Now, all your Vette fans may get a little upset at this topic, but here it goes:

I own a 1991 BMW M5. Wonderful car. It is probably the best handling car I have ever driven. I also own a 1984 Corvette. Although the cornering and ride is stiffer in the vette, it doesnt handle as well.

I live in Sicily, Italy, and for those of you who do not know, road rules are not enforced here. Imagine driving PCH with no cops! Driving here is the next best thing to driving on a track. I have had the opportunity to put both cars to the test.

Reading this forum, I see a lot of tips about speed and acceleration modifications. There is not too much about suspension tuning.

My vette is totaly stock, can anyone suggest some mods to make it better than my M5??

Bill

:cheers:

 

R-D Racing's camber-brace and cross-bar. Both have a GP going on until August 31. Also, Dave at R-D Racing has an 84 that he autocrosses, give him a call, I'm sure he can answer all of your questions.

www.r-dracing.com


[Modified by STL94LT1, 11:43 AM 8/25/2002]

 

On the Dutch forum we did cover this recently. The original shocks are to weak. You need for example Koni's to improve the handling.

An other solutions is to install coil-overs or even better have custom made coil-overs and adjust the subframe.

I think you should start on the shocks. Try progressive ones. More comfort on the day to day ride and when you want to rock it will adjust.

The first C4's where very stiff, but in the US didn't like that so GM made it softer. Koni's will make te car the way it was mend to be, i gues!

 

If your going to compare an 84 to a 91 maybe you should compare your 91 to a 98 also. :rolleyes: just a thought : :cheers:

 

Go to www.dougrippie.com he has tons of suspension mods there. including coil overs

 

ET1bill, i agree with you. I have a beautiful low mileage 89 convertible. I love the car, but it's scary at high speeds. Apparently the models that you and i have are famous for having "Nervous Steering". I recently purchased the Camber Brace from R-D Racing. Dave was also gratious enough to send me alignment modifications that he said will make the car handle like it should. I installed the brace yesterday, and having alignment done next week.

I used to autocross a 71 Porsche 911. That's pretty old technology, but that card handled better at high speed than anything else that i've owned.

I like a lot of things about the Vette, so i hope i can get to to hold the road like it should. I will try to make a post about the results after the aligment.

 

Also install polygraphite sway bar bushings to improve cornering with little or no effect on ride quality.

 

I can second the comments on stock c4 handling. I owned a 78 Alpina BMW 535 between 2 Vettes (69 and 95). Alpina is the BMW equivalent of Doug Rippie or Lingenfelter, and was the forerunner of the M5 today. The characteristic of German high performance handling most missing from a stock Vette is that the rear end stays put. It tracks the front without fail unless you induce power-on oversteer with the throttle. What the track guys call transition handling. Stock C4 Vettes are twitchy and tend to lose the rear end in a corner, IMHO.

The good news for Vettes is that Doug Rippie figured this out years ago. A few years back in a Road and Track test of 7 modified Vettes on a track, the DRM car "felt like it was on rails" and outhandled all others, turning in the best lap times. The secret is three mods to the rear suspension- new trailing arm brackets, new camber brackets and a rear steering knuckle modification. Together these tame the Vette's rear end. Shocks, springs, sway bars, coil-overs alone won't do it. The basic geometry of the rear end needs improvement. I am sure other Vette tuners now understand this as well.

With the DRM modifications on my 95 (as well as the Camber Brace and a Roll Bar), it now feels like a German BMW, but at a higher level of hp and g forces. My BMW felt in control at 0.9 G. My Vette now goes 1.1 G on Goodrich KD's with the same feeling of being in control. 0-60 in the BMW was about 5.7 sec. The Vette is 4.0 sec on a cool day.

I am so envious of your being able to let it all hang out anytime you want on the highway. Texas roads are too straight and way too crowded.

Keep it on the pavement.

 

I've been autocrossing my 86 Coupe in SCCA BSP since 1998. I started off with the stock suspension on this base coupe. I then put on Poly bushings (except for the rear trailing arms) all around and listened to all the hype from Vette Brakes about their "Sport Springs" and put them on. The car was very stiff and the rear end would step out anytime I got on the throttle.

I went to a driving school put on by Evolution and had Sam Strano drive my car. He said the rear spring was way too stiff. He said to go back to the stock rear spring and see how that worked. I made that mod and it handled a lot better, but still had a lot of oversteer. At the first event this year, I decided to disconnect the rear swaybar and have just loved the way this awakened my cars handling. Now I can get on the gas in a corner and the rear end stays glued unless I just hammer down on the gas.

I run the Koni Sports (yellow) in the front (1/4 turn hard) and Koni reds in the rear on full soft. BTW, my wife likes riding in the car a lot more with the softer rear suspension, too. Also, the car takes on bumps without the usual C4 drama, now.

