Liquid1

This past weekend I was at NHMS and was not really satisfied with the handling of the car and I'm wondering if part of the solution could be upgrading the suspension. There were a couple of issues but the main problem is the car frequently felt floaty and unsettled as I tracked out which made me late on the throttle until I felt the car settled down. I felt the track was quite a difficult one for the Z to handle, the pretty severe dips in T3, T10 and even T12 to some degree causing the front air dam to scrape and Active Handling to come on which was another contributing factor to my lack of confidence in how the car was feeling.

The car is a basically stock 2008 Z06 running Michelin Pilot Sport ZPs in stock sizes. I have about 15 days of track experience and run 1-3 weekends per year. I have been cleared to solo with the last three clubs I've run with and I consider myself an intermediate level driver. The car is driven mostly to, from, and on the track.

Note that others on the forum have experienced similar issues, such as:

http://forums.corvetteforum.com/c6-z...lp-advice.html

And I also note that many people rave about how the car feels and handles after making a suspension upgrade, which has me thinking that maybe this is a solution. Are most C6Z's running stock suspension or have you upgraded? If so, what to? Thanks a lot for your help.

Bill Dearborn

The car shouldn't feel floaty with the stock suspension and dips shouldn't really affect it that much. I scrape the air dam at least once per lap at the Glen and I use the noise as indication I am going fast enough for the turn I am about to enter. If I don't get the scrape I haven't been on the throttle hard enough. You may get some issues with getting on the power coming out of bumpy turns or ones that crest a hill near the apex but the car should otherwise feel planted on the surface. Increased rear toe can get rid of the tendency of the rear end to break loose when powering through out these types of turns but the rear suspension is a little too stiff on bumpy surfaces. For example, the toe of the boot at the Glen has concrete on the line as you enter, apex and then track out. The concrete is bumpy as you track out. I can accelerate on it but can't push the throttle very hard until the rear wheels clear the concrete. Otherwise the back end wants to snap out. Once clear of the concrete I can literally go from half throttle to full throttle. People with coil overs seem to have much less trouble with that turn. I went to the DRM tuned Bilsteins and they help but I suspect it takes more than shocks to tame the car in that situation.

Bill

naschmitz

I've got a lot of laps at NHMS and the Glen. NHMS being a roval has special issues -- the transitions across the NASCAR oval onto the road course are very, very abrupt. The bump in T12 causes the rears to catch air right as you need to be putting down power for the main straight. And the bowl turn has its own unique suspension requirements.

First off, I usually don't run with active handling but do remember one day at NHMS when I forgot to press and hold the TC button for 10 seconds. I tried to do it on the track, but could never get 10 secs of one handed driving. Even in Competitive Driving mode (just two quick presses) active handling takes over in T3 when you hit the hill. Don't remember it being as obtrusive in the other turns, but T3 was 2nd gear in my base C6 trying to put down a lot of power to climb the hill, only to have active handling play with the rear brakes and throttle. Add to that it was unpredictable in its inputs, lap after lap.

As long as the C6Z is not hitting the bump stops (my base C6 was sprung much softer and was bouncing off the stops) you should probably try the track again without active handling to see if that fixes the problem. I know there are a couple people running C5Zs with stock suspensions that you could talk to there if you ran last week with COMSCC.

If you are unsettling the car because you are hitting the bump stops, then your only solution would be a suspension upgrade. Nothing will make you slower than hitting a bump stop and unloading a loaded tire.

autoxer6

Sounds like your are working the car pretty well! We are all trying to drive the car at the limit of its capabilities. Keep in mind what an upgraded suspension will do. It will raise the limit, meaning you will have to be faster to truly be at the new higher limit.

Good drivers wont wait for the car to settle down, they will drive through it and have the experience to know where the limit is. Maybe try to get an experienced racer to drive your car so you can see what they drive through and when they have to wait for it to settle.

Just because active handling comes on doesn't mean you did something wrong. It makes me uncomfortable because it starts to intervene and I'm not always sure what it is going to do or when it is going to do it. Maybe you would be more comfortable with it off?

Upgraded shocks, springs, bars will make the car more responsive and settle faster, but it doesn't make you more capable of driving at the limit. I'm a fan of driving these cars in near stock form. They are compliant, and dont have any bad manners.

My 2 cents... YMMV

Liquid1

Thanks Bill, I've run at WGI a fair amount and it is a much more compliant track than NHMS. I only have issues there coming into turn 1.

My best laps were just under 1:23 but I felt like I was managing the car way too much and that the car would have been significantly quicker if I wasn't forced to manage it so much. It was also not confidence inspiring to have to work it so much. I agree with your comments about raising the limit but I am also looking for something that will feel better as it approaches the limit.

Solofast

At this point you are pushing stock shocks, which are by their very nature a compromise, past the point where they were ever intended to be.

Stock shocks are made for the street and designed not to shake the fillings out of you teeth, but you are to the point that you are asking them to do more than they ever were designed to do.

Upgrade to a set of Koni's or other top shelf shock and the car will feel more tied down, mostly because of improved rebound control.

0Johnny@MTI

You might be at the limit of your stock suspension. Generally I find that happens with upgraded brakes and larger sticky Tires. The factory shocks are built to 1 be comfortable and 2 to be mass produced. A set of coil-overs will help leaps and bounds when it comes to settling your car at speed.



If you want give me a call. I can give you free tech, and set up a set of our coils for your Z.

froggy47

IMO (and don't take this the wrong way, but you did ask), I would not change anything until you are driving the car.

Right now the nannies are doing most of it, per your description.

It does not surprise me at all that on a rough track the car would feel squirrelly with AH stepping on your inputs (gas/steering/brakes).

Have a good instructor drive the car as is & see what you both think afterward.

naschmitz

Nannies at NHMS are very intrusive running 1:23 laps. Take them off and you will see that sub 1:20s at NHMS Chicane-Chicane are well within the abilities of a stock C6Z.

Liquid1

Thanks gents. I am opting for the DRM Bilstiens based on all the forum feedback and will start experimenting with running with the AH off to see how much that helps.

To clarify: I was running the South Oval configuration; A sub-1:20 chicane chicane on stock rubber is a bit beyond my skill level at present.

JeremyGSU

I have a C5 Z and have the DRM shocks on order. I currently have the Johnny O'Connell stage 1 package and was amazed at how much of a difference that cheap suspension makes over stock.

Perhaps look into some sway bars if you're ordering the DRM's and I think you would be happy with how your car handles, especially for the money.