AP Racing, Freaky Parts, 996, Cooling? School me on BBK to help pad consumption

[bigjae46]

Appreciate that perspective bigjae46. Cost not-withstanding, sure going with something like an AP kit makes sense, but even then I still don't feel that I KNOW it will work. Maybe on track, but will no dust boots bite me on the street? I know your StopTechs have boots, but like you said it may not make sense to buy StopTech right now with their supply issues. Not to mention that if I don't spend money that I didn't need to spend, that's money that can go to those same costs you mentioned: registration, hotels, fuel, etc. Right now with the stock brakes I don't feel that I'm at risk of ending a weekend early. Travel with spare pads an rotors and I'm good to go.

I think there's value in exploring lower-cost solutions. I understand that it's not for everyone, and there's a chance I end up with a pricier kit in the end, but with kits like your StopTech seeing such significant price increases in the last year or so, along with FCP's lifetime replacement pads/rotors, the economics have changed and I like exploring the options 😄

I really don't understand the whole not having dust boot on track thing. IMO, its marketing and only makes you look cool to other guys in the paddock to say that you don't run dust boots on your calipers. A simple titanium shim with deal with a potential issue. You have to do something like....run the pad to the backing plate to cause an issue.

The OE dust boot is massive - if that hasn't caught fire yet then I think a BBK with the dust boots will be fine.

A day at the track is worth at least $500, maybe more depending on how far and which track. I instructed a guy in a Jaguar F-Type at COTA. He literally drove 1 session because his brakes were vibrating like crazy - cost him $1000 just for the track fee.

[mrgizmo04]

Thanks for the thoughtful response, I have thought (and over thought) about this whole subject a lot and at a certain point, I need to just get the car out there with some setup, try it, see how it does, and then change as needed. FWIW I have a set of stock calipers with brass pins and PFC08 pads that I can put on there if these retrofits turn out to be a nightmare. Yes I do want it to look cool though, Brembos are cooler looking than stock calipers, I'm not denying that part. I'm a highly visual person and I do not try to pretend otherwise lol.

Here's my thought process on the brake setup I've landed on as a starting point, please let me know if I'm off here or missing some big points. My understanding is that stock for stock, early cars have a more rearward bias than later cars, due to a different master cyl. So I looked at the brake bias numbers various people have come up with for later cars using Megane front calipers with 345mm rotors and 996 rear calipers, which seems to be a happy starting point, and ballparked that the DB9 front calipers with the slightly larger 44/40 pistons and 345mm rotors should kind of counteract the early car rear bias created by the master cyl. Maybe I'm wrong and TBH I am not an equations kind of guy, so if anyone would be willing to run these numbers and see where it actually falls, that would be very interesting and helpful to the greater knowledge bank.

This is my first time building an e46 for track but not my first rodeo with track cars in general, so I know it's not as easy as just throwing parts at the car. Weight wise, I removed the rear seats and gutted the trunk carpet, but I'm adding a rear brace and roll bar, so it's probably going to be a wash. I'm running off the shelf KW Clubsport 2 way adjustables so yes, I will have to test and tune and see how this whole system works together. I'm aware that might not be the ideal damper and spring but it's what I have, so I'm going to run them for now. I also have a GT4 style rear wing and front lip which I will also run because, not gonna lie, they look cool and I want that just as much as actual performance benefits. I'm running 18x10ET25 wheels with NT01 used spares, and I'll end up likely on a 265 200tw tire after those are done. I will also likely end up doing a MK60 retrofit in the not so distant future. But again right now, all of that stuff is just sitting in my garage because I have no time to dedicate to the car.

Nate, I can tell you that I see some serious track guys running some serious times with me in advanced groups with stock calipers and just upgraded pads/fluids/cooling ducts on stock rotors. That said, their cars are fully gutted, so that setup has enough heat capacity for them and works. For the full pig that our cars are at 3500+ lbs (with driver), that setup might not be ideal.

Having been through various combinations of stock f/r, st40 f/r, 996 f/r, I can tell you that the rear 996 kit is a solid upgrade for our cars. Caliper is not modern, but it is radially mounted, much stiffer than stock, retains same rotor size but pad size increase is rather significant for heat capacity. It also works really well if you trim the dust shield to let the heat radiate to cool the rotor, given the rear has the parking brake surface so cooling is limited. You just need to watch that pads don't make it down to the backing plates, since 996 rotors are x24, while ours are x20.

Fronts are trickier. Depending on your philosophy of running same pads front to rear vs split mu, you will have to play around with your driving style. I've settled to make the 996 kit work on my car even though the fronts are a bit subpar in terms of bite (smaller piston sizes), and pad size increase is minimal vs stock for additional heat capacity. I trick the less bite part with the higher mu front pad (3 variables that impact amount of f vs r bite are rotor diameter, piston sizes, pad mu). Also where the titanium shims come in and Vorshlag cooling deflectors.

If you are going to do mk60, I say do it first so you don't have to run through finding the setup that works for you with mk20 and then again mk60. DB9 on stock 325 rotor will move your bias forward more than Megane on 345 (as you note 44/40 vs 40/40 piston sizes). You will have to see how that feels to you and what you like.

Having run flat ride coming down to 350 spring, I didn't want to go lower given the weight xfer forward with more rear bias of 996 setup.

I like tinkering (although less so in past year or so, time not permitting with family/etc), and am a fan of "upgrades" as needed, but that path is not for everyone.

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[Pklauser]

That's good intel on running the rears too thin with 996 calipers, I hadn't heard that. Is there enough space that you risk actually popping the piston out?

Stoptech question: is an ST40 caliper always an ST40 caliper? Eg. If I got a used ST40 kit made for another car, would I just need brackets, lines, and rotors for my car and be good to go?

[bigjae46]

Stoptech question: is an ST40 caliper always an ST40 caliper? Eg. If I got a used ST40 kit made for another car, would I just need brackets, lines, and rotors for my car and be good to go?

Nope. Some calipers are designed for 28mm and 35mm rotor thickness in addition to the 32mm rotor spec'd for the M3. Also the pistons are tuned to the cars OE bias.

IMO, buying a used BBK is a waste because the cost to replace the wear parts is majority of the cost of a new kit.

[mrgizmo04]

Pistons popping or pads themselves falling out/jamming. The horns that hold the pad in the caliper are made to fit around a wider rotor. Backing plates are around 4mm, remember also as the pad wears, the rotor wears, and that creates more space. I posted a lot of info on similar subject when people were looking at AMG/Cayenne/etc caliper which are made for like x32-x36 rotors and were mating them with CSL x28 or e9x x30 rotors. What fun. Like I said before, people will do crazy things for bbk bling, compromising safety.

To add to what Jae said, one thing that stays constant on st40 caliper is the pad. I can run the same pad on my s2k st40 328x28 as I did on the m3 355x32. The hats/bells are different on different cars to offset the rotor, the mounting brackets for the caliper are also different to mate to each car's knuckle and account for rotor diameter, etc. That said, could you find st40 calipers off whatever car that is made for x32 width and 42/38 piston sizes (m3 spec). Yes. You will need to get the mounting brackets for m3, rotor hats, etc that adds up.

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