jcp907

Hello all! I have been a long time member and have finally purchased a C5 Z06! I would like some advice with regards to what rules to build the car to, for the road course. I am sorry for the long read, but want to present the relevant facts in order to get the most relevant replies.

A little about me:
I live in the Orlando area and have run Sebring and Roebling Road so far. My physical size offers some limitations in the cabin. For instance, my shoulders are 27.5” from the floor when sitting, which makes seat choices limited due to belt angles. Additionally, in the stock seat, I hit my head without a helmet. It must be replaced.

I am competitive. My focus is to improve as a driver, but, I want the car to be a stable platform as quickly as I can afford, particularly with regards to maintenance costs. This will be accomplished through HPDEs and PDX’s in 2015. A driving coach might be hired. I predict that I will want to move to timed events for 2016. I am uncertain if wheel to wheel racing is desired.

A little about the car:
2002 Z06 with stock powertrain ~29k miles and it came with the following:
Brey Krause Harness Bar
Brey Krause belt mounts
04 Z06 Shocks
02 Z06 Shocks
Pfadt adjustable Sport Shocks (already blew one out)
Koni Yellow shocks single adjustable
Carbotech pads XP10/XP8 f/r
Superblue fluid
Continental street tires and another set of Z06 wheels for the rain

I have made the following changes for the next event:
Motul 600 brake fluid
DRM Brake ducts up front, not yet installed
Stoptech brake lines (new)
Hankook RS3s 255/17 front 285/18 rear
I have also purchased 18x10 and 18x11 CCW Classics with Continental scrubs (perhaps prematurely).

Issues to resolve
Seating:
I ordered a Kirkey seat and removable Sparco wheel.

Braking:
I lost my brake pedal a bit at my first outing at Sebring with the XP10/XP8s. This was after a few “good” laps and I suspect it was due to fluid overheating. I have replaced the brake pads with the same material as they were thin up front and ordered the DRM ducts (without the hub mounts-yet). These are yet to be installed.

Additionally, I believe that I want a more aggressive front pad, as the pedal pressure seems higher than I would like for braking zones: T1 at Roebling, T17 and T7 at Sebring. This MIGHT be related to the stock seat and trying to stay in it, but a compound change might be considered. Additionally, in T7 of Sebring, the rear of the car seemed unsettled with the Pfadt shocks. The Konis are on it now.

Bushings:
The stock bushings are pushing out of the control arms in front, particularly the top arm I have a 2nd set of control arms and am considering Delrin or Spherical bushings. Delrin allows a more competitive classing in Autocross, but this is secondary to reliability on the road course.

Sway bars:
I am running a Pfadt (I believe it’s the fatty) up front with the aluminum adjustable arms and the stock rear. I will probably replace swaybars this year.

Stance:
When I purchased the car, it was lowered on stock bolts. It is probably too low. I get loose when autocrossing and it’s an unpredictable loose In other vehicles if I get loose because of my right foot, I feel it coming on. In this car, the rear has surprised me 3x in 2 events. I will raise the car, corner weight it, then align it.

Questions that I have now:
Is there a class that is more budget friendly, that has a few competitors other than TT3/TT2 in Nasa with the C5 Z06?

Is there a measurable difference between the spherical bearings and the Delrin bushings on the control arms on track or regarding maintenance?

Is the stock spring sufficient as I move to dot R Compounds or should different leafs be considered? Or coil overs?

Why would one choose a staggered wheel/tire setup for the road course?

Thank you in advance for any and all input!

froggy47

I'll just take one question, I am lowered all the way on stock bolts & am NOT AT ALL prone to oversteer. A little tight if anything. Lowering BY ITSELF does NOT make a car oversteer.

Now, IF you are bottoming out your suspension due to other issues (shocks?) then yeah, that'll spin you out. If your rear alignment is wrong then yes, that'll spin you out.

Lowering with ALL other suspension components engineered correctly is a good thing. How many race cars do you see raised up in the air (not counting rally cars)? That's right, none.

Suspension needs to work 100% together & it's tricky to DIY unless/until you have it well figured out.

andy3101

The kirkey aluminum seat should be braced in the back. Fia rated composite seats do not need to be braced but the aluminum ones from kirkey should be. (Safety concern)

crimlwC6

Sounds like you've carefully considered stuff, good for you.
Don't touch the motor
Sphericals are better
Upgrade brakes now (i use wildwood calipers with stock rotor sizes). This will save you money and time in the long run. I recommend forum sponsor tce todd.
My car is light (2850 ish without driver) and sits high on stock leaf springs. Works great.
You don't need coilovers until you get GOOD if ever.
Don't touch the motor.

jcp907

Thank you for the replies!

