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Suspension setup... theories?

K

kmillar

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I have a '90 FE1 coupe and have upgraded the front brakes. I do want to get more into autocross, I've read Fred Puhn, Herb Adams and kind of remember Guldstrand's ideas on suspensions. I may be generalizing ...Guldstrand and Puhn recommend a high spring rates, then tuning the suspension with sway bars. Herb Adams has a different theory that you keep the spring rates moderate and go for the biggest bars you can get, that way the suspension remains relatively settled over bumps.
Back in the '80's (I'm showing my age), there were some suspension shootouts in some car mags, I've been looking at posts and sleuthing the internet but can't find any hard data comparing one setup with the other.
Does anyone have any articles, personal experience backed up with hard evidence? Thanks
 
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1996 LT4 Collector Edition
Is this car your daily driver, or a weekend plaything? If it’s your daily driver, stick with the stock springs, upgrade to Z51 Bilsteins, and get the biggest sway bars you can find. Change out the rear toe-control rod for something with spherical rod ends, and get a good alignment with as much negative camber in the front as they can give you, probably only a degree or so. Have them set the rear camber to match whatever they set at the front.

At some point, you will also want to upgrade the rubber bushings to urethane, lower the car a bit, and get even more negative camber up front, but these steps are quite a bit more involved.

This is the basic setup on my daily driver. While I haven’t done any autocross with it, it works very well for track days at the local road courses.
:w

Barry
 

Notorious

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Highly modified '95 A4 coupe
I too would do everything else (and have) before stiffening the springs. My spring change will be to coil-overs for a number of reasons. But necessarily having them stiffer is not among them, nor is optimizing the car for auto-X for that matter.
But anyhow, if you're like me and most other beginning auto-X drivers, practice and technique will gain you much more than anything else at this point.
 
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Messages
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Location
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1996 LT4 Collector Edition
I forgot to mention probably the most important thing...... tires! A good set of grippy street tires (not R-compounds, at least not at first) will go a long way toward better handling.
 

c4cruiser

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87 Gold Z52 Coupe 02 EB Z51 Supercharged Coupe
Are you concerned about moving between classes?? Typically, any sort of suspension change in SCCA or NCCC will move you out of a stock class. I'm not up on CCCC rules if you run in that Association, but modding the suspension will get you into some sort of modified class jsut about anywhere. With SCCA, you could install a Z51 suspension, but you have to add everything to your car that came with Z51 to remain in a stock class.

What is the overall condition of the suspension now and what is the mileage on the car? Are things like ball joints, tie rod ends and bushings original? One way to improve the car's handling is to replace these components with new ones.

Tires will be a big help and you can do this relatively cheaply. I run Kumho Escta MX tires for cold days and wet weather for autocross and even for track days. You can get them thru the Tire Rack in 275/40-ZR17 and they do ship to Canada. If you have friends in the States, have them shipped there and get them installed locally) no customs duty, no GST, no extras to you.

If you want to start modding, go with larger sway bars and poly bushing for them. Go with the Z51 sizes. Another mod you can do is the Bilstein Z51-specific shock or if you have money to spend, look at the Koni adjustables, or Penske adjustables.

Also get a Camber Brace from R-D Racing http://www.r-dracing.com/Camber-brace.htm This device is a big help to stiffen the front frame.

This page http://www.vbandp.com/instructions/htmlinstruct/align.htm will give you a good start for alignment specs. But when you go to do an alingment, it's important to have the suspension components as tight as possible. This is where replacing any worn stuff comes in.

Another upgrade you can do is a Z51 steering rack. It offers quicker steering and is a bolt-in. The original Z51 racks came with a PS cooler that is unfortunately no longer available from GM, but you can get an aftermarket cooler from the typical companies that have tranny coolers. I use RedLine power steering synthetic fluid in my 87 and I don't have any issues with hot fluids/high rpm during autocross or track days.

Vette Brakes has some good suspension packages for the later C4's including a version of the suspension used on the Corvette Challenge cars. They are pricey, but VB&P does have good stuff.
 
K

kmillar

Guest
Suspension setup

I am looking to stay in the stock class for now as I need alot more seat time. The car has the VP Advanced street setup for alignment. If someone can point me in the direction of a nice PS coolerwith lines, that would be great as the first time I went autoX'ing , the PS pump made alot of noise, I have since changed out the fluid for synthetic.
Does anyone have experience with adding bigger sway bars and what improvements in cornering resulted. Thanks for the replies.
Does anyone make nylon bushings for the front end instead of poly?
 
S

speedmaster4

Guest
Does anyone have experience with adding bigger sway bars and what improvements in cornering resulted.
?

in general, increasing the rear spring rate, via stiffer springs and/or stiffer anti-roll (aka ''sway'') bars, will increase oversteer (''loose'' in cornering)...increasing the front end rate will do precisely the opposite and increase understeer (aka ''push'', also currently improperly termed ''tight'' by nastycar dimmies)

but this is only a GENERALITY as there are many other factors which are important to cornering capabilities...it is possible that in a few set-ups the opposite effects will occur.

sorry that i can only answer like a tv weatherman, but ''handling'' is a very complex subject.
 
K

kmillar

Guest
Suspension Theories..

Thanks for the reply, as my car has the FE 1, which is the smaller sway bars. I thought one of first things I would do is install a cross brace and a camber barce, see what that does . After that it would be the sway bar route, starting with the Z 51 bars. What do used sway bars go for these days?
 
S

speedmaster4

Guest
here we go again

GENERALLY, a more rigid frame CAN be ''set up'' to handle better than a flexible one.

BUT, your car has already been ''set up'' to the flex characteristics of the ''stock'' body/frame...many hours of testing, with different combinations of spings, shocks, tires,etc. were tried to get the optimum handling package...adding bracing will change the flex character and quite posssibly REDUCE the cornering ability in stock form...may ''feel'' better, but only lap times will tell the real story
 

Notorious

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Confederate States of America
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Highly modified '95 A4 coupe
sorry that i can only answer like a tv weatherman, but ''handling'' is a very complex subject.
Very accurate assessment but still bordering on understatement. :L Handling, like anything else that enhances performance is a series of compromises. Your basic goals are first individual corner weights and managing them during the dynamics that occur when thrashing a car around various types of corners, braking, acceleration and etc. Also, you want to maintain optimum tire contact with geometry, spring rates and shock combinations that limit the amount of time that solid contact is reduced in any number of situations. Complex? Of course it is. But gaining an understanding of just what your chassis is going through is half the battle. Then begin making changes, evaluating and see what works best for what you're doing with the car as well as what suits your comfort level and driving style. There are many good books on chassis set-up that will help anyone, regardless of what they think they know, gain more understanding. It's a very intriguing subject. Read, read, read.
:beer
 

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