At the end of the 2019 track season, I have started looking at upgrading my brake system to a setup that is track-focused and proven. Having researched the field on what is available and what is coming down the pipeline(MPP/StopTech), I decided to with a setup that is a full track without much consideration for the street. @RedwoodMotors was extremely helpful in discussing the three different AP Racing options available for Model 3. During the discussions, there was never any sense of pressure to make a sale, felt more like talking shop with a fellow gearhead. I appreciated that a lot.
I was using RB460 4pot 380x32mm, a street/track setup for most of 2019, this changed my perspective on what I want in my next BBK. AP Racing Radi-CAL Road & Track was briefly considered. However, having had RB460 street/track BBK, I didn't want to try another system that made any concessions for the street. Additional consideration of the overall weight of the brake system quickly eliminated the Road & Track version kit. So it was down to the two track only kits, Competition and Competition Plus. Both of these kit have the same 372x34mm 96 vanes J-hook rotors. The difference between the two is the caliper, specifically the width of the calipers. The Competition Plus version is designed for the endurance race, and it uses 25mm thick pads. Just to put that into perspective, the stock P3 red Brembo caliper pad is 15mm thick. The pad cost for 25mm is the same or slightly higher than the 18mm uses by Competition. The caliper of the Competition Plus (9668) is 402gram heavier than the Competition (9660), which means the entire setup is 804g heavier.
Here is a chart I created to track the weight of my brake system. I didn't include the weight of the brake pads in this chart.
As you can see, there is a definite winner in this chart. The AP caliper is almost 50% lighter than the stock P caliper. Lightness benefits all aspects of driving. 1000g = 1kg = 2.2lbs
Impression:
Immediate, direct, and linear are the best objectives to describe the experience with AP Radi-CAL Competition KKB with Endless EX99 pads and Endless RF650 fluid. There is zero slack or delay between the pedal press and braking force. Conversely, the release of pedal results in an immediate release of the brake. No stickiness. Part of the directness feel attributes to the anti-knockback springs (AKBS) behind each of the pistons in the caliper. The force of the springs inside the 9660 calipers are 4lbs and 7lbs. In essence, pushes the pistons outwards slightly so the pad is grazing against the rotor. This functions to remove the gap between the rotor and the pads. The gap is inevitable in all rotor/caliper system as the flex of the brake system/suspension system during driving would knock the piston back into the caliper. You can read more about it AKBS and other technical research with 9660/9668 calipers at Essex website. - Essex Designed AP Racing Radi-CAL Competition Brake Kit (Front 9660/372mm)- Audi RS 3 (8V) | Essex Parts Services, Inc.
While the 9660 caliper is very light in weight, it is also super stiff. This stiffness is apparent in the linear translation of pedal travel to brake force. I had a chance to perform a few stops from 70mph+ to 10mph, 50mph to 10mph, the increase pedal travel from 70 to 50 is linear incremental. Compare to other systems I have experienced, where the pedal travel is less linear with the exponential amount of pedal travel with an increase in speed.
The location of the bleeder valves is another design differentiator on the AP 9660/9668. Both valves are on the inside half of the caliper, with one on top and one at the bottom. The typical caliper would have one valve on the top of each caliper halves. I suspect this will make maintenance easier, as I would only need to bleed the top valve for quick air bleed. While the bottom valve would be used for a full flush, being at the bottom will help flush out any solid particles in the system.
At the time of purchase, I did make one concession for NVH is to opt for the anti-squeal clips. The clips with Endless EX99 made this setup virtually silent for street driving aside from two specific situations. The first situation is when you apply brakes after you change motion from forward to reverse or vise versa. 9660/9668 calipers do not have tension springs that pinch the side edges of the pad. When the brakes are applied with the direction of motion different than last time when the brake is applied, this will cause the pads to shift a bit in the caliper and produce a single clack sound. The second situation is with the J-hook rotor. J-hook rotors are known for their ability to keep the pads clean. Unfortunately, the shape also produces a constant buzzing sound whenever there the pads are grazing the rotors while in motion, which is the case with AKBS installed. Without an engine to mask any noise, this buzzing sound is audible even with the windows closed, the sound increase in volume with speed increase. The constant buzzing sound is reminiscent of the saccade but without the ebb and flow of volume and pitch. However, but removing the AKBS, it pretty much eliminated the buzzing noise.