Understood, and I do believe I was bottoming the bump stops causing a rather rapid increase in roll stiffness. Rear traction went away with no warning. I would expect RS3s to offer some warning if it was throttle related.


Thank you for the great advice. Question, Until I install a cage, the seat will be against the rear bulkhead. Is that sufficient for HPDE/PDX? If simply being against it isn't sufficient, would bolting it to the bulkead be sufficient? Alternatively, is bracing it to the harness bar sufficient?

Unfortunately, none of the composite seats that I have sat in allow a belt passage that is high enough (in relation to my shoulders), and all of them have my helmet against the roof.

Thank you for the advice! Even though I don't like the don't touch the motor part...

jcp907

What tires and sway bars are you running?

63Corvette

I'm sorry, but I have a completely different suggestion from those above.
SELL this car and buy the best ($$$) C5 Z06 RACE car that you can afford....prefferably one built and developed by a name builder like Phoenix, or a former C5 national champion, This method makes you instantly competitive and is more financially efficient. The other method (yours) requires you tofirst spend money to build your car, and then MORE money to develop it into a competitive racer. Bad idea. Your choice Ideally you want to spend your money and time DRIVING your car, and not working on it

jcp907

I have considered this...two ways, actually. Buying a completely developed car means bringing more money to the table at the time of purchase. That will take time given my situation (4 kids, three college age, and one two year old). The second method that i have considered is purchasing a higher mileage C5 and building it. For the next year, this is the car I will be running and the modifications that I will be making will be reversible, barring incident on course.

With that said, I am still hoping to hear more thoughts and opinions, particularly with regards to whether NASA TT2/TT3 is the best game in town or not.

blkbrd69

1st: Race platform.
Can you flat out afford the serious cash outlay to race?
I have done a bit and its just stupid expensive. I run a quick C6Z in advanced run groups at Sebring and I would be stretching my budget to "competitively" race a Miata much less a C5.

Building a car:
Have built a few and its lots cheaper to buy one used, unless you own a very good shop and are a 1st rate fabricator. Making the jump from fun at HPDE's to racing is huge. There is no turning a car back once it's properly caged for wheel to wheel racing.

Seats;
If you are tall you may have an issue with the harness bar not being high enough especially with a Hans device. My Cobra Suzuka and shark bar fits my tall torso well with the center of the tall harness holes at about 27" Sitting on the floor with MTI brackets I am very low in the car.

Brakes:
Just get used to buying a "true" race pad and SRF fluid. Sebring is rough on brakes and turn 7 is a bear. Lots of good calipers out there.

Bushings;
Yes sphericals are better, but gets hard to justify the price? Look at Vansteel's delrin. Impossible to tell what the car and alignment is going to do with old stock bushings.

Coaching;
You state you are competitive. Is that competitive by nature, or are you flat out quick running sub 2:30's at Sebring in a stock C5 on street tires?
We have some great instructors in Florida. As you progress through the HPDE classes you will get a feel for what you need.

Engine; Do not change a thing yet.......Have you closely read the Time Trial rules as far as weight and HP? May have to Detune!

V4kerker

jcp907 I'd recommend if you haven't already read Zenak's stick on his C5 Z06 build and tracking it. I still use it from time to time.

I think the answer to question 1 is No. There's not a more budget friendly class than TT in NASA for those running a C5 Z06. Jcp907 there's nothing cheap about competing on the track against others unless you just compete against yourself or running a spec car maybe.

I'm guessing you have very little seat time and recommend you spend money on safety and seat time first. I like 63corvettes thinking. Get one already built.
Start talking and hanging with the TT guys at the NASA events to learn from them also.

Hope it all works out for you.

jcp907

Thank you for the time you took to reply.

Yes, at some level (I may find that the level is autocross). I am going to do what I can with what I have in HPDE this year and determine the answer to this question. The Miata isn't an option...I've tried.

