Racingswh

It's a 2010 C6Z and the car is not a street car. Is there anyone who might be able to give me some advice on what makes these cars quick in the corners I would appreciate it more than you know. Currently the car is tail happy in steady state fast sweepers like 2 and 5 at Watkins Glen making it fun but slower than I would like and a little unnerving for my Wife who regularly drives the car. The suspension is completely adjustable but it does still have factory bushings albeit new ones. Quite frankly I don't know where to start and would be guessing at best at ride height, spring rate, sway bar and damper settings. I can just turn it over to someone else but I would really enjoy learning to do this setup myself. Even if it's pointing me towards books on setup as long as they are Corvette relevant that would be great. Most of the tracks we go to are in the Northeast. Like to use it for some fun in NASA TTU and then ultimately some W2W at some point. Let me know your thoughts. Thanks in advance!

morris

Having experienced a lot of this as I learned, through experience I can provide my experience. You didn't really talk much about the details of your suspension setup so its hard to focus in on any one thing, but I can offer some shotgun observations I have had.

Things that affect oversteer, include alignment most importantly rear toe and too a slightly lesser extent front toe. Swaybars, front to rear air pressure and how stiff the front coilovers are in relation to the rear coilovers. I have also found that the monoball setup made my car much more consistent and predictable in corners, it helps to keep the suspension setup and alignment from changing due to deflection under power and in hard cornering.

What tires are you running and front to rear pressure hot, are you on coilovers and what are your swaybar settings do you have any adjustment, what do your alignment specs look like?

I have also found that Anthony at LG motorsports is a wealth of knowledge and guidance and is always willing to take a phone call.

Racingswh

Thanks Morris!!

Suspension is as follows:

Penske double adjustable coil overs with remote reservoir of which I literally know nothing about

Pfadt heavy rate adj sway bars front mid setting and rear full stiff

Hoosier A's or R's 315/30/18 38-40 psi hot front 345/35/18 34-36 psi hot rears

Camber -2.7 F and -1.5 R

Toe 0 F 1/4 total toe in R

No camber lock kit and squishy factory bushings

I do not know what the ride height is supposed to be nor where it's measured from.

I was hoping someone could tell me what spring rates I need and I will have the dampers valved properly for them.

Hope that paints a better picture of what I have to work with and how clueless I am at this point.

morris

Oy, those are a lot of levers to adjust. Here is a good start that might help some in terms of a place to start. http://execstudio.com/tech_suspensio...understeer.htm

I know exactly zero about the double adjustables so I won't go there but playing with the stiffness (damping) will make significant changes to how the car handles / oversteers. It looks like you would benefit from adjusting the sway bars if you soften the rear that might help a lot at least it has for me.

I also run lower hot tire pressures on my Z06 32-34 hot, lowering the front pressure from where you have it should also help. I would also look at your alignment as it, specifically the toe can have a major impact on understeer and oversteer. Be aware that toe out in the rear will cause the car to oversteer.

If it were me and I didn't want to just send it to someone which in your case might not be a bad idea given where you are starting from I would make sure I had the correct alignment settings for a track car. Then adjust the sway bars and then the tire pressures . The challenge is that if you don't know what the dampening settings are on your coilovers that could very well be where a large part of your issue is. Rear toe out though could very well be the biggest culprit.

Again if it were me and I couldn't get it solved by the above approach and it still didn't get to where I needed it to be I would then take it to a shop that knows Corvette race cars or at least talk to them on the phone and get there guidance regarding proper setup of the motons and spring rates, but my assumption was that when you purchased the Penske's that the springs provided were correct for your cars setup.

Actually the more I think about it I would talk to an expert shop because fooling with all these variables and unknowns will take up a good bit of track time and I would rather spend the track time driving rather than adjusting. When you have a solid baseline of known items its not that bad to tweak one or two things here and there to dial it in. Call one of the Corvette race shops that sponsor this board and see what they recommend for a starting point on the coilovers, at least you will know if you have the correct springs and dampening before you go to far down the money pit.

Keep in mind that I am no where near an expert on this stuff, I do this for a hobby and have learned some from reading, some from experts and a lot from trial and error.

68sixspeed

I don't even know where to start there either, especially without knowing the spring rates. But a couple comments, the near-square tire setup must turn in great but that wide of a front tire might be contributing to the "tail happy" handling. Also, if the rear bar is on full stiff, I'd start there, go to the middle setting or even full soft and that should help tighten the car up. Last, check what the "starting point" settings should be on the shocks.

