but add tubular upper control arms in the front and non-adjustable loweres with at least one "johnny joint" in the rear. Along with single adjustable shocks all the way around.

3. The level 2 coilover or shockwave system linked above (whichever you can afford).

I've always heard great things said about Mark at SCandC and found his book to be a GREAT read. This of course is just my opinion and you know what they say about those...

Oh and a 275 in the rear is CLOSE without a rear frame notch, I assume you roller the fender lip already? Have you measured to see if the rear is centered to the frame? If its not you'll need all 4 rear control arms to be adjustable to get it centered.

[SSLance]

I'm guessing that your car sits pretty low Ernesto? You might be bottoming the suspension out causing some of the twitchiness. How much bump travel does your front suspension have now?

Regarding the rear and tire rubs, double adjustable upper and lower control arms can be used to square the axle up in the frame as well as dial in the pinion angle. I have run 275s on my car for a long time and with the right backspace they fit fine with no rubs. I did have to move the axle over just a touch though as it was not square in the frame when I started.

[85GPLEf41]

thanks! for your responses! I priced the kits above from ridetech which means the upper SPC arms wouldn't work right? I was considering the lowers as well but seems like it's not gonna work with coilovers... so for know option one or two is my choice.. I haven't rolled the rear fenders but gonna have to do that soon as well as measure my bumpstop travel.. I did have to use a 5/16spacer on the drivers side wheel to clear the frame that doesn't rub the passenger side does. guess i'll look for double adjustable arms for the rear. as for the car lowered but its not lowrider low....lol I didn't do before and after measurements.. here a pic

[carguykeith]

thanks! for your responses! I priced the kits above from ridetech which means the upper SPC arms wouldn't work right? I was considering the lowers as well but seems like it's not gonna work with coilovers... so for know option one or two is my choice..

Correct SPC arms would work for my #1 and 2 above but not with ridetech, since they have proprietary arms for their truturn system.

[UMI Tech]

Hey Ernesto.

We use the Proforged talls along with our arms. We also use various spring and shock combinations and are working on a front coilover system to be released in the next few weeks.

It actually looks like you have a ton of parts already. I think you could get it sorted out rather inexpensively.

Our 1" rear Pro-Tour bar would be a good addition.

Like Lance mentioned, you may need to investigate a bit and find exactly where the twitch is coming from so we can address that.

[T-CHRGD]

I've always heard great things said about Mark at SCandC and found his book to be a GREAT read.

Give Mark a call. He will be glad to go over your options, and what would work best with what you already have.

[Rwolf15241]

Have you boxed your frame yet???

[IMG]https://www.pro-touring.com/attachment.php?attachmentid=105113

[85GPLEf41]

Ramey that Monte reminds me of one of my first G body back in the day same color but nowhere near as sick as yours! I have been following your build thread on G body forum! would your coilovers be compatible with the spc lowers? I have gotten advise as to go with ridetechs arms and coilovers but already spent the moolah on the spc brand new uppers and have a chance to get the new lowers at a good price.... I haven't called Mark as i'm on a budget...lol! but I will. I noticed the twitch is real noticeable at higher speeds and seems like a bump or even a slight turn of the wheel makes it pull to either side. I initially thought it was from the steering linkage with moog parts from rockauto and it took allot of the play out but the "twitchiness" is still there I've been reading possible Bumpsteer?? got it aligned at some shop but I don't think they got it right maybe? as for the frame boxing no I haven't yet my frame has some damage due to some previous owner jacking it up on both sides from the open ends and bending the c channels! grrrrr! I'm on the lookout for a new frame so I could notch and box the frame, as well to replace bushings. Maybe I should start there first before the suspension upgrade!.... Damn! I thought I was making progress!!

[grr456]

I raced a G-Body sportsman car for several years. Ride height is pretty important. We actually ran between 6-1/2" and 7" in the front and 7" in the rear. Either run a dropped spindle or tall ball joints to lower the car back down. Run some toe-out and caster to help with the twitchiness. And finally, bump steer is really bad in these cars. Do whatever you can to minimize it. Howe racing makes an adjustable center link to help adjust bump. A symptom of bad bump steer would be if you hit a dip in the road, the steering wheel will literally slip out of your hands and the car will go where ever it wants.

If you've put aftermarket spindles on your car, then bump could be the culprit...

Just my .02......grr

[85GPLEf41]

"A symptom of bad bump steer would be if you hit a dip in the road, the steering wheel will literally slip out of your hands and the car will go where ever it wants."

yeah it does that or if I turn the wheel a little it over exaggerates it making it wander.... but I have stock zq8 spindles which are basically the same as the g body spindle except for the divorced hub bearing.

[marolf101x]

The bumpsteer inherent in the G-Body is why we offer a TruTurn kit:
http://www.ridetech.com/store/1978-88-gm-g-body.html

Since you have swapped spindles (though they should be the same) you'll want to run your bumpsteer numbers to know exactly where you are.