Brake Project and Interest: AP Racing CP9668/9660 Kit

DarkJak

Price breakdown:
10/19/22

Calipers: $2100
Brackets, lines, bolts and hats: $850
Rings: $900
Bobbins: $125
Total: $4075

I've spent way too much time researching brake kits for my Z and not being fully happy with any of them and have decided to work with a shop to manufacture bracket and hat adapters for the AP Racing 9668 calipers for the 370Z with 370x34 or 36 mm rotors with 72 vanes. Hardware made with 6061 or 7075 aluminum.

Would anyone be interested in this? It would help reduce my manufacturing costs and my goal is to be competitive with the Stoptech trophy kit on pricing while offering better cooling.

ADVANTAGES OVER THE TROPHY KIT:

• Lighter caliper by 1.5 to 2 lbs vs Trophy kit.
• Thicker pad (25mm) that can provider much more life for just a tiny bit more cost per set
• Stainless steel pistons vs aluminum on the Trophy kit (upgraded pistons cost $1200 from Stoptech)
• Higher 72 vane count (dissipate more heat)
• Wider air gap in rotors (pump more air)
• 370mm rotor maintains compatibility with most 18 inch wheels
• Similar rotor replacement cost for better heat dissipation
• Can switch between 9660 and 9668 with the same hardware to save on upfront cost.

ADVANTAGES OVER THE WILWOOD AERO6 KIT:

• Still lighter than the Aero6
• Thicker pad by 5mm
• Larger, better flowing rotors
• Much easier pad changes
• I assume stiffer caliper (for sure much stiffer than the Forged Narrow Superlite)

ADVANTAGES OVER THE (NONEXISTENT) ESSEX AP RACING KIT:

• Will actually exist (Essex has been stringing me on over 2 years on this and won't just take my money)
• Almost certainly cheaper
• Rotor replacements will for sure be cheaper
• Potentially better cooling rotors (by a bit, not by much)

CONS:

• Due to how damn expensive these calipers are, you'd have to source them separately, but I'm looking through suppliers who can keep costs below $1300 per caliper. $1000/ea if going 9660.
• Calipers have fixed piston sizes, not as many options like Stoptech does, so you'll need pad stagger, such as XP12/XP10 front/rear.

ESTIMATES:
Around $1500 give or take 250. This should cover the hats, rotor rings, bracket, all hardware.
Doesn't include pads, since people have large differences in preference.
Timelines are likely 2 to 3 months out between my initial designs, 1-2 revisions, several test days, and finalized hardware run.

GOALS:
I will be testing these myself first. I mainly test at Blackhawk Farms Raceway, which is very hard on brakes.

On the rotor side, my goal is to lower my rotor temps by at least 50F over my current wilwood 72 vane setup, which already lowered by 100-150F over my Z1 2-piece setup, which at the time, already lowered by around 100F over stock. So vs stock I'd estimate 200-300F lower rotor temps. This should be reasonable because these are wider, larger, and have a better vane design. They must also come in lighter than my custom Wilwood setup, much lighter than stock.
On the caliper side, my goal is to at least double my pad life, via thicker pad AND cooler temps. It must come in lighter than the stock Akebonos including bracket.
I figure people on the forums would be interested in the progress on this.

Current state:
All crucial dimensions taken for OEM brakes
Handful of shops identified for rotors and CNC work

Next steps:
I need to get a pair of 9668's.
Mock up bracket to test against current 355 rotor setup to validate offsets
Finalize dimensions
Decide on rotor ring
Model brackets and hats

7/8/21 Update:

• Calipers sourced, pending payment.
• Bracket and hats initial designs submitted to first shop, and paid for.
• Rotor rings finalized and ordered, pending shipping (may take a while).
• Caliper bolts ordered.

What's left:

• Finding reliable supplier for bobbins and hardware kit (may need to be from the UK directly)
• Finding reputable brake line source. I believe our calipers use M10x1.0 so may not be too difficult. But may just get a longer line and skip our weird front brake line tomfoolery.

7/8/21 Evening update:

• Bobbins and hardware sourced, awaiting order confirmation
• Rings shipped!

7/9/21 Update:
All parts ordered. Now just waiting as parts come in.

7/10/21 Update:
Rings came in!

7/12/21 Update:
Brackets and hats manufactured! Will see how tolerances and initial measurements were. Fingers crossed, but will be a while before next update.

7/13/21 Update:
Oh wow, FedEx international shipping is amazing....
Calipers delivered today!

7/16/21 Update:
Hats and brackets arrived today!
Fitment test was perfect on the hats and I am feeling good on the bracket.
In the home stretch!

7/20/21 Update:
Bolts and washers came in!
Mounts right up, now just gotta grab some pads from a friend so I can test fit while I wait for my Glocs to come in!