I used to build and maintain cars as a full time job. However, I have zero Vette experience. I have been involved with F Bodies, Fox's and SN95s in AS and rebuilt one of Lou's old World Challenge cars and I took care of it when it was campaigned in World Challenge T1. Our driver took Rookie of the year in that car with me as car chief. We also took that car to SLA front suspension in 1997 and had fun in ITE. I have also been involved with a GT3 RX7. This was all in the 90s, and I have forgotten a lot, but I have a decent idea on what it takes. With that said, buying a sorted car isn't out of the question.

I also understood that it's irreversible once it's a race car. For the next 12 months, I expect the modifications to be reversible and I'll evaluate whether I proceed with this car, or move on to something else.

I have to lay the seat back to fit under the roof, but the seat I ordered is also at 27" for the top of the belts, and I anticipate having to cut the holes a bit more. Because of the layback, I don't think the bar will be too low, but thank you for pointing that out. It's something to pay attention to.

Do you have a suggestion on a true race pad compound/caliper? I don't see a reason to go larger on the rotor. 10-4 on SRF.

Ther price difference is about 400 more for shpericals, so it's not terrible. Vansteel and Phoenix delrin are both considerations, as is LG for Spherical. I am not aware of others, other than Pfadt/AFE if they begin offering them again. This is a spare set of arms that are being modified, so I can swap back to sell the car if desired.

Competitive by nature. Not fast, but I am confident that will improve. My first time out at Sebring was my only time, to date. It was in Oct when it rained half of Sat and I saw the result of a friend go into the tire wall coming out of 7/8. I stayed tentative, broke conservatively, and ran 2.42s. I was content with that. I hope to run mid 2.3x next time out on street tires. I have requested Ian Stewart to be my instructor, and he has offered assistance with autocross advice. Here is a video of that last outing at Sebring. I was purposefully conservative under braking as the car was new to me, and it was my first track day in since 1999.
Pay no attention to the accelerometer in that video, I moved the phone when it was calibrating.


Understood and agreed. Yes, I am familiar with the rules. I'll be close to 3400 lbs with me in it (285). I shouldn't have to de-tune much, if I have to at all. It put down 369 as it sits on a Dynojet.

jcp907

I have read Zenak's sticky...a few times! It has helped me a lot!

Thank you for confirming that TT3 will be the least expensive class to run in. That is what I figured.

I do have very little seat time and I will change that. I want to get the car as close to TT prep, sans cage, as I can, in HPDE. Who knows, perhaps I will sell the C5 and get into an IT car at some point. But for now, this is what I'll be running!

Good advice on hanging out with those that are doing it, thank you!

crimlwC6

I've got stock springs and pfadt old school SA shocks until my drm ones arrive, ran last weekend with one c6 shock due to leaking pfadt shock. I have pfadt joc sway bars. I'd call up Lou at LG for suspension. I actually experimented with running my shocks at less than stock rebound last weekend. I say that just to point out that the typical slam it and run everything super stiff ain't always the answer. Sounds like you know your way around the car. The other thing I strongly recommend when you go full commitment is laying the radiator forward.
I just pulled out my ls1 with 10k track miles and 92k overall miles and it just needs some minor work. Was running strong when I pulled it, don't touch the motor!

JRitt@essex

First, congrats on the new car! The C5Z is a classic, huge bang-for-the-buck, fun and fast car. I'm sure you'll enjoy getting to know it immensely. I tracked one for several years and I'll always miss it.

For track use, brakes are one of the weaker points of the car. As others mentioned, Sebring can be a bit evil on brakes. My advice would be to address them early and properly in your build. I've been selling Corvette brake packages on this forum for roughly 10 years now, and I currently represent Essex Parts Services/AP Racing. AP Racing brakes were used on the C5.R, the C6.R, the C7.R, and the Corvette Daytona Prototypes. Essex imports and distributes AP Racing, and we have a range of brake packages that vary by spec and price. A few features will determine which package is best suited for your needs:

• Budget
• Rule Set
• Length of Session/Race
• Wheel Fitment
• Other Planned Modifications
• Tire Choice
• Tracks Driven

It sounds like you've answered some of those already. Rule set is a big one. I'm also guessing you'll be on far stickier tires once you get competitive, which will change your brake requirements.

We split our competition big brake kits into two main categories: Sprint or Endurance. Regardless of which route you go, all of our Competition Kits feature professional grade features such as stainless steel pistons with anti-knockback springs, high vane count endurance racing AP J hook discs, anodized caliper finish, and reasonably priced spares. These kits were designed from the ground up with exactly what you're doing in mind.

