clib

I've searched the forums - but Debating which way to go. Car is a C2S, now with SC/Intercooler installed last year. Did a couple DE events last year and will do more. Need to replace rotors (shuddering with braking and runout 0.008).
Question with the SC and doing some track days does it make sense to upgrade to something like big reds. Fade wasn't a huge issue on the track but most of those days were before the SC, and I don't push to the limit, its also my driver. I'm supposing the higher speeds will increase demands.

So the question is do I just replace current setup pad/rotors as needed until I notice fade becoming an issue, or upgrade now? Will there be less need to replace rotors going forward with the bigger setup?
Anyone know of a big red setup for C2S they want to sell?

thanks for any input.

bill

element

What pads are you running? Are brake ducts in your plans? Main issue with brakes is holding and removing heat.. bigger calipers will hold and ducting will remove. On my past car (Mini cooper) as I got faster I was starting to cook the pads, so I would get uneven pad build up.. fade as well. I tried track only pads, but they would also overheat, so went with a BBK and problem solved. I didn't do ducting, but was an option.

phil.

clib

thanks. I have been using just the stock pads at this point. Hadn't thought about ducting.

jdistefa

Front big reds here:
https://rennlist.com/forums/for-sale...-calipers.html

Much has been written about this. The stock brakes on your C2S are pretty good and stepping up to big reds represents expense and extra weight.

If you're tracking occasionally a totally reasonable approach is simply to upgrade your brake pads. IMHO Pagid RS19 or RS29 "yellows" are an excellent choice. Upgrade your brake fluid to something like Motul 600. Have your brake lines checked and replaced if any concerns. Use Porsche/Brembo rotors for replacement not the zimmerman crap.

RonCT

As others have suggested, there's a lot in front of you before you need to upgrade the brakes. The shuder you have is probably pad material that transferred to your rotors. It will wear off after a week or so of street driving. Basically, you're melting the pad and it's sticking to the rotor making for an uneven surface.

First order of business is to change to a track pad for the track and leave the street pads for the street. About 45 minutes to change out before and again after an event.

And when you change pads you should change fluid. I always use Castrol SRF because it's dry and wet boiling points are almost equal. Change it once in the spring and I never touched fluid again. Yes, it's expensive, but the labor saving of never dealing with fluid, even after 10+ events, was priceless.

As to pads, I've tried them all and there's no such thing as a "hybrid" pad that works on the street and track. You just have to get used to changing. And for the track my favorites were Pagid Yellow 29s followed by Blacks. Depending on which Porsche, I've used Blacks at the back and Yellows on the front for better bias.

Once you find your rotors spider cracking then you can start to look at ducting as the next step. Long after this might be Big Reds.

Bill Verburg

if you stick to the factory 993 setups, you have 3 primary setups and several additional variations, which to choose from depends on your idiosyncratic goals.

the main setups are stock, 993RS, and 993tt

the 993Rs and 993tt both use the same larger rotors and provide significant increases in thermal performance but only small increases in brake torque. The better thermal performance results in longer component life, both on a per track session and season long basis, For best life slotted aftermarket floating versions of at least the front and purportedly the rear rotors too are available.

The big difference besides the thermal performance is the brake bias. Adjusted to the same line pressures the following are the f/r brake torques in N-M for each
standard
2230/1390
RS
2306/1618
tt
2306/1155

So if you want more rear brake use RS, this is a desirable way to go but the car needs to be set up right to use it, low, stiff and effective lsd are mandatory

if you want more front brake use the tt, this unfortunately puts more of a heat load on the fronts and exacerbates longevity issues

brake torque can be further tuned even in a stock setup w/ pad choice I use Pagid RS29 front and RS19 rear to get a tad more front. Many use one of the yellows in front and black in back to get more rear, it depends on what you are comfortable w/

The primary reason to use a higher performance brake fluid is because of thermal issues, if the pedal is going soft during a track session but pumps up it's usually because too much heat was transferred to the fluid from the rotors, I haven't found that to be an issue w/ the bbks but have never used the stock so can't comment on that. The other reason to use higher performance fluid is pedal feel, I've just started to experiment w/ Prospeed 683 and in the limited use i've had it does seem to have a better pedal that the ATE200 I was using.

2S didn't come w/ bb's, the 4S used the same bb setup that the tt came w/. Though I've seen references to C4S w/ the 30/34 2s rear calipers and rotors but never seen that setup except on the very early 993Cup cars.

clib

thanks for the input guys. I don't mind the idea of changing to track only pads - is that primarily to save the pads for track use, or worse street performance with a track pad?