So far, I am very impressed with the AP Racing 9660 setup. Again, thanks to Redwood for helping with this setup. Can't wait to try it on the track.
I was using RB460 4pot 380x32mm, a street/track setup for most of 2019, this changed my perspective on what I want in my next BBK. AP Racing Radi-CAL Road & Track was briefly considered. However, having had RB460 street/track BBK, I didn't want to try another system that made any concessions for the street. Additional consideration of the overall weight of the brake system quickly eliminated the Road & Track version kit. So it was down to the two track only kits, Competition and Competition Plus. Both of these kit have the same 372x34mm 96 vanes J-hook rotors. The difference between the two is the caliper, specifically the width of the calipers. The Competition Plus version is designed for the endurance race, and it uses 25mm thick pads. Just to put that into perspective, the stock P3 red Brembo caliper pad is 15mm thick. The pad cost for 25mm is the same or slightly higher than the 18mm uses by Competition. The caliper of the Competition Plus (9668) is 402gram heavier than the Competition (9660), which means the entire setup is 804g heavier.
Here is a chart I created to track the weight of my brake system. I didn't include the weight of the brake pads in this chart.
As you can see, there is a definite winner in this chart. The AP caliper is almost 50% lighter than the stock P caliper. Lightness benefits all aspects of driving. 1000g = 1kg = 2.2lbs
Impression:
Immediate, direct, and linear are the best objectives to describe the experience with AP Radi-CAL Competition KKB with Endless EX99 pads and Endless RF650 fluid. There is zero slack or delay between the pedal press and braking force. Conversely, the release of pedal results in an immediate release of the brake. No stickiness. Part of the directness feel attributes to the anti-knockback springs (AKBS) behind each of the pistons in the caliper. The force of the springs inside the 9660 calipers are 4lbs and 7lbs. In essence, pushes the pistons outwards slightly so the pad is grazing against the rotor. This functions to remove the gap between the rotor and the pads. The gap is inevitable in all rotor/caliper system as the flex of the brake system/suspension system during driving would knock the piston back into the caliper. You can read more about it AKBS and other technical research with 9660/9668 calipers at Essex website. - Essex Designed AP Racing Radi-CAL Competition Brake Kit (Front 9660/372mm)- Audi RS 3 (8V) | Essex Parts Services, Inc.
While the 9660 caliper is very light in weight, it is also super stiff. This stiffness is apparent in the linear translation of pedal travel to brake force. I had a chance to perform a few stops from 70mph+ to 10mph, 50mph to 10mph, the increase pedal travel from 70 to 50 is linear incremental. Compare to other systems I have experienced, where the pedal travel is less linear with the exponential amount of pedal travel with an increase in speed.
The location of the bleeder valves is another design differentiator on the AP 9660/9668. Both valves are on the inside half of the caliper, with one on top and one at the bottom. The typical caliper would have one valve on the top of each caliper halves. I suspect this will make maintenance easier, as I would only need to bleed the top valve for quick air bleed. While the bottom valve would be used for a full flush, being at the bottom will help flush out any solid particles in the system.
At the time of purchase, I did make one concession for NVH is to opt for the anti-squeal clips. The clips with Endless EX99 made this setup virtually silent for street driving aside from two specific situations. The first situation is when you apply brakes after you change motion from forward to reverse or vise versa. 9660/9668 calipers do not have tension springs that pinch the side edges of the pad. When the brakes are applied with the direction of motion different than last time when the brake is applied, this will cause the pads to shift a bit in the caliper and produce a single clack sound. The second situation is with the J-hook rotor. J-hook rotors are known for their ability to keep the pads clean. Unfortunately, the shape also produces a constant buzzing sound whenever there the pads are grazing the rotors while in motion, which is the case with AKBS installed. Without an engine to mask any noise, this buzzing sound is audible even with the windows closed, the sound increase in volume with speed increase. The constant buzzing sound is reminiscent of the saccade but without the ebb and flow of volume and pitch. However, but removing the AKBS, it pretty much eliminated the buzzing noise.
So far, I am very impressed with the AP Racing 9660 setup. Again, thanks to Redwood for helping with this setup. Can't wait to try it on the track.
