Well, the hemming and hawing is finally over. I finally committed to the Essex AP Racing 9449 rear kit. The front kit is so great that I just wanted to complete the set. And of course, again, Casey at Racewerkz just had the rear kit just sitting there ready to go. "Yup, just come on up anytime to check it out." Dang that Casey!!!! So yeah, this is what my car looks like now:
From a technical standpoint of overall braking power, I don't know where I'm going to be with the new kit versus the old kit. As much as I'd like it to be straight math of piston size/pad size/annulus height/rotor size, I don't think it's that easy because there is a variable I didn't anticipate----Weight.
Over the weekend, I did the install. Initially, I was just focused on getting the kit on the car and not worrying about anything else. The first installation instruction was to wash the new rotor to get the rust inhibitor off the rotors. So, I did that. Once the rotors were washed, I decided to disassemble the existing Stillen AP kit off the car. I pulled the Stillen rotor off the car-------and I'm holding the Stillen rotor/hat-----and I'm like, damn......this Stillen rotor/hat feels a LOT heavier than the Essex rotor/hat I just washed. So I pulled out my digital scale, and the weight difference between the two rotor/hat setups is interesting. Essex: 13 lbs 15oz vs Stillen: 22 lbs 5 oz. That is 8.38 lbs lighter per side! That's 16.75 lbs of rotating weight just on the rear wheels. And it's worth noting that the Stillen rotor is 75% worn too. So, a new one would be a bit heavier. I never thought the weight difference would be so dramatic. And there were still several other parts to consider.
I'm showing you the pictures of the rotors so you can see it for yourself:
So, then I started weighing everything.
The Essex caliper is lighter: 4 lbs 12 oz vs Stillen at 7 lbs 7 oz. 2.68 lbs lighter per side. 5.38 lbs total.
The Essex caliper bracket is lighter: 10oz vs Stillen at 1lb 12 oz. 1.125 lbs lighter per side. 2.25 lbs total.
The Essex pad shape is lighter: 13 oz vs Stillen at 1 lb 3 oz . 0.375 oz lighter per side. 0.75 lbs total.
That means just the rear Essex kit is a total of 25.13 lbs lighter (12.56 lbs per side) than the Stillen AP kit. All the weight is unsprung weight, with 16.75 lbs being rotatiing mass, and 8.38 lbs being non-rotating. I'm hoping that much weight loss on the hub will have a noticeable impact on multiple things---braking, acceleration and damper movement.
Initially, while considering the rear kit, my main focus was on the fact that the Essex rotor is 1.5cm smaller than the Stillen rotor, and the pad shape on the Essex is smaller. (I don't know how the piston diameters compare between the two. I know that the pistons diameters are the exact same for all six pistons when comparing the front Stillen CP5555 and the Essex 9668.) Talking with Andie from Cobalt Friction, we decided to increase the torque in the rear pads, so I ordered XR2. (Used to be XR3). Here are the two pad shapes. Essex on top, Stllen on botton.
Anyway, I am curious to drive this new setup. hmmmm there is Auto Club this weekend with Speed District....But there's a GTA time attack Buttonwillow next weekend also with Speed District! Or there's a Bimmer Challenge at Big Willow that same weekend with Speed Ventures!