Quickshift_C5

Hey everyone. I recently purchased and installed an AP Racing Radi-Cal brake kit from EssexParts. As with most folks that purchase a kit like this, I did a lot of research beforehand and tried to find out as much info as possible. After thinking it over for a couple months, I decided to make the jump and get this kit for a C5Z I just picked up to build for HDPE's and possible Time Trials later on. I have another C5Z (supercharged, 638rwhp) that I've owned for quite some time, and have tracked it a bit. I stopped tracking it after constantly dealing with the heat, brakes, and wondering if the motor was going to pop at some point. Grabbed a new BRZ back in 2013 and thrashed it for several years worth of HPDE's. Sold that to get back into the seat of another Corvette on the track.

So, along with adding the usual coolers, I decided to take a hard look at the brakes this time around. The car is currently stock power, and will be for a couple seasons while I do cooling and safety first. However, it won't stay that way. I originally looked at the AP Racing Sprint kit, but wondered how well it would work on the hottest days at Road America, and then with slicks and more power down the road. The Sprint kit has some pretty amazing hardware, and uses the OEM size rotors. They seemed like they would be up to the task, but I also found myself looking at the other boosted Z in the garage. So, primarily due to how long consumables last, the ease of maintenance (read: lack thereof), and in the extreme off-chance this car breaks down and I decide to swap it over to the other car for a while...I decided to look at the Endurance kit instead. I contacted Jeff of Essex to get his opinion as well. The Endurance kit was really the best option, and while the boosted car would honestly benefit from an even larger disc, it would still work for the most part. It uses a 14" full floating disc, 6piston caliper, and an 18mm thick pad. Since the Radi-Cal kit was only $300 more at this point, I went with that. It's the best choice for a better caliper design, cooling, and resale value down the road. In all, I purchased the Radi-Cal kit with Ferodo DS1.11 brake pads, and rear Spiegler lines with Ferodo DS1.11 brake pads. I'll be starting out using OEM C5Z wheels that are 18x10.5 on all 4 corners wrapped with fresh Toyo R888R 295x30x18 tires.

I was pleasantly surprised when the package was delivered. These things are a work of art!



There were no issues with installation. There was a detailed set of instructions included that made it pretty easy, including tools needed and torque values. This kit could easily be installed in about 3 hours max, likely less for the experienced folks. My install took a while, as I have very limited time during the week to work on it. I cleaned up the components before getting started, including washing the rotors completely with soap and water. I finished the install this weekend and a buddy dropped by to bleed the system and do a high pressure check for leaks. The usual bleed sequence was used, starting with the passenger side rear. For the AP calipers on the front, I started with the bottom bleed screw. Interesting thing to note is how much I could see the rear calipers flex when the pedal was pushed. The Radi-Cal calipers didn't move...at all. We double checked the torque on all components and did a final general check before taking the car for a test drive. Oddly, the first 10-15% or so of the pedal was a bit soft and then the brakes would bite down hard. We kept going and about 15min later, I worked the pedal hard at a stop light. Light turned green, and we got moving. The car in front of us started braking for the next light and I went to use the brakes as before, but it felt like we darn near went through the windshield. I assumed some air was stuck in the ABS system or somewhere else, but after that...the brakes were incredibly sensitive and felt absolutely amazing. There is absolutely no soft feeling or flex felt in this system. It's just an absolutely rock solid pedal, and it stops RIGHT NOW. The DS1.11 pads were a great choice.

Now for the bittersweet part. Sadly, we didn't get a chance to really use them hard or do the burnishing process (bed-in) due to a loud howling noise from the rear diff. When I got the car home right away and up on jack stands, we found oil all over the exhaust, axle, electrical connections, etc. When I purchased the car, the dealer did the output shaft seal on that axle due to a leak. I found this when I asked them to put it on a lift. They even provided the paperwork saying they did the work (I still have a copy of it), so I assumed they hadn't cleaned up the mess. This is only my 2nd time driving the car since I bought it, and hadn't cleaned it up yet. In hindsight...I would have cleaned the darn thing up and noticed it was STILL leaking. Shame on me, I guess. Anyway, drained the oil and there appears to be metal shavings, which is a bummer. Calling the dealer in the morning. Car is down for a while.

With my short time driving the car with these brakes installed, I can tell it's going to be an amazing system for many years to come. I absolutely can't wait to thrash them at Road America and see what it's like to finally drive deep into T5 and not worry about the brakes for a change. I'll be keeping this thread updated with my impressions of the setup once the car is back on the road. I'll also keep a log book of the consumables, including how much wear the brake pads see in a day at a given track. If anyone has anything they would like me to track, let me know and I'll get it done.

I also appreciate Jeff's (of EssexParts) pleasant attitude and willingness to answer all my questions. Every time I shot him an email, he easily responded within the hour. Their customer service is top notch. Thanks!

Here is the starting point on the brake pads, at exactly the 18mm thickness that Essex/AP advertise.


Here are a bunch of random photos of the kit and components.

Quickshift_C5

Using an OEM C5Z 18x10.5 wheel, the brakes have a good amount of clearance. I did absolutely nothing to get them to fit beyond simply mounting the wheel.

The calipers clear the wheel face by about 3mm.


The disc clears the barrel of the wheel by about 2in.