7/31/21 Update:
GLocs came in! They are FAT. My friend's pads were worn but these, oh boy.

Pics:

Attached Images

	hardware2.jpg (567.9 KB, 28 views)
	hardware.jpg (558.8 KB, 22 views)
	Rings.jpg (366.3 KB, 31 views)
	20210713_094208.jpg (422.6 KB, 47 views)
	20210716_103135.jpg (743.0 KB, 33 views)
	20210731_180530.jpg (152.5 KB, 34 views)

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OptionZero

wondering . . . why not Brembo GT?

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DarkJak

9668 is lighter, has way thicker pads, comes at a lower price for the same quality (Brembo GT line requires the GT-S caliper to be comparable, maybe even the GT-R), and has way easier pad changes. I also find way better documentation around AP Racing calipers.

I just don't like the caliper as much. I see a lot of people on other platforms run the 9668/9660 calipers and they absolutely love them.

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cv129

Some seriously thick pads with the 9668.

A nice article on 9660 vs 9668:
https://www.essexparts.com/news-blog...9660-or-cp9668

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DarkJak

Yup! Hoping to EVENTUALLY make some of the cost back via less frequent pad changes.

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Rusty

Used to be able to get the AP Radical II BBK's for the Z from Stillen and a few other places in the states. Then all of a sudden. Everyone quit selling the kits. Just as I was ready to squeeze the trigger for them.

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SeeThruHead

interested.

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Images too big fix here

Spooler

Did you look at Stoptech? Make sure you get the brake bias correct otherwise it will no work correctly.

JARblue

He literally mentions it in the 4th sentence.

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Spooler

LOL, I didn't see it. I checked on the Stoptech's for my car and they were dang expensive. 8k and change.

DarkJak

Yes, and Stoptech Trophy, even the STR calipers, have aluminum pistons.
And their rotors aren't as effective based on vane design and count.

I decided after some comments on my FB thread to use the AP racing 372x34mm discs.
Finding the bobbins are the toughest part. They really make them hard to find in the US if you aren't buying a full kit from Essex, but I have part numbers I can get from the UK.

Brake force with 9668's is 12% less vs stock calipers with the same rotor diameter. Moving to 372mm rotors makes brings it to a 7.5% reduction, easily compensated for with pad stagger. Or, once my project funds recover, new calipers for the rear.
Stoptech's kits DO keep it at 100% +/- 1% change. 92.5% is still closer to stock than Wilwood's kit, which is at 91.5%.

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DarkJak

SAME! I'd finally convinced myself and checked they'd fit my wheels.
Been on quite the research journey since then and I'll be ending up with a better setup than the Radical street kit would've been.
We dodged a bullet there though. The rotor rings with the Radical kit are no longer available.
The ones I'm using will remain supported by AP for much longer. So many kits use this size. (Literal worst case, once I get the initial designs manufactured and tested, switching out to new disc sizes will not be too painful either. Both design wise and money wise. I don't expect this to be necessary though)
The 9668 caliper is also far more popular than their Radical street kits.

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09 7AT|MCS 2WNR|Topgunz Rotrex|Ecutek (Eugene)|Maxxis RC1|Titan-7 TS-5|OSG LSD|Rear Mount Derale Oil Cooler (WIP)+25 Trans Cooler|Fismo|G-LOC R12/R10|Zeta III L|NLR Wing and Splitter|CJM Pan and Fuel Hat|Radium Surge Tank|AP Racing CP9668

cv129

That's a lot of work done, thanks for sharing!

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Hotrodz

Nice work! The big elephant in the room is the OEM ABS system. It still sucks. I am not saying the BBK upgrade will not bring gains but because the ABS system is lacking there is still more on the table.

Sent from my SM-G965U using Tapatalk

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DarkJak

Oh yeah. I believe there's braking performance to be gained shifting bias a bit rearward but am wary of it because I've heard ABS consistency gets worse, especially if rears lock first. I'll let Austin Hertel and other folks pioneer the MK60 swaps before I jump on that.
So far, my ABS doesn't get in my way.

Rotor rings ALREADY shipped out, should get here Monday. Bracketry and hats I expect a few weeks lead time. I'll just get to start at the AP rings for a few weeks while I wait on everything to get here I think.

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@stupidtoycars | My track vids
09 7AT|MCS 2WNR|Topgunz Rotrex|Ecutek (Eugene)|Maxxis RC1|Titan-7 TS-5|OSG LSD|Rear Mount Derale Oil Cooler (WIP)+25 Trans Cooler|Fismo|G-LOC R12/R10|Zeta III L|NLR Wing and Splitter|CJM Pan and Fuel Hat|Radium Surge Tank|AP Racing CP9668