Screamin Z

Loosen the rear bar. Full stiff is way too hard. I'm running on the 3rd or 4th hole.

Take big swings with the bars. Fine tune it with the shocks.

morris

And the tire widths should be fine, I am running the same size on my 09Z and the car is setup pretty neutral.

jlutherva

I would recommend you pull the Penske's and send them to Steve Horn at Penske (610-375-6180). Ask for a reasonable road course set up. They'll put them on the shock dyno to test & configure them. They turned my 8300's around in a few days. Total charge, including shipping was $45.

That will nail down at lease on variable.

Jim

Racingswh

Thanks everyone for the advice so far! I will definitely soften the rear bar. I also notice it seems like that bar acts as a lever arm when I hit curbing with the inside tire it seems to lift the outside loaded tire off the track as well for some fun snap oversteer excitement.

Good idea sending the shocks to Penske. Thank you for that suggestion. I will put the car on the scales so I can give them as much info about the car as I can. I will do that asap.

How low can I make the car and how stiff? Can I run it an inch off the track with 1000-1200 pound springs or does this negatively effect the suspension geometry? I am assuming the front needs to be lower as well as stiffer so the roll centers have and maintain the proper relationship. What rake seems to work the best? Is there enough length on the frame rails to get a meaningful measurement or do you measure ride height at other points?

morris

I think most people measure the gap between the top of the tire and the fender. Basics of ride height as I practice it.

You can run the car as low as you want the lower the better, its better for aerodynamics and cornering. Now the big caveat is that if you lower the car too much you will limit the ability of the suspension to travel, this is bad. If the track you are driving on happens to require more suspension travel than your car has available because it is super low it will be a problem. I would give you my settings but I have drop spindles which let you lower the car and maintain full suspension travel. The other thing is that if you lower the car too much the tires will scrub the wheel well when cornering hard and quite possibly rip the plastic wheel well covers out. Also as you adjust the rake and ride height of the car you will also effect the balance of the car, once you choose the height you want I would get the car corner balanced

Racingswh

I am thinking the monoball and drop spindles are the LG units?

I didn't think measuring from the fender was the preferred way because of body panel differences from actual shape to mounted positioning differences? That's why I have always measured from a fixed chassis position typically at or near the suspension pickup points on a confirmed level surface which is not always that easy to find. My garage floor while it looks nice and flat is anything but. In addition the chassis needs to be straight and the pickup points the same at all four corners of the car. Not always the case. I am guessing mine is but the previous owner drove it pretty hard.

For the purposes of getting it close Morris what tire sizes do you run and what's the gap over the tires now? Also what spring rates to you run to keep the fenders off the tires while still maintaining a reasonable level of grip over bumpy sections of track.

That's my only concern about high spring rates is how skittish the car feels over the washboard bumps. On smooth tracks it works well.

This is the car being driven by my friend and previous owner of the car in a TT in 2011. If you look at turn 6 at 2:36 of the video he get's through there about 90 mph and I was seeing the car get nice and loose about 80 mph last weekend. He and I drive a little differently as he shuffles and I don't but application of power is comparable. A 1:25.9 lap with oil dry down and being held up a bit coming to the line is pretty quick. I know the car has it in it but he used to pay for setup either guys from Penske came down and rode with him or he sent the car out. I want to be able to do all this myself. He had the whole car set back to street livable settings in order to sell it not having any idea I would be the one to buy the car so I am starting from essentially scratch.

morris

I am sure that there are more exact points on the car to measure from that allows one to compare one car to the other, as you said the frame is probably a more precise measuring point. My perspective is that for me I don't care I don't need it that precise for my purposes. The fender gap for me is easy to measure and provides a consistent baseline from change to change on my specific car for me that's all I need. Some guys want to wring every last ounce of performance out of the car similar to a professional race team, I have no illusions about where I am in my abilities and more importantly my willingness or lack there of to push the car to 100%. Maybe for the I want to drive Formula one crowd it matters for me a guy that does 10-20 Track sessions a year not so much.

Yes I run a full LG suspension including monoballs and drop spindles which also have built in negative camber.

I run the same R6 sizes you do, 315 up front and 345 in the rear all 18's of course.

Unfortunately I don't remember the spring rates, it was recommended and setup by Anthony at LG and it works so I never bothered. With that said I have run a couple of different coil over setups. The spring rate needs to be stiff enough that the car doesn't squat due to down force from the wind, it should also combat the amount of lean when cornering and accelerating / braking. Spring rate is also affected by the amount of aero parts or more specifically the down force your specific car generates as well as the weight of the car a 2500 pound z06 might require different springs than a 3100 pound Z06, my point is that while you can look at what others are using keep in mind the variables that might make your needs the same or different than theirs. I would manage the track surface bumpiness with the shock valving or in your case those double adjustable shock settings.