Dirk Miller

For the past year, I too have been lining up everything for this same addition to my C6. I must be extra hard on brakes cuz on 4 different occasions I got them way too hot. The last time I lost my brakes my stock calipers spread > than an 1/8 of an inch. This led me to decide not to track anymore until I got better brakes. I've been exceptionally impressed with the way Jeff Ritter of ESSEX explains the AP Racing line. Over the next couple of months I'm planning to step up to the CP9660's on my front and stay with my OEM rears. Thanks for the post, I'll be interested in reading more in the near future.

Olitho

Do you drive with stability control on or off?

fleming23

I just put the same Pro5000R kit on my C7 and had a similar sensation with the soft pedal initially. After a quick trip around the neighborhood, I brought the car back home and did another quick bleed (I use a Motive power bleeder) and sure enough, a few air bubbles came out of the top bleeders on both sides again. I may do it one more time just to be sure but assume this was due to everything being new and dry. Just a thought.

I am a fan for sure! I installed mine Saturday and went to the track yesterday. It was way too cold to try and threshold brake but the bite was fantastic!

Quickshift_C5

Great, I had assumed it was this also. Unfortunately, due to the other issues I didn't get around to bleeding it again. I had my buddy use the pedal so we could do a high pressure bleed and check for leaks. But also have a Motive bleeder that I then used afterward to pull a bit more fluid through the lines and make sure it was all fresh stuff.

I will make sure to do another bleed, tap the calipers a bit with some wood, and make sure all air is definitely out. Thanks for the feedback.

apex26

I had a similar experience with my C5Z. Jeff was very helpful, he did recommend I upgrade from the front sprint kit to the endurance kit--I did, and he was right. ( on a hot summer day I even managed to crack a used front J hook rotor at a test and tune autocross--which was run, line up, run again for at least 10 runs straight) He also gave me a great deal on a set of Ferodo pads to start off with. I was having issues every session with the stock calipers. Tip: there will be lots of air bubbles clinging to the inside of the new caliper. Take a piece of soft wood like a hunk of 2x4 and rap the caliper sharply to dislodge the bubbles so they float to the top. This kit integrates perfectly with stock rear brakes, just using the same pads. Ferodo is expensive, so I get Raybestos ST47s from Randy at Randall Race parts for a screaming bargain, and they are awesome. Sorry Jeff, but that's how I can afford those fantastic brakes.

davidfarmer

I've been running these over a year, extremely happy with them.

JRitt@essex

Thanks so much for all of the nice comments and feedback guys. We really appreciate your business, and we're glad we can help you guys better enjoy your time at the track while also making you faster!

JRitt@essex

Nooooooo! Sorry to hear about your woes Quickshift. I hope you get it sorted and back in action sooner rather than later!

crimlwC6

Olitho, are you wondering how he got spread that quickly? I've raced my C5(just over 3000 lbs) for almost four years with stock rear calipers and EBC yellow pads (just upgraded the rears to WW HH) without spread or fade.

Dirk Miller

Sorry for not responding back sooner, but I went out of town for a week without my C.F. password.
I drive with my stability control off. Along with that, I use DBA solid rotors, Raybestos ST43s, high temp race brake fluid, have brake ducts connected to rotors and drive with Hoosiers. The tracks are Thunder Hill, Sonoma and Laguna Seca. Hope that info helps.

Quickshift_C5

Small update. Drove the car briefly yesterday around town and a short highway drive trying to diagnose the rear diff noise. At low speed, the noise from the pads clacking/clunking around is crazy loud. Decided it was unbearable on the street and ordered the retainers with the spring clips from Essex last night. Will report back after those are installed, but I suspect the noise will be completely gone.

it would clunk on every bump and seam in the road. When slowing down, I could lightly tap the pedal and release and it would clunk every time as the disc caught the pad and it bounced back and then pedal pressure pushed it in again.

fleming23

When you go from drive to reverse and hit the brakes, do you have a pretty noticeable pop from the front? I think it is just my pads shifting (I do have the retainers) but the first time it happened I thought I hit something. The pads are pretty grabby at low speeds so I don't think that helps.

Quickshift_C5

I haven't noticed that happening yet in the ZO6. It did happen on my BRZ though with DBA T3 rotors and Carbotech XP12 pads.

I'll test that a bit next time I drive the car.

sccaGT1racer

Also check your upper control arm bushings?

fleming23

Car is too new for that, and it only started after installing the AP kit. It sounds and feels like the pads are shifting. I'll keep my eye on it.

YYZ06

have you re-checked the torque on the caliper brackets? I noticed when I installed my kit this spring that the old caliper bolts have a shoulder on them that gives them a slightly larger diameter. I noticed quite a bit of play in the bracket with the supplied bolts so I used new stock bolts. If the bolts aren't up to the 125 ft/lbs then the noise may be coming from the caliper brackets .

I have lots of other projects going on with the car so I haven't been able to drive with the new AP brakes.

spearfish25

Even my OEM iron rotor setup has pad clunk when I don't use stock pads. My Raysbestos ST43s are excellent but if I go over a bump the pads clank like a sway bar bushing that needs grease.

Quickshift_C5

UPDATE

Received the spring retainers today to keep the pads fixed in the rotor to eliminate the clacking/clunking noises. Installed them, and all noises are gone!

IMPORTANT: For anyone installing these spring retainers, make sure they are installed in the right orientation. The springs are not aligned dead center. The springs need to go toward the outside edges of the caliper. See the 2nd photo for a visual reference.