FASTFATBOY

Ok, a little back story.

I have over 5 years of track time, most of it in a 99 Z28. In Jan I bought a C5 Z06. Car is stock, lowered on bolts with a few bolt ons and makes 395 ish to the wheels.

I have 3 events in it now, I have been running 5 year old Hankook RS3's, tires are pretty hard as they 21 sessions on them and about 1/2 tread left.

My best lap at Barber in the Camaro is a 1:47.2 on older BFG R1's(5 years old, were bought out of old stock that had about 10 sessions on them)

I ran the Hankook on Sat, no grip best was a 1:47.0x. Car has no grip...slides, pushes...just all over the place. I almost spun the car multiple times.

Sunday I put the 6 year old BFG R1's on the car, no better...same lap times.

Sunday I had a major butt pucker at the top of turn 3(hill), the right rear hit the painted rumble strip when it was about 38* out. I almost crashed it(vid coming).

Also at the top of 3, the car comes off the ground if I run hard up the hill. It is VERY unnerving. I slowed up the hill after those two pucker moments.

Who runs wide open up the hill into 3 at Barber? Yours come off the ground?

The Camaro was a 3800lb BARGE, it would very lightly lift up. The Z06 I feel like Luke Duke.

I guess I will sell off all my old tires and get some better new ones. I figured I would burn them all up. Hell at this rate it will take years they are so hard.


Thoughts? Is it the tires or just me?

At 8:25 is a small butt pucker, at 13:47 was a Code Brown moment.

You can see how easy I have to be on the gas. In turns 2-3 you see me shaking my head...it just won't turn, can't give any gas....just riding.


https://www.youtube.com/watch?v=Z5HN...ature=youtu.be

brkntrxn

David,

Tires. Sounds to me like they are shot. They are the main culprit, but you will not know for certain unless you change them. For what it is worth, I will rarely run a tire over a year old for any meaningful data acquisition laps. There are just too many variables in them to know if they are still good or not.

I ran Barber in February of 2014 and was flat from T2 across the T3 hill and down to braking for T4. However, my car is full aero AND I was in my ST3/TT3 tune. I would think that I would still be flat through there in my ST2 tune since I am aero'ed.

I also ran TT3 that weekend and here is a lap or two: But again, this is not an apples-to-apples comparison for you.


Maybe some of the factory-stock type guys will chime in on their experience there. But my money is on crappy tires.

fleming23

I hold it to the floor and let that baby drift across the track coming up over the hill in my 3200 pound fiberglass hoopty Granted I was short-shifting.

This was on Toyo 295/38 R888s running roughly the same lap times as you.

fleming23

The hill between turn 12 and 13 is sort of the same way. My car comes up off the suspension and sort of drifts over to track out.

FASTFATBOY

I have though about it today a lot, I think it's tires....every time I tried to get more speed from the car it would just slide all over the place.

Brkn, what gear is in that car?

Screamin Z

T3 at barber bit our car and spit it back out across the track. It's a turn that shouldn't be taken lightheartedly if no aero on your car.

With over 600hp to the wheels I could stay to the floor all the way to the apex. But had to maintain neutral throttle as the car unloaded. Now with aero its wide open in 3rd gear and it's a ball!

brkntrxn

Stock 3.42 rear gear with stock M12 trans gears. Nothing special.

bags142

Sorry to slightly thread jack, but I have never run barber but plan to in 16. I have run Rd Atl a few times and on video this looks no worse than the bridge at RA, speeds seem within about 10 mph.

Clearly from what I am reading, it is not the same. So what makes the back end so light? Is it the MPH difference? Or is this hill much more of a "point" at the crest?

Thanks and sorry to go off topic on ya

Phoenix64

My Firebird broke last weekend, so I drove 8 hours round trip to get my daily driver and run sunday.

Flat up the hill, and 235 street tires to boot.


I've run my stock C5 Z06 and my firebird formula at barber and Rd atl on 3 different sets of tires. The cars ran very similar times when on the same tires, but my firebird weighs 3100lbs.

It's possible you lowered it too much and are hitting the bump stops, I've heard that will make a Z06 twitchy.

brkntrxn

The incline is steeper and the crest at the top is "sharper" and you are turning more than T12 at Road Atlanta.

I can spin my tires at the crest of T12 at RA over the double-bump under the bridge and see the revs increase momentarily. I don't think I ever did that at Barber, but the Barber T3 crest feels more sudden.

fstrthnu01

FASTFATBOY, that weekend I met you, I did almost the same move in the rain. Had to hot pit and clean out my underwear.

