Socalconstruction1

Thanks for the offer, but it's not needed, it's not even close. You will stop a mile before me, even if your on stock tires. I ran 1:26 at streets with my stock calipers and I was getting brake nockback, (I've since got new SKF bearings thy fixed that and had I got a chance to get to streets again with some working brakes I think 1:25/24 would be what I would run) I'd be at 1:30 or more with the Wilwood Calipers I have on now, I have to be so light on the pedal I have to coast into turns and slow down very slowly. Really takes the fun out of it as I usually hit turns very hard.

AORoads

I also have no solutions but thinking out loud: maybe TCE or you can answer. Has there been any test (or IS there any test) of the brake Master Cylinder? Is it possible some combo of things you are using is "fooling" the computer re ABS activation/full-on clamping?

0Todd TCE

Gottcha. The term 'pre bed' is one used by the industry to describe rotors that have been dyno'd by the manufacture before shipping taking the rotor through a number of heat cycles etc. As long as you had no previous material on them I don't see that being your issue.

0Todd TCE

Beyond my pay grade. I don't do electronics and indepth master cylinder and booster work. It would appear maybe that there is a situation developed on this car that is 'over boosting' the pressure. From the pure hydraulics standpoint if the OP is pressing with the same effort as with the stock brakes then the clamping force will be nearly identical as described in the post on piston area. Whatever is elevating the clamping (if not too much pad) is not the caliper.

I hope we can read soon of some findings

Mordeth

This is why I never sell my OEM stuff until I am 100% sure that whatever I have changed works. These things were designed by GM as a complete system. The minute you change one significant part, it needs to be tested and validated on your particular application prior to discarding old, working parts.

If we assume nothing else is wrong with the braking system, assume that the fluid is fresh and flushed and assume the pads, rotors and lines are installed correctly and bedded correctly and assume that your tires aren't hosed (tires stop the car, not the brakes and ABS activates when it detects wheel lock ie., loss of friction/traction), then first thing I would do is rip off those calipers or try different tires. I realize that the clamping force hasn't necessarily changed, but you need to start eliminating variables. My guess it is either tires or calipers.

Do you have or know anyone with OEM calipers you can borrow? Any shot at getting or borrowing back your originals? Or any shot at trying a new, fresh set of tires?

I would reset everything back and determine if the issue persists. This would isolate the issue.

Socalconstruction1

Yes massive mistake by selling the OEM stuff. and yes fluid is brand new SRF, bled with T2, inwent back to the same pad material "Carbotech XP12 " so that I could eliminate every variable, as of now the only thing different is the calipers. I am headed to thebtrack today to try two last options, first I will run the Polymatrics H in the rear, hoping that adding more braking in the back will help, after that I will swap in some brand new Toyo R-888s. I really hate using a brand new set of tires for testing, I was saving them for some hot laps, if the new tires don't work I'll have just waisted my best lap times. Also, I'll be tossing the Wilwood Calipers and going back to OEM. I have 0 doubt that going back to OEM will solve my issues, just trying not to throw a pile of money in the trash so doing everything possible to make the Wilwoods work.

I also forgot to mention that the brake shop who installed my stuff has multiple track cars that they own and do wheel to wheel racing, so they know their stuff.

Anyway ya I'll update this post on Monday when I get back. Thanks again for everyone's help here.

Mordeth

Good luck. I think you have a decent plan. Keep us posted and be safe!

hungryhippo

Are you sure they sent the correct part #'s?

Socalconstruction1

You know that is something I never even thought about, and no, I have no idea if they sent the correct part numbers, however they do fit perfectly, and lign up with the rotors as they should. I'm not even sure how to check that, but good idea.

Socalconstruction1

2 things about this system that is constantly on my mind is that the front pads have 1/2" less surface area than my OEM pads, and, the rear rotors had to be changed, OEM is 13.5" and I had to Install 13". Both of those changes in my optioniin would be a downgrade, I always thought bigger rotors and bigger pads were always better for better stopping and heat dissipation. I was actually told by Wilwood that the front pads were larger than my OEM before I bough them, and when they arrived and I saw how small they were I looked them up online for comparison and they do have less surface area. When I called Wilwood back about it their specialest, "Carl" told me they have more mass, because their thicker "17 MM" as opposed to 15mm OEM and that's why he said they were bigger.

Not sure if that hat means anything, but I know I didn't like that anything was smaller than OEM on an "Upgraded" braking system.

IN hindsight, those upgraded Pistons and high temp seals for my OEM calipers are sounding like the ultimate upgrade for basically nothing, as in "Cost" . On a Z06 GS car.

brkntrxn

My money is still on the tires. You say the braking is no longer linear, you are partially correct. In my opinion, your new setup has more clamping force at 30% than your previous OEM setup. And at 30%, you are overpowering the tires. The extra clamping force may be exasperating a fickle ABS module that was already present but never showed. It will be hard to tell.

Again, these are all "internet" opinions from our experiences with our own cars and Todd's vast experience with the brake kits. Until you change parts and test a few things, we will not know.

I am as curious as you and everyone else on what you find.

