Hello from a new 2002 C5 Z06 owner. I purchased a 150K mile car recently in hopes of doing some HDPE track time this year with it. As you might expect, the car drives lazily down the road just fine but spirited driving reveals a looseness that makes it difficult to maintain an apex nailing arc without some sawing on the wheel. Likewise nose bleed braking gives you a lot of quick jerks on the wheel to keep it in your lane. I suppose the alignment could be something that isn't helping the issue, but I still believe there's a general wear issue here.

Being new to the Corvette, I was wondering if I could hear from some other Corvette owners that autocross and open track their cars. Other than wheels/tires, what gave you handling confidence behind the wheel, made the car seem like it was a part of you on the track? I thought perhaps step 1 might be all new bushings? I was looking at the AFE poly ones? Any experienced HDPE driver, please chime in - I'm an infant here.

As background: I have a rebuild/redone Miata that feels like a go cart; razor sharp turns with just a flick and everything is so precise (now). I'm looking to get closer to that and get this thing on the track.

Thanks for reading and double thanks to those that share!

Ken

 

Sounds like the car is under steering. “sawing” the wheel upsets the car, so my guess is you are turning in too early. If you are diagnosing this with street driving, wrong place. Probably you have a tight grip on the steering wheel. This fires larger muscles in your arms and makes for choppy turning. Watch the racers, very light grip. Two hands at 3,9 and only move your right just to shift. move closer to the wheel, arms at 90 deg, so your seat back probably needs to be up more than you are used to.

Brakes. C5’s don’t have a reputation for powerful brakes. More than adequate for starting into HPDE, though. So since i suspect you have more to do with steering, then maybe braking technique needs some suggestions. You are probably seated too far away from the pedals. Your knee should be 75 deg bent when your rt foot hovers over the brake pedal.Then, as with steering, you use smaller muscles to brake, an you have more braking control.

Now your car. Unless you know the bushings are shot, leave them alone and focus on the steering rack and the tie rod ends. Then shocks next, if you are not sure. A good alignment is next. Also worn bearing hubs are likely at that mileage. Worn hubs have a distinct noise, and it will feel like you are herding the car down the road, not driving. Then tires

Not sure about your description of your brakes, but you may be activating ABS under light braking. This is a sign of the wheel speed sensors losing signal (another sign of worn hubs!).

You need some help diagnosing the car and only fixing what really needs to be fixed. If you start modding now, you will spend your hard earned dough on stuff you do not need. Set the car up for your and your instructors SAFETY. That is what impresses me when a NOOB describes his car. Your first HPDE’s you will see Miatas with one blown cylinder passing you.

My kids live in Frederick, and SOMEDAY I hope to get up there, see them and spend a few days running at Slum-it Point. If you are not too far from there, I would be happy to look your car over.

 

Wow!! That is GREAT information to give to anybody thinking of racing a C5 Corvette

I learned something today.................

 

Yes check all the bushings in the suspension as well as all the tie rod ends---
Check your tire wear also
Both front and back to see if the tires are wearing badly on the edges--If so you need a 4 wheel alighnment
Finally I would recommend also changing both the front and rear sway bar bushings to POLY this will give you a stiffer feel in the corners and plant the car better and flatter
I also have had excellent results with installing a SOLID rear Trans mount--This reduces flex when powering out of a corner--

 

Get the following: new sway bar endlinks front/rear - MOOG are good choice for stock sway bars
new sway bar bushings - poly makes sense to use here IMO as it won't drastically erode the cars ride on the street vs swapping out for poly bushings in the A-arms/motor mounts etc
new outer tie rods/toe links front/rear - can get a MOOG part for the front, for the rear Ecklers sells a good "heavy duty" version of the OEM part
new inner tie rods - may or may not need, fronts are much cheaper than rears but also endure less stress....

