Road Race car suspension?

[Adam Connell]

Ok, My GN is not and never will be a full drag car... Here is what I do with my car: It's a daily driver, I play with ricers on saturday nights, and I hang out and cruise with a lot of supras, cobras, and other Hight speed High hp cars... We sometimes see speeds that this car was never designed for. I also go to the track maybe 4 or 5 times a year. I need to keep this car on the ground and in control, and the stock suspension isnt cutting it. The front end seems to get really light at 110-120 and it makes me really uncomfortable.

So, where should I begin? Im running 245/255 50-16 Z rated tires on GNX clone wheels to start. So would boxed or tubular upper and lower rear control arms help? The Bushings on my car are supposedly all poly and were replace 10k miles ago.

So would something like THIS package help with a set of 1in lower stiffer springs and new performance shocks?

How good is the stock front suspension?

 

[Gary Wells]

I prefer to individually piece together parts/components for suspension improvements, but if I were to buy a suspension kit, that kit shown would probably be high on the list and Mike and Marianne are the some of the greatest Turbobuick people to do biz with. Outstanding honesty, integrity, price and performance all wrapped up in one retail shop.
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http://www.pro-touring.com/forum/showthread.php?t=23299
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HTH

 

[Top Speed]

I went with the Hotchkis TVS System. It lowered the car 1" all the way around. Car is very stable now at 130+ MPH which is as fast as I have gone in it.

 

[Dewey]

You'll definitely need to get the car lower to get the air from underneath it. If you make a habit of running 120mph plus I'd say the lower the better. The aerodynamics of these cars are only marginally better than a school bus. The kit you're looking at is good. I like the KYB gas adjustable shocks and they're relatively cheap. And if you don't have them, look into all the available body braces, namely the rear seat braces, and the front uppers and lowers. New body bushings with the GNX upgrade make a significant difference in body roll.

 

[UNGN]

I think you should work on the front end before the back end if you want the car to feel more secure at high speeds.

There are lots of dirt track car parts that can be adapted to a street G-body that will make it feel much more secure at high speed.

Lower the front end down with Howe taller Lower ball joints and performance springs, put on good shocks and get adjustable upper control arms to give you 4 or more degrees of caster, swap the rag joint for a universal joint, put in better lower control arm bushings and the handling difference at high speed will be night and day from what you have now.

Then you can go to the back end.

 

[Gary Wells]

FWIW:
On my post above, I did not mean to imply that I had an actual road race system suspension, but a very good street suspension compromise.

 

[Adam Connell]

Thanks guys, yall have put me in the right direction! First things Im going to do are Eibach springs and New shocks, then the rear control arms. We will see after that, Im going to look around for my g-body circle track parts.

 

[TURBOPOWERED68]

i loved the hotchkis front and rear lowering spring kit with KYB's (gas adjust).
it felt great on the high end and not too hard on the bumps.

 

[Ormand]

The aerodynamics of these cars are only marginally better than a school bus.

You mean better than the AVERAGE school bus. Some exceptional school buses are probably more aerodynamic than out old Buicks. It's a big handicap if you are playing with a Supra or a late model F body, at anything much over 60 mph. Lowering the car will help some.
The front suspension was designed by GM for heavy understeer. At that time, their folks believed that understeer was safer for the average buyer, so almost all the GM cars (after the Corvair went away) came with lots of built in understeer. There are several "fixes" for the front geometry, including the camber curve correction from Hotchkiss and Global West, and the taller "U" joints used by Savitsky. There are some trade-offs with some of these, though, so read all the forum info before you jump.

 

[dproberts05]

suspension

If you haven't committed to anything yet, you might want to consider a system from Air Ride Technologies, I've heard thier systems make old muscle cars handle like exotics.

 

[Adam Connell]

I have definately not committed to anything at all, and I have heard the same thing... I completly forgot to check them out!

 

[Gbodyolds]

for the front suspension I highly recommend you check out the stage II kit from Marcus at SCandC (www.SCandC.com). the stuff you showed from fullthrottlespeed.com is made by H&R and while it is good stuff your suspension will benefit a lot more from some Currie lowers and Edelbrock double adjustable uppers. for a good swaybar in the rear stay away from anything that mounts like the factory one, you really want something that mounts more like the H&R bar, but the H&R bar is really a drag bar not a handling bar. Just wait a few months and there will be one on the market from SCandC. the Eibach springs are definately a good choice what shocks are you looking at ? its hard to beat Bilstein's with out going for big bucks on coilovers

 

[Ormand]

for a good swaybar in the rear stay away from anything that mounts like the factory one

Why? What are the disadvantages of the stock mounting? GM liked it, but maybe because it was cheap.

 

[Gbodyolds]

I copyed this from SCandC, it sums it up pretty well.