Sprint
Our front C5Z Sprint Kit was initially designed to comply with SCCA T1 rules. Many people use this kit for DE's, Time Trials, and/or 20-30 minute sprint races. It features the same size disc as OEM (325x32mm), and the discs are interchangeable with OEM discs if needed. It uses a 20mm thick, commonly available pad shape, and heavy duty 70 vane discs. It fits behind the OEM wheels without a spacer. We also have a matching rear Sprint Kit if you decide you'd like one down the road. It uses the same caliper body and the same discs as the front. Our Sprint kits are arguably the best bang-for-the-buck available.

Endurance
Our Front Endurance Kit was designed for those running 18" wheels who wanted a larger heat sink. It features a 72 vane 355x32mm disc (same ones that won the 2012 championship on the Action Express Corvette DP's), mated to a six piston caliper. We also have a matching rear kit for future consideration.

You can see some of the development history on these kits here.

Regardless of which way you go, the DRM ducts are a great idea and I would move forward with installing them. You'll want the added airflow they provide.

I'd also recommend starting with one of our front BBK's, then assessing the rear needs. Many of my customers find that pads and lines are enough in the rear.

The fact that you've already had brake fluid fade (soft pedal), and you quickly burned up a set of pads, all while on your first outing on street tires should give you a pretty good idea of what to expect in the future! When you're chasing a lap time, having to take cool down laps or bleeding brakes between sessions is about as much fun as gum in your hair.

Some people on this forum will tell you that you don't need a BBK. Need is a strong word. I will tell you this after equipping hundreds of Corvettes with brakes over the past decade, and owning the exact car you now have: The C5Z is FAR more fun to own and track with a good big brake kit installed on the front. You'll have more confidence at every turn (being a competitive person, you'll find that this is a big deal), you'll spend less $ in the long run on consumables, and you'll waste a LOT less time bleeding brakes and swapping discs and pads.

I'd encourage you to check out the product links, and read some of the customer reviews on our Essex blog. There are many customer reviews of both our Sprint and Endurance Corvette kits there. You can feel free to call or email me at any time. Good luck, and enjoy getting to know your new ride.

As for staggered wheels/tires...My track setups were always square front and rear. One of the good budget ones was rear OEM C5Z06 wheels with 305 slicks at all four corners. That was my favorite setup that felt the most balanced to me.

Also, I ran 2004 Z06 shocks, T1 sway bars front and rear, and 5mm lower on stock bolts. That was it on suspension. It was a simple, cheap, and effective suspension setup that didn't have too many variables. I went that route after having double adjustable shocks on my prior car. Not tinkering with my suspension settings really allowed me to get intimately familiar with what the car could and couldn't do under all track conditions, types of turns, etc. I'd recommend keeping it as simple as possible if you really want to focus on driving (which it sounds like you do). IMO, it's more fun to just get in and drive the same car every time, rather than constantly twiddling shock settings while chasing 0.1 seconds.

ps I forgot to say, I had height issues with my Z06 as well. I'm 6'4", and the OEM seats were misearble. I ran a Sparco Roadster seat on Hardbar seat rails. It had good bolstering, but lower sides than many race buckets, so it was easier to climb in and out of. I currently have an aluminum seat like a Kirkey in my Miata, and it can be tough to climb in and out of depending on how limber/mobile you are. Then again, the Miata is like a soda can on wheels...not exactly roomy! The quick release steering wheel will be a big help for you I'm sure.

jcp907

Jeff, thank you for this great post!
Are you at PRI? If so, what booth?

Budget-I'd rather spend more on racing than on the car, when it comes to maintenance. I don't mind spending now, to save later. But, I want to do it with a plan.

For instance, the Konis and stock springs will be the way I go, for the foreseeable future.

I am leaning towards the Delrin...I am probably not good enough to notice a difference between them and the sphericals and they are 400 less money. They are also better on the street for when I drive to an autocross. If someone believes that the sphericals are much better (are they worth a half second on a 1 minute course?), please tell me why!

Rules-will be HPDE for 2015=no rules, evaluate, learn and commit or bail on a TT2 or TT3 build or purchase, unless this Nasa announcement on Thursday changes things.

Length of session-I probably can't afford to build for more than 20 minutes at a time.

Wheel fitment-I'd like to fit Z06 wheels without spacers

Other mods-Slippery slope. I'd like to stay away from Aero as that opens the wallet-suspension is necessary etc.

