I've had the 350mm brake rotor upgrade on my car for a few years. I loved the look, but felt braking was still a little squishy with the Hawk pads on the car.

Fast forward to having a set of 997TT/GT3 6 pot calipers in hand from a friend and would like to ensure the entire kit feels noticeably better than what was outgoing. When I had a BMW Z4M, I really liked the initial bite of the brakes day to day (ZCP brakes/rotors).

That said, I don't plan to track the car (I have before, but prefer my dedicated e30 / cayman) for this.

Any brake pad recommendations?
Is the GT3 master cylinder an added benefit to push the additional fluid?
I've got slotted rotors and don't plan on changing those.

Or alternatively - is all the above very incremental for how much it would cost/effort to do? I'm about to swap all my suspension links out for a big 120k mile refresh, so while in there...

 

I just did this conversion myself.

Do you have 350mm rotors in the back? The brakes noticeably bite more and i also have the GT3 MC. Made sense to do it at the same time as well as stainless steel brake lines. The only real cost will be new pads, and extended bolts for the caliper up front if you're already running rears at 350mm and the bleeding process if you replace your MC. Have to bleed the clutch, brakes, and would recommend ABS as well. You can do it with a Foxwell or durametric - but would recommend two people as I failed miserably doing it alone.
I'd convert to Tarret studs while your in there for the calipers.
I went ahead and replaced all my brake line brackets and swapped the bolts to studs for those as well. Running hawks but can't comment as they're not really broken in yet.

Will it be distinctly noticeable if you're not on the track? probably not. Will it look great? yep.
Curious that your brakes currently feel squishy though...

 

I've got the 350mm rotors out back as well, along with the extended bolts for that.

I wouldn't say the brakes are exactly "squishy", but just not terribly "bitey". I've had the car on the track with the current setup and it was fine - but I wanted more initial grabbiness day to day that was commensurate with the car.

 

Makes sense IMO as you've changed the bias with larger rotors without adding more pad surface to grab it with (going to 350mm up front without larger calipers. maybe?

If that's the case, then I would say you'd definitely notice a difference with the larger calipers. They're the most expensive part of the equation from my experience. When you're doing the multiple bleedings you can reuse your brake fluid until the final flush. I went through aprox 5-6 liters getting all the air out, although mine was completely dry.

Let me know if you have any questions about this conversion, My car just got back on the road this weekend so it's all fresh in my head. Just to edit:
If you're at 120k, i'd definitely swap out your lines / brackets / bolts. Just be careful as they can be seized and you don't want to cross thread anything. I opted to replace just about everything on all 4 corners while I was in there. I have all the parts lists I can share. Good time to check your e brake and tighten it up as well if needed.

 

I spent time researching and gathering parts to upgrade to a 997.1 TT caliper setup on my GTS. GT3 front calipers have smaller pistons than the TT 6 pots. The bias using GT3 front calipers will shift to the rear. The TT 6 pots will keep the bias about the same as a Carrera S setup. Your S calipers should feel rock hard when depressed as the MC in the S is the same part as TT and GT3. I have been running my S calipers with 350mm rotors as well and they feel firm. The GT3 front caliper reduces the volume so it should firm up the pedal feel.

I recommend Endless MX72+ or CCRG pads for street and canyon driving. They are not cheap but are worth it.

 

Are you saying the master cylinder is not worth the upgrade then? Or maybe I'm just in need of better pads rather than going the full 997TT caliper route

 

@hexagone Do you have a C2 or C4? 997.1 or .2?

Here's the P/N for the MC:
997.1/,2
C2: 997.355.910.00
C2S: 997.355.910.10
GT3/C4/C4S/4GTS/TargaS/Speedster: 997.355.910.30 <----

Not trying to disagree someone who has definitely done more research than me, I just did it cause I was replacing everything anyway and why not - but it's a different part number and at least my brain tells me it works better - but I didn't test it with my stock setup versus upgraded bits. Price was about the same as putting a new 910.10 back in.

 

997.2 C2S

And the TRW part number comes back as a roughly $200 part, so if there's notable improvement it's a minor addition everything considered

 

I have the 350mm Girodisc rotors which keep the stock calipers like yours. I swapped between Hawk ceramic pads for street and PFC pads for the track. There's a night and day difference especially in terms of initial bite. The Hawks feel squishy and actually have no bite when it's cold/rainy for the first brake application, it's a little scary. I don't know what pads to recommend for street use but I remember the OEM porsche pads had pretty good bite if you can deal with the crazy dust they produce. Definitely try different pads before going and changing parts because I think that'll make the difference in bite you're looking for. I've driven GT cars on track and the bite/performance of the 350mm Girodisc rotors with PFC pads was equal if not better than a stock GT3/GT4.

 

While we're on the active topic -

My 350mm front slotted Turbo rotors on the stock C2S pads don't seem to make contact with about 10mm of the most inner portion of the rotor. From what I've seen with other folks' 350mm setups, I assumed the sweep (contact area) of the existing C2S pads would make full contact, but it doesn't. So I've got a rust ring that's left which is bugging me enough to resolve all this at once. Any idea why this would be? I realize the spacers move the caliper out some distance, but I haven't seen this issue with others.

 

This was my line of thinking as well as I know it's now a new part so failure is less prone. Again, the annoying part is the ABS and Clutch bleed. Clutch bleed isn't so bad if you have a crowfoot with an extension and a small drive. The ABS bleed required someone in the car while I bled the brakes. Not mentioned in the porsche workshop manual is if you should run the ABS motor per caliper VS per bleeder. I opted for the latter giving plenty of time for the motor to relax between bleeds.

 

Carrera Alex is totally right. If you have a C2S you have the smaller MC so upgrading it to the larger unit will firm things up. I have a GTS and when I was planning on upgrading, I found that I already have the larger MC. If you have a C4S or TT it would also have the larger MC.

The 6pot front calipers will help friction and heat dissipation by adding surface area. What I was trying to convey was that there are two sizes of 6 pot piston sets. It will be good to know if your calipers pistons are the larger ones from a TT or smaller ones from a GT3 so you can see how it will affect your bias.

 

I had to order new hard lines as well for the 6 pots. It looks like your C2S uses the GT3 lines just like my GTS. Here is a chart from nwGTS.

 

This is handy!

I’d recommend replacing your hardlines anyway while you’re in there as well as the brackets for them.

 

I have totally given up on my Hawk Performance Ceramic pads.
When I was tracking the car the DTC60 was incredible.
But I regret ordering the Performance Ceramics as my daily's.
Same comments as others... squishy and not confidence inspiring.

I have a full set of Endless MX 72's front and rear on there way.
They are supposed to have better bite but only a little more dust than the Hawks.... we will see,

To the original poster, the caliper upgrade is not your problem.
Get rid of the Hawk Performance Ceramics!!