OK, this will be fairly detailed post, as the development of the kit has been wrapped up, and we wanted to share the results.
First of all, big thank you to RB Performance for working through the development of the kit, Buddy Fey who helped us with some of the calculations, fellow Viper racers who shared their experience with brake bias issues, and Jon B. of Viper PartsRack, who came through on the last moment delivery of a tie link part that saved our weekend (which was the last opportunity for an extensive test this season).
Cliff’s notes: The kit delivers, and the car FINALLY has that “Racecar Feel” under hard braking.
Details:
We finally had a chance to test Rear Brake Bias/Balance kit, developed by RB Performance. Last weekend was a great chance to test it against OEM configuration, as we were using same tires and brake pads, and similar aero setup, as our last test day on the same track (when we had OEM calipers on the rear axle), with nearly identical weather conditions as well – alternating cool/dry weather, as well as some rain.
WetAndDry.jpg
We were using RB XR70 rear pads, and Sintered (100% Metallic – originally developed for CCM rotor kit) front pads, with the open slot, 2 piece RB rotors (ACR-X/wider annulus size in the front, OEM size in the back). The car was on BF Goodrich G-force R1S tires.
kit.jpg
From the first session with the kit, it was clear that the piston size calculation was spot on. Both initial engagement, and the car’s balance under moderate-to-hard braking was significantly improved.
As you can see in the snapshot (typical of many laps’ worth of data we reviewed), we can exert higher braking force on the rotors/tires, and, thus, achieve higher deceleration forces. As a result, we started to use later braking points in corners where significant braking was required (by 20 to 40 ft., on average), without loss of car’s balance. Not having rear ABS interfere on initial brake application was a critical part of being able to maintain the balance, and to build up optimal tire slip angle.
ForceTrace.jpg
Looking a little deeper into the data from the whole weekend, we can also see that there’s a reduction to rear ABS interfering (by about 30%), even though overall force applied to tires on deceleration, is greater.
brakeABS.jpg
Even the front ABS engagement is slightly reduced (unexpected result), likely resulting from an overall improved balance of the car under hard braking.
Finally, statistical analysis of average forces applied per wheel, show a consistent shift towards 50-50 “loading” of front and rear wheels under hard braking. OK, this sounds a little complicated – the bottom line, is that the grip across all 4 tires is maximized as the balance of the car is improved.
BrakeBalance.jpg
We improved our best time on this track by 0.9 seconds this weekend, with majority of gains coming from both shortened braking zones, as well as improved balance of the car under braking and on turn-in.
The weekend brought a mix of dry and rain conditions, and braking performance was consistent and predictable in all situations.
