NoradIV

Hello Guys,
I have completed my first season of lapping with my newly acquired 2002 C5 Z06. As I have been recommended by many different sources, I have kept my car mostly stock and I focused on seat time, so that was two sessions a week (so about 40 sessions) and 6 track days. While being an absolute blast, it was extremely expensive and exhausting.

I have done the following changes before or during the season:

1. Upgrade from stock pads to Hawk HP+, then to PFC11 (blank cheap disks)
2. Swap brakes lines to braided steel
3. Install an OMP First-R sport seat.
4. Replace tires 3 times (went through a set of continental extremecontact dws06 and a 2 sets of Michelin Pilot Sport 4S)
5. Replace all fluids for Redline and Gulf RF1000 (for clutch and brake), twice for the transmission and diff, and at every 2.5k miles on the engine.
6. Replace all belts
7. Replace valve springs
8. Upgrade stock radiator for Ron Davis with EOC
9. Install Diff and transmission coolers from DougRippie
10. Bypass the about-to-fail steering column lock
11. Replace the factory titanium "axleback" with a modded steel one (wanted to know how it sounded before chopping the titanium one). The stock one is just too quiet.
12. Not done by me, but mentionning it may be important. The previous owner thought it was a great idea to get rid of the factory wheels and get a set of garbage 20x10.5/19x9 Scorpion wheels from Cray.

I've been a carguy for the last 6 years, so I have somewhat of an idea where I am going. Not planning is expensive, lead to problems and may end up with a car that is not balanced, so I figured I would post here and have an idea of what to do. I use my car as a weekend cruiser/track car. I would eventually like to have it dedicated for the track, but the C5 is just way too cool not to drive it.

I am listing the following problems I have encountered with my car this year:

1. I believe I have a slight detonation at WOT in the 3000-3500 rpm range (a couple of tick tick tick sounds)
2. The brakes become incredibly unpredictable about mid session. Sometimes, I hit ABS, sometimes, I hit the floor with no brakes, sometimes everything is fine. I tried pre-pumping the brakes, short and intense burst or less pressure for longer, nothing works. I would like to add that we have small tracks in Quebec, so my average speed is about 50-60 mph. The brakes will remain shitty for a while after the track. Bleeding seems to help, and driving the car on the street for a couple days also appears to help. Not sure if it is boiling fluid or hubs becoming loose when hot.
3. There is a pretty loud growl coming from the back in the range of 45-70 mph. Growl frequency follow speed, not gear leading me to the rear axle being the problem. This happened after one of my weekly 2 sessions evening on a very hot day (I suspect lubrication failure due to fluid overheat) one day before I received the DRM coolers. I pulled both the fluids and passed them through a coffee filter with no metal shavings in both of them.
4. I have noticed some liquid inside my air intake flex tube (the one between the filter and the throttle body), and my throttle body had some dark gunk on it. Not sure what this is, but I will have to investigate.
5. My tires have a bad wear pattern, where just the outside get chewed up.
6. My tie rods are loose.

So, what I want to do next year is to substantially reduce my track costs and work on reliability (so that I don't have to replace broken parts). This season did cost me about 25k Canadian pesos, which was about 10k more than last year budget. This year, my budget is realistically 10k. I have to reduce my costs. To do so, I will reduce my season to max 8 track days and will let go the weekly track sessions. This should reduce my cost on fuse parts (brakes and tires), which were about 9k in costs (About 2000 in pads and disks, 1000 in fluids and the rest is PS4S) and get a track oriented alignment (after replacing my tie rods), which should make my tires wear more evenly.

I also want to find a set of 18x10.5 inch wheels in order to reduce cost of tires and have a better selection of them, as well as be able to do a tire rotation. I will be looking at buying two used sets of factory wheels, using the 17inch for street tires and 18inch for track tires.

I am unsure if I should replace my axle right away, or if I can keep it for another season. My garage (Zekes) suggested I buy another one since they are not really comfortable rebuilding it themselves. Shipping it to the states is not an option due to the 999% duty rate.

