gkmccready

A couple of years ago when I first picked up the C6 Z51 and took it to the track I refered to it as an understeering/oversteering pig for everything past turn-in.

Got an alignment on the car from a local Corvette shop (-1.1f, -0.9r, touch of toe-out front, in out back). Back to the track, still all stock on the Supercars. It no longer felt like I was dancing on a knife-edge after turn-in, but I still can't roll on the throttle *at all* until I'm just about done tracking out... anything but maintenance throttle and the tail wants to step out.

The local shock shop wanted somebody to test their new KONI 3013Sports. Put those on the car. Car behaves worse than with the stock C6 Z51 shocks. Doesn't seem to matter how much or how little rebound I dial-in.

Throw a set a Pfadt Pfatty swaybars on the car. Stiff front, soft rear. Car is flatter, but behaves the same requiring a lot of waiting to get in to the throttle. Pull the Pfadt rear bar, put on a base model bar. Still can't get in to the gas apex-out *at all*. You'd think this set up would understeer like a pig. At this point we added more front negative. Running about -1.7deg.

Back to the stock swaybars with the KONIs on the car, but with CCW C140s with 295/30r18+305/35r18 Toyo R888s on the car. Ran the car this way at two events, including last years Spring Mountain Corvette Days. Same thing. Have to wait, and wait, and wait to get back in the gas.

Pull the KONIs and stock springs and install HardbarUSA Penske 8100s with dual-rate springs, and Pfadt Poly bushings. Set -2deg front, wherever the camber plates put the rear. +1mm front toe, -2mm rear toe. The car is a bit better, but I'm still a far cry from being on the gas apex out.

During all this I've tried rakes varying from 0 (which was as delivered), to +1/4".

Note that the car is great at turn-in. Not pushing, not sliding, no issues. Stable under braking, too.

I'm pretty frustrated. There's not much left to change in the suspension. That leaves the driver. I've had folks follow me, or ride with me, and it's possible to drive around the issue by just waiting a long time to get back in the gas. I know guys in front of me are getting in the gas off the corners much earlier with no fuss. The Corvette has torque, which is new for me, but I've been successful with my well modified RX7 Turbo, Pro7, 1st gen RX7, Miata, and even my old Civics. These cars all reward carrying speed through the corner.

It's been suggested to me that I should slow more at entry with the Corvette but that just feels like over-braking the corner. As I mentioned I've got plenty of grip at turn-in. Heck, if you discount the fact I can't roll in to the throttle at all until well past the apex the car behaves well through the entire corner.

Is this a function of the C6 versus C5? I've tried to follow the "common wisdom" of alignment and the usual changes to try to get the car happy to accept more throttle apex-out. Nothing seems to be working for me, at least not to the degree I expect.

Anybody else experiencing this? Anybody have any ideas? I wish I had in-car to show, but I don't. Am I just expecting too much? It sure seems like others are not suffering from this issue... are you counter steering the entire way off the corner? I can't believe that...

Oh yes, none of this shows up on the autocross course. At least I don't notice it at the local Corvette autocrosses I took the car too when it was stock.

AU N EGL

did you have your Tq management reprogrammed?

reprogrammed so it does not come on until a very highr rpm level or latal Gs. It can not be turned off but tuned to come at some level the car will never experiecne.

c5s do not have this Tq management

JiminVirginia

305s in the rear strike me as not enough tire. I run 345s back there in autocross trim (and there are still issues getting the power down, but it's better).

AU N EGL, how does one "reprogram torque management" in the C6? Never heard this one.

Z06Fix

HP tuners.

gonzalezfj

Correct, with 295s up front, 305 is not enough rear tire; try 345s. Also you might want to try some Hoosiers instead of that Japanese stuff. You won't believe the difference.

Finally, if you are used to gutless cars (no torque to speak of), generally referred to in politically correct mode as "momentum cars", you need to reprogram your mind when driving a Vette. You cannot punch the throttle at the apex and steer your way out. You need to roll on the power as you unwind the wheel. If you are at the limit of adhesion at corner entry, how can you add power unless you start unwinding the wheel?

Frank Gonzalez

Jason

This might be stating the obvious, but try apexing later.
Don't add throttle until you can start to unwind the wheel. String theory.

AU N EGL

meat. Big fat meat. er tires. I run 305 up front and 335 is the rear on my C5.

take your C6 to get a dyno tune by a great tuner. They will do wonders for throttle response, and especially tq management, not to mention a ponies or three,plus better fuel management.

alignment

front -2 to -2.5* for street track combo. ad a degree for track only -3 to -4
caster MAX but equal on both sides. Normally one side you can get more then the other. so make them equal
Toe: 3/32" to 1/8" OUT but 1/8" is easy to measure.

rear -1.0 to -1.5* for street track combo more if track only -2 to -3
Toe: 1/8" IN.

the camber plates are great but I think you need more toe front and rear. for auto-X then LOTS of Toe

and corner balance is mandatory for performance

C6400hp

Try everything the same as now except take rear toe in to 1/4". I would not get to crazy with toe out in front, the C6 seems pretty sensitive to anything more than 1/16" out in front. You may also want to consider 1/2" of rake as raising the back will add some grip to the rear.
One change at a time.

gkmccready

I agree with the Hoosiers, but this is/was supposed to be my mostly street car so the Toyos work great for being able to leisurely drive to and from events. Fitting bigger rubber under C6 non-Z body panels is painful, though, the 295s on 18x11 already rub the fenders. There is room for more out back, though.

