Brake Issues Summary
I'm going to try to keep this as summarized and brief as possible, although it'll still be very TL;DR for most...
Up through Sept 2011: My brakes were fine. I still had my original OEM rotors on the car, and Hawk's HPS street pads, and no real braking issues. I had been to a few light track events / Auto-X with this setup. No vibration, just the to-be-expected weak bite and brake fade.
Sept 2011: I decided to give 2-piece rotors a shot for the rotational weight savings, while also upgrading to Carbotech's XP-8 pads for a little more track-worthiness. The rotors were from Relentless. I chose them because they were one of the only claiming a 2pc for the rear with a real weight drop back there. I had actually ordered these and PAID IN FULL for them on May 25, 2011. They didn't arrive until Sept 9, a full 3.5 months later after a very long email thread with me bugging the vendor about ship dates and getting a constant stream of broken promises all that time. And when they did arrive, some of the minor hardware bits (rear caliper pins) were missing, so I had to wait another week for him to ship those.
Also, when they arrived, the fronts were the expected 10 lbs lighter per corner, but the rear rotors (which also involve adding a custom spacer between the two halves of the rear caliper to make the caliper accomodate a thicker rotor, so it's not a simple swap...) were actually *heavier* than my 1-piece OEM rears. He did a lot of backpedalling on that and claimed I was the only one to measure that, and I must have freak OEM rears or something. Whatever. He wasn't in a mood to take back half the kit, and claimed I could use the cooling upgrade in the rear anyways (the rotor did look considerably beefier with much better cooling vane setup). So I went ahead and installed the damn thing.
Late 2011: The new setup bedded in ok. It got through one full track weekend sometime in Late 2011 without any obvious vibrational problems. I did get ice-mode for the first time on this setup. In retrospect: XP8+XP8 (matched pads F/R), plus much cooler-running stock rear rotors, plus all the heat that happens up front on the track -> more likely to hit ice mode, because the fronts fade a lot faster than the rears do, leading to rear lockup before front.
Jan/Feb 2012: Had another track even that went smoothly. After that, started noticing a slight steering wheel shake while braking at high speed on the street. Could be any of a number of things, although rotors are the most likely candidate. Tried to do some rotor cleanup before an upcoming track event: sand off pad deposits, sand down the pads nice and flat, and re-bed the pads to the rotors. It seemed to clear things up somewhat at street speeds. Got to the next track weekend and from the very first session (this was TWS, it has some *very* high speed brake zones) the shimmy in the steering wheel under braking was coming back with a vengeance. I ended the first session short because I was worried I had a real problem on my hands.
Spent that whole day trying to debug mid-event. There was a race mechanic shop on duty with a mobile garage setup for the event, had them go over the car as well. They said the suspension and bearings were fine, and it had to be the damn front rotors (which seemed insane, since these are supposedly very high quality rotors, and this only their third track weekend and they've been on the car barely like 4-5 months). Keep in mind also that before these rotors ever went on, I was already aware of all the stupid things people do to make rotors go bad, which is why my stock ones lasted 2.5 years and were still going strong. I never stand on the brakes at a stop, I never ride brakes, I always cool them down spinning before parking the car, etc. Anyways, as a last ditch hail-mary effort to save the track weekend, I let a local auto parts store try to turn the RA front rotors on a lathe to get me running again. It went poorly, the rotors got worse. Most likely their lathe and/or lathe operator just couldn't cope with doing a proper job on slotted rotors, but who knows. Called off the weekend and went home.
March/April 2011: I did some measurements to confirm the front rotors, as mounted on the car at the time, were definitely out of spec on runout. Also confirmed that the aluminum hat was showing zero runout down to 1/1000th (the precision of my dial gauge). Hard to say it's evidence of anything since they'd already been through that horrible lathe job as well. Called up RA on Mar 10th, complained a lot about the rotors' short lifespan. Blame the customer, blah blah, offered me a set of replacement front rings at retail w/ him covering the shipping. So I said ok. I had a track event coming up for April 21-22 weekend, so he had about 40 days to get me some replacement front rings. He failed to even get close to being ready to ship them on time (although at least he let me know so that I could come up with an alternative in time for the weekend).
So I ordered a set of cheap (but supposedly high quality) 1-piece rotors from Z1, the slotted upgrades they sell for $198 a pair, front and rear. Slapped em on, and made it through that April track weekend fine. I also had the Stillen front brake ducting installed for this weekend for additional front cooling (I had homebrew ducting before, but it was just to the wheel well not the back of the rotor), and upgraded the front pads to XP10 for more front fade resist. By having a better pad up front + better ducting, and not having excessive rotor cooling in the rear, my ice-mode problems seemed to have gone away.
Mid-May 2012 - At this point I was completely ready to abandon my RA kit and didn't even want the damn replacement front rings. Weight savings in the front aren't worth the reliability issues, and the rear kit is a total joke (caliper mods; heavier rotors; more weight to the outside w/ the aluminum hats; too much rear cooling contributing to ice-mode). I didn't even want to talk to this guy anymore. But he still had my CC info, and when the front rings were finally ready he went ahead and billed me and shipped them, since they were ordered just for me. I hadn't really cancelled my order either, I had just given up on him and stopped calling him, so I guess it's a grey area. Whatever. I shelved them and figured maybe I'd try them again at a later date when the Z1's wore down or something.