I don't know how to fix the brake problem. I will try to buy better disks, which should improve ventilation. I could also make better ducts. I've read somewhere that the hubs could be part of it as well, but trowing money at a problem without understanding it is not a proper way to diagnose an issue.

I've researched about the pinging issue, it appears to be deposits caused by the PCV, and a seafoam treatment was suggested. I am not quite comfortable removing the intake to do it, but if I don't try, I'll never learn. Perhaps adding a oil catch can would mitigate that problem.

I am unsure about the liquid in the intake flex pipe as well.


So, I have trown a lot of thinking out there. I would like your opinions. Be harsh, I don't mind, I just wanna learn.

Thanks for reading.

mattastick

I've got a set of 4x 17" front wagon wheels with Conti ECS tires sitting in the garage, if you wanted that setup cheap-ish. It'll make buying wheels a little bit harder, but the tires are in great shape (~2k miles, 6 wet autocross runs at Solo Nationals last year). When I sold me car, the guy didn't want these, so they're just taking up space now.

Other than that, your tire wear is because that part of the tire is getting too hot. More camber will help, and stiffer bushings too. I was amazed at how much delrin bushings helped the tire wear issues on my C5.

FAUEE

Step 1 is lose the ghetto wheels. They're adding a lot of weight, and way out leverage wise, making EVERYTHING worse.

Your tire use seems excessive, I think you need to consider something that's up to the task of tracking more. Let's not immediately blame your brakes for these issues when it really could be the tires. Those are good street tires, but clearly on your big trims they're not up to the task on track.

How many rotors did you crack? If you weren't cracking them frequently, it wasnt your brakes, you weren't getting them that hot.

That said, I'd probably look into a bit more aggressive pad, I'm sure carbotech will chime in with their offerings.

As far as the axle goes... you sure it isnt wheel bearings? If your shop wont rebuild ot, I'd find a new shop. Maybe try the dealer for getting it rebuilt if that is the problem.

NoradIV

How would the tires be responsible of a shitty and unreliable brake pedal? The problem I have is a mushy pedal or a pedal with a long travel, which occurs mid session.

I cracked 2 of them. Also, are you familiar with PFC11? Because I have compared them to DTC 70 and they are better at handling heat.


No, I am not sure, but the standard "shaking the wheels when the car is in the air" was not conclusive (aka the wheels are tight), also the sound really appears to come from the middle of the car.

When I pulled the oil after the change, instead of being transparent and amber, it was a thick brown, muddy like texture, and that was 2-3 months after I originally changed it. Unfortunately, I have no idea how to isolate that problem, but I assumed it was because I spoke with a couple people who all had this problem.

tommyc6z06

Thanks for mentioning Zeke's...I was wondering who, here in Montreal would be knowledgeable about Corvettes. I have an issue that I need someone with experience and familiarity to diagnose for me (I won't hijack your thread ;-) )

tommyc6z06

whoops! Just phoned Zeke's and apparently the shop is closing next month. Retiring. So...I'm back to square in finding a Corvette knowledgeable shop in Montreal :-(

AND0

It looks like you got a really solid foundation with the C5Z and all the cooling mods. Just a couple more tweaks and you should be in really great shape.

Bill Dearborn

A few comments on the brake issues. First, the stock C5 front floating calipers are notorious for tapering brake pads under heavy usage. Most of the tapering is along the length of the pads and is the same on both sides of the car except for being in the opposite direction. That tapering can cause the long pedal you are experiencing. The first time I tracked my 97 I had 2700 miles on it and by the second session at Watkins Glen the brake pedal would go all the way to the floor. When I took it to the dealer after the event they warrantied the brake pads due to the tapering. Things that can make the tapering worse are worn caliper pins, worn caliper brackets or loose wheel bearings. You can attempt to reduce the tapering by the way you apply the brakes. First, push the pedal to get the pads in contact with the rotors and then push hard to slow. This can be done over a very short interval and will slow the tapering Vs just jumping on the brake pedal when it is time to brake. If you plan on keeping the brakes make sure your caliper pins and brackets are in good shape. Another thing you can do between track days is to swap the pads from one side of the car to the other. In other words take the driver's side pads and move them over to the passenger side while maintaining them in the same orientation to each other. Doing that will use the wear applied by the caliper counteract for the tapering.

