syzygetic

I have a 2015 981 2.7 / 6SP that I've been tinkering with since, well, about 2015. So far, X73 suspension / Cobb Stage 2 / Fabspeed Sport Headers / Numeric CNC Shifter / Function First Transmission Bushing Insert. I love this thing, it handles like a dream, and makes you really pay attention to driving fundamentals, since it's not wildly powerful.

The rotors are up for replacement this fall, naturally worn out, and I've been assembling parts to do an upgrade, but I figured I'd pick the brains of the folks here, since you all know your stuff, and this project is in no rush; I hate getting halfway into something and find that I'm missing a part or whatever.

I have assembled:

• 2x front calipers, 6 piston, +pads
  • Left 991.351.423
  • Right 991.351.424
• 2x rear calipers, 4 piston, +pads
  • Left 996.352.425
  • Right 996.352.426
• 8x M12-1.5 caliper bolts (999.067.053.09) << Note that I'll use the Tarrett Engineering 85mm studs for the fronts, at least.
• 2x front rotors, 350mm
  • Left 9P1.615.301
  • Right 9P1.615.302
• 2x rear rotors, 330mm
  • Left 996.352.405
  • Right 996.352.406

Questions I have for the group:

• Do any of you have experience with this kind of swap? See anything wrong or have any advice with my parts choices?
• Should I replace my brake lines while I'm at it? OEM or one of the stainless braided lines out there?
• I won't need any spacers with these calipers, right?
• Can I fit 350mm rotors on the rear with the 996.352.425 caliper if I wanted? The wheels will clear it, in my case.
• I hear people generally saying that the stock master cylinder is enough for this configuration - anyone think otherwise?
• Should I be flashing any software to retrain PSM?

I really appreciate the expertise here. Thanks all for reading!

thecajunboy

Would appreciate if you could share your assessment of the headers/tune combo. Looking to do something similar but $/HP doesn't seem to warrant it. But trading up to an S doesn't happen easily or economically either.

syzygetic

Happily! I'll do it under separate cover to keep this thread clean, but yeah, happy to elaborate on the stuff I've done with this car... here's the thread:

https://rennlist.com/forums/981-foru...-7l-981-a.html

9eight7

I haven’t done this upgrade but do recommend steel brake lines while you’re doing it. You’ll empty the system anyways so replacing a 12” brake line (or whatever length) is super easy. My new car has steel brake lines but I haven’t tracked it yet to know the difference.

Are you running slicks?

syzygetic

Not running slicks, just my street Pilot 4S tires, but I normally go to the track when they’re low enough that I finish them off/change them shortly after my track day.

I don’t expect this to really impact stopping distance cold much, the stock brakes are adequate and exceed the traction of the car. I do expect this to help with heat, though, and, done this way, it isn’t a lot more money than buying stock parts anyway to do the rotor swap.

9eight7

I don't know much about brakes but have noticed a few things. In general, rotors and calipers get bigger with respect to tire size (traction) when comparing the whole P car lineup. You might want to do some more research before buying everything or consulting with a shop/expert.

What are you trying to achieve by doing this upgrade?

txbdan

I'd just put on "S" front brakes and call it a day. The rears are the same between base and S. They're excellent even driven hard on track.

You don't need aftermarket SS lines. Factory lines are braided inside. Factory brake lines haven't ballooned under braking since like the '90s.

Kitc2246

Do the Tarrett studs for the rear plus the brake line bracket stud kit which does front and rear.

You already seem to be on the slippery slope, but as already asked what are you fixing? What you have proposed IMO is overkill for a DE car. I would upgrade the rotors to Sebro slotted, track pads and SRF or equivalent brake fluid before upgrading calipers. If this was inadequate you probably need a Girodisc or other big brake kit for the front only.

I have Sebro slotted. Ferodo DS 1.11 pads and Motul 660 fluid for my 2013 Boxster S. My son and I backed to back the car at VIR last year with more aggressive Raybestos ST43 pads and edge cracked the Sebro slotted. Warrantied the rotors from FCPEuro and no issues this year after two weekends.

While all of this is DIY I'd also recommend you consult/work with a shop

syzygetic

I’m not fixing anything, totally get that. It is just rotor replacement time, and second hand calipers as described aren’t expensive, so I figured go big in advance of a possible BGB swap when this 981 gets older. I don’t drive as much as I used to, so I don’t mind committing to more frivolous projects in the name of fun!

Kitc2246

Do you DE at Summit Point?

slivel

+1
Porsche brakes are among the best engineered in the business. They are a system and by mixing components you may get a combination that won't perform to your expectations. When front and rear brakes are not originally engineered to work together, your Fr/Rr balance may be dangerously out of whack. An adjustable proportioning valve would almost be mandatory IMO. Also strongly recommend working with an experienced race shop.

nhnguy12

It looks like Suncoast sells a similar upgrade as a package:
https://www.suncoastparts.com/product/sku3509x1fbk.html
https://www.suncoastparts.com/product/sku330981rbk.html

Curious as to whether they use the same parts you have listed.

It also looks like Girodisc sells/sold 350mm rear rotors to for the 996 rear calipers so it seems like it can be done:
https://www.girodisc.com/Rear-Rotors...bo_p_6474.html

Let us know how it goes! The rotors on my 981S are almost due for replacement and I'm thinking of doing something similar.

syzygetic

Yep, this is exactly what I'm recreating. I believe they're using the same parts, and I verified with them that the master cylinder supports the six piston rotors just fine.

I was really hoping to hear whether anyone on here has done something similar, and what their experiences might have been, since, of course, I'm worried about fitment, but I think that'll be ok... I'm more worried about brake balance and feel once this is on.

Thanks for the input, I'll see if my shop can recommend something on this front.

I haven't yet, one day! Summit Point is closer to me than VIR, but I've always been going to VIR.

syzygetic

Ok, I actually did this, and here's what it took, in the end:
Front Brakes-
Rotor, Left: 9P1-615-301-A
Rotor, Right: 9P1-615-302-A
Calipers: 991.351.423, 991.351.424
Pads: 991.351.940.02
Bolts (studs): Tarett Engineering BCSK-85

Rear Brakes-
Rotor, Left: 981.352.403.00
Rotor, Right: 981.352.404.00
Calipers: 970.352.425
Pads: 9Y0.615.415.J
Bolts: M12-1.5x85mm or 9A7.007.585.00

Everything bolted right on, no fitment issues, no drama. On the front, the little metal bracket which holds the flexible portion of the brake line to the wheel carrier no longer lines up, so I had to do a little modifying there (aka drilling a new hole in the sheet metal to allow for the new position). There might be a sheet metal part number out there which would work, but I couldn't find it.

Performance is spectacular. In a way, I wouldn't recommend this for inexperienced drivers, because the brakes now far exceed the tires' grip, so you could potentially get yourself in trouble by using them irresponsibly. That said, they are undeniably capable, and this upgrade is actually not too expensive done the way I did it, with 80% used parts from eBay. If you want to save yourself a little trouble, grab the kit from Suncoast, I am certain it's similar, and they are wonderful to deal with.

nhnguy12

Thanks for the update!