Tires- Road race R comp for practice, A6/A7 for times eventually.

Tracks-Southeast primarily. Homestead, Sebring, Daytona, Roebling, Road Atl, perhaps others. Daytona and Sebring would be the most frequent, I suspect.

Is there a reason phenolic pistons are more popular?

This is valuable information!

I want to clarify that I was running on 60% (at least) worn pads and believe the lack of mass contributed to the fade, as did overbraking. It was expected going into the event, but I knew I would be conservative as it was my first time out on the track in many years, and first time in that car.

More valuable advice, thank you for that!

I will probably move to square rear Z06 fitment.

I am not much taller than you, but only have a 34" inseam and my height being in my torso is the issue. Being 285 lbs is also a contributing issue. I am not limber.

Thank you for the time!

troyguitar

There is no cheap place to run a C5Z anymore now that NASA got rid of TTA. SCCA autox AS class is ok if you run a totally stock car, but for road course every class is basically an unlimited spending contest.

In the Southeast in TT you are running against $100k+ MTI cars, good luck with that.

63Corvette

I absolutely agree with jeff on this matter

Bad Karma

I have the similar itch to get myself into W2W as well. It seems to me that one of the most economical ways to do that would be to go through NASA and compete based on power to weight. There could be some good competition with others like SCCA or a local smaller club, but as mentioned it can becomes a spending contest. Not that it won't at an ST1-ST3 level, but seems a little more manageable. What I suggest it keep an eye out for participation results, it would be nice to avoid being in a class where you are only racing one other car.

A lot of how you build the car depends on what class you want to run. Going with NASA opens up a lot of options, but if you decide to try and run a stock class than that will change your build plan.

From what I have read the difference in Delrin to Spherical is significant enough to make you want to go with spherical. I think best bang for the buck here is the do it yourself LG Motorsports kit, the other one that catches my eye is the Doug Rippie kit that they machine and install.

For your seat have you tried sitting in one of the composite seats without the bottom seat cushion, I've seen really tall guys run on the street with the pad in but pull it out for going on track to gain the needed headroom?

Personally, I wouldn't trust the PFADT shocks, there were too many versions and I've seen enough posts about guys chasing down leaks that I would steer clear. They could be partly responsible for some of your odd handling characteristics. Also I would keep an eye on tire pressures when you come into your oversteer issues; I found early on my tires would start to feel a bit slippery in a longer session when the pressures got too high, I've never run RS3's so I don't have any personal experience with them.

JRitt@essex

No worries. We actually have two booths at SEMA. Essex Parts Services booth 4276 and the AP Racing booth 4815. Go to the AP Racing booth and ask for Daniel. He can show you the options for your car.

It sounds like either of our Competition Kits could be an option. The Endurance setup offers a bit more longevity on the consumables (pads and discs), because they are larger. They don't wear as quickly, and don't need to be replaced as often. That longevity is offset by the higher initial purchase price.

The smaller Sprint Kit will fit inside the OEM 17 Z06 fronts, and the larger Endurance Kit will fit inside the rear OEM 18's when run on the front. So both kits will technically fit OEM Z06 wheels...just depends on which configuration you want to run. The larger kit will give you a bit more 'headroom' for future mods.

I've had a couple customers find the limits of the Sprint Kit on certain tracks under certain conditions. To my knowledge I don't know of anyone ever fading the Endurance Kit. That inlcludes big HP C6 Z06's, supercharged C5's/C6's, etc. I usually tell people that the Endurance Kit is the "do it once and never think about it again solution," whereas the Sprint Kit is the "most likely enough, but not guaranteed solution."

Regardless of which way you go, they're both quality kits, and they hold their value. If you decided to go Sprint, you could always sell it on the used market and upgrade to the Endurance if you ultimately choose a class that allows bigger discs and calipers.

Stainless steel pistons are expensive. As such, they're not used in most mass produced calipers. Plastic and aluminum are cheaper.

Yep...as pads burn closer to the backing plate, the lack of mass causes them to heat soak and burn more quickly. The last 5mm burns up much faster than the first 5mm.

If you're at PRI, definitely go by the AP Racing booth and check out the products. The calipers and discs will be there, and someone can give you a tour.

jcp907

Will do!

Ooops, I meant aren't more popular. I would suspect that a good phenolic would have insulation qualities that are superior to stainless. What I don't know is whether or not they would be durable and consistent.