I broke the drive shaft in July for the second time at Autobahn and so I cannot take the measurements you are asking for thankfully I am flying up to Katech to pick up the car tomorrow, so I could do it later in the week if it would help. But in the mean time you can see the gaps in this photo

Racingswh

Thanks for those pictures. As you can see my car sits way too high in the front especially and your pictures allow me to be able to directly compare it to visually anyway something I know is used as a track car. Thanks very much!

morris

Steve, I am glad your getting some value out of the conversation and yes I agree that the front might benefit from coming down a bit

TorontoC6

Here's my setup



That's monoball suspension, full aero, LG Bilstein custom valved and spring coilover. Running -3 camber on 305 and 355 Hoosiers

#13 Vette at Watkins Glen, April 2013

Racingswh

Thanks for that picture. How tall are the tires 680 rear and 645 front? What spring rates with the aero? Any tire temps from the Glen? How about lap times? Cool canards!!

Your car is awesome and my Wife loves it as well. After some checking it looks like those must be S100's 355/650's and 305/645's. How do you like them compared to the A or R6?

TorontoC6

Yes you got the tire sizes, 305/645 front and 355/650 rear R100's (last years compound - not the new improved compound). They have more grip than the R6 (have not run A6 recently) and last ~6 track days. Lap times at Watkins are 2:11 (that was in April with a cool track) but I know I can take at least 3 seconds off that. Maximum lateral grip is 1.6g measured with Traqmate.

I am now running Pirelli slicks and find that they have the same level of grip as the Hoosier's and more grip than the Continental slicks. Recently at Mosport I ran a 315/650 (I could not source the 325) rear on a 13" wide rim and had no issues with oversteer and could still pull 1.6g and turned a 1.30.

I like to use scrubs as you can't beat the price (<$500 for a set of four).

The aero really helps. Climbing the esses at Watkins you can get on the throttle hard and the car is very stable.

Racingswh

This is me at the Glen last month. I drove the Vette one session and the Viper one session the whole weekend. This was in the Viper. We didn't have the Race Keeper in the Vette yet. Lap times were 2:11 in the Vette in a **** ton of traffic with my Wife in the car!! Corner exit speeds at key points were fairly close so I think my lap times to be maybe 2:09's right now in it's current configuration in light traffic.

Don't laugh but the goal is to be sub 2 in the Vette at the Glen which is going to take a little work (mostly on me behind the wheel ) but don't think it's out of the question at all.


I have used the scrub slicks with great success in the past wanted to know how you like them so thanks for that input. I will see what GT Racing Tires has on hand once I run out of the Hoosiers.

The work starts now for Summit in October so I have 6 weeks to get the car ready. It's a track I know very well and am excited to go down and see what it will do. I am hoping to be in the 1:18-19 range there. Whatever it is it will be fun!!

5280Racer

Just like everybody has said... Get the coil overs off to a certified builder... and have him set them up or at least find out whats in them for valving. You will want to change valving and spring rates depending on how you plan to compete with the car like adding aero and what not. I run Penske's as well. there is a **** the reservoir for quick change and on the bottom there is a small hex head for more adjustment.. do some ready through penske and online to get a better understanding of what your adjusting.. typically with a very well set up suspension you don't need much for sway bars. I run stocks with my own hiem links. get a camber kit from van steel for 375 and some mono ball bushings if its in your budget.. the camber kit is simple and can be done with basic tools... thats a decent start.. by now means am I an expert but thats where I would start. then tailor it to your driving style.. what works for you might not work for others...


Bad pic but I run Pirelli DH 315/675R18 fronts and 325/705R18 rears... very very sticky and fun.

Racingswh

I have seen that pic and admire your build skills.

Tall tires f and r. Interestingly in other cars I have been pretty quick on tires with a taller more compliant sidewall specifically some Michelin slicks we used to run.

Coil overs are coming off Saturday and sent out. Bars are going to be checked and backed off a bit. Camber kit and monoballs are going on. really curious to see what happens when the suspension compliance is reduced considerably. I am curious what spring rates will be recommended for the car. For now I will not run any significant aero.

I really appreciate all the advice so far. It's been what I am looking for. Thanks! Any other helpful tips are always welcomed regarding car setup as well as driving techniques. I don't know what I don't know until someone teaches me!!