I am NO expert but maybe you hit the apex a little early that run? I was told to hold the curbing just a tad longer than you were before heading up the hill?

sperkins

As good as a stock C5Z is, it really leaves a lot to be desired for on a road course. With that said, there are several cheap, if not free, mods you can do to drastically help it do what you want it to.
First, (assuming you have stock springs) ditch those rear lowering bolts and get back to stock length rear spring bolts. Lap times prove that the rear ride height on a softly sprung C5 is critical - the front not so much.
Next, check your alignment. It sounds to me like maybe you have a rear toe problem. Pull some tapes and see what you have both front and rear. A whack alignment will cause massive handling problems and destroy your tire budget.
They're not cheap, but one of the best mods you can do is a larger front sway bar and adjustable end links (on all 4 corners). The larger bar alone will be a huge improvement even without endlinks, but the links will be critical if you can find an opportunity to have the car corner balanced - which brings me to my next point. Get the car corner balanced. There are many forum members here in the SE, myself included, with scales and the knowledge to accomplish this for you and no I would not recommend having this done at a big name shop - trust me on this. Sometimes you don't always get what you pay for.

Lastly - Tires. It's always tires, but tires are expensive and easily ruined with an ill handling car. Do yourself a favor and address these issues and I promise you'll enjoy your track days a whole lot more.

FASTFATBOY

I hit the curbing at the top on the inside, when it's that cold out it's very slick...same as when it's wet. I knew better, and it reminded me lol.

I am doing something wrong there, I have never had this issue before. When I was there with you I was running the same lap times and didn't have the problem.

New rubber is going on the car, we will see then. I should be a good bit faster in this car than I am and I think the tires may be the culprit.

I ran the same lap times in a 3800 lb 99 Z28. Every time I tried more entry speed to lower the lap time and get more speed....the car would go haywire.

sperkins

BTW - Nice saves in the video. I think the code brown moment was mainly due to hitting the curb (along with an ill handling car - the curb didn't help things). Watch some of your other laps and you'll see that you used more curb at the 13:45mark or whatever it was.

FASTFATBOY

Were you there this past weekend? There was a car similar to yours pitted across from me with Tony Cook.

I did lower the car on the factory bolts, it is not all the way down and I did pay attention to proper rake.

The car has the Pfadt performance/street alignment on it.

-1.3 camber front, 0 toe
-1.0 rear, toe in slightly.

Thanks for all the help guys, this board is the shiznitty.

FASTFATBOY

I don't think my line through there is that bad, I think it was a combination of really old tires and a really cold track. I really think I can run quicker on my Pilot Super Sports.


Here is the cars height.

sperkins

I was not at that event, but I probably would have gone had I known about it as I need to shake down the new car.
Alignment numbers look pretty good, but have you actually checked it yourself? Don't ever trust a printout that the $8/hr guy gives you at the tire store.
I would raise the rear simply by tightening each adj bolt the same number of turns. It'll take 5 minutes and it's easy to undo if you'd prefer to have it lower for the street. Just make sure not to thread the longer lowering bolt so far up that it rips the axle boot - that's why I suggested getting stock bolts back there.

FASTFATBOY

Car has stock bolts.

Have no way to check alignment, a good buddy can at the dealership, He's not a hack.

Supercharged111

Really sounds like tires to me. Running a local and recently repaved track this year, I decided to run last year's RA1s to conserve this year's RRs since my lap times were very competitive. I actually turned the fastest lap time of the weekend, just ended up 2nd except for the final where the POS car broke. At any rate, I felt the car was a bit on edge but drove it as is. This was July. Come September I take the pole by .001 seconds on the same set of last year's busted *** tires. Once the track warmed up, it was all I could do to keep from crashing the damn thing (my CMC car). I was on eggshells every time I entertained the notion of touching the skinny pedal with 260 sea level whp (I was at 4700'). I had no confidence braking off the front straight (my line involves cranking the wheel then doing a double apex, sometimes the car isn't fully settled) and no confidence going offline or attacking a competitor (again, off line). I decided to try the not cycled out RRs on this very forgiving track and the car was transformed. Initially I thought I had some understeer, but after talking with my fellow racers came to the conclusion that I was just entering too fast with my increased confidence (based on my butt's feedback from warmup that morning). I ended up winning both races that Sunday and not due to a dramatic drop in fastest lap time, rather due to the increased/renewed confidence I had in the car that resulted in absolute consistency. Plus some sweet luck on lap 1 that put me in front in the first place.

johnny c

david, common man. tires from 2009 aren't good. if you got a tire budget get some rivals. i bet a fresh set is much faster then the older r-comps. i too throw out all my tires after they seen a winter.

and watching the video i would say that you still have the wheel at the same angle when you go over that crest. trying to grab that much steering, wide open throttle, and going over a crest is asking for trouble. Randy Post said that you want to have the majority of your tuning done before a crest. i would try to apex that turn a little later.

but that's my $.02 i'm just a brake guy.