BillV: Thanks for the clarification and actual numbers on the different setups. On a motorcycle I have pretty good feel for what is happening, I am far away from telling whether I need more/less front:rear bias at this point. Right now it sounds like I will start with pads.

RonCT: I use ATE Super Gold and change it yearly. I have not notice softpedal after hard use as an issue but will pay more attention. Ron are you saying I would get the same runout figures (0.008) due to pad deposition? It definitely hasn't improved with street use and I thought once above 0.006 was warping. They are the original rotors with 43k on them also.

RonCT

Can't tell for sure from a post, just gave you a "typical" when starting DE and heating up the brakes with stock street pads. I used ATE Gold when I started DE but it needed to be bled / flushed often because as it picked up moisture it lost it's properties. SRF pretty much never breaks down - try a search and you'll probably find the wet / dry chart and see what I mean. So while SRF is $70 a liter, it typically took me 1 liter every spring and I never had to flush / bleed until the following spring.

May not hurt to get a new set of rotors and some track pads. The point of street vs. track pads isn't to save one or the other, it's to use the correct pad for the different uses. Track pads will squeal like a school bus on the street and street pads on the track will melt and glaze up (and not stop you very well as you advance).

Bill Verburg

a 993 w/ either tt or RS brakes at most tracks fdriven by most drivers won't heat the fluid enough to boil most fluids, remember the bigger the rotors the lower the temperature they run at for a longer time, certainly ATE200(AKA gold/blue) will be fine for a full season of use on these cars. Cars w/ smaller rotors will run them at higher temperatures for more of the time, rotor temps that are high enough to transfer enough heat to the fluid to boil it will require the best available fluid most 911SC & Carrera fall into this category. After 6mo in most climates all fluid will absorb enough water to be roughly 50% of the way between their wet and dry spec

ARRANGED BY DRY BOILING POINT:

DRY:401F -- WET:284F --- DOT3 MINIMUM (GLYCOL BASE)
DRY:446F -- WET:311F --- DOT4 MINIMUM (GLYCOL BASE)
DRY:500F -- WET:356F --- DOT5 MINIMUM (SILICONE BASE)
DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)
DRY:500F -- WET:???F --- FORD HEAVY DUTY DOT 3 PM-1C (new since 2006)
DRY:527F -- WET:302F --- AP RACING 551 ($12.799/0.5L OR 16.9 OZ)
DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4
DRY:536F -- WET:388F --- ATE SUPERBLUE/TYP200 ($9.95/1L)standard in most German cars
DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3 PM-1 (pre 2006) ($4/12 OZ)
DRY:570F -- WET:284F --- WILWOOD 570 ($5.65/12 OZ)
DRY:570F -- WET:284F --- PERFORMANCE Friction Z rated ($6.27/16 OZ)
DRY:572F -- WET:410F --- AP RACING 600 ($21.49/0.5L OR 16.9 OZ)
DRY:590F -- WET:???F --- TILTON TBR-1 ($11.95/0.25L) (new since 2006)
DRY:590F -- WET:518F --- CASTROL SRF ($79.99/1L 0R 33.8 OZ)
DRY:593F -- WET:421F --- MOTUL RBF 600 ($17.99/0.5L OR 16.9 OZ)
DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS ($26.75/0.5L OR 16.9 OZ)
DRY:608F -- WET:390F --- AP RACING PRF660 ($28.99/0.5L OR 16.9 OZ)
DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610 ($11.95/12 OZ)
DRY:613F -- WET:424F --- ENDLESS RF-650 ($33.00/0.5L OR 16.9 OZ)standard for 996/7 Cups
DRY:617F -- WET:399F --- MOTUL RBF 660 ($28.99/0.5L OR 16.9 OZ)
DRY:622F -- WET:???F --- TILTON TSR-1 ($17.95/0.25L) (new since 2006)
DRY:626F -- WET:???F --- FERODO FSF050 Super Race Brake Fluid ($39.99/0.5L OR 16.9 OZ)
DRY:626F -- WET:417F --- WILWOOD EXP 600 ($20.25/0.5L 16.9 OZ)
DRY:635F -- WET:430F --- PROJECT MU G/FOUR 335 ($45.00/1.0L 33.8 OZ)
DRY:683F -- WET:439F --- PROSPEED RS683 ($39.95/0.5L OR 16.9 OZ)

ARRANGED BY WET BOILING POINT:

DRY:500F -- WET:???F --- FORD HEAVY DUTY DOT 3 PM-1C
DRY:590F -- WET:???F --- TILTON TBR-1 ($11.95/0.25L)
DRY:622F -- WET:???F --- TILTON TSR-1 ($17.95/0.25L)
DRY:626F -- WET:???F --- FERODO FSF050 Super Race Brake Fluid
DRY:401F -- WET:284F --- DOT3 MINIMUM
DRY:570F -- WET:284F --- WILWOOD 570
DRY:570F -- WET:284F --- PERFORMANCE Friction Z rated
DRY:550F -- WET:284F --- FORD HEAVY DUTY DOT 3
DRY:527F -- WET:302F --- AP RACING 551
DRY:446F -- WET:311F --- DOT4 MINIMUM
DRY:527F -- WET:347F --- VALVOLINE SYNPOWER DOT3 & DOT4
DRY:500F -- WET:356F --- DOT5.1 MINIMUM (GLYCOL BASE)
DRY:500F -- WET:356F --- DOT5 MINIMUM (SILICONE BASE)
DRY:536F -- WET:388F --- ATE SUPERBLUE/TYP200 std in most German cars
DRY:608F -- WET:390F --- AP RACING PRF660
DRY:601F -- WET:399F --- BREMBO LCF 600 PLUS
DRY:617F -- WET:399F --- MOTUL RBF 660
DRY:572F -- WET:410F --- AP RACING 600
DRY:626F -- WET:417F --- WILWOOD EXP 600
DRY:593F -- WET:421F --- MOTUL RBF 600
DRY:610F -- WET:421F --- NEO SYNTHETICS SUPER DOT 610
DRY:613F -- WET:424F --- ENDLESS RF-650 standard for 996/7 Cups
DRY:635F -- WET:430F --- PROJECT MU G/FOUR 335
DRY:683F -- WET:439F --- PROSPEED RS683
DRY:590F -- WET:518F --- CASTROL SRF

clib

Thanks again all for helping me understand this a little. I see it gets more complicated the more you start to understand. The combinations/alternations must be huge and I can see its easy to get unintended consequences.

I understand this is a comparison using same line pressure, but why did the turbo come with such a big front bias? or was that redistributed with a different PV set up on the TT as delivered? I would think the TT would need less front bias due to the 4WD.

As percentage I get:
Standard: 62/38
RS: 59/41
TT: 67/33

Trying to avoid changing PV etc I can see why the RS is a better match. I understand the heat with a front bias change, but would think too much rear bias would also make the car tail end tend to be more loose in hard braking - or with ABS is this not a true factor?

jdistefa

The whole reason a 911 eats other cars on the track is grip: grip under acceleration out of the corner and grip braking into the corner. That silly motor hanging out over the *** of the car helps minimize weight transfer to the front contact patches = more rear tire grip for braking. You also tend to have 1/2 to 1 degree less camber in the rear end, plus a wider tire, both of which favour optimizing rear braking capacity. In conjunction with an LSD (and some skill & *****) a 911 is a late braking weapon

Bill Verburg

the 993 hydraulic bias is
standard
1.572
RS
1.472
tt
2.061

C2 and RS use the same 40bar p/v the tt and C4S use a less aggressive 55bar valve. The valves reduce rear line pressure by ~ 50% above the knee specified by the #.

all 911s from '69-83 were 1.596, all 930s from '78-89 were 1.604

why they used so much front on a tt or C4S I dunno, could be something to w/ awd or it could be something the legal dept came up w/

the more rear bias the more the car has to be setup to take advantage of it, you want it to be low and stiff and not have all the rubber found in stock suspensions and an effective lsd is icing on the cake. Stock street lsds are not particularly effective even when new. The RS used a 4 plate 40/65 lsd with twice the brake away torque of a street lsd.

clib

as a late followup on this thread since posted last year I replaced my rotors that were worn and got some track pads (pagid yellows). With some stickier tires I have found this combination to be working well through 4 DE weekends since that time and no issues of wanting more braking at this point or problems with fade etc. While the look of the big reds is cool, at least for now and my limits, the braking and heat dissipation capabilities of this set up are fine. Thanks for the advice.

Bill Verburg

The issue that you are likely to have is that the rotors will crack out, I'm surprised that you have't mentioned this. Especially in the front track use will cause cracks to spread from the holes, the rears won't crack as fast and will have time to develop really deep grooves in addition to cracking.

Non drilled 322x32 front rotors on floating hats is the way to go

Carrera51

If you are running the factory drilled rotors, like Bill said, ditch those and get some two piece slotted rotors. Coleman will make them for you and they are reasonably priced. If they have done these already for another customer, they will probably ask you to send them one of yours. A friend got their rotors for his highly modded 964 Turbo race car and they have held up well.