Here is a picture showing the tapering of a set of pads from my C5 days:



If you look at the backing plates you can see something else that seemed to help the brakes. The C5 backing plates have a sharp edge on the side of the plate. File this off so the pads will move freely in the caliper. Otherwise they tend to stick. I filed the ends where they fit in the bracket and where the caliper anti-rattle spring pushes in the center of the pads.

The growling sound you can hear maybe your wheel bearings. I had to replace all 4 on the 97 when I started hearing a growling noise that I thought indicated a failed diff. The dealer mechanic found the right front hub was worn by removing the hub and turning it in his hands. That way he could feel the grinding in the bearings. Once that was replaced the noise reduced but to get rid of it we had to replace all 4 hubs. Luckily, the replacement was covered under warranty.

The only way to avoid being affected by the pad tapering is to change over to a fixed brake caliper like a Wilwood, StopTech, AP Racing, Brembo, etc. Do not even think about the C6Z calipers.

Unusual tire wear could be because of loose hubs.

Bill

Soloontario

Here are a few suggestions that may help
1) get those tie rod ends fixed absolutely. You can't have a good track alignment without functioning parts
2) get a real track alignment meaning at least neg 2 degrees camber up front. You will not have any trouble with tire wear on the street and braking performance only drops a little
3) get some used Speedline wheels 18 x 10.5 and run a square set up. I am not sure that it is actually much faster than running a smaller front wheel but being able to rotate tires to all 4 corners is really good.
4) you are lapping and not competiting in which case a really robust tire is a good idea. Stay away from Rival Ss and RE 71Rs. I use Sport Cup 2s but even the Michelin Super Sport works ok if not fast. Having adequate camber and proper toe will make your tires last much longer. For predictability you might even try Toyo 888Rs or Nitto NT01s but neither are ok in the wet. (Shameless plug, I have a set of 295/30-18 R888Rs for sale that have only seen 300 km of road driving, one lapping day at MIR and 2 Ontario Time-Attack events)
5) for the brakes,
a) make sure you have good fluid. I am a huge fan of Castrol SRF. Expensive but wonderful
b) of course you can spend $$$ on two piece rotors and 4 or more piston calipers but to stay more frugal, I really suggest the KNS kangaroo paw rotors. Way better steel than Napa, better design, better cooling and not all that much money.
c) I have used Carbotech 10s, 12s, PFC 11s and Raybestos ST43. The Raybestos is clearly the best pad for my purposes. Not too hard on rotors, easy to modulate and taper less than the others. Also wear much longer than the others including the very pricey PFCs
That being said, I do not do as many events as you and tend to change pads and rotors as soon as I am home (or often at the track which is way easier than changing pads and rotors on a fixed type caliper) to keep the Raybestos material on dedicated Raybestos rotors.That way I don't lose pad material being scraped off on the drive to and from the track. I just use the cheap stuff for the street.

I am interested in Bill's idea of rounding the edges of the mounting ears for stock type pads. This makes a lot of sense and is something I don't do but will definitely be planning on next season.

NoradIV

****. I wasn't aware of that. I just called Doug and he confirmed. Their shop was slowly degrading over time, lost 2 employees.

What a shame. I've been doing business with them for 5 years now. The best engine builders I've seen in quebec. Back to finding a decent garage...

Alright, my conclusions weren't too far from where I should be headed.

Is there a way to know if the hubs are the problem? Would getting them hot cause the issue? Because when cold, I do not have this problem.

If hubs get loose under heat makes me wonder if 2 piece disks would also help reduce the amount of heat reaching the hubs, thus possibly fix this problem? Not trying to say that SKF hubs aren't the solution, but they are about 1k canadian pesos once they reach my door (price based on SummitRacing), so I want to make sure that these are necessary before putting in this amount of money. If I go that route, at least it could be a combined job with the tie-rods, since I have to remove them to access the hubs anyway.

