2MCHPWR

Hi - today was my first time at NJMP Thunderbolt, and it was with the chicane.
Previous setup was -2 front camber, -1.5 rear, stock bushings.
Since then i put on pfadt poly bushings, removed like 80 pounds of carpet and passenger seat and got a more aggressive alignment (-3 front, -1.6/1.8 rear), swapped hawk blues on autozone rotors to dtc 70 front / 60 rear on DBA front 2 piece rotors.

stayed the same:
T1 sways, rear set to softest.
275 A6's.

I think it was 88 degrees outside.
Car was very loose on corner entry.
I was running in the competition mode but in my last session, I turned it off and still spun.
I spun in every session. Was very loose. I have lots of video to analyze but I was very unhappy. Doing it again tomorrow.
At hotel so can't post up videos now but will in a day or two.
thoughts?
Ben had some good advise and he said to ditch the T1 bar and put in a stock z06 bar. Sounds like a good place to start. I'd rather have a car that understeers.
Cold air pressure in rear was like 23 and hot was 28.
front cold was 25 and hot was 30.
Front felt fine.
thanks!

mountainbiker2

Z06 rear bar or no bar.
Less neg. camber in rear.
More toe in for the rear.
Lower the rear.
No trail braking.
Smooth turn in.

I don't know you, but spinning every session sounds like over driving to me. Although the car might not be helping you much either.

Steve A.

2MCHPWR

yeah i think i was over driving. but not really sure. was watching my last session and i was off the gas completely and hands/steering wheel movement was smooth.

2MCHPWR

here's my last session spin:

http://www.youtube.com/watch?v=KSfm5...ature=youtu.be

3rd session spin:

http://www.youtube.com/watch?v=35Uk6...ature=youtu.be

froggy47

Everything Steve posted is spot on,

BUT

That's what I call dumbing the car down. A car that oversteers a bit is dream come true car, enjoy it, savor it, don't kill it off.

You have to learn to love the car, be nice/easy with it. Learn to drive it.

Give it a chance. It's a handful, but if you learn to handle it, you'll be in heaven.



So, having just watched both videos, neither one of those spins should have happened in a properly sorted out car, you have NO REAR GRIP, that's not oversteer, IMO something is not set up right on the car.

Have a seasoned driver take a few laps & keep us posted on what you find.

mountainbiker2

Tell us again, are you using TC, active handling? If so, maybe it's applying the rear brakes for no reason. I'm sure some of the experts will chime in.

andy3101

I agree with the other ideas put forth, I will add a couple more observations. By no means am I am expert.

I believe with the Hoosiers you will want a higher hot psi in the rear than in the front. 28 psi hot seems low. My Hoosiers I run hot 32 front 36 rear.
I agree with softer rear sway or you can try stiffen up the front bar.
Another option is to go with a 295 or 315 rear tire. This will help with rear end grip.
I assume you are running stock springs and shocks? So no adjustments there.

Watched the one spin a few times, I suggest trying to keep your hands on the wheel at the 9 and 3, also putting a piece of white tape at top dead center of wheel to help you locate straight when you get into a spin.

How many sessions have you been on hawk drc 70/60? Race compounds seem to grab more than you think while trail braking. (puts too much weight forward and takes the weight off those rear tires creating the looseness)

fatbillybob

You might find that to get more than -1.5 at the rear people tweak the ride height which also effects the rear thrust when some locking camber plates are used. Some can just crank the adjusters and some cars have the range. Rear camber change the thrust. Have you checked the thrust and did you complete the alignment when the camber was changed or did you do those changes thinking they would not effect other settings?

Maynor29

I was behind on you a couple of laps today (White BMW) in one of the sessions and you looked pretty composed with only a little wiggle from the rear. I'm with Andy.. I can't speak for the suspension setup but I've haven't heard of many folks running A6 tire pressures that low, hot.

I'm usually in 37 range hot for best traction. 28-32 cold depending on outside/track temps.. We're obviously on different chassis's so YMMV.

Still, might be worth one session trying higher rear pressures (only) to see if it makes a difference... One variable at a time etc.

sperkins

For a TTA setup on 275's.
More rear toe in - about double what you have (see note below).
No nannies. Computer assisted braking is a bad thing.
Low front ride height
High rear ride height.
Cold pressures low 20's with 2lb split f/r.
I'd bet dollars to donuts that your car is pig heavy in the front. Yank as much weight as possible from the front and run lots of fuel or add ballast in the rear. Do you know your corner weights?