That alone will tighten things up quite a bit

If not good enough consider swapping out shocks - my recommendation would be DRM valved bilsteins - pretty much best bang for buck - I am running Bilstein sport shocks on my 03Z - def a lil harsh on street, they have 30k miles or close to it on em now, I plan on replacing w/ DRM valved version which should be a lil smoother on street & more "dialed in" for the car in particular

The leaf springs are probably still in decent shape although inspect the factory bushings they may need replacement

lower the car slightly on stock bolts - I found about 1/2" front & 3/4" rear is a nice compromise between street/track

finally get a track alignment & legit tires Nitto NT01, Toyo R888R, Michelin PSS etc

 

Thank you to all who answered. I have been to Summit Point many times, (FATT, SEAT TIME) and am not too far away from there. -75 minutes. -Not in this car though.

I purchased 17"s for the vette and did indeed plan for the Toyos to be used at the track. I'm totally with you on Ecklers HD tierods units and will do that. Interesting comment about the solid mount for the rear, how much vibration/noise does that add on the street? Agreed on poly sway bar mounts, probably go with swivel end links. The car came to me already lowered but it may be too much actually.

I dont plan to set records, I just want to be safe and finish the day with all four wheels still under me.

Thanks again everyone.

Ken

 

So you are going 17’s all around?. It was common 15-20 years ago to use 17’s from the c4zr1 as they were 11 inch wide. using 17” c5z fronts all around would take away tire grip you need in the back. Most C5 track guys either run 18” all around, or the Z oem 17/18. If you are thinking bbk later, your range of choices for bigger front calipers goes down with the 17 fronts. I run an AP racing bbk with 18/18 oem speedlines. Requires a 4mm spacer so the front caliper clears the spokes. That requires the wheel studs to be longer.

 

agreed on the square 18” setup or sticking w/ stock. Honestly- I decided to keep stock wheels & powdercoated gloss black, ptd center caps to match w/ corvette logo in red - looks great on my black C5Z. Now - I was on the fence initially either thinking of going to an 18/19” forgestar setup OR 18” square to open up more tire choices. But then I found more 17” tire size options out there like 275/40R17 used to be only 1 or 2 types worth putting on vette- now I have that size w/ Toyo R888Rs 305/35R18 rear. You don’t have to worry about issues w/ stability control w/ stockish tire setup. Just food for thought

as to your other question- I meant “solid” endlinks as in non-adjustable steel moog ones, greasable tho. The fronts are 3 piece “heim-link” adjustable style you are talking about.

 

Oh, gotcha. I didn't realize there was such a thing, good to know.

Yes 17x11 rear,17x9.5 front. These will be Autocross and track wheels/tires. They have the correct offsets for C5Z. I was thinking I might try 315's on the rear. Hopefully I can get them to fit alright given they are 17 inch and smaller height.

I know there's no such thing as too much brake but this car is so far beyond anything I've ever had before in the braking department. Summit Point's main course will certainly test them though.

Speaking of,: what weight oil do you guys recommend for track runs? 15W-50?

Ken

 

I run 15w50 Mobil 1 add a qt above full. Never worried about taking it out after a track day. Take it easy on the car for cold days when cold, and switch to 5w30 in the winter

If you have a lot of miles on the car, you probably have more blow-by than when it was new . What happen with these cars is they pump a lot of oil areund the engine, and sustained high rpms at the track fill the rocker area with oil. Then, one of the needed crankcase vents on the valve cover goes under oil. (look at the hose on the rt valve cover, how low it is) If your pcv system is not perfect, this will send oil into the intake. Catch cans will help some, but not a total solution. A good investment would be a new 2004 valley cover, as that is where the pcv crankcase vent orifice slit is. They are only a hundred bucks or so. Then, when the intake is off clean all the standing oil out of the intake. I hope you have a remote clutch bleed line on your car. A stuck clutch pedal will cost you a lot ruined track weekend, tow bill, and having to put one on anyway. Every month there are agonizing posts on this. Guess what, happens to C6’s and7’s too.

When I ran stock calipers, i used Raybestos ST 47 pads front and rear. Half the price of CarboTechs, and just fine.

Ran Summit main many times, but the Shenandoah is much harder on brakes because it is small and tight.