Could be. Bearings feel tight to me, granted I'm not loading them up the way a corner would.
My other theory-in-progress is that I'm stuck in a taper cycle. I haven't changed rotors and pads at the same time yet. I think there's a possibility that: rubber guide bushings tapered my rotors -> tapered my pads -> new rotors, same pads -> tapered my rotors and so on.
This evening I plan on pulling the pads and seeing the amount of movement the caliper has with the brass guides to run that by the hivemind.
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Double tapping is the right way to prevent knockback. First one straightens out the pad and seats the pistons square.
But, you are still running stock calipers and getting knockpack/taper, that points me to need to swap your wheel bearings. With brass guides your caliper actually sits pretty firm, but rotor oscillates due to tired bearings. I haven't heard of knockback on stock calipers, even from very spirited hpde guys and spec racers.
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I quietly wonder if your pad taper issue is coming from the initiation of pad doubletap.Leave a comment:
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Valid question, DSC is totally off when I'm on track.
On the ABS side of things, let me explain with a general update. I just spent three days on Summit Point Main, where I was experimenting more with double-tapping the brakes to fight knockback. Double-tapping has made a huuge difference in my braking, and is helping me stay out of ABS. My assumption is that the knockback in the front was causing the rear to lock up, getting me into ABS. Heck, since double-tapping the pedal, I had to adjust my heel-toe since the pedal is now that much higher in the braking zone.
Hence my focus now shifting a little more towards my taper issues, since those are surely exacerbating the knockback.
As far as DTC70s being the bitiest pads in the world, yes they are bitey, but I disagree with the sentiment that they're un-modulatable. I had no problem staying out of ABS with them in the rain this weekend once I started double-tapping the brake pedal.
The other change I'm about to make to the car is suspension. On Dominion a couple weeks ago, a fairly rough track, I really started to feel how the (PO's 😛) H&R springs were letting me bottom out under braking, again leading to ABS activation as the car skipped across bumps in the braking zone. I'm thinking if I get some suspension travel, and can reduce my pad taper some, the subsequent reduction in ABS will help things last a little longer.Leave a comment:
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First question those with brake issues should answer is whether you use any safety net from DSC, or its cousin MDM/M track mode on later cars. Latter is still way too intrusive and will jam the grabbies many bars of line pressure full force into the rotors as you start doing fun things (braking into a corner or full throttle accelerating out), keeping you out of the walls. Sometimes it is easy to butt feel it working but sometimes it is not. It will overwork (and potentially overheat) even the better setups out there and will make the brakes pop, crackle and smoke in the pits. You will also see miserable pad/rotor wear.
DTC70 are a SUUUUUPER grabby compound, I would not run them on anything less than the super 200s (RS4 are endurance). Engaging ABS introduces full line pressure pulses and vibrations that also put more heat into the system and pulverize pads/rotors.
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Having used a couple of these on different cars from different sources, FCP, Bimmerworld, it seems like they all come from the same supplier. I wonder if quality is going downhill. Someone at the track said he had a lot more play in his Bimmerworld set than his FCP set 🤷♂️Originally posted by Estoril View PostLeave a comment:
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I've said it before, but the 996 based kits simply don't have enough thermal mass- they're using the stock sized rotors.
Even the cheaper AP 8350 caliper kit uses 32mm thick rotors (vs. 28mm for stock sized rotors). That's a pretty big difference. Also, the vanes are better, the floating hat, etc.
It was mentioned already that you can get a version that has 1" thick pads- far longer lasting pads. Also, brake pistons and seals that are made for track use.
I don't think you need all four corners. The other big plus is the 8350 kit will fit under 17" wheels and definitely the stock 18s.
I would get the ducted backing plates for the front and duct the rotors.Leave a comment:
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I've used both - neither with any pad taper issue. I used old-school Turner IIRC. Suggest you check your pins for straightness and for marks that might suggest binding/rubbing. Make sure pad "ears" are 100% seated of course. If it continues, I'd pull the affected wheel(s) and make sure pads are reasonable placed and tight after multiple braking events.Originally posted by Pklauser View Post
Make sure your choice of brass bushings are a correct fit for the car and don't allow for excessive movement over the slider pin.Leave a comment:
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How's people's pad taper with brass guide bushings? I've got a Bimmerworld set, and honestly they still allow for a lot of movement, resulting in some extreme taper. Been wondering if moving to one of the "long" kits like: https://www.iemotorsport.com/product...-long-version/ would help at all. 🤔Leave a comment:
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Back from the track, brakes worked great … unfortunately it was super cold (in the 40s and a little sleet, love OH weather). So will wait for the summer for a real test.Leave a comment:
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Thanks for that update Maxhouse97, eager to hear if the ducts and SRF get you there. I've been a Motul 600 guy as well, but maybe I'll make the jump. I'll be at Mid Ohio and PittRace in May with Chin if you're doing either of those events!Originally posted by Maxhouse97 View PostLeave a comment:
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OP referred to me in the original post, so wanted to clarify where I ended up:
- Front: FreakyParts Megane front on 360mm E90 rotors for a bigger heat sink, Volvo S60R Hawk DTC-60 pads from FCP, SS brake lines, Vorshlag brake cooling ducts. Minor rust ring, not very noticeable.
- Rear: 996 with Rally Road brackets on CSL rotors, base DTC-60 Boxster front pads from FCP on rear to prevent rust ring. SRF fluid all around. 996 are noisy under certain conditions on street, could be the pad.
This worked to 85% effectiveness (minor fade) my last track day minus brake ducts and SRF (used Motul 600), based on street experience I expect those two adds to get me to 100%. Headed to Mid-Ohio this weekend. Was about $1500 for front and about $1000 rear. Very happy and looks great.
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Really appreciate your thoroughness Fresh1179, sounds like we've gone through a similar journey and you appreciate the consumable expenses. Couple of questions and comments:
Fwiw I too like the feel and modulation of the DTC-70s, I don't find it offensive, though I do agree, the dust/slag is pretty rough.
What is appealing to the StopTech rotors over Zimmerman blanks to you?
Is the reason you recommend 25mm over 18mm about pad costs, longevity, heat capacity, what exactly? I ask because my 17" Arc8s are going to require even more spacer if I go with that larger caliper. Not ruling it out, but the cost delta between a set of RS4s in 255/40R17 to 265/35R18 is nearly $500 so factoring all of this into it, not to mention needing different wheels. Swapping to the Bimmerworld 17s will give me more clearance, but again that will effect the economics of the whole thing.
Where did you buy your AP Radicals? I see Essex has their CP9668 (25mm) kit here at $5399 and CP9660 (18mm) kit here at $5099, each with 355mm rotors. I can't just walk by N15 design though who has comparable kits for $4290 $3890 respectively.
Were you running ducting throughout all of your BBKs? I hear you on limiters and hose, but I also plan to keep this car streetable and I'd really rather avoid dealing with hose. To be honest I figured going with a 355mm and those big Radicals, you would negate a lot of the need for hose, but it sounds like maybe that's not the case? What is your take on the Vorshlag approach?Leave a comment:
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