"There are 2 main reasons why it`s better than a factory style bar. The first is that the rate of a 7/8" dia. factory bar when sitting on the workbench is about 247lbs/in. but when you bolt in onto the 19.5" long lower control arms the rate drops to a really lame 47lbs/in due to all the extra leverage! That`s why there are companies making HUGE rear bars for G bodys. Fact is it takes a bar of well over 1.30" dia. to get the same rate the factory rear bar is supposed to be. But that leads to a problem with the 2nd reason,binding. When the rear axle articulates the arms need to be able to twist to maintain free movement. That`s why hard bushings and solid box tubing arms often cause problems. Now what happens when you bolt a swaybar to the lower arms? In order to twist now they have to bend the bar. The thicker the bar the more resistant to bending and the more the lower arms remain fixed. In extreme cases I`ve seen several bars that broke where they bolt on the arms,it takes a LOT of binding forces to do that! Makes for an exciting ride when they break too!"

 

[Gary Wells]

I run the FTS&S bar rear sway bar, which is virtually identical to the ATR rear sway bar, along with BMR tubular rear fully adjustable UCA's with the spherical bearing at the frame (front) side & factory rubber at the rear side, Global West tubular LCA's with the spherical bearing on the front side & the Del-A-Lum bushings at the rear, Kirban front & rear stock height replacement stiffer springs, installed the missing body bushings with factory rubber, including the GNX bushings, Bilsteins, SCnC Street Comp II package, GTA rims, and I love the way the car now handles with the suspension mods that have been done. Before the FTS&S 1 3/8" rear sway bar, I had the 1" Global West rear sway bar, and the car just simply leaned too much in sweepers such as medium to tight freeway on & off ramps. I would have liked to try a 1 1/8" or a 1 1/4" rear sway bar, but none is made for our cars that I am aware of. I have no detectable suspension bind whatsoever, let alone any that I can attribute to the 1 3/8" rear sway bar. HTH

 

[Ormand]

In order to twist now they have to bend the bar

First, I don't believe that this statement is true. It's fairly easy to look at the LCAs, and the sway bars, and see that the LCAs can twist without bending the sway bar.
Second, I understand that the way the stock bar is mounted doesn't maximize the resistance to roll. But the GM engineers sized it to get the resisstance they WANTED, based on analysis and on testing. So, SC&C is just dead wrong when they state "Fact is it takes a bar of well over 1.30" dia. to get the same rate the factory rear bar is supposed to be" The factory bar provides exactly the amount of roll resistance that the GM engineers determined that they wanted. I've noticed some other errors in that web site, so I'm not surprised by this one.
Just for example, from this very posting. "The rate of the factory bar is 247lbs/in." Anybody who knows anything about suspension design will recognize that the number they quote is for a SPRING, not for a sway bar. The stiffness of a sway bar is in units of torque/angle displaced, NOT in force/linear displacement.

 

[UNGN]

Marcus is just saying a 7/8" diameter bar, mounted to the frame would provide equivalent roll resistance to a 1.3" bar mounted the way the factory bar mounts.

I run a 1.6" herb adams bar on the 2+2 and though I like the reduced understeer, I'm not so fond of the weight and the binding (and the bending forces on the LCA's).

 

[turbofish38]

I run a 1.6" herb adams bar on the 2+2 and though I like the reduced understeer, I'm not so fond of the weight and the binding (and the bending forces on the LCA's).

Same here. I was running some aftermarket square hollow tubes and they are distorted something terrible.Part of the problem is that the mounting holes weren't reinforced like most of the aftermarket arms sold today. Someday I've got to replace them. I'm thinking of those solid aluminum bars. Sometimes I can get away without running the front bar. It kind of makes up for the added weight.

 

[Gbodyolds]

I was originally running boxed stock arms with an ATR bar and tore the arms up pretty bad in a very short period of time, when I switched to Hotchkis arms I went in to a turn pretty hard and 2 of the mounting bolts broke off the swaybar, scary $hit when you hit a corkscrew at 80ish and loose a swaybar. I have since upgraded to Currie arms but I am still using the ATR bar which I really want to get rid of and will be at the end of the year.

anyone want a package deal on an ATR bar and Hotchkis LCA's ? only a few thousand miles on them, be up for sale late 06 early 07

 

[Ormand]

Marcus is just saying a 7/8" diameter bar, mounted to the frame would provide equivalent roll resistance to a 1.3" bar mounted the way the factory bar mounts.

Is that what he's saying? The way he said it, it means something entirely different. And a 7/8 bar mounted to the frame can provide almost any roll resistance, depending on all the other factors involved besides bar diameter. And when you use a statement like:

same rate the factory rear bar is supposed to be

it definitely says that you THINK you know what the factory wanted, better than they do. My guess is that the GM guys got exactly the rate the bar was "supposed" to give. Something about seeing all those race cars with GM design, like the Corvettes at LeMans, that makes me think they do a pretty good job.