The ultimate brake upgrade page.

[JHanson]

A question for Bill Verburg if he comes back: Bill, in your opinion what is the best brake upgrade possible on a 911SC with 16-inch Fuchs wheels (six and seven inch width)? I know about the 930 setup at $5,000 plus, wondering about others. I know to stay away from the Boxster kit . . .

Thanks!

[Geronimo '74]

I'm not Bill by a long shot, just so you know...

What's the reason for the upgrade? Racing, trackdays? streetrod?


If you can lock the brakes during hard braking, there's little to gain in braking power by upgrading.

If you need more efficient cooling to eliminate brake fade, look at bigger ventilated disks, increase airflow going to the disks, upgrade brakefluid,...

[Bill Verburg]

Originally Posted by JHanson

A question for Bill Verburg if he comes back: Bill, in your opinion what is the best brake upgrade possible on a 911SC with 16-inch Fuchs wheels (six and seven inch width)? I know about the 930 setup at $5,000 plus, wondering about others. I know to stay away from the Boxster kit . . .

Thanks!

What Geronimo said

part of the discussion should be the wheel and tire used as the grip that the tires develop will always be the limiting factor is a single stop. More brake torque wants more tire grip. This comes from either stickier tires or wider, lower profile wheels & tires

For multiple stops it depends additioanlly on the thermal properties.

Honestly stock brakes are very good, cool them, use pads appropriate for the use, use fluid w/ higher temperature range, lighten the car, learn to use less brake

If more is needed a small + is to switch to 3.2 Carrera fronts.

After than it's a big jump to 930s,

I haven't seen an aftermarket version that fits 16s that I could recommend

[kent olsen]

As Bill says great big brakes that lock up the tires are counter productive. Big brakes need big wheels/tires to handle a heavy car. And then a 50% increase in braking ability might be 3-4 inches in sweep area, while going from a tire with 6 inches of tread width to 9 inches adds another 3 inches of contact and seems like a balance. Then consider the brake is squeezing the caliper but with out some down force from the car at the now higher speed nothing squeezes that extra 3 inches of tire to the roads surface.

If you add power to your heavy car then your braking speed may be higher and larger brakes would seem logical. Next you'll run into brake fade so changing to drilled and or slotted disc's would be next.

If you are a track junky then the big brakes and wheels/tires are cool. On the other hand without 500 hp the Porsche is a momentum car, mine is a 72 and the idea is to keep as much speed as you can.

After 20 years of playing with my 72 and lot's of track days, east and west coast, this is my combination. Weight reduction (now 2200lbs), 245 hp at crank 9:1 pwr/weight), running 205x50 tires on 7" rims. All I've done for brakes is replace the front calipers with SC calipers giving about 20% more in the front, stock rear brakes and drilled and slotted discs.

These are my opinions not to contradict anyone

[CPS996]

Admins, Is it possible to "Sticky" pages like this?

[sp_cs]

Originally Posted by JHanson

I know to stay away from the Boxster kit . . .
Thanks!

Curious why?

[Bill Verburg]

Originally Posted by sp_cs

Curious why?

It's probably in the above stuff somewhere, but once again
The function if the brakes is 2 fold
1) apply braking torque to the wheel
2) process the heat generated in 1

There are several restrictions that need to be applied to any modification of stock brakes
1) f/r bias must be maintained, while more front is safer more rear is desirable from a performance perspective.
2) pedal ratio must be kept w/i a fairly narrow range, the exact spec will depend on boosted or no and how much leg the driver is willing to employ and for how long
3) the brakes must fit w/i the wheels used
4) the tires should be adjusted up in grip when brake torque is raised
5) calipers should not make the processing of heat more of an issue than it is stock. This is particularly relevant to track cars.

Boxster conversions to 911 brakes are not an upgrade because the violate rule 1 & 5

Rule 1 - stock f/r bias for all 911 through '83 is 1.491, this is a great place to be, for track work bias a little less than that can be employed but to do so the car wants a really effective lsd and wants to be lower and stiffer

F & R Boxster change has a bias 1.669. This isn't dangerous and is fine for street use but gives up a lot of performance in track use as the fronts are doing too much work which causes more thermal issues and the rears are loafing along doing little to help the cause. Boxster f w/ Carrera 3.2 rear is better w/ a bias of 1.554, still not as good as stock.

Rule 5 - the Boxster calipers do generate more brake torque but brake torque has rarely been an issue w/ 911 brakes. Heat is and always has been the primary concern. Boxster fronts generate 1839n-m of torque @ 70 bar line pressure. 911 brakes generate 1444n-m @ 70bar line pressure, this 27% increase in torque going through the same rotors causes at least 27% more thermal issues. The pads and rotors and fluid have to run at higher temperatures when they were already near max to begin w/.

[H-viken]

Originally Posted by kent olsen

If you add power to your heavy car then your braking speed may be higher and larger brakes would seem logical.

Higher speeds and less time between corners. I.e less time for the brakes to cool.