My next experiment will be to go to the 96 base spring which is the softest of all C4 rear springs.


[Modified by Stealthvette, 3:14 PM 8/25/2002]

 

Just to add another thought. Notice the progression of the stiffness of the suspension of C4s through their evolution. The 84 had a very stiff suspension with the rear almost as stiff as the front. In 89 the Z51 suspension had a much stiffer front than rear. By 96 the rear spring was very soft.

I have found that a quite stiff front spring coupled with a soft rear spring with no swaybar is a great way to make the car handle better in real world situations as well as autocross.

You'd think that this would make the car into a wollowing pig. But it hasn't happened that way at all. In fact the stiff front spring coupled with soft rear with no swaybar insures that power can get to the ground effectively coming out of corners and stay glued to the pavement on rough surfaces.

 

I'm not. Koni and other are producing adjustable dempers. On top of the demper you can turn a **** stiffer or more comfort.

If you want grip you need a stiff car. 91 had these installed but they are still not as stiff compared to for example Koni's.

 

Stealthvette, now that is some interesting and unconventional thinking, I'm very intrigued about what you have done. Does it just improve the tracking "feel" or in fact has it proven to make it faster on the track. Well hell, isn't true that NASCAR does not use rear sway bars?

Thomas

 

I've not been too happy with my FE1 suspension and was seriously thinking about bolting on Z51 parts (95 C4)

But I just had it aligned by Dick Guldstrand without any
major modifications and I would estimate that cowl shake and steering
shudder common top-down driving are reduced by 75 %. I'm not
saying its ready to run slolem but its pretty darn tight now.
No doubt bigger, stickier the tires exaserbate alignment problems.

BTW anyone looking for a vette shop in the L.A. area, check out
Guldstrand. They're very good at what they do and they know why you
drive a vette. :cool:

 

I know what your all saying. The first few years of C4 was a little oversteer happy. I have an 87 with the base suspension. The rear is about three times stiffer than it needs to be. The Front is kind of soft. I am considering a softer rear spring and stiffer front spring. Of course, even doing it is a different story.

 

Well, I autocross with Atlanta SCCA which averages 180-200 drivers per event. Last year I was finishing in the top 20 with the swaybar attached. Now I'm finishing in the top 5 overall at every event using the PAX handicapping between class factor. So, yes, the car is handling better at the track. I'm going to the national championships for SCCA in Topeka next month and will find out even better how it works.

Here's the deal. Top Z06 drivers in SCCA Stock classes (autocross) are dialing in close to half inch of toe-in on the rears to get the rear end to plant in the corners. What does that tell you? It tells me that the Z06 is an oversteering pig in stock form so the hot drivers are doing this extreme measure to plant the rear. In their class they aren't allowed to change the suspension except for shocks and alignment settings.

In my class all that is free. Conventional thinking is "stiffer is faster." I used to believe that, too. Until you really start to think the problem through. Corvettes have huge amounts of torque that can't be used in most of our cars on a handling course because the rear end is too tight and making everything skittish back there. The problem is that a stiff rear tends to transfer weight towards the front of the car. Some tuners have compensated for this by making the front even stiffer and then throwing $4500 shocks at those stiff suspensions to control everything. So, I decided to experiment with a different direction and it has worked marvelously for me on my 86 coupe. Having a stiff front spring and soft rear spring and no rear swaybar the front suspension tends to transfer weight to the rear and with an unbound backend power gets down better and the rear end stays planted.

The comparison to BMW handling is interesting because BMWs have some of the most supple and compliant suspensions in the world. I think my setup helps the car work in the corners to get the power down to make the car faster on the track.


[Modified by Stealthvette, 10:23 PM 8/25/2002]

 

BTW, you can see my car in action on my website at:
http://apexbenefits.biz/ABS-Mtrsports.htm

 

Koni Sports (yellow)

R-D Camber Brace

Harness bar or Autopower etc. roll bar.

Proper alignment - Vette Brake Products - Advanced Street setup.

Poly bushings

You will be amazed how well a C4 handles.

 

My 86 never acts "twitchy" in corners.. I'd have to do something really insane to lose control of it, even when i'm going waaaay too fast. I'm no "race car driver" but I do wear the outsides out in no time. I just point it, give it gas, and it goes faster and faster around the corners, changing direction, without any hesitation or 'nervous' feeling.

It's a z51 car with the stock spec bilsteins.




[Modified by Kale, 10:16 PM 8/25/2002]

 

The big problem is when you start competing. You want to use all that power to get out of the corners but you can't jump on the gas because it will oversteer big time if you do.

 

My 92 handles like a dream. It will step out if you get on it real hard, but I think overall it's a good combo. The 275/40/17's all the way around seem to make a difference over the cars with mixed tires sizes.

I don't really AutoX so I don't have too much experience but I have done it a few times. I know that even with the top out it will run around the track quite nicely.