Early June 2012 - I was sure at this point the RA rotors were to blame, since swapping in those cheap Z1's seemed to clear up the problem. But then.... I started getting the same issue on the Z1s! Vibration under high-speed street braking, getting progressively worse. I again tried some simple pad deposit remedies right off, and it did help for a little while, but the problem came right back pretty shortly. Cancelled a track event or two while the rest of this unfolded...
June, July, August 2012 - Given same problem with two different vendors' rotors, I figured I must have some other underlying issue, even though two different shops claimed my suspension/bearings were ok from pulling on things. I figure not all suspension/bearing problems are obvious in that way, they might only appear under certain torque or loading while running the car.
So, one by one (swap a part, do basic brake maintenance, test the car with some brake bedding, find out the problem is still there, order more parts, wait a week or two to arrive and have time to install, again...), I replaced: the front wheel bearings, the front outer tie rod ends, and then finally the whole front lower control arms (it has the lower ball joint, and on this car you replace the whole arm to replace a bad ball joint). After each one the car tightened up a bit and felt a bit better, but ultimately the braking shake was still there in the car. I also re-built the calipers at the same time I replaced the tie rod ends, in case they were sticking at all (seals / dust boots, etc). I was at a loss.
My next thought was that perhaps one of those suspension parts was loose and was a contributing factor to both sets of rotors going bad, but once the damage was done to the rotors I guess it doesn't go away. So, it's time to try new rotors with all this newly-awesome suspension maintenance. So I pulled the fresh RA rings off the shelf and put those back on the car for a spin. Bedded them in and sure enough got the same vibrational problems....
This is the point where I was about ready to drive the car off a cliff. RA -> Z1 -> RA front rotors all showing the same problem, yet I've swapped everything else that could matter to this up front and that didn't fix it either. Went to (another) front end shop, and relayed the important bits of this story, and asked the guy to dig around for anything but the rotors that could be causing the front end shaky-braking he could obviously feel on the test drive. He inspected / pulled on everything and said, basically, "There's no freaking way your problem is anything but rotors, your suspension is really tight and perfect, and these rotors are bad". WTF. He also took a stab at turning the RA rings, total failure as before, but I'm not yet convinced anyone can successfully lathe a slotted rotor (and to boot, this second set of rings were on a full-float hardware setup, so it was about impossible to lathe on that hub anyways...).
So now we arrive at 3 weeks ago... I ordered another fresh set of Z1 front rotors. Put them on the car, indexed them to 1/1000 or less, mounted everything up, went for a test drive / bedding session (cringing the whole time).. and it went flawlessly. The car felt so straight, smooth, and true under braking I just couldn't believe it. So that last mechanic was definitely right. At that recent point in time, the fresh RA rotors were the only cause of my problems.
Conclusions? - Honestly, beats the **** out of me. I can think of a number of scenarios, all highly-improbable, that match all the data over time above, and I'll list a few of them, but I really don't know.
1) It could be that my suspension and bearings were always good enough to not be a serious problem, and that the first RA rotors, first Z1 rotors, and second RA rotors all had varying degrees of manufacturing issues, taking varying amounts of (in some cases, zero) time to become prominent issues in the real world. Metallurgy, tolerances, etc. And then my second set of Z1's were flawless. Given all my vendor problems with RA, and the fact that he's such a low volume vendor with a semi-shady history I wish I had read up on before doing business with him, I'm totally ready to write off both sets of RA rings as bad-from-the-mfg, but I'm a bit hesitant to write off the first set of Z1s as being bad rotors....
2) It could be that I had a suspension/bearing problem, which would lead to some vibration, which would in turn destroy rotors and make them continue to vibrate even after the original problem was cleared up. This would explain the first set of RA's taking a little while to go bad, the first set of Z1's taking a little while to go bad, but then it doesn't explain the 2nd set of RA's being bad right off the bat on a clean suspension/bearing setup.
3) It could be that the whole original problem was shitty RA rotors, and I had a chain reaction of problems from there. As in: the first RA rotors went bad early due to metallurgy / heat issues, and started vibrating the car badly under braking. During the track event that happened at (some really hard shaky braking hits) + some highway/street miles after, all that shaking from the brake rotors caused premature wear and looseness in ball joints and/or tie rod ends and/or bearings, which then lead to that being the issue that appeared and damaged the Z1's while they were on the car. Then I cleared all of that up, and the second set of RA's was bad from the get-go, and the fresh Z1s on completely cleaned up suspension/bearings was fine.
Right now the car feels perfect, I've even gone out in the middle of the night and done some track-level braking tests, and it's flawless on the Z1's with all the new suspension/bearing bits in place. One week to my next track event (after having cancelled a few over the past few months due to all of this
), so the real question is whether the problems are gone for good after another track weekend or two. Time will tell.