Socalconstruction1

Yes I could see how it's possible that sticker tires could possibly help, however I didn't buy this kit so that I would have to run brand new Hoosiers everytime I drive the car, I specifically gave every last detail to Wilwoods top guy when choosing my kit, told him how I used the car and what mods, brands and sizes I ran. My 4 track day old R-888s have the same grip in the corners as they did in the second day. With Toyos I've noticed the first day/heat cycle they have an Insaine amount of grip, by day 2 or second heat cycle they have dropped off a bit, still very good, but def much less grip, and they tend to maintain that 2nd stage/level level of grip until they chord. I will chord the fronts in 6-8 days, rears maybe 10.

Also, with my OEM calipers, they stop on a dime wether I've got in 5 year old run flats or brand new Toyos R-888s Braking points change slightly of course as does my cornering ability, but the car handles, acts and feels the same reguardkess of condition of tires . I still have 100% pedal range. No on off feeling like I get with Wilood. My Wilood kit is supposed to be s street/track kit, not a pure race kit

Suns_PSD

You need to measure caliper pistons and compare that to what Wilwood says it should have.

I did see a similar thing happen to another car many years ago. It was caused by the incorrect brake booster being installed. It had some crazy pressure and when you barely touched the brakes they were way too sensitive. They would lock up if you tried to use them much at all. Just an aside...

JRitt@essex

This doesn't sound to me at all like a pad or disc issue. In terms of their impact on brake torque/bias, pad changes don't have nearly the impact that piston bore changes do.

As Todd said in his first response, this sounds to me like the calipers have the wrong piston bores. Have you had a chance to measure the pistons in the Wilwood calipers vs. stock? If they were designed to run on the OEM Corvette discs, the total piston area of each caliper should fairly closely match the total piston area of the equivalent OEM caliper. At the very least, the ratio of piston bores in the front vs. rear calipers should be similar to the stock ratio.

hungryhippo

It's definitely not a tire or pad issue. I run the aero6 in front and a different model 4 piston in the rear, with xp10/xp8. No issues braking with NT01's or michelin super sports.
How are your front and rear tire diameters? Have you tried turning active handling off? I agree with the piston sizes being a possibility. When you get custom options like the thermolock pistons and nickel finish, theres more chance of a mixup. I don't know why they wouldn't upsell you on larger rotors, i believe the front can be had in 15" and rear in 14"

0Todd TCE

I mentioned this in the very early post. Going on to say that the larger bore Aero calipers would usually make for a longer, softer pedal.

You can easily do this by pulling out one pad and noting the diameter of the pistons in the caliper. (ore possibly the imprint on the back of the pad if clear) The small bore caliper, equal to that of the oem spec, is 1.625 (1) and 1.125 (2). The larger bores are 1.75 (1) and 1.375 (2) which makes for a pretty noticeable difference.

0Todd TCE

*The product is not a BBK, it's the caliper kit for oe size 14" front rotors.

The base number for that caliper is a 120-13289 and 90 (R&L) and can be fit with thermlock pistons.

Reviewing the part numbers it would not be possible to get the nickel thermlock with the 5.4" piston area and into this kit. That bore spec is only available, as I see it, with the 20mm wide pad. That would mean the caliper and mounting would not fit the bracket kit and and align with the rotor center line.

That being said if someone in the know like me was putting together something of a custom build and making a change in that DBA rotor and hat they could have mistakenly ordered the larger bore in the kit. If you ordered this from a warehouse or Wilwood directly however it never would have fit as delivered in the white box.

NemesisC5

ErnieN85

Socalconstruction1

Ok guys, just got done with my first run of the day, and here's the deal. I have on my Carbotech Pads which have much less grip than the Polymatrics H compounds, and instead of trying the H in the rear with my 4 day old tires like I was first going to try, I decided to go straight out with the sticker tires R-888s it's got out here and didn't want to be changing tires in the heat. I'm 3 seconds faster than last time out and think I can shave another 1/2 seconds in my next run. The brakes feel good now but I'm still having a hard time trusting them from last time out, I'll continue going deeper into the braking zones to see if or when they lock up. As of now they seem to be fixed, HOWEVER, I think after 2/3 more track days on these tires the same issue will come back, so that being said, I think this Wilwood brake kit are only good for Hoosiers or full race slicks. They can become dangerous on my Toyos whenever the tire falls off enough to lock up the brakes. I'll be out here for two full days, should be 5/6 25 min sessions per day. So will see how they hold up throughout the weekend. Just thought I'd update everyone here.

I like the Toyos because I can run them hard with a lot of grip for 6+ track days. Hoosiers and or slicks you might get 3. Cost and durability are key. So changing to slicks is not an option or anything in interested in doing. So it looks as if I'll have to make a change with the calipers. They do not work they way Wilwood told me they would "Perfectky with my Toyos" they should be described as "For slicks only"

For comparison, I feel as though my OEM calipers stop the car just as fast as the Wilwoods, I think because the OEM has plentys of clamping forsce to max out the Toyos and when the Toyos or any other tire you run fall off your braking will stay safe and consistent with OEM. , I do believe with some Hoosiers the Wilwoods would stop me faster. Basically, the Wilwoods have way to much clamping force for my setup/ties "Toyo R-888s"

I am at Chuckwalla Vally Raceway. Just FYI. 94 degree weather.