tmak26b

I have been tracking my stock C6 for a year now. I have been pretty happy with the car except I seem to struggle quite a bit at the high speed turns and high speed braking instability. I personally feel that the problem has to do with the relatively soft shocks that came with the car. Also correct me if I am wrong, but downforce seems to be lacking in the rear of the vehicle. Do you guys have the same issue or are the shocks making that much of a difference? I am seriously thinking about investing a set of shocks. What are the options? PFADT? Konis? Penske?

Thanks

Z06_BluByU

tell us more about your car. Base C6, Z51, Z06 or ZR1?!?! any modification or is it stock?? What tracks?!?!

tmak26b

Z51 stock except for pads. The instability problem is at every track where the turns are over 90mph

OCCOMSRAZOR

Three things come to mind:

1. Check your alignment and if you plan on tracking your car, add camber.

2. Make certain that your shocks are in good shape. Upgrade to a Bilstein sport or equivalent.

3. Check the rake of the car. These cars run better at speed with the front lower by 3/4" to 1".

Don't worry, it is easy to fix!

Bill Dearborn

You really shouldn't have any high speed stability problems with a C5 or C6. When I got my 97 the alignment from the factory wasn't even close so that would be one of the first things to check. If your car doesn't have many miles on it the Z51 shocks should be fine. I have driven several students Z51 and base C6s and have never felt any stability issues under braking from 90+. As for stability in the turns you may have to add some maintenance throttle going through the turns. You can't float a C5/C6 through a turn or the backend will start to come around on you or seem like it is tightening into the turn. They are a little tail happy and the way to control that is to just add a little throttle to plant the rear. It doesn't need to be a lot but you need enough to make sure the weight is balanced from front to rear. I have been tracking C5s for 12 years and that is what I found out when I took my brand new 97 to Watkins Glen the first time. Completely different animal than my 86 which had a lot more understeer than the C5.

So get the alignment checked and make sure the tech sets it for the Service Preferred settings with no tolerances. Then see how it handles the turns and if it still feels unstable add just a little throttle going through the turn.

Bill

tmak26b

Unless .05 degree of toe in is too little in the rear, alignment shouldn't be an issue as I just had it aligned. Adding camber actually decrease straight line stability. I am using zero toe in the front, but it still shouldn't be this bad. I just felt the back end was lifting quite a bit, never had comfortable feeling at the high speed turns. I still think the problem lies in the shocks or the aero package of the C6. I suspect shocks being the more likely option as no one have this problem.

Dreamin

What pads? Running too hot of a pad in the rear can be problematic...

Dreamin

0.05 deg is not a lot of toe in (it's less than 1/32")... but even that amount should not be giving you the symptoms you describe.

AU N EGL

+3

tmak26b

I am leaning toward bad shocks (20K miles), the car does roll quite a bit, I will also get my tranny mount and the front end check out. I guess aero is not an issue in this case from what it seems like

Solofast

The one thing about aero, is that you really don't feel much other than it is loose. In this case since it is happening at higher speeds so it is more likely to be aero related than a lot of other things. I'd check the rake first. It costs nothing other than finding a flat piece of concrete to check the rake.

AU N EGL

rake has a lot to do with high speed stability

tmak26b

what is the rake?

rustyguns

well written

OCCOMSRAZOR

The height difference between the front and the rear. You can do a search for discussion of it in this forum, but basically, you want the car to be lower in the front than the rear. You can do a quick check by measuring the bottom of the rocker panel behind the front wheel and in front of the rear wheel. You want to make certain that the front measurement is about 3/4" lower than the rear.

In a nutshell (and many smarter people than me will probably chime in) the air flow creates a high pressure area underneath the hood that will "lift" the front end at higher speeds. This is why you see ducted hoods on Corvette race cars.The ducts allow the air to flow through, thus reducing the high pressure air build-up. By making sure the front end is lower, it helps offset the lift, and keeps the front end from getting "light."

tmak26b

Let me check that out. Thanks. I am also thinking about biting the bullet and buy a new set of shocks too

rustyguns

again very well put.

longdaddy

no offense, but it sounds like you just want to buy some shocks go for it, why not!

tmak26b

I want to make sure there are no other problems before I blow money into the car.

Bill Dearborn

One thing we don't know is what he is calling high speed turns. Is he talking 105+ mph in the turn or just 60 or 70? Another thing we don't know is how he is driving those turns. Is he an expert driver with lots of instruction and many track days? Does he have an instructor riding with him telling how to go through the corner or is he just a street driver that got turned loose with insufficient experience/instruction on an open track? All makes a difference in trying to help him.

Bill