[H-viken]

Is there a weight comparison between different set-ups available somewhere? Calipers, pads, rotors all weighed together

Johan

[Bill Verburg]

Originally Posted by H-viken

Is there a weight comparison between different set-ups available somewhere? Calipers, pads, rotors all weighed together

Johan

While there is a weight penalty it is almost insignificant

here's some data,

Inertial cost in n-m
SC front rotor ~2.6
930 front rotor ~4.5
205/55 on 7x16 Fuch ~28

[JHanson]

Curious why?

The Boxster kit increases thermal stress on the stock rotors. The car will stop better initially, but repeated stops will actually exacerbate fade. (So I understand. I believe Bill will corroborate.) Edit. Ack, I see he did.

My use is virtually all street. However, we have several nice mountain roads nearby, and I've been able to overstress the brakes on long, twisty downhills, even with premium pads and fluid. So I'm interested in practical upgrades.

[JHanson]

I haven't seen an aftermarket version that fits 16s that I could recommend

Thanks very much Bill. That sounds like a negative on the Stop Tech system.

[Bill Verburg]

Originally Posted by JHanson

Thanks very much Bill. That sounds like a negative on the Stop Tech system.

I just don't know enough about the Stoptech BBK to have an opinion.

[H-viken]

Originally Posted by Bill Verburg

While there is a weight penalty it is almost insignificant

here's some data,

Inertial cost in n-m
SC front rotor ~2.6
930 front rotor ~4.5
205/55 on 7x16 Fuch ~28

So the penalty in terms of rotational mass is negligible. How about adding unsprung weight?

If also negligible, then there is no real downside, except financially, to install the larger 930 brakes.

Johan

['76 911S 3.0]

Originally Posted by JHanson

Thanks very much Bill. That sounds like a negative on the Stop Tech system.

Although I have yet to see how they perform, the StopTech kit does fit under my 15" Cookie Cutters

[earlybroncoguy]

https://forums.pelicanparts.com/porsche-912-technical-forum/988261-how-i-fit-boxster-calipers-vented-rotors-my-66-912-a.html

[otto in norway]

Hi all
Bringing back this thread.
I have searched for information on how to fit 964 turbo calipers to a 911 SC. But little info is out there.
I suppose there is a fair bit of adaptations for it to work, but someone must have done this? The brake balance seems to be good for this setup as well. And they aren't that enourmous either, which is a good thing. I'm using 17" wheels though, so I could go slightly bigger in theory, I believe.

The reason I'm asking for that setup is because it might be cheaper than 930 setup, but still used for a turbo car. You see, in Norway, a big part of getting your car approved with more horsepower than stock, is to prove that you also have upgraded the brakes to match the performance. So I need to fit brakes that are from a high horsepower application originally. 964 and 993 C2/C4 brakes might not be sufficient to meet this "requirement" from the controller.

Anyone?

[runner4fun]

I am doing a 1983 SC coupe back-date project now. We recently fitted the big red 996 turbo calipers to the car which were much less expensive than 930 calipers. We are using 930 rotors with the calipers. Adapters were needed to fit the calipers but all assembled well. My wheels are 17" Braids.

[otto in norway]

Hi, thanks for the tip.
Do you have any specs to the piston size for those?
I would have thought that the 930 rotor would be too small for those calipers?

Anyway, I'm really curious to see if anyone has done 964 calipers on a 74-89 911.

[Bill Verburg]

Originally Posted by otto in norway

Hi all
Bringing back this thread.
I have searched for information on how to fit 964 turbo calipers to a 911 SC. But little info is out there.
I suppose there is a fair bit of adaptations for it to work, but someone must have done this? The brake balance seems to be good for this setup as well. And they aren't that enourmous either, which is a good thing. I'm using 17" wheels though, so I could go slightly bigger in theory, I believe.

The reason I'm asking for that setup is because it might be cheaper than 930 setup, but still used for a turbo car. You see, in Norway, a big part of getting your car approved with more horsepower than stock, is to prove that you also have upgraded the brakes to match the performance. So I need to fit brakes that are from a high horsepower application originally. 964 and 993 C2/C4 brakes might not be sufficient to meet this "requirement" from the controller.

Anyone?

964t brakes to a 911 is fairly easy, the brake bias gets moved more front than I prefer but not as much w/ as much negative side effects as w/ some others
In front you use 993 2 piece rotors, these are 322x32mm. remove the hats and discard them, replace w/ flat aluminum hats. The calipers will need an adaptor to bolt to the 911 strut. Both adaptor and hats are available form places like VCI.

In back use a 309x28mm 930 rear rotor from a '78-89 930. The calipers will need to be modified by filling the existing mounting holes and redrilling the holes to fit the 911s 3" OC mounts, Here's a pic of the filled and redrilled rears





finally, use a 930 '78-89 m/c

I would caution against any of the 996 calipers especially 996tt as bias gets moved way forward, most owners end up having to also use a racing twin master set up