And I don't punch any inputs. :-) I'm talking about barely adding throttle when her butt wants to step out.

gkmccready

I don't have a tune, but can you explain why you think the torque management would influence this?

gkmccready

-1/4" rear toe sounds inviting for the track, but definitely not something I could drive to/from the track. Easy enough to mark the tie-rods and try, though.

1/2" rake is on my list of things to try, but going to 0 rake from 1/4" actually added rear grip, too.

davidfarmer

I honestly can't tell from your post if it is driving style, or a car issue. You simply can't put your foot to the floor in a Corvette the same way you would in an RX7/Civic, but you should certainly be apply some throttle as soon as you get off of the brake pedal. Corvettes don't like to coast through corners, as the rear gets too light.

I was just thinking this morning (while watching the ALMS Sebring race) that I love a car that turns in well, steps out slightly when I apply throttle, allowing me to "unwind" the wheel, which ultimately allows me to accerate AND turn with less steering input, maximising acceleration and minimizing scrub. Full throttle is almost always reserved for post apex (sometimes post track out) in a Z06, but you can still be accelerating and carrying a lot of speed in a Vette without being at full throttle.

C6400hp

Just for FYI, when I had stock Z51 bars, running RA1 275/305, I really liked -1.3 camber front, max caster, 1/16 toe out with -1 camber rear and 1/8" toe in, 1/2" rake. My car sees dual duty as well and I cant imagine running an alignment on the street much more aggressive than that. Again, I would probably try the 1/2 rake first since it is easy enough to do and wont cost much if anything.
Just remember the one change at a time thing.

trackboss

Without actually watching how your car behaves on the track and then driving it for myself I can't suggest a whole lot. One adjustment that is easy and makes a noticable change is ride height. Try lowering the rear at the track. Don't worrry about measurements. After its all set up initially just count the turns on the collars of your dampers at the track and make a note.

gkmccready

This is what I call "maintenance throttle."

"Slightly" is the key word. At the apex or a little after as I start to unwind the wheel I give a little more throttle and it starts to get loose rather than plant. I fully admit this could be entirely a driving style thing since I have come from the land of momentum cars... even the turbo car had little torque but a reasonable amount of horsepower. But even in these cars it's a roll in to the throttle and not a stomp. With my C6 there's no way to go full throttle until you're well on your way to your track-out point unless you want to counter-steer or the revs are low.

trackboss

One thing you may want to try with your driving style is a different line. When I first went from racing nose heavy sedans to shifter karts I quickly learned to enter the corner completely differently. Turn in early, which would normally induce understeer, and get on the thottle well before the apex. I've found on my C5 that I do something similar. The american iron cars I'm used to racing require being thrown into a corner aggressively to be fast. On the C5 I've noticed it just simply is much more precise. Much smoother and always on the throttle sooner than what I was used to.

gkmccready

Just to set expectations here... maybe I'm just expecting too much from the car. Since I'm not sliding at entry it feels like there should be traction left to accelerate, but any attempt to add throttle results in the rear getting loose. It's easy enough to modulate that, but it really feels like it should be able to take the bit more throttle and say "thank you sir, may I have another?"

Alternatively, is it possible I'm adding too little throttle to get the weight transfered to the back and have it plant? Catching a slide by adding throttle is fairly common, but I'm a bit leary to add more when the car starts to feel loose mid-corner.

yakisoba

You said that you had no way to go full throttle before the apex unless you wanted to countersteer?

Sounds normal. I slide the C5 all over the place on 275 888's. If I had my "druthers" I'd rather run fatter tires, but this is what I have to work with. 6 or so segrees of slip angle is what I shoot for, and I can feel it when I hit it. I just can't get there consistently! Practice, practice...

Your alignment sounds pretty good to me, especially if you want to drive to and from.

davidfarmer

Sounds like driving style to me............in 3rd gear at full throttle, you are putting 1600ft-lbs of torque to the rear wheels. While high rpm acceleration might not be that much greater than other cars you've drive, the low rpm torque mid-corner is enormous.

Remember, you can never exceed 100% of the grip of your tires......the moment you add throttle in a corner, you WILL lose rear lateral grip. 1600ftlb on the rear tires is something like 1350 lbs of force, or nearly 0.4 g's of potential acceleration you are adding ON TOP of the 1.5g's you are already pulling mid corner. You can't add more without taking something away.

After a race weekend, my ankle is always sore from spending so much time at part throttle........you are still accelerating like crazy, but it's easy to expect too much.


***these numbers are all made up, please excuse any completely idiotic mistakes I've made. Also, this may all be in vane, and you could have a bad diff or something and your car really is bad****

davidfarmer

btw, I SUCK in momentum cars. I've trained myself to do everything to maximize my (near) straight line acceleration, that I'm slow everywhere when I'm in a car that has low torque.