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I recently acquired a 1990 C2 Cabriolet. Without spending my kids inheritance I would like to upgrade the brakes for more security on the street. Many of the kits are nice but very expensive. My understanding is later 964s had better brakes the. The 89 and 90 versions. Any thoughts on how I can enhance the brakes without braking the bank?
Porsche are known for having good brakes. Before owning my 964 I had only owned new 911’s so I was pleasantly surprised by the stock brakes on my 30yr old RSA. For road use on a stock motor the stock brakes as long as well maintained will be ample. I am upgrading mine for my specific use case and I can tell you there is no longer a budget big brake upgrade. Before my time and before the surge in 964 prices you used to be able to upgrade to big reds at a reasonable price, unfortunately not any more.
I recently acquired a 1990 C2 Cabriolet. Without spending my kids inheritance I would like to upgrade the brakes for more security on the street. Many of the kits are nice but very expensive. My understanding is later 964s had better brakes the. The 89 and 90 versions. Any thoughts on how I can enhance the brakes without braking the bank?
I think you are talking about the rear calipers that changed from two pots to 4 pots in the rear starting with model year '91 for the C2. I did that change years ago because one of my old calipers had a stuck pot. You may be able to pick up a pair from a dismantler and refurbish them. You will also need to change the brake bias valve to the new version. However, like others say, the stock brakes on a 964 are more than adequate for normal street use.
As other have mentioned, your brakes are quite adequate and have more than enough braking power. I replaced mine only because I had a great deal on a set of 993 C2S rear calipers and I checked with Bill V. who told me they would work great with no real need to change the bias. Do a search if you are dead set on changing your rear brakes, Bill has some great info and tables on what works with our cars and how it affects bias and other parameters.
I recently acquired a 1990 C2 Cabriolet. Without spending my kids inheritance I would like to upgrade the brakes for more security on the street. Many of the kits are nice but very expensive. My understanding is later 964s had better brakes the. The 89 and 90 versions. Any thoughts on how I can enhance the brakes without braking the bank?
There were only 2 different brake setups used on all normal C2/4, ie not including RS or turbos
1 was 4/2 the other 4/4
The only difference between them is the rear calipers, the 4/2 use 2 piston rear calipers and 4/4 us 4 piston rear calipers
the 4/2 has better bias because it generates more rear brake torque, the difference isn't huge, 1.643 bias ratio for 4/2 and 1.889 for 4/4
@ 70 bar line pressure the difference in rear torque is 1341 lb-ft vs 1167 lb-ft
both generate 2348 lb-ft @ the specified line pressure in front
for comparison 964 RS generate 2381 lb-ft front and 1390 lb-ft rear, not much difference
so why is the RS desired, because it uses much larger front rotors, this expands the thermal performance envelope for track use and really severe mountain usage
another upgrade path, again upgrade more because of thermal properties than brake torque properties, is the 993 Big Reds(these are not a full implementation as used on 993RS because the rear setup from a 993 cannot be fitted to a 964 w/o major compromise)
these use the same rotors as the 964 RS but different calipers for 2230 lb-ft front and 1390 lb-ft rear, bia is slightly worse because these bigger calipers actually generate a little less front brake torque
another issue w/ either 964RS or Big Red is that the m/c need to be updated as well
none of this is cheap and as has previously pointed out for street driving the tires are the weakest link the braking chain
now if you are willing to spend some big bucks the Brembo aftermarket 6/4 as used by Spyrex is very impressive
front brake torque is 2621 lb-ft, rear is 1412 lbft and bias ratio is 1.857 or right around where the stock 964 4/4 is
thermal reserves are truly massive for a 964s weight and power
Just for comparison my favorite for these cars(964/993) unless something like Rothsport 4.0 is installed is 993RS
front 2306, rear 1618 and bias ratio of 1.426
This is a truly ideal system for these cars
and one last time it's the tires that hook up to the pavement and any of theses system can overwhelm the tires ability to grip, ABS helps of course but in a coarse manner that actually is less effective than threshold braking,
these use the same rotors as the 964 RS but different calipers for 2230 lb-ft front and 1390 lb-ft rear, bia is slightly worse because these bigger calipers actually generate a little less front brake torque
Bill, this is something I've been wondering about. Correct me where I'm wrong here, please!
The 993 TT uses the same front caliper as the 964 3.6 Turbo and 928 GTS with 44/36mm pistons and the big pads (132x58mm) on the larger surface 322x32 rotor.
The 964 RS, 964 3.3 Turbo, and 993 use the "medium red" S4 front caliper, with 44/36mm pistons and the smaller pads (132x48mm) on the smaller surface 322x32 rotor.
Doesn't the "big red" have a smidge more brake torque, like 2300 n-m at 70 psi vs 2220 n-m for the "medium red"? Am I mixing this up?
I have the front and rear Brembo GT kit for 964 with 355mm/328mm rotors and 4 piston calipers, the braking is excellent but complete overkill for the street.
Bill, this is something I've been wondering about. Correct me where I'm wrong here, please!
The 993 TT uses the same front caliper as the 964 3.6 Turbo and 928 GTS with 44/36mm pistons and the big pads (132x58mm) on the larger surface 322x32 rotor.
The 964 RS, 964 3.3 Turbo, and 993 use the "medium red" S4 front caliper, with 44/36mm pistons and the smaller pads (132x48mm) on the smaller surface 322x32 rotor.
Doesn't the "big red" have a smidge more brake torque, like 2300 n-m at 70 psi vs 2220 n-m for the "medium red"? Am I mixing this up?
no, because it's the effective radius of the pad, not pad area, that counts.
The slightly narrower 964RS/t pad has a slightly larger effective radius than the later 993RS/tt.
Guys, first hats off to Bill, as I did read his posts like 20 million times to be double sure what I'm doing.
I made a "kit" for a narrow body 964, honestly not because of lacking of the braking power, but because these brakes just don't match my perception of the 911
Front upgrade is easy (to whatever you want), but rear must follow and that's tricky. I had to scratch my head plenty of time to finally sort that out.
The hub offset is wird, the NB 964 rear rotor is very deep and I really wanted to make it according to Bill's tables with the bias and so on.
I like to use stock parts, so if one needs replacement it should not be an issue.
Front calipers are 996TT/997C4S ones.
Rear calipers are... Brembo ones from not a Porsche, but that look and measure as needed with 30/34 calipers (would be better with 30/36 but it's out of my budget completely) but fit the 996TT/997C4S rear rotor width.
Rotors are 996TT/997C4S all corners so 330mm diameter (big reds are 322mm diameter) and 34mm width (fronts) and 28mm (rears).
Stock emergency brake works (just needs like 25mm extension for the cable).
Made of 7075 T6 billet aluminium and Helicoil inserts for threads.
I used 25.4mm master cylinder (I don't like the feel of the 23.8mm one from C4, that is sufficient by the way).
18573773[/url]]Very cool. Is this a one-off or a product you're thinking of bringing to market?
Thanks!
I’m not sure if this can compete with the big names kits in the market.
Anyway all the R&D here is my IP and I own all the projects, simply because I did it on my own.
Making another set or 20 is just a price tag for the CNC shop… in theory.
The rear adapter monolith makes 90% of the cost of the CNC / 7075 T6 billet.
01-13-2023, 11:31 PM
Brake upgrades