Was the drivers weight simulated when the alignment was done? If not, you probably have close to zero rear toe or maybe even positive in compression. Forget what the printout says - they can make it read anything they want. Put some weight in the seat, stand/bounce on the door sills, roll it around and then check it yourself the old school way with tapes.

Oh and comp mode is useless on a road course. That's for drag racers.

AU N EGL

How old are the tires ?

Aggressive alignments need new tires

drivinhard

for all out speed, he's actually a bit high

Painrace

Guys above are spot on!

Check rear toe in and add a little. Increase rear tire pressure. Make sure all suspention parts are tight. I like about 1/32 toe out in the front. You want enough rear camber for the tire to ride on the inside 1/3-1/4 of the tire in a straignt line and all of the tire in a corner. The only way to really check that is with a incert pyrometer. You want 10 to 15 degrees hotter on the inside of the tire and about the same temperatures in the middle and out side to slightly lower temperatures on the outside. No more of a total spread that about 25 degrees if possible. Pyrometers don't lie. However, you must have a hot lap in and someone who knows how to punch the tires ready when you come in and also some one to write down the readings. Temps should be into the 200's.

Good luck!

Jim

redtopz

Watched both of your vids. All these setup ideas are fine and I would pay particular attention to what Sperkins said since he runs 275's. Alignment can make a big difference and if you're not limited by class rules try running larger tires in back. I would add some toe out in front and less rear camber.

However, you can drive your car today and not spin as long as you apply throttle at turn-in and throughout your turn. Do not coast while turning in or your rear tires will lose grip. You either need to have your foot on the brake pedal or on the gas. What you have to do is brake hard in a straight line, trail brake until your rear end starts to come around, and then immediately get on the gas to plant the rear end throughout the turn. It needs to be a seamless transition. In your case, you might want to skip the trail braking at first since it looks like your car has a tendency to lose rear grip. It looked to me like your first spin was caused by turning in with the engine braking the rear tires. This is just a suggestion based on what I learned the hard way and you may already be doing this. It's hard to tell from a video.

sothpaw2

Great advice! That's how I've driven rwd for a long time now since I don't like oversteer. Always in the gas except for the braking zones. Throttle is your friend. Trail braking would make me faster but I still run comp mode since mine's a daily driver and I don't think it likes trail braking much.

I would really have the rear alignment checked to ensure the toe is correct back there; toe out would be very bad.
If it were me I'd run less neg camber out back and front and ensure plenty rear toe in.

AU N EGL

What does your Bimmer weigh ?


Many of the vette guys run A6s low 20s cold and mid 20s HOT for best traction. Upper 20s and low 30 or above is too high and gives that greasy over steer feel

Bill Dearborn

I agree. Don't trail brake. Brake in a straight line do your turn in and use the throttle to plant the rear and get you through the turn. The C5 is an off throttle tail happy car in its stock form and needs some power to keep the rear planted. Something about your setup is making it even more twitchy. Too much rear camber may be the issue but I really don't know. I never ran more than -1 rear camber on my C5s and they always performed well that way.

As some others have mentioned more rear toe in might help and it is something you can do at the track today. If you have the correct wrenches, turn each rear tie rod one flat toward more toe in and take the car where you can drive it in a straight line to see if the steering is still straight (checking thrust angle). If you have a way to measure what you are doing (toe plates) and a laser level to check thrust angle that makes it even easier.

Once you start getting around the corners without spinning then work in a little trail braking on the corners where it will benefit you.

Bill

Maynor29

It weighs roughly 3k with me in it including fuel, LSx etc. Obviously, my opinion is mute because I don't know the Corvette chassis well enough but I've driven on enough Hoosiers that those pressures caught my attention.

Interesting data point for me at least. Curious to see the outcome of this one.

John

Bink

What's the correct way for him to punch temps??

PushinTheLimit

I watched both videos... kinda hard to tell but my observation is that it looks like you're still braking while you are turning at corner entry. If you're still braking hard at that point, you're car will feel very loose and spin like you did. Those new bushings should allow your car to turn better at corner entry compared to it being slightly pushy at corner entry with stock bushings.

I would say try changing your technique on that instead of changing the car... the car looks good otherwise from what I saw out of the rest of the video.