As one of the first Audi application with the new AP Racing RadiCal BBK system, I've been running with them for about four months now. I had used them on the street as daily drive as well as two track events so I felt that there's sufficient usage that I can really say something about the system.
I purchased the set from sonic tuning. There was quite a lot of delay with my order which caused me to miss one track event. Considering these are the first sets, it's understandable. At least they have good pricing. Then Stillens who actually distributes these BBKs stepped in and helped me through the process. Jim Hodgman from Stillen has gone back and forth with me on some technical issues. Great guy and great service from Stillen!
Ok. Here's the review part:
Visual:
These calipers are simplify massive! Very good looking, much better looking than the old 6-pot AP BBK setup. I've got quite a lot of compliments at the track for its looks. One thing I'm not very happy with is the paint. I got the caliper in red. First of all, it's really easy to scratch. The caliper actually came in scratched already. During the shipping, there's a lot of rubbing against the shipping foam which caused the surface to be scratched. And it is extremely easy to chip compared to the paint on the black OEM caliper made of recycled boat anchor. I've already chipped a couple of spots during my installation. Be extra careful when taking wheel off. Nothing too major but I hope AP can really improve on the paint quality.
paint scratch after shipping
Installation:
This took me quite a lot of back and forth to get it installed. I did the whole installation myself.
First they shipped me two identical calipers for the driver side. I didn't realize until I put one of them on. Then had to take it off and wait for the correct caliper to come in. Again Stillen was really responsive throughout the process. After completing the installation finally, I took it out for a drive. There's severe vibration braking at highway speed. It vibrates so much that braking above 70mph feels unsafe to me. I took the wheel off to inspect and found out that the caliper mouth is not centered around the rotor, causing one side of pad to drag against the rotor. As a result, wheel is not sitting flat. I got on the phone with Stillens again. Jim double checked their CAD and insisted that their mounting bracket is designed correctly.
As a workaround, he proposed to ship me some shims of different size to space out the caliper from the wheel hub to make up the offset. With the shim installed, you can see that it's much more centered:
Vibration gone. Finally, after so many dramas, I can drive. Anyone else running this kit on your B8/B8.5, please let me know if you have similar problem. One thing I wish they had done is to include a set screw hole in the rotor. Would have been much easier to install with a set screw.
Performance:
Ok, we buy these kits mainly for their performance not looks. Here's my setup:
Front rotor: 370mm x 36mm cross-drilled and slotted two-piece. Rotor weights slightly heavier than OEM. If you are looking to save some unsprung mass, may want to try something else.
Rear rotor: Stillen cross-drilled rotor to match the look (OEM drop-in replacement)
Pad: Ferrodo DS2500 front and rear. This is the pad of choice that came with the kit. It is a semi track/street pad. No noise but quite dusty. Brake dust shows an reddish hue in direct sunlight. Will need consistent cleaning. They takes a few brake applications to warm up until they really start to work, which was annoying at the beginning but then I got used to it.
Fluid: Torque RT700. Much more expensive than the common Motul RBF600 but well worth the price. I've been to two track events with them. Pedal remained firm and no need for bleeding. I say put your brake bleed money onto the right fluid.
SS brake lines front and rear
I had little issue daily driving with this setup. Nor are there much benefits other than the all-mighty look of the BBK.
First track event with this BBK at Laguna Seca, there has been some issues. It's not very consistent. It takes the abuse very well some times but other times, ABS kicks in really early under hard braking then there's little stopping power. Or it just simplify just feel weak. I also had a couple of experienced drivers testing it on the parking lot off the track. They all complained about the annoying warm up phase and more importantly, how weak the stopping power is after some abuse. It doesn't feel like fade. We all concluded that it's most likely a pad problem and I was about to swap some other track pads.
However after the track event, the system worked much better so I decided to give these pad another try. Initial bite is much harder and the inconsistency is gone. Pedal remains firm. Braking is very linear. Super easy to modulate. I think the poor experience I had from the first track event might have been insufficient bedding. Obviously, after driving on the track for two days, it is well bedded. Second track event at Thunderhill, a very fast and hard braking track. The BBK performs to the expectation. Stopping power might be a little bit more than stock brake, Harry's lap timer recorded -0.8g compared to -0.7g with stock brake at the same turn but it's probably within measurement tolerance. Fade is totally non-existent throughout the entire weekend. It just works and you don't have to worry about it! It's amazing how hot it is fresh after the track but it does take all the abuse with no complain. I remember my stock brake fades after 3-4 laps every single session. Rotor is still in perfectly healthy shape after 4 track days. No weird pad deposit or crack.
Overall, very happy with the kit for both the look and its performance on the track despite of all the dramas I had being an early adopter.
(the "deposit" on the rotor surface is from washing)
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Originally Posted by Leor604
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