About swapping the brake pads, I did that once when I replaced my disks at mid wear (because they cracked), however, I have been told that any "irregularity" on the pad may carry uneven wear on the disk and made me assume this would be bad for the disk. Seeing you do this, I guess my understanding wasn't correct? If else, yea, I will start doing that as well.

I do have taper, but its far less than what you have. However, I use my car on the street quite a lot.

I do not have money for a big brake kit here. Apparently, the way to go is essex, but the price is just unreal.

I already tried Castrol SRF (actually went through 3 bottles of it by bleeding brakes after 3 events). There is no change between those and the gulf RF1000, so I went back to the cheaper option.

I'll try the raybestos ST43. Plenty of love for them here. Will try Bill's method as well.

Btw, thank you guys, your help is much appreciated.

NoradIV

Ok, so, based on your feedback, here is the new planning. I'll try to make things in order of priority and stop when I reach the end of my budget.

1. Install remote clutch bleeder (forgot to mention, the transmission is VERY hard to shift, and the clutch fluid was never replaced on this car. I replaced it from the top, but I couldn't get the entire line bled due to the extreme **** placement of the clutch bleeder)
2. Have a mechanics diagnose the source of the sound.
   • If it is wheel bearing, replace hubs for SKF
   • If it is rear axle, replace axle and eat ramen for the rest of the summer
   • If it is transmission, sell house and have transmission rebuilt
3. Replace tie-rods and get car aligned.
4. Get an oil catch can
5. Do a top end cleaning using seafoam or GM top end cleaner
6. Find 18x10.5 wheels (either buy 2 sets of used c5z06 wheels or buy 4 new)
7. Upgrade brake ducts using the quantum kit

Am I on the right path?

wtb-z

I have heard from other sources (never used them myself) that the Michelin P4S can have issues with edge wear. So I would encourage you to try a different kind of tire if that's the case. I think the stock hardware on the C5 can get enough camber to keep most street or streetish tires in a reasonably happy place on the track. Running square and being able to go front to back will help as well.

tommyc6z06

Please let me know if you know of any other places. Its hard to believe that in a city of 2 million people, with a vibrant car culture, that there are no shops left that are familiar with these cars...

DudeWithAVette

I am far from an expert but from everything I've read and discussed in person, brake fade issues won't be resolved until the rotors and calipers are upgraded.

Switching to higher heat carbotech pads and fluid helped but I still experienced a change in pedal feel during a 20 minute run.

It is quite a bit of coin, but after nearly hitting barriers twice last season due to brake fade, the AP racing Sprint front kit is getting put on my car this off-season.

NoradIV

Vibrant car culture? You mean all our racetracks being closed? Or the fact that no one can afford a nice car anymore because of the endless tax increase thanks to liberals?

tommyc6z06

I hear ya...I pay $650yr for plates on the 7l engine, instead of being taxed by fuel economy rating, like elsewhere. And even that is ridiculous because in theory we’d pay for our supposed excessive consumption at the pump.

Anyway, don’t get political...but our liberals have just been ousted in Quebec and will be Federally too in 11 months. Hopefully the example being set forth in Ontario now, will spread...although apparently Quebec is still anti-pipeline (wtf? didn't see that one coming).
One can only hope, but car culture is being replaced by kids wanting newest iphones. Academia is not our friend. Glad to have grown up and lived when i did.

And having said that, we are fortunate to live in a Golden Triangle as far as race tracks are concerned...close to 3 of the best on the planet. All natural terrain, ex-F1, old school high speed tracks; Le Circuit, Mosport and The Glen. I'm new to Corvettes but have raced all over North America and it just doesn't get better than these three. So, at least we are fortunate in that regard (as long as LCMT stays open).

But...I still need to find a local Corvette 'specialist' to help